UKC

Scary experience last night, any opinions welcome.

I'd finished work and gone off into the first warm evening for ages in search of a few miles and a big hill.  I found the hill but chickened out as it was commuter time and a busier road than I thought, one to save for 7 am on a Sunday!  I retraced my steps back down the fairly big hill I'd ridden up to get to the very big hill, a road I had not ridden before.  It was long steepish and wide and perhaps in chagrin at missing my prize I thought I'd open it up for the descent as it looked very safe to do so.

Hit 30mph and the road surface was 'corrugated' like any country road that is due for a resurfacing, so I thought I'd slow down a bit and put the brakes on.  At this point what I can only describe as a 'resonance' started feeding back to me, in my mind from the front wheel, kind of like a juddering.  Perhaps I braked harder at this point, red flares were starting to go up, I think the speed slowed but the 'resonance' increased.  

At this point I remember thinking 'this is going to hurt', coming off at c.  20mph onto tarmac in shorts and short sleeved top, but somehow I managed to slow without coming a cropper and pulled to a shaky stop.  I can smell my brake pads.  A quick visual check of the front wheel and pads and all looks ok, stop at a village mile further up and take the front wheel off for a better inspection.  Brake pads worn but not worn out, wheel looks fine.  Put bike back together and cycle 8 miles home, paying careful attention to how it rides, it's totally normal.

So what happened?

Was it the corrugated road surface?
Was it overbraking?
Is there some deeper problem with my bike/wheel?

Obviously I am going to take the bike to the shop who service it and get them to have a look, just curious if anyone has experienced anything like this or can offer any insight.  Also very grateful that I am not sitting here oozing blood and lymph onto dressings all over my body.

Could just be speed wobble and nothing wrong with the bike. Essentially just resonance and vibration that can seemingly randomly occur. I don't know how to add links sorry so you'll need to Google it! 

https://selleanatomica.com/blogs/homepage-blog/the-speed-wobble-surviving-t....

There's a mildly worrying video of someone slapping the top of their bars to deliberately induce it somewhere.

Edit - ha! I can add links! So here's the video too.

youtube.com/watch?v=xODNzyUbIHo&

Far out, 6 minutes and UKC brings home the bacon.  That exactly describes it, including the wobble getting worse as I slowed which seemed counter intuitive (the word terrifying fits too!).  Still going to take it to the shop but this is really helpful. 

It's frightening,  had it only once coming down from the top of Great Dun Fell, quite quick and there's a straight bit high up in a cutting that gad the wind funnelling up it. 

My little brother who was 1/2 a minute behind got it even worse, so much so the half minute was nearly 5 at the bottom. 

That's the one and only time it's ever happened to either of us. Other brother who was in front didn't get it at all.

Mark

This is terrifying - I had it once on a steep descent with drystone walls either side. The only thing I found afterwards was a slightly loose headset

Speed wobbles are terrifying. I had a horrifying one recently, turns out I had a slightly loose headset as well. I've only noticed it on road bikes, I'd be interested to know how common it is with slacker geometry.

A really effective way to damp it down when it does happen is to clamp the top tube of the bike between your knees, or even just press one knee hard against it. This in essence adds mass to the frame, changing how it resonates and killing the vibration. I had an older allow bike that did it regularly at around 27mph down a hill. Its a resonance thing related to the mass of the bike and vibrations from the road surface, possibly, but not necessary compounded by looseness or trueness of things.

I used to get this fairly regularly but touch-wood haven't had it in a long while. For me it was too low tyre pressure that caused it.

Glad you got off alright!  I came off at 34mph straight over my handle bars and broke every single rib on my left side, four in multiple places, my collar bone in two places, bleeding on my lungs and considerable road rash all down that side.  It did hurt!  On the plus side I did this as an ambulance was driving past

Cheers

Toby

Speed wobble - press your thigh against the tube to stop it

Ouch, and for a second or two that's what I thought was going to happen to me! Hope you are now recovered.

My old Planet-X used to have resonance points at 40kmh (frightening) and 80kmh (terrifying) but as someone said it can be alleviated my pressing your thigh into the top tube to act as a damper. I don’t know why it did it, combination of not a particularly stiff frame (also frightening in the corners) and stiff wheels perhaps.

I believe a slightly out of adjustment headset is a common (though not necessarily the only) contributary cause to speed wobbles.

