Scary as **** isn’t it ?!!

So, heres the story.

Bought a Genesis Equilibrium end of last summer. Had a few great rides on it before it got stored away for the winter. Last week I got some new wheels fitted (Miche Altur) and also adjusted the saddle to a more forward position.

Went for a ride Friday afternoon, nice dry day and it was great.

Went out again Sunday morning (damp) and every time I descended a hill the front end wobbled uncontrollably. Very Very scary on wet roads at 40mph!!

So, any tips on stopping it? Its odd that the changes I made (wheelset and saddle position) were fine on Friday. I am thinking the saddle position will have more effect than a new wheelset so I may move it back and see.

Would a longer stem help?

Any other ideas?

Happened to me first ride out on a new road bike, terrifying. I think you tend to tense up in expectation of it happening again, which doesn’t help either. I did all the obvious stuff like tyre pressures, making sure the headset was correctly adjusted, checking QRs properly tightened, looking for play in wheel bearings and general slack etc. I don’t know what stopped it, but it hasn’t been an issue since, including on some very fast descents in the Alps.

This might help. As might putting some more weight on the front end. Bigger tyres maybe. Different tyre pressures. I don’t think there’s a single answer, but small adjustments can be enough to sort it out. All a bit voodoo. Try to relax and good luck!

Squeezing frame with your knees seems to help a bit as well.

Squeezing frame with your knees seems to help a bit as well.

Yeah, I have read all those type answers. What I really want to do is stop it occurring in the first place rather than trying to deal with it once it starts.

I did notice before last weekends rides, when on the turbo, that there was some serious amounts of flex in the front end if I twisted the bars from side to side while the front wheel was in a block. I think I may try a stiffer (and probably slightly longer) stem as a first attempt.

You don’t even need to squeeze, just touching one knee against the top tube is usually enough to stop it.

ive only ever experienced it riding no handed though, and even then only on a light steel frame.

Rule things out one at a time, try the saddle back in its original position first, as that’s the easiest thing to change.

I know it’s bloody unlikely, but given that you’ve noticed what appears to be serious amounts of flex, and a new speed wobble problem, I’d be having the forks out for a VERY close inspection for cracks in the fork legs and steerer.

I know it’s bloody unlikely, but given that you’ve noticed what appears to be serious amounts of flex, and a new speed wobble problem, I’d be having the forks out for a VERY close inspection for cracks in the fork legs and steerer.

Good point, I will look it over tonight. It does seem to be more of a flex in the stem (cheap stock one), but then I never noticed it before fitting the new wheels.

I’d go as far as to whip the forks out and check them as well as checking the frame very carefully (particularly the front triangle) if it really seems to be flexing that much and has developed a speed wobble.

Of course it could be the wheels/saddle position (and even the wet roads) are contributing, but you don’t want to find out the hard way that you had a crack!

I had it couple of weeks ago – absolutely shat myself and had to get off the bike for a few mins when I finally managed to stop at the bottom of the hill.

I belive it was due to the front wheel bearings being a bit worn / hub misaligned.

If it happens again, the biggest thing I was told is relax – hard to do as your natural reaction is to tense. Also the knee on the top tube will help.

I’ve only had it once on a looong alps decent, going into a tunnel which was lit but with those orange lights and I had dark glasses on. I seemed to lose balance somehow really weird feeling resulted in me  tensing up and a wobble followed.

I’ve since ridden that same descent have a dozen times on the same bike, more relaxed, not in dark glasses no tension no wobble.

I had this on my new Genisis Volare, coming down from Croix de Fer, mother of all speed wobbles, turned out that when the tyres had been put on the wheels at Mavic, the inner tube had been folded over on itself, new tube put in correctly- wobble cured.

Check your headset adjustment.

Lots of armchair and spurious theories but as usual Sheldon Brown has the lowdown on speed wobble

https://www.sheldonbrown.com/shimmy.html

That’s actually really interesting, because the only time I’ve experienced it was on my old cougar (90s steel, Reynolds 653) the lightest frame i owned. It was also the largest at 22.25”, i went for 21.5” on my next frame when I eventually sold it.

it was also fitted with relatively heavy wheels, 105 hubs, 32spokes onto mavic open pro rims.

