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 Note the year and month and be advised that some of the older information may now be out of date.
Threadless headset conversion – 2006.07
I have a 2002 Dawes Galaxy tourer with a quill type stem. I have installed an A-head converter and a 40 degree stem. The converter still relies on a quill expansion plug to hold it in place. On tour creaking noises and nasty rust/sweat leaks often develop from the stem. Much tightening sometimes cures the creaking temporarily, but the rust continues in spite of extensive grease. I would like to convert to genuine A-head (threadless steerer tube) forks, and see that the Super Galaxy has this. Is it possible with my frame?
Nick Farnes – Olney, Bucks
Creaking and rust: yeugh, I didn't realise those quill-to-threadless converters were such awful, ill-fitting quality!
Yes it is possible to fit a fork with a threadless steerer tube. It needs to be the same diameter as the threaded steerer on your existing forks, 1-inch or 11/8, and you also need to buy the corresponding size of threadless headset. (Threadless is a more useful term since it describes the design difference, whereas A-head is the trade mark of one manufacturer of such headsets.)
Snag is: in 2002 the Galaxy still had a 1-inch steerer, whereas the 11/8 size has since become the standard for mountain and touring bikes. It's bigger, it's stronger, it makes sense. One-inch threadless headsets are found only on racing bikes and becoming uncommon there too. (Don't buy a "hidden" or "integrated" headset by the way: that's also something peculiar to racing frames and a bad idea even for those!)
So you'll not be able to use a current Galaxy fork and may need to get one custom-built to fit. Fortunately there's any number of framebuilders in this country who can easily do that – at a price. Make sure the fork has a long steerer tube on it and get a load of spacers, since you clearly wish to raise the handlebars higher than they originally were on this bike. You'll probably also need a shim to fit your existing stem, which I'll wager is 11/8-inch internal diameter.
Chris Juden
Shimmy – fridge magnets – 2004.01
Folowing the Q&A on shimmy in the last issue, readers suggest a couple of other things that may trigger this effect.
Bryan Colbourne of Bishops Tawton, Devon associates shimmy with chilly weather. One time he got so cold the bike simply shivered in unison! Another shimmy event (and another bike) involved all the classic factors: hard, narrow tyres (20mm), lightweight frame (notoriously flexible 531-Pro tubing), smooth road, high speed (30+ mph), plus a day too cold and a group too slow for Brian to get warmed up. Brian reckons the other factors have coincided before and since on this bike, without shimmy, which leaves a lack of damping from cold, tense muscles the likely culprit. It’s plausible that cold might have a similar effect to nervous tension.
Bill Byth of Banchory, Aberdeenshire reckons that a wireless computer magnet (that had to be mounted further from the hub) induced shimmy in both his lightweight road bikes. Quote: “My Vitus 'Magic' 997 road bike would start to shimmy between 38 and 43mph and my 7005 winter trainer with Alpino carbon forks would shimmy at 28 to 30mph with and without panniers. I tried both bikes with five different front wheels, all on different 23mm tyres, without curing the shimmy. At the suggestion of the guys in the Edinburgh Bicycle Cooperative in Aberdeen, I tried balancing the spoke magnet with a matching diametrically opposite one. Hey presto, no shimmy! I haven't fully recovered my descending nerve yet, but so far so good up to 48mph”. Having experienced lots of shimmy episodes during his experiments with wheels and tyres, Bill confirms the life-saving efficacy of pressing one leg against the top tube!
Both cases involve something which acts as the “final straw”: an extra factor that when added to bike that is already somewhat prone to shimmy, tips it over the edge. We’d all be safer if bike designers would steer a bit further from that edge to start with!
Chris Juden
Shimmy – 2003.11
Could you please tell me what causes a bike to get a side to side wobble as the handlebars at speed? This has happened to me twice now at about 35 to 40mph on two different bikes. Is it something to do with frame geometry, riding position, or the set up? The first time it happened was on an aluminium framed racing bike with alloy forks. The shaking was very violent and did not stop until I had virtually come to a halt. The second time, on a Cannondale CAAD 2 aluminium hybrid with steel forks, it was less violent. Can you please shed any light on this as it has dented my confidence in descending the many hills in Dorset. I am 6ft tall and weigh 12 stone.