I had the same experience in 2012, I wrote this thread which also has good advice on a few different possibilities/remedies.

For me, ever since that day I’ve generally been ready to clamp my cross bar with my knees when I’m going fast to stop the wobble.

https://www.ukclimbing.com/forums/biking/high_speed_wobble-506886?

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

Take it easy on roads you don’t know. Glad you were okay.

I had this happen today coming down from Honister towards Buttermere - the road is very bad though where the tarmac has been rucked up from cars (probably when the tar is softened in the summer months when its warm and drivers braking hard). Descending down Newlands though at 45mph was fine.

I've also has it coming down from GDF at 50+mph but like others have said try and either hold the top tube with your knees or press a leg into the frame to reduce it. Still quite scary though especially on rim brakes!

I used to have a cyclocross bike which did this when braking hard from high speed. Cantilever brakes on carbon forks. I had it with me on an alpine holiday once, descending the cols around the Maurienne was a bit tense sometimes. A google revealed that this bike was notorious for this, though being a crosser it was never designed for 20km+ of fast descending and hairpins. It was fine for tearing about in the woods.

Had it on my current gravel bike, though not so bad, when descending Superbagneres last year, chasing a high max speed for Strava vanity. I thought the relatively long and slack gravel geometry would make it stable. Nope, though it is a Cotic Escapade so the bendy steel frame may be partly to blame. My max speed was disappointingly low though it felt fast in places, dangerously so in a way that significantly higher speeds on road and touring bikes never have.

Glad you didn't wipe out. Have a google for footage of Tom Pidcock or Julian Alaphilippe descending the Galibier with your heart in your mouth. I think it was Jonathan Vaughters who said that crashing on a descent would be like sitting naked in a car doing 60mph and opening the door and jumping out.

Funny how alike how threads are, glad to hear you are still on the bike twelve years later!

Yeah the whole way home I was thinking of Tom Pidcock, and the enormous cojones that it must take to give him the edge in descending.  It's not beginners he's going past, but professionals who do this day in day out and must be pretty close to the edge themselves.  

Yes, I hadn't realised it was 12 years ago.  I still think about it almost every time I'm going fast downhill.  So, on the plus side - it was a very unusual experience for me, either a one off, or I have learned to manage it by putting my knee on the top tube or using the front brake more.  Best of luck.

Thanks, all mended except my collar bone which is still broken in the middle but apart from being wonky to look at it does not matter.  Also just about recovered from shattering my right arm and breaking my left wrist!  I’m really hoping that’s me done for injuries for a good long time.

Cheers

Toby

I had that descending from the top of Snake Pass eastwards a couple of years ago. Steering started wobbling. I looked down and I was doing 57MPH, which made me very acutely aware that I was wearing nothing but Lycra and a helmet, so a crash would be rather bad news. Thankfully it didn’t take much to slow down enough to a speed where it stopped, but it was bloody terrifying.

Horrible, isn't it ? all I can say is the last couple of times its happened to me, I've noticed I was a little cold and was therefore a bit tense in myself.

Pressing your thigh against the top tube works to an extent, but you're fighting the problem rather than fixing it.  What you have is gyroscopic wobble - wheels spinning fast and they've got all our of kilter.  

Some not so basic cornering stuff now....

Stand up on your pedals and then push one one side of the bars forward - you'll find that the saddle smartly smacks your thigh on that side as the gyroscopic effect of the front wheel tilts your bike.  What then happens if you're seated is that as you push one side of the bar forward, say the right side, the bike wants to tilt to the right, but the rubber on the road starts to track to the left, which moves your centre of gravity to the right of where the bike is, but also the direction in which the bike is leaning, and so round to the right you go.  If you also have your weight on the outside foot you'll carve a smooth turn to the right, despite turning your bars to your left.

So what you have is a wobble induced by something that is making your whole bike shake, and steering inputs (perhaps from a loose headset or a worn wheel bearing) is making you bike behave as above.  You can also induce it as someone said above by initiating a movement and then lettering it have a fit on its own.  To stop it, if you're on the left hand side of the road, push forward with your right hand to stabilise the gyroscope and induce a firm movement in one direction only.  This will also make the bike move out to the right, so beware of traffic.  If you're in primary, then either side will do.

Also practice cornering by active steering...