The following questions and answers have been collected from the pages of the CTC magazine. The most recently published are at the top of the list. Note the year and month and be advised that some of the older information may now be out of date.

Valve support – 2006.05

Michael Bromby of Leeds joins many others exasperated by the inner-tube valve problem reported here recently. Every tube he bought, from bargain bucket to the most expensive brands, would last no more than a month before springing a leak at the base of the valve whilst he was pumping it up. So worried had Michael become about topping them up, he was risking other problems by riding soft tyres. Eventually he hit on the simple idea of cushioning the disastrously delicate junction between valve, tube and rim with an extra layer of rubber salvaged from one of his many useless tubes. Four months later a relieved Michael Bromby is still on the same tubes. He speaks of a fiddly assembly of rubber strips, but I reckon a simple washer, with a stretch-to-fit hole for the valve made with a leather-punch, would be just as effective and very simple in use.

Mark Newberry of London, has an engineered solution. With a drill, he widens the hole in the inner, tube-supporting surface of a modern, double-wall rim, so that the usual valve retaining ring passes through it. Mark screws that ring right up the valve stem before fitting, so that the valve is supported by the ring resting upon the outer wall of the rim, instead to being suspended from the tube. When the optimum position has been found for the ring, to match the depth of rim, it can be glued with threadlock or crimped in place. Another ring screwed on from the outside holds the valve rock-solid and allows it to be pumped with no stress at all to the (apparently nowadays) delicate junction between valve and tube.

But he asks: should all this really be necessary? Good question!

Chris Juden

More on valves – 2006.03

A number of correspondents have suggested that an increased incidence of inner-tube valve separation reported in the last issue of Cycle, may be due to increasing use of directly-attached pumps and double-wall rims – as much as poorer quality tubes. There could be something in that, although directly-attached pumps were generally adopted by touring cyclists (replacing the gentler but inefficient flexible connector) a good 15 years ago. The mini-pump however, is a recent phenomenon and its use does require a lot of pumping, with the attendant risk of yanking the valve to and fro. However I reckon more people also have track pumps nowadays and do most of their pumping that way, which is undoubtedly much easier on the valve.

Double-wall rims also became ubiquitous many years before the valve-shedding plague. So I think there is a tube quality problem, but if we have to live with it then careful pumping and smoothing off the inside edge of the valve hole – which is often very sharp and inadequately cushioned by the rim tape – will surely help. In addition to using a track pump before the ride, we can nowadays have an efficient on-the-bike pump that employs a flexible connector. Best examples (most efficient first) are: the Pneu-Force Superpump (call 01977 795330), the Topeak "Morph" range, Cyclaire, Bikers Dream and the Sigma-Sport Lambda and Alpha Jets.

Opinion is divided regarding those screw-on valve retaining rings: some think they help to keep the valve from see-sawing when you're pumping, others that they help to drag it through the hole. Taking my cue from those modern tubes that don't even have any threads on the stem – with which I've never had any trouble – I leave them off. Some correspondents have gone to the length of drilling out their rims for schraeder (car-type) valves, which being 2mm fatter, have more rubber anchoring them to the tube – and also lack a retaining ring.

Chris Juden

Valve flu – 2006.01

Please find enclosed the remains of a "Specialized" tube that split when attempting to pump up the tyre (which was not flat). As you can see, it cannot be patched. Fortunately I had another tube. This is only the second time I've seen this type of tear in 20 years of cycling: both recently, both Specialized.

Margaret Robb – Oxford

I've been in this job 22 years and it's only recently that members have complained much about valves separating from tubes. And it's not just Specialized. Price competition has also led European manufacturers to import inner tubes from the Far East, and the timing of this outsourcing corresponds uncannily with a rush of complaints across my desk. I do not think any are still made in Europe and no brand has escaped the fatal valve shedding disease – although some seem to have it worse than others! (Schwalbe, whilst not immune, appears to be less infected.)

If you complain to the bike shop, they'll counter with the suggestion that you pulled on the valve when pumping it, pinched it when fitting the tyre, or fitted the tube squiffy, or whatever. Doubtless that is sometimes the case, but it doesn't explain the explosion in such failures. The ease with which complaints may thus be deflected however, does explain manufacturers' state of denial.

Do you remember when Michelin tubes had valves that were clamped in place by a nut and washer? It must be 20 years ago, but if you still have one of those tubes, salvage the valve and keep it to mend these modern failures. I nowadays carry an old nutted valve in my puncture kit. They're a bit short for today's deep rims, so I also carry a valve extender.

Chris Juden

Inner tyres – 2006.07

Some of my cycling friends have taken to lining each of their tyres with another tyre - i.e. two tyres on the same wheel. They achieve this by taking a well worn tyre (usually 700×19C), tearing out the bead-wire and fitting this inside the "good" outer tyre (ideally 700 by 23, I believe). The effect seems not unlike that achieved by using kevlar tyre-liners (e.g. Mr Tuffy) but far cheaper. The advantages claimed for this practice are increased resistance to punctures, longer tyre-life and the psychological advantage for racers of training on heavier wheels, particularly in the off-season.

Do you have any comments? Is there a down-side?