Mike Pring – Halstock, Yeovil
That’s shimmy. It’s a kind of vibration where the frame twists and the front wheel gyrates (wobbles) so as to lean and steer alternately left and right. Like any vibration it has a natural frequency that depends upon characteristics of the vibrating system. The key factors in this case seem to be the torsional stiffness of the frame, steering geometry and distribution of weight on the bike.
Vibrating systems “resonate” (the vibration grows instead of dying away) when they are excited (jiggled) at their natural frequency. This happens to a shimmy-prone bike when wheel rpm and wobbles per minute correspond in some way. At other speeds rotation cancels wobble; but around its critical speed the shimmy extracts energy from the motion of the bike to become increasingly violent.
Like any vibration, shimmy can be damped. The main sources of damping apart from air resistance are the front tyre and the rider’s body. Only last year this magazine reported the serious injury of Clive Oxx, a CTC councillor, when thrown by a violent shimmy witnessed by the group he was leading. I examined the bike. It’s one he’s owned many years, it’s never shimmied before and I found nothing wrong with it. Clive had simply fitted a slimmer, smoother front tyre than ever before and inflated it very hard. Broader, softer tyres provide much more damping.
A firm but relaxed hold on the handlebars also provides sufficient damping to ensure that shimmy does not develop beyond an occasional slight shake, even though the bike may be moving at shimmy speed. Once you have suffered high-speed shimmy however, it is hard to remain relaxed when riding fast, especially on the same bike, down the same hill.
It
is almost invariably downhill – where gravity feeds the speed that feeds the shimmy – and a smooth road (Clive’s hill was recently, beautifully resurfaced). For although a surface defect may trigger the shimmy – or a stone, a gust of wind, an involuntary twitch from the rider … a rough surface inhibits its growth by randomly disturbing the front wheel.
Never attempt to fight a high-speed shimmy. It’ll be too rapid for any human response and you may instead make it worse. You need to apply passive damping. This is easily done by gripping the frame between your thighs. Simply resting one leg against the top-tube will damp out most cases of shimmy whilst you gently apply the brakes.
A stiffer frame, more trail (an aspect of steering geometry) and less weight on a bike all seem to increase shimmy frequency and speed. That’s usually a good thing to do: because higher frequencies are easily damped – even the skinniest tyre a narrow tyre may do it – and the higher speed may well be faster than the bike ever goes. A heavier rider however, or heavy luggage on the bike, may bring shimmy frequency/speed down into the troublesome range. But there are many different ways to distribute luggage on a bike with radically different effects. The addition of front low-load front panniers often reduces shimmy to a walking-pace weave that’s slow and easy to steer out of.
Bicycles
should be designed so they won’t shimmy under any reasonable circumstances; but that’s simpler to say than to do, especially since we also want our bikes to be lightweight, comfortable and easy to steer – all of which tend to increase this behaviour. Cycle designers have little to go on, for although there is some published research on motorcycle shimmy (“weave” and the alarmingly named “tank slapper”), that does not provide exact predictions even for motorcycles.
So if you’re stuck with a bike that shimmies at an annoying (up to 20mph) or dangerous (about 30mph) rate, the first thing to try is different luggage arrangements. You can’t do anything about frame stiffness or angles, but a bit less fork offset (rake) will increase the trail that keeps the front wheel pointed where it’s going, or maybe one with wider blades (stiffer sideways). If that’s to no avail: it’s always possible the bike won’t shimmy under the sucker you sold it to!
And remember the leg on top-tube life-saver. Any of us might need it one day.
Chris Juden
Mountainous headache – 1998.01
Technical Forum has dealt at some length with headset fit etc., but what about the question of headset durability on seriously used mountain-bikes? Since I bought my first mountain-bike in 1984, the headset has been the greatest maintenance problem of all. I have tried Shimano, Ritchey, Kona, Stronglight – you name it, I’ve probably cursed it.