It would almost shimmy on command, at anything over about 20mph.

It only did it riding no handed though, one finger on the bars would stop it, or a knee braced against the top tube.

When I had it (steel Salsa, 50mph, descending Mt Ventoux) a very slightly loose headset was the culprit.

40mph + spokie dokies = epic wobble. Went into the central reservation on a thankfully quiet A road.

I’ve only had it no handing as well.

Read Sheldon guys, nowt to do with loose headsets, cracked tubing, loose hub bearings…

Mrs kilo had a monumental wobble on her road bike coming down a descent in Ireland where it’s easy to hit extremely high speeds, it was a loose headset.

As per cynical and mr smith speed wobble and loose headset wobble are VERY different things.

Tightening a headset probably stopped it happening again because you didn’t achieve the right conditions again.

Yes but it’s reasonable to eliminate loose headsets, loose bearings qr’s etc before you decide it’s a speed wobble based on Sheldons page more so if you’ve been tinkering with the wheels and other bits

Yeah fair point.

Going faster will help*

*Maybe

Speed shimmy is speed shimmy.

Wobbles due to loose headsets or whatever are very different, if you’ve had speed shimmy you’d know the difference.

And if you haven’t you might not hence the various replies

kilo

And if you haven’t you might not hence the various replies

Yes, that’s why it’s worth checking your headset. It’s always worth eliminating.

And as said at the beginning of the thread, it’s also worth checking the bike for cracks, in hidden spots like the inside of the chainstay at the BB area, or the front fork at the inside at the crown.

Tyre pressures can be a cause too, although that’s usually visible and obvious.

There’s plenty of reasons for a bike to shimmy/wobble/weave/tankslap. It’s simple to check for most of them.

I’ve had shimmy on steel bikes due to over loading and fast descents, I’ve had wobbles due to a headset, and due to a slowly deflating tyre.

The only bikes (where there was no underlying defect) that I can remember getting shimmy on were quality steel classics lightweights, and pressing a leg against the toptube damped it.

Timothycdbarnes, I had the same thing, 50mph+ coming off Mt Ventoux, rounded a corner, gust of wind, bladed spokes (Ksyrium), terrifying shimmy which was getting bigger and bigger. I loosened my grip, relaxed and slowly brought it under control. Scary moment, much more terrifying than any mtb incident!

mildbore – Yep I pretty much did the same. Relaxed, leant back, gingerly applied the back brake.

To those suggesting that the loose headset had nothing to do with it – my evidence suggests otherwise, I’d never had it before nor have I had it since on that bike in similar conditions. I adjusted the headset that day (having thought about the possible causes and found it slightly loose) and there has been no re-occurrence since. Generally speaking that Salsa La Cruz is a very stable bike – 71 degree head angle and I’ve ridden it round the gravel ‘classics’, Paris Roubaix etc with no issues, although I doubt head angle has too much bearing on it. The bike certainly meets the other criteria on the Sheldon Brown page – primarily thin steel tubing.

I couldn’t tell you whether it’s ‘real’ shimmy or not, as I’ve not experienced it before or since. However, as it happens you can judge for yourself as I had a GoPro strapped to the bars at the time – you can see the vibration really get going at about 10:10-10:20 here, then disappear as I slow the bike down.

https://www.youtube.com/watch?v=IUBJlUEnFeQ&t=605s

I appear to have cured this now, but in my usual “all out” style made several changes all at once so I cannot identify which one or ones helped the problem.

1. New tyres (the conti classics were very tight and on inspection did not sit evenly on the rim)

2. Added extra spacer below stem (to take a little weight off the bars)

3. Moved saddle back .5cm (was moved forward before shimmy started)

4. New stem (the stock one was very flexy)

Pedal harder through it. Something will happen!