Peter Johnson – Hamilton, New Zealand

Sure the “inner tyre” method works: at cost of increased rolling drag made even greater by inevitable frictional movement between tyre and liner as well as the distortion of layers of casing in a way the tyre designer never intended. It all depends what you count as worse, but I presume speed is of the essence if using 23mm tyres already: otherwise you’d be riding a touring bike with its almost as fast but much more puncture resistant and practical 32mm tyres.

A less effective but much nicer kind of liner is made by removing the valve and slitting the belly of an old inner tube. Just as effective (as an inner tyre), but hardly any more drag than a normal tyre, is the thick layer of natural rubber in Schwalbe “Plus” and Vredestein “Max” tyres.

Chris Juden

Wonky valve syndrome – 2004.09

Often when I replace a tyre, the valve ends up sticking through at a silly angle, in spite of my care to place it in square at the start. I have then to half-remove the tyre again, perhaps several times until it's right, because I know from experience that if I don't, I risk an irreparable puncture right next to the base of the valve. Do you know any special tricks to avoid this?

Ben Gosling – Lavenham, Suffolk

It helps to put a bit of air in the tube before fitting; and have the tube laid snug in the half-fitted tyre, valve exactly adjacent to hole, before poking it through. Then push the rest of the tube over so it lies in the rim before starting on the second tyre bead. I always start opposite the valve and work symmetrically toward it, then flip the wheel over for the final tight bit. I don’t know if that helps avoid a wonky valve but it sure helps fit the tyre, since the whole length of fitted bead can be pushed down into the well. Push the valve up as the last bit of bead pops over and you’ll not trap its base.

After that I find it’s usually straight enough anyway. If not, here’s an easy trick to straighten a wonky valve. It simply reverses how a valve gets that way if you ride on a flat tyre.

Before inflating, stand the wheel on the ground with the valve at the bottom, wonkily pointing away from you. Press down on the ends of the axle and trundle the wheel forwards – the direction the valve points when it’s at the bottom. As you roll it, the slightly loose tyre will precess around the rim, dragging the tube with it. After a few complete turns the valve should have straightened. Tight-fitting tyres need rolling further.

Chris Juden

Grippy old roadster tyres – 2004.05

For utilitarian use I still ride an old "sports roadster" with 26 x 1 3/8 (37x590) tyres (little worry of theft), using un-made tracks where possible. In response to my enquiry for more grippy covers, the dealer's supplier came up with Nokian Speed-Hakkapelitta, which are apparently for cycle speedway and really durable. They have proved superb: no more slides on the muddy bits, and are modestly priced. The dealer has since done a steady trade in them.

B Horstmann – Cheadle, Cheshire

Pressure matters – 2004.01

I was interested to read Paul Mortimer's account of the problems he has had with exploding tandem tyres, and Chris Juden's advice.

I had similar experiences in 1999 and 2000 while touring in France with laden saddlebag and rear panniers. I weigh about 14 stone (90kg) myself. On both occasions it was with a rear wheel with a "hooked" rim. The first tyre to go was a Continental Top Touring 2000; it went off with a great bang and there was a long split in the sidewall. Fortunately I was close to a town where I could buy a replacement. I put the failure down to the flimsy sidewall of Continental tyres and made a mental note not to use them again. The following year I had a similar experience, with the bike similarly laden, but this time the tyre was a Michelin Tracer. Again, the sidewall had split. This time I had a spare with me.

I brought the damaged Tracer back and took it to my local dealer; Everndens of Paddock Wood, who passed it on to the Michelin rep, who reported eventually that the company couldn't find any inherent fault in the tyre which might have caused the failure. But the dealer then let down the rear tyre on the bike I was riding at the time and invited me to re-inflate it with my own pump. I had a Zefal plastic-barrelled pump and managed to get the tyre up to about 55psi. The dealer then pointed out that the recommended running pressure was, I think, 90-100psi and said I would never achieve that with the pump I was using. For normal riding the under-inflation was not a significant problem, but under heavy load it would, as Chris describes, accentuate the flexing of the sidewall and the hook of the rim will then saw its way through the fabric.

Chris advises Paul to "inflate the tyre very hard" and suggests possibly exceeding the manufacturers recommended range. But first you have to be able to reach the recommended range! So I invested in a track pump to use at home, a metal-barrelled Zefal pump to carry on the bike and a small pressure gauge which I also take with me. I have since toured several more times, sometimes carrying camping equipment as well, and so far, touch wood …!

Pat Morgan, Maidstone, Kent

Good point. Unfortunately one cannot assume that the cheap pump that comes with a bike is capable of properly inflating its tyres.

Tandem tyres – 2003.09

I have just had a nasty accident on a tandem and I would like to try and get to the bottom as to why. If you could run through the following and give me some advice, or direct me somewhere that might know I would really appreciate it.

Recently during a ride my rear wheel just blew out (by which I mean a loud bang and instantly deflates). This happened whilst we were stationary and along a flat section of the road. We were not carrying any weight on the bike and the brake pads were correctly aligned to hit just the rim and not the tyre.

Yesterday, this happened again, but on the front wheel whilst we were travelling downhill. Unfortunately, this resulted in a trip to the local hospital to get cleaned up and for my stoker to be treated for concussion. This has now left me with zero confidence in the bike set up and would like to understand what causes a tyre to just go bang? The tandem is a 3 year old Burley Samba with 26" wheels. I am running Continental touring tyres and the brakes are V-Brakes. The rims are not labelled.