My present bike, a Cannondale with the 1.25 inch size, has a Shimano XT sealed bearing unit which cost a whopping £55. The bottom race was as gritty as it’s unsealed brethren after one winter. Yes I do strip and clean occasionally.
I took the worn parts to a bearing shop: “that’s not a precision bearing chief – just a rubbish ballrace costing coppers to make”. Next door the mountain-bike emporium were making inch and a quarter stuff obsolete (tough luck for their customers of the last four years!). But they found a sachet containing two bearings: “£29.99 is the right price, but you can have them for £20.” I had one. Ten pounds for a crude, short-lived ballrace.
The headset is the bane of my life. I might be advised to strip and clean it more often, but I jolly well do not want to. I like to keep the bike in tune, but pulling out the stem and all the concomitant filthy fiddling should have been consigned to history years ago. Cartridge bottom-brackets – at £15 for two years of trouble-free pedalling – are cheap and reliable even in northern grit and peat. I cannot help but feel that at £55 a headset and £30 for inevitable spares (over the same period) I am a victim of stone age technology and blatant profiteering.
Alan Kind – Newcastle-upon-Tyne
The problem here is the lack of a front mudguard – to deflect the continuous blast of wet grit thrown off the front tyre. No ordinary seal can withstand much of that. Since mudguards are passé on mountain-bikes one must find another way to shroud the lower head bearing. A sleeve cut from an old inner-tube works okay. Or you can buy a neoprene cuff that fastens with Velcro so that no dismantling is required. ‘Lizard Skins’ is a popular brand, contact Raw Marketing (0131 467 6467) for further information.
For post-stone-age technology, I’d recommend the WTB New Paradigm headsets – available from Bikenet dealers, tel: 01454 201700. These feature Grease Guard lubrication points, through which you can pump fresh grease to push out any crud that may have got past the seals. Threaded or threadless versions are offered, but only in 11/8 size and at a cost of nearly £90. It is possible to grease inject some other headsets, by drilling a small hole in the right place and fitting a tiny screw as a stopper
Chris Juden
More on headsets – 1997.11
With reference to Marjorie Jones’ Headset Eater, I too had an Orbit which chewed one headset after another in less than one year. After fruitless dealings with repair shops I took it to George Longstaff. He simply put the forks in a lathe, switched the machine on, and told me that the problem was due to a badly positioned steerer tube relative to the fork crown.
He fitted a new steerer tube and Campagnolo Record headset, and sent the resprayed and re-assembled frame to my home in Essex. Results: 1) A securely packaged frameset arrived undamaged. 2) The paint job was first class. 3) No more headset problems. The frame is a 22½in by the way, so not large or small.
Michael Elleston – Borough Green, Kent
Note: in their XTR, Deore LX and XT headsets, Shimano not only arrange the angular contact ball bearing cartridges back to back (for greater resistance to off-axis loads), but also locate them in self-aligning housings. Try one of these if you seem to have an alignment problem. It’ll cost less.
Part of Marjorie’s original problem was that only another Shimano 105 headset would fit, due to the fact that the steerer was cut short to suit the unusually low stack height of this model. A new steerer tube could of course be longer and allow other, better headsets to be fitted.
Jens Thorsen of Copenhagen points out that only the top stack of the 105 lacks height. The bottom stack is much the same as any other headset. And as these are the parts that generally wear out, an easy solution is to fit just the lower stack from a better model – e.g. any Stronglight needle-bearing headset – leaving the unworn shortie 105 top stack in place.
Chris Juden
Headset eater – 1997.07
My cycling was transformed after I read your Petite Test cycle review a couple of years ago. I purchased an Orbit Expedition, 18in, and have thoroughly enjoyed cycling ever since.
However the bike EATS headsets. It’s got through two in as many years and now I need to fit a third! The problem is, instead of the headset turning smoothly it clicks almost as if indexed. This makes slow speed riding very wobbly indeed.