Paul Mortimer – Guildford

I'm afraid that this "edge splits" problem, of tyres chafing through and exploding where they rub against the edge of the rim, is common with tandems nowadays – or any heavily laden bicycle. It was unknown 15 years ago and seems to have arisen since rims were given hooked edges to retain folding or very high pressure tyres. The edge radius of these hooks is much sharper than was allowed on straight-sided rims – which have all but disappeared from the marketplace. Tyre sidewalls have also become thinner and with a thinner coating of protective rubber – it makes them roll better – but with stiffer treads – a side-effect of puncture resistance. So the sidewall is more highly stressed. So good tyres have a chafing tape applied to the beads, which should also reach far enough up the side to cover the whole contact with the rim. Sometimes it doesn't, and sometimes this merely transfers the stress concentration to the point where the tape stops. The Tandem Club collected data on this a few years ago. Schwalbe may be a bit tougher than Continental, but no brand of tyre seemed entirely immune from the problem.

The key to avoiding edge splits is to reduce tyre movement at the rim edge. There’s two ways to do that. (1) Choose a narrower tyre or a wider rim, so the rim width (measured where the tyre fits, between the flanges) is 60% to 70% of the tyre section. (2) Inflate the tyre very hard, so it presses against the rim with enough friction not to shift up or down when the tyre rolls against the road. So paradoxically, fitting a narrower tyre and pumping it harder is better! The heavier the rider, the harder the tyre must be inflated to stop it shifting under that weight. The markings on tyres only take account of solo use and tandemists often have to exceed the maximum marked pressure – sometimes by a substantial margin. Good quality tyres can take a lot more than they say, provided that the fit is good.

Even these measures are not a guaranteed cure. Avoid accidents by inspecting the junction between tyre and rim for any sign of bulging after every ride. And, especially after suffering one of these failures, you'll often find that the edge of the rim has become roughened by abrasion from partly frayed casing cords – armed with grit particles picked up from the road and/or flakes of anodising worn from the rim edge. Any replacement tyre will be chafed even more rapidly by the roughened rim edge. Avoid this by smoothing the inside faces of the rim flanges with fine emery.

Chris Juden

Long valve tubes – 2003.05

I have Vuelta Airline wheels using 622 x 32 tyres on a Claud Butler bike.

I am having trouble getting hold of suitable inner tubes with long valves - the normal valve is about 29mm long but I need valves about 38mm long. Any idea where I could get them?

Richard Hebden, Liverpool

Most tyre manufacturers have a long valve option in most tube sizes and these are likely to become easier to buy, perhaps eventually the only version, since rims are increasingly “aero” shaped.

For now, for that size tyre, I'd suggest the Schwalbe tube "size 17" which with an "extra-long valve" is product number 10429463. If your local shops are behaving stupid, try Orbit’s Freewheel Gearshift mail order, since Orbit fit these tubes to bikes. Actually: even Schwalbe's standard presta valve is 40mm, extra-long they give as 60mm.

But if you have an inventory of older, awfully short-valved tubes (e.g. Michelin), or wish to be able to use any handy replacement tube in an emergency: get some valve stem extenders and keep them in your puncture kit. These ought to be stocked in any racer-oriented shop. At least they'll know what they are and (possibly) where to get 'em.

Chris Juden

Folding tyres – 2003.03

I'm obviously new (really a returnee) to cycling and I am a bit lost with the terms used now. I have been searching the web and the CTC shop in anticipation of buying my next set of tyres. Can you help by telling me, what are "folding tyres"?

Ronald Rumley – Wokingham

Traditionally tyres have steel wires wrapped into each bead (edge). They stop the tyre simply expanding under inflation pressure until its sidewalls pop over the rim flanges.

But steel wire is heavy and it’s good for tyres to be light – although the effect of rotating weight is exaggerated by cycling folklore. And whilst providing some flexibility – enough for fitting etc. – steel wires do not allow a tyre to be folded compactly. (However there is a way of rolling a “rigid” tyre in three without excessive distortion of the beads – see diagram.)

Folding tyres substitute a bundle of Kevlar fibres for steel wire. Kevlar is lighter and as the fibres are thin and flexible, the tyre can be rolled up small for storage or to carry as a spare. (I guess you could get the same effect with many thin strands of steel, but nobody does.)

Kevlar is used because it is much less elastic than most polymer fibres; however it does stretch more than steel. Accordingly: folding tyres are generally made a bit tighter and expand to fit the bead-seat upon inflation. Sometimes you’ll hear a pop as it jumps up onto this shelf inside the rim. And as a precaution against over expansion, folding tyres should only be fitted to rims with hooked flange edges. Almost all rims are nowadays like that and although folding tyres were originally made only for road racing and sport riders, you can now get mountain-bike and even touring models. They’re just as strong as rigid tyres, in fact you’ll find that only the best quality tyres come in a folding version. It is entirely for this reason that folding tyres may be said to be “faster”. The Kevlar bead merely saves a bit of weight.

Kevlar may also be used in the tyre casing as part of a puncture resisting belt. These two entirely different uses of Kevlar in a tyre may cause confusion, but a folding tyre is always described as such. CJ

Punctures – don’t give up! – 2002.11

Having "commuted" for the last 35 years I was dismayed that Mr Griffiths of Maidstone had given up after three years blaming tyre reliability as the root cause and also at the concept of using ground down tyres on the inside of a clincher cover.