My current headset is a Shimano 105 SC (HP-1055). My local bike shop tell me that the only thing they can get that will fit is another the same, because of the short steerer length (but did admit, when pressed, to not knowing what was available from Stronglight, Primax, etc.). They also said that this is often a problem with very large and very small framed bikes, because (he said) when you turn the front wheel on such bikes, instead of the head tube staying level it rises and falls slightly, hence putting more wear on the headset.
My questions are: What can I fit that will last? Is this a genuine problem with small frames, or is he having me on, since I am unable to see this rise? Should I be getting back to Orbit on the grounds that the geometry of the front forks is incorrect?
The headset on my husband’s Super Galaxy, which in addition to everything else does a daily 15mile commute, has lasted seven years with no signs of wear yet. Surely it’s not too much to expect a similar life from mine?
Marjorie Jones, Southampton
Small frames have an entirely justified reputation for eating headsets. And although you don’t say so, I expect that your husband’s frame has a longer head-tube. This spaces the two head bearings further apart, which helps them resist some of the forces acting upon them — forces from bumpy roads and braking that make the fork-end waggle to and fro.
This theory about rising and falling head tubes if a fine example of bikeshop mumbo jumbo. It derives from another superstition about the ‘correct’ steering geometry being one where there is no rise or fall as the handlebars are turned. All practical bicycles fall and then rise as the handlebars are turned, but some fall more than others and some return to the original (straight ahead) height when turned at right angles. This special case applies when fork rake equals trail. No one ever rides a bike with the steering turned at right angles, but it just so happens that putting rake equal to trail produces reasonably acceptable handling characteristics. Some people read great significance in this geometric coincidence, although touring bikes handle better with a bit more trail than rake and tandems become easier to steer with less.
I digress: in most cases the initial fall is slight for normal steering angles (but can easily be shown with a spirit level) and in any case has no effect upon the life of the headset. (I owned an old tandem that visibly dropped as the handlebars were turned and was a pig to steer below 15mph! Its antiquated headset still turned fine.)
So what’s the solution? Well the easiest and cheapest (temporary) cure for ‘indexed steering’ is to dismantle your existing headset, throw away the inadequate number of balls in cages, buy a load of loose balls the same size (usually 5/32 inch), set the full complement of them (usually 25 per bearing, don’t try to squeeze in 26) into generous helpings of grease and reassemble. Because there’s a few more balls now, they cannot drop into the little dents made by the caged ones in the races; so the headset gets a new lease of life and will probably turn smoothly for longer than it did the first time around.
The best kind of headset is the sort pioneered by Stronglight and also made by Primax, that has needle bearings in a back-to-back arrangement. The effect is like spacing the bearings further apart. Stronglight call this an ‘X-type’ headset (as distinct from their A9 and Delta headsets that position both bearings the same way up: the usual ‘back-to-face’ arrangement). Some of Shimano’s latest headsets (but not 105) have ball bearing cartridges that are not only arranged back-to-back but also in self-aligning seats — which is a further advantage if misalignment is contributing to premature wear.
Unfortunately the Shimano 105 headset has an unusually low stack height (33mm), so it can be difficult to fit anything else to a fork that’s cut short for this model. Instead of buying a fork with a longer steerer you may be able to have a few mm milled off the top of the head-tube. With this modification, and perhaps omitting the headset lock-washer, it may be possible to fit a Stronglight X13 (36mm stack height).
Another idea is to replace the headset brake hanger with a clamp-on stem or brake bolt hanger (both made by Tektro). This can be worth some 2 to 4mm.
Rudelli (previously known as Primax) recently announced an X-type headset called Misura, which thanks to a clever internal locknut has a stack height of just 32mm. This is short enough to be a direct replacement for the Shimano 105. Only snag is: there’s nowhere for a headset brake hanger. So whichever solution you choose you’ll probably need one of the Tektro hangers mentioned above.
Chris Juden