For what its worth I have the following comments:- I keep a diary of mileage recording details of any mechanical failures: punctures, parts replaced etc. Consequently I have an abundance of reliability data. I know what works well and more importantly what does not work well. (The accumulated mileage now stands at about 175,000 miles.) Punctures occur every 900 miles approximately but do occasionally sadly come along in two's and three's. It is totally impractical to repair an inner tube "on the road". At least two spare tubes in good condition with a maximum of two patches (preferably one should be brand new) must be carried, along with a spare folding tyre to put on if there are any doubts about cover damage or thorns/embedded glass that cannot be spotted on a wet cold wintry night, rushing home to meet an important appointment. A puncture now results in only about an eight minute delay: not a problem when setting off fifteen minutes early.

Tyres must be inflated to the recommended pressure and checked at least once a week to spot any loss of air before being let down on the road. A track pump makes this job easy. I hang my go to work bike up in my garage. It's surprising how many defects can be spotted when a bike is raised from the ground and rectified before failure on the road.

I have never fitted a ground down tyre to the inside a cover or ever tried a proprietary skin inside, although about ten years ago I used to fit a narrow section tub inside a clincher. This appeared to work fine but the ride was poor and the wheel suffered with bearing and spoke problems. This proves one of the basic law of physics: that misery can only be converted to another type of misery! I always buy good quality tyres. At the moment I am using Continental Ultra Gator Skins in 23 section. Fine for now but my favourite tyres on training and time trial bikes (I finally got rid of tubs) are Michelin Axial Pro. These are the very best (narrow) tyres I have ever used: if you know of a better one would you please let me know.

Colin Moore – Middlesbrough

Tyre Savers or Tyre Comb? – 2002.09

M Griffiths solution to the tyre problems, i.e. buying a car again, is rather drastic and expensive. Over a period of several years I used to commute from Watford into central London, averaging 4000 miles yearly, being rarely troubled by the puncture bug. I am sure the reason for this was the fitting of tyre savers/flint catchers which flicked out any road debris before it could penetrate the tyre tread. I still use them at the present time, but my stock of them is now very low and I am finding it impossible to replace them. Does no-one manufacture this simple device any more, and if not, why not? I am sure if they were available people would use them.

As a matter of interest, the tyres I used to use were the old Michelin Elan, followed by the Michelin Bib Sport 25, which both used to give many miles of service.

Peter Moir – Rickmansworth

Tyre savers are now a d.i.y. job, which is okay because they’re quite easy to make out of old stainless spokes and bits of plastic tubing. I’ve never bothered myself, since modern tyres do actually seem to be a lot more puncture resistant – if you buy the right ones – which is probably why this device is no longer manufactured.

I don’t know if Mat Salter of Bridgwater has ever seen tyre savers, but the “Tyre Comb” he’s written to tell me about is rather similar. It’s made from a 2mm spoke, 5cm of brake cable casing, an electrical ring connector and a self-tapping screw. Cut the head off the spoke, keeping 15 to 20cm of the threaded end, bend this into the shape shown and screw the thread into the cable casing, which makes a nice springy handle. Mat suggests you fix the connector onto the other end with the screw so you can hang it from the handlebars by a piece of string or a hook fashioned from the rest of the spoke and a reflector bracket, but I think some people would rather pocket the tyre comb as it is.

Either way, after you ride through litter or thorns, you can stop and spin the wheels whilst pressing the comb against the tyre to knock out any sharp stuff. Okay, so you could use a gloved hand instead – and transfer goodness knows what to your handlebar grips!

Mat’s tried fixing a tyre comb in situ, like a tyre saver, but finds it noisy, difficult to align and that it kicks up a mist in the wet, or dust in the dirt, or both. (I recall clubmates having similar problems with tyre savers in the 70s – another reason I never bothered with them.)

Chris Juden

Tyre-size confusion – 2002.07

I’ve had two letters recently that highlight the confusion caused by the time-honoured way of describing tyres by outer diameter and width.

Geoff Clarke of Walton-on-Thames bought some 26×1.25 Michelin tyres from Settle Cycles upon the reasonable assumption that these were the same thing as 26×1¼. Unfortunately they have completely different bead diameters. Tyre beads sit upon bead seats – kind of shelves inside the rim. The diameter inside the tyre beads and of those bead seats is the one dimension that can be measured on both tyre and rim. It has to be the same for them to fit, but these two are 559mm and 597mm respectively.

The International Standards Organisation describe tyres by this diameter, preceded by the tyre height, both in mm. One and a quarter inches equals 32mm, so the full ISO descriptions of these two tyres are: 32-559 and 32-597 respectively. For the overall diameter: simply double the first number and add the second.

You may be wondering why 26×1.25 is so much smaller than 26×1¼. Well it’s all a matter of history. The latter size is quite easy to understand: 26 inches minus twice 1¼ inches equals 23½ inches, which equals 597mm. But it doesn’t always work out so neatly. When Dunlop invented 27×1¼ they deliberately made it too big, so people who’d bought their rims couldn’t fit French 700C tyres – which were derived from 28×1¾ and hence should have measured the same. That’s right, those skinny modern racing tyres are evolved from a fat old roadster! Tyres developed differently abroad. Rather than invent completely new sizes with the same outer diameter, narrower tyres were made to fit existing rims. I guess that’s because, unlike Dunlop, foreign firms made either tyres or rims but not both. As road surfaces improved, stronger tyre casings were developed to take the higher pressures demanded by narrower tyres, followed by slimmer rims to suit, but still the same internal diameter.

In the case of 28×1¾ that diameter would be 24½in, which equals 622mm. Sounds familiar? Should be: a modern road bike is typically equipped with one inch (25mm) tyres designated (according to ISO) 25-622. The full, correct imperial designation of such a tyre is 28×1¾×1 and you’ll sometimes find those markings on tyres of Dutch or German manufacture. (It’ll often say 1⁵/₈ instead of 1¾, this is not an exact science.)

So where does 700C come in? The French, being French, devised a metric way of disguising the fact that their tyres were rooted in England. The overall diameter was roughly translated into mm, 28in is about 700, and the widths were classed A (1³/₈ was as slim as they could make them back then), B or C (1⁵/₈ to 1¾ and as fat as they came). The fact that you have a slimmed-down version is signalled in the French system by inserting the actual size thus: 700×25C. Why they started out with the fattest 28 incher I do not really know, but it’s probably to ensure interchangeability with tubular (sewn up, glued on) tyres. These appear to have a longer tradition of making narrower tyres fit the same size rim and uniformly fat ancestors (the 26in tubular is called 650C and equates to wired-on tyres with 571mm bead).

This brings us back to 26×1.25 – another slimmed down version of an even fatter tyre. Strictly, we ought to call it 26×2.0×1.25, but it’s derived from an American tyre size and Americans do things their own way! Why the decimal inches? That’s bike boffin code for a wired-on tyre derived from a hook-bead design. Hook-bead is where the tyre hangs onto the rim by a bulge on the edge of each bead hooking into channels in the edges of the rim. It won’t stand high pressures, which is why this method of attachment died out, but whilst that was happening, rims were made that could accommodate both. Wherever you see decimal inches you have one of these old American hook-beads. Fortunately, whilst the Yanks also had a whole mess of assorted width and diameter hook-beads, only a few of the resulting decimal inch sizes have survived and swum the pond to Europe, where they’ve all but eliminated every existing species smaller than 622!

Unfortunately, since hardly anyone nowadays knows or cares about what these numbers really mean, they get them in the wrong order, miss them out, put c instead of C, etc. etc. Which brings me to the second letter: Peter Hopkins of Loughborough has just acquired a Dawes Double-Edge tandem equipped with tyres bearing the oddly mixed description: 26" × 47/54! Well I think we can probably work out what that means by now, though not exactly, since this tyre hasn’t apparently made it’s own mind up about whether it’s 47mm or 54mm section. Such variation would be a virtue in an inner tube, but one expects something more decisive from a tyre!

I think we will all be much clearer about the size of tyres and what fits where, when all customers and suppliers start to go by the ISO descriptions instead of more or less mangled versions of traditional measurements. The old numbers may be more familiar, but are all too often misleading. For a reasonably complete list of equivalent tyre sizes, see the CTC website.

Chris Juden

Hutchinsons Hardly Excel – 2002.05

A while back I bought six Hutchinson Excel 28 mm tyres. I fitted the first one on the front wheel of my Randonneur. After about 500 miles the tyre developed a serious kink. The tread was hardly worn, there were no cuts of any kind, no flints or slivers of glass. The tyre had only been used on tarmac at the correct inflation pressure and no pothole damage had been sustained.

The interests of safety dictate that only a perfect tyre should be on the front wheel, so I moved this dodgy tyre to the rear as I hoped to get a few more miles out of the unworn tread. Cycling with a severe kink in the rear wheel tyre produces a slight sideways twitch on every revolution, which is only really noticeable on very smooth road surfaces; so most of the time it wasn’t a problem. However, each twitch causes a slight rubbing action on the tread and after about 1,500 miles a hole appeared – one tyre consigned to the dustbin.

The second tyre was fitted on the rear wheel. This one also developed a severe kink after about 800 miles and eventually had to be scrapped after around 2000 miles because of a hole at the kink.

The third tyre I also fitted on the rear wheel, but this time I decided to give it extra support with an inner tyre. What is an inner tyre? Well you take a scrapped tyre that still has a reasonable amount of tread, you cut off the beads and remove about a one inch section. The cut edges at the removed section are sanded down to a feather edge (I used a sanding disk). If you don’t do this you will eventually end up with a puncture. Then this inner tyre is placed inside the outer tyre and you get a tyre with twice the thickness. This gives extra support to the tyre and incidentally produces fantastic puncture resistance. I’m sure you’re thinking this is a daft thing to do but it works. The third tyre is still kinkless after more than 4,000 miles.

D. Armitage – Wollaton, Nottingham

A refinement of the inner tyre trick is to obtain one of a smaller section than the outer tyre, e.g. a 25-622 inside a 28-622. Then you only have to cut off the beads and can otherwise fit it complete.

Chris Juden

Ill-fitting tyres – 2001.09

Recently I treated myself to a new touring bike and acted on advice advocated in Technical Forum and had my wheels made up using Alesa Endeavour rims in the hope of avoiding the 'exploding rims’ syndrome. So far, having covered several thousand miles, your recommendation seems sound, the rims showing no discernible sign of wear.

Although having solved one problem, I seem to have created another in that my chosen tyres, Continental Top Touring, seem to stubbornly refuse to sit centrally on the rims. This has the effect of making the rim appear off centre with a corresponding up and down motion when riding. I am now spending a fortune on sea sickness pills! Have I missed the obvious or is my tyre/rim combination unworkable?

Tim Mount — Taunton

Probably it's the tyre. As I mentioned in February (Vittoria tyre trouble), whereas rim diameter is closely controlled, tyre manufacturers are a law unto themselves!

I have Conti Top-Touring on the same rims and they fit fine. However they are a few years old and not the new 2000 model. Lately Continental have tended to make tyres a tighter fit — to be extra sure they won't blow off. So it's most likely one of your tyre beads (or both) is a bit small to sit easily on the ledge called a bead-seat provided for it in the rim, resulting in one section of tyre bead stubbornly remaining down in the rim well, so the tyre dips in that place.

Am I right? Does it look like that? If so, the solution is to use lots of chalk or talc when fitting the tyre. Then inflate way beyond normal pressure (up to 50% over the maximum marked on it, you'll probably need a track pump) until the tyre stretches enough for that last bit of bead to pop up onto its seat. Then you can let the pressure down to normal.

It's also possible (with non-folding tyres, especially if bought mail-order) that the bead wire is kinked and this can inhibit seating. Go around the tyre and manually unbend any visible kinks — it's quite easy to do.

For people with tyres that appear too big, so it's tricky to fit and inflate them without one section lifting too high and maybe even blowing over the rim, first check for kinks, then if necessary build up the rim. I use PVC insulating tape, taking care to ensure that it goes right into the corner between the bead seat and the rim wall. The rim is often wider than the tape, which I divide by slitting the outside of the roll with a Stanley knife and then tape each side separately. (Not because I’m mean, but to avoid filling the well with a double thickness of tape!) Wrap the tape around once or twice for an uneven seater, three or four for a blower, or as many times as it takes to make a diameter on which the tyre fits snugly.

Chris Juden

Beware the wobbly tyre – 2001.07

At 5.25 this morning my Continental Top-Touring 2000 tyre burst just as I set off for work. Assuming it was a puncture I returned inside to change tubes in the light, but when my finger went through the sidewall I realised I had a written-off tyre. Ironically it had burst just below the warning to mount only on hooked rims, with the split exactly underlining the word “HOOKED”!

Inexplicably the tyre had gone out of true on the rim several weeks ago. At that time it had been my rear tyre. Even switching it to the front did not correct the alignment. Close inspections during my attempts to re-align and when changing the tyres around did not reveal any other danger signs.

Another warning may be apt on Continental tyres: to beware imminent sidewall failure if it goes out of true!

Mr W J Houlder – Pontefract

Vittoria tyre trouble – 2001.03

After the Stevenage Audax event the front tyre of my bike deflated whilst riding back to my car. I merely loaded up and returned home. Later I found that the tube had been pierced by a broken end of the tyre retaining bead wire, which had worked its way through the fabric. The break appears to have occurred at the join, where the wire diameter is slightly larger. (Each bead is a single strand, welded into a loop.)

The tyre is a pretty new 23-622, rigid bead (not-folding), Kevlar belted, Vittoria Techno Twin-Tread rated 115psi max. It has not been removed from the rim since fitting – without difficulty to a Mavic MA40 rim using talc and VAR tyre levers – and has been run at 100 to 110 psi.

This failure is unique in my experience but could have had serious consequences. Have you heard of any similar situations? This particular tyre has a strong following amongst my friends, none of whom has had this trouble, but we are now in some doubt.

If you have heard of any similar instances perhaps there is a common thread? Any comments or recommendations would be most welcome.

Derek Titchner – Essendon, Herts

I guess it’s a one-off as you seem to have done everything right. I’d only say that the MA40 is an old design of rim with a barely adequate depth of well – which tends to make tyre fitting more of a strain on the bead.

I’ve heard of one instance of the same make of tyre (Vittoria Flash M23) blowing off the same model of rim. Serious injuries did result from the consequent high-speed crash. This was a folding tyre, and though the bead did not appear to be broken it’s hard to tell because these beads are several thin fibres. Upon subsequent examination it did seem a suspiciously easy fit on the rim. Tyre manufacturers, whilst demanding a tolerance of only ± 0.5mm upon the bead diameter of rims, have persistently evaded the issue of equivalent standards for their own product. So whilst this tyre may seem oversize, I could not prove it. (P.S. I’ve mislaid this other person’s contact details but not the wheels. So if you’re reading this and want them back please get in touch!)

Chris Juden

High pressures call for hooks – 2001.01

I was recently looking for a 27 x 11/4 cover and I noticed on a Continental Top Touring the moulded instruction "use only with hooked rims". I have another which appears identical but does not carry the instruction. Do you know if there are in fact differences in construction between them, and what are the implications of ignoring the instruction?

John Arthur, Middlesbrough

A spate of similar emails led me to research this issue. Generally: any rigid steel-beaded(non folding) tyre that does not call for more than 5bar (70psi) can safely be used with straight sided rims. With higher pressures however, or the flexible beads of folding tyres, the bead stretches away from the bead-seat and hooked rim edges may be needed to stop it lifting too far in one place and blowing off. Continental are especially keen to ensure this does not happen, so they not only make their tyres a close fit but also mark "use only with hooked rims" on any with a higher than 5 bar maximum pressure. All modern rims are hooked so it’s seldom an issue. However the market for the 630 (27×1¼) size concerns older bicycles and rims mostly without hooks.

Talking about 32mm (1¼ inch) section tyres: the original Top-Touring was rated up to 5.0 bar and had no such warning. When the Top-Touring 2000 was introduced Continental rated this slightly higher and also boosted the Original to 5.5 bar (75psi). This took both tyres into the “hooks only” category, along with the 32-630 (27×1¼), 5.5 bar version of the Sport 1000. Possibly this change came from a slight improvement in casing strength. Or maybe (since consumers often associate higher pressure with higher quality) they simply asked how high can we make it? I can’t see any difference in the design. Certainly all three still have steel beads so I reckon they should be safe enough on old-fashioned straight sided rims provided you don’t inflate over 5 bar.

John Arthur has followed this advice with no problems on his Conti Top-Touring tyres. However some alternative makes – marked with higher maximum pressures and no other restrictions – have been reported to blow off old 27 inch Weinmann straight-sided rims even when carefully inflated below 5 bar. So it appears some other manufacturers are keener for your custom than your safety.

and hooks call for high pressures

On the other hand some riders report severe problems with Continental touring tyres on the designated type of rim! In some circumstances the hooked edge can bite through the casing, resulting in sudden and unpredictable deflation! These circumstances seem to involve two or more of the following factors: too low inflation pressure (note: high-pressure tyres need pumping at least once a week); a heavy rider (tandemists have worst problems); rim with sharper than average hook or prominent extrusion die-lines; rim where previous chafing has roughened the hook.

Such failures are not exclusive to Continental. According to member feedback it seems most other makes of tyre are more or less vulnerable. It may simply be that high-mileage riders are especially drawn to Continental tyres by their puncture resistant and durable treads, that nonetheless roll very well.

All I can suggest is to smooth the “biting edges” of hooked rims (e.g. with emery paper) – then pump the tyres good and hard and often.

Chris Juden

Take care with new tyres – 2001.01

I came off my bike recently, I think as a result of a combination of a polished road surface (quite dry and no loose stuff) and a downhill bend – negotiated safely many times previously, but this time I had a new back tyre.

My son was quick to tell me that motorists are advised to drive cautiously with new tyres until they’re “scuffed in”, but I don’t recall seeing a similar warning with regard to cycle tyres. Have I missed it?

Peter Hawker – Chelsfield, Kent

I’ve not noticed any advice like that from cycle tyre makers, but I expect it applies just the same. No doubt a bit of whatever they use to release the tyre from the mould gets left behind in the tread. And if this stuff stops it sticking to the mould, I don’t suppose it’ll help grip the road.

New tyres often look very shiny or have a bloom (like the skin of a grape) – perhaps indicating an oily or waxy surface. So I guess it makes sense to go easy on the corners, at least until they take on a reassuringly dull matt appearance.

Chris Juden

Capable dealers – 2000.01

Several readers have rushed to correct my unduly pessimistic and unpatriotic advice in the previous magazine, about availability of 26×1½ tyres (French size 650B, or 584mm bead according to ISO) in this country. Mr G E Hall, CTC member and proprietor of ‘The Cycle Shop’, Haxby, York (tel: 01904 766390) was the first to be dismayed that I should “point people to foreign shores when there are very many capable cycle dealers and wholesalers in this country”. He says he has no problems obtaining 26×1½ tyres from his local wholesaler and generally keeps some in stock.

Tom Wells is Ceredigion DA secretary and also a ‘capable cycle dealer’, with 35 and 44-584 Michelins and 40-584 Hutchinson available from New Image Bicycles, Pwllhai, Cardigan (tel: 01239 621275).

Mr D Pilgrim has bought spare 35-584 Michelin World Tour tyres for his Globetrotter tandem from Swifts of Forest Hill and his local shop in Fakenham. And there may be life in the old size yet, for it is alleged that this size can be found on new bikes from Yamaha (XPC-26 electrically assisted models).

Finally John Dawton writes from Walton Street Cycles – probably the most capable dealer in Oxford. He agrees that this size is obsolete but says there are a lot of obsolete cycles still running! Old Post Office and butcher’s bikes for example. So they keep a stock of these and several other obsolete sizes of tyre – with rims to suit. Only steel though, and only for stirrup brakes. He says that 584mm rims for calliper brakes, in alloy or steel, are not available in the UK. Or maybe there’s an even more capable dealer out there ...

Chris Juden

26×1½ = 650B – 1999.11

I have recently finished restoring a Sun tandem of unknown vintage which had lain in a garage for the last 20 years. Whilst the rear wheel had to be rebuilt, the front is very sound and true so I am loath to replace it. The tyre currently fitted – and thus at least 20 years old – is marked “Dunlop 26×1½ – Inflate hard” but the diameter of a modern 26×1³/₈ tyre is fractionally too large. There are no markings on the alloy rim. Do you have any ideas what size of tyre will fit and where could I get one?

Neil Lawrence – Chelmsford

This wheel is an old British size with a bead seat diameter of 584mm: smaller than the 590mm of a 26×1³/₈ and bigger than the 559mm mountain-bike diameter – onto which could be fitted a similar sounding 26×1.50. (The bead seats are the kind of shelves inside each side of the rim upon which the tyre beads sit when it’s inflated, i.e. roughly corresponding to the internal diameter of the tyre.)

This old 26×1½ size became obsolete some 30 years ago in Britain, but until recently remained fairly common in France (and Japan), where they call it 650B. Replacement tyres are still stocked by some French retailers and there’s a bunch of enthusiasts for this size known as “Confrérie des 650” who keep tabs on where and what’s available. For further information contact: Gérard Hourcade, 9 av. Jean Moulin, F–64150 Mourenx; or tel: 00 33 559 603145. One known French mail-order source is Gilles Berthoud S.A., Route de Montrevel, F–01190 Pont de Vaux; tel/fax: 00 33 385 514646 / 306512. Amongst others in 650B they sell the Schwalbe HS159 Special Tandem.

Chris Juden

Original and Best – 1999.11

I have been riding on Continental Top-Touring 32-622 (700×32C) tyres for several years. I find them comfortable, puncture resistant and very durable. My local shop advises me to change to the new Top-Touring-2000.

I would appreciate your comments.

Peter Bell — Carrickfergus, Co. Antrim

The only benefit offered by the 2000 is extra puncture resistance. As the original Top-touring is already extremely puncture proof, just as durable, lighter, more comfortable, rolls easier, feels more sure-footed in corners and costs less: I find no reason to downgrade to the new model.

Many other discerning tourists agree. And whereas Conti has been able to withdraw the original Top-Touring from their home (German) market, it remains a best seller in the UK. I find it singularly heartening that sometimes customers really can keep a good product going after the marketing department have decided we ought to want something new and induced dealers to spread that message. Let’s see how long we can keep it up!

Chris Juden

Tractor tyres – 1998.01

Alan Pocklington – proprietor of Spa Cycles, Harrogate – raises a point that has also interested me (as a farmer's son) for some time. Most mountain-bike tyres and some touring tyres, e.g. Continental TT2000, have a V-shaped tread. Arrows on the sidewall generally indicate that these should be mounted so that the V corresponds with the direction of front wheel rotation, and points the opposite way on the rear.

Tractor tyres also have a V-shaped tread. On tractors these are fitted so the V points the same way as the rear (driving) wheels rotate. So when they slip the angled tread blocks displace mud etc. outwards to the sides, digging down to firmer ground.

Why are cycle tyres fitted the opposite way? Mud, rather than being pushed aside, will surely pack into the middle under the action of rear wheel driving and/or front wheel braking – perhaps increasing a tendency to slip. I put this question to Continental AG in Germany, who promptly replied with the following text from the ‘Conti Tyre Bible’: “the front tire’s tread chevrons should be pointed to enhance braking and steering by ‘scooping’ the earth forward. As the rear wheel’s main function is to provide accelleration, its chevrons should be directed to the rear”.

So there you have it: tractors dig, bicycles scoop. Which still doesn’t explain the difference. So I pestered them some more; and to their credit I got another reply: a long one I cannot print in full which basically says that bicycles must not be compared to tractors.

I suspect that tractors dig simply because they can; i.e. digging always works, but only if you have the power and stability to sit there doing it. Cycle tyres (even on mountain-bikes) are relatively narrow and inflated to a higher pressure, so perhaps they don’t need a tread to penetrate into firmer ground. There is a suggestion that scooping gives bicycles the more immediate results they require – especially in drier conditions. Indeed we find that some rear mountain-bike tyres have arrows pointing opposite ways not only for downhill (braking) versus cross-country (driving), but also for dry (scooping) versus mud (digging).

We should not, however, be too impressed by such technicalities. For according to Continental: “there is actually very little scientific activity going into (cycle) tread pattern design, but far more personal discussions and sharing experiences”. (Yet more respect to Conti for telling it like it is.) They go on to say that sidewall imprinting is a general recommendation, not a requirement, and that some people have tried the tyres the very opposite way and find they perform well. So if you want to ride like a tractor that’s okay by them

Chris Juden

There’s only one Mr Tuffy – 1997.07

A short while ago two plastic tyre liners were fitted to my cycle. Some 400 hundred miles later the rear tyre deflated to be followed 6 miles later by the front tyre. Inspection of the inner tubes revealed multiple splits of 3/16ths to 1½ inches. The splits were consistent as being a result of the rather sharp edges of the liners cutting into the tubes which were normally inflated to 70 p.s.i. It would be interesting to know if any readers have had similar problems or can suggest any other cause. The cycle shop which fitted the liners were somewhat puzzled but very kindly took responsibility for the affair.

K Roberts, Halifax

The only tyre liners I can recomend are original Tuffy tapes: the Mr Tuffy brand, which apparently lack a UK distributor at present. No doubt this letter will remedy that! Members using other tapes have reported similar punctures to those reported above, due to inadequately feathered edges. Or even worse: some tapes become brittle and develop lengthwise tube-eating cracks!

Even Mr Tuffy is not without his faults. For whereas the edges of this tough but flexible tape are nicely feathered, the ends are simply cut off square. This can lead to punctures where they overlap. They may even chafe inside the tyre and weaken its casing. This is usually avoided by moving the tape from time to time — before it can do too much damage at any one point — but this is as troublesome as mending the occasional puncture. The solution is also to feather the ends of the tape: either by abrasion or spreading with a heated knife etc.

Chris Juden