Speed Wobble!!!!!

davep123

Thought I was dead!!! Serious speed wobble at 85kmh last week. I was literally hanging on for dear life!! The bike was all over the place and i though i was a gonner! What the hell causes that? an experience I don't want to repeat. Has this happened to anyone else. I've been down the hill loads of times before at the same speed so why the massive wobble this time? First and and hopefully last in 30 yrs of cycling.

jgsi

Thats a variant on 'how quick am I?' ww
anyways http://en.wikipedia.org/wiki/Speed_wobble
keep yourself in check next time

marz

I've experienced a couple of speed wobbles, both times as my speed approached/exceeded 50mph.

Never really find out why, though a friend of mine thought my front tyre pressure, which was a bit low (90 rather than 110), may have been the cause.

jonomc4

your all my heros.

davep123

JGSI wrote:

Thats a variant on 'how quick am I?' ww
anyways http://en.wikipedia.org/wiki/Speed_wobble
keep yourself in check next time

Have you ever experienced this? Nothing to do with keeping yourself in check!

jgsi

davep123 wrote:

JGSI wrote:

Thats a variant on 'how quick am I?' ww
anyways http://en.wikipedia.org/wiki/Speed_wobble
keep yourself in check next time

Have you ever experienced this? Nothing to do with keeping yourself in check!

What do you want me to say?
Shift your backside backwards off the saddle and you'll make 90kph?

davep123

No. It wasn't a "look at me look how fast I can go post" I was wondering if the wobble had happened to anyone else and whether it was common. It was shit scary and has never happened before at that speed and really don't want it to happen again. I was asking whether you had actually had it happen to you?

jgsi

On a motor bike once , hit a raised catseye.. sent it a bit awry.(steering dampers do help) . on the bike nope.. I have been on fast down sections.

maybe you were just a bit tense without knowing it and it started

sungod

i had it just once and only mild, but that was more than enough, it seemed due to a crosswind making the front wheel unstable at a certain angle rather than the classic wobble

there are umpteen possible causes, wobble depends on the overall dynamics of the system (you+road+bike+air), so there are many parameters, some related, changing any will change the behaviour

aside from ensuring the bike is mechanically sound - tyres mounted ok, no significant wear/damage, things that should be tight/loose in the correct state, bearings correctly preloaded etc. etc.

the rider is the main mass and energy source within the system though, so that's where you need to try and control things

holding the bars too tight or tensing up can increase wobble - unfortunate, as these are just what reflex tends to result in

wobble can be increased by efforts to forcibly control it - the lag in your reaction time means by the time your muscles are moving 'against' the wobble, it's already switched back and you end up amplifying it, staying relaxed helps avoid that

pressing one or both legs against the top tube is good, i tend to do this whenever not pedaling on a fast descent, it helps damp the system and lower the chance of wobble in the first place

lifting weight off the saddle can help control it, or otherwise shifting centre of gravity

davep123

Cheers for that. I'll try the knees on the top tube next time. I remembered not to brake but as for keeping relaxed.....easier said than done. Lasted for about 10 long seconds. I was convinced something (frame, wheel) had broken it was that violent Have checked the bike and its all good and has been riding well all season. I will be definately checking my speed on that descent next time. The freaky thing is that it's a bit of road have been down a lot and never had a problem before.

clickrumble

I've found that you can accelarate through it.

DevonClimber

I have had this on a previous bike, shimmy is the term I believe, after checking everything over it still happened. Dropped a frame size and problem sorted(I know that doesn't help you).
As said before, wheel alignment, headset, bearings etc all to be checked, knees on top bar sometimes works. The way it was explained me was think of a ruler, holding one end on a desk and twanging it,not sure if that analagy works however, it is usually down to vibration travelling down the bike and flaring at the rear like a ruler twang.

davep123

http://www.youtube.com/watch?v=VfngbsIU ... ure=relmfu
Watch this if you haven't experienced it. 30 secs in.

iampaulb

davep123 wrote:

I'll try the knees on the top tube next time..

I do this a lot, when im coasting down a steep decline. I learnt this trick Downhilling in Morzine, grabbing my saddles with my thighs to control the back end. I find it helps a lot, stay one with the bike so to speak. :P

dw300

iampaulb wrote:

davep123 wrote:

I'll try the knees on the top tube next time..

I do this a lot, when im coasting down a steep decline. I learnt this trick Downhilling in Morzine, grabbing my saddles with my thighs to control the back end. I find it helps a lot, stay one with the bike so to speak. :P

As with most things bicycling, most people think it's the bike and not the rider. But any time I've ever had it, it's been tension in my hands arms and shoulders. The fact that once you can convince your body to let off the brakes and relax your grip that it stops, shows that it's an influencing factor.

In addition to knees on the top tube, i've tried ass back as far as possible, holding saddle with thighs, and getting yourself as low as possible. And of course relax and I try to avoid use of the front brake over 30 mph.

I find that, if I'm trying to go fast, I never get a wobble, but if I'm on an unfamiliar, narrow, twisty road, with a loose surface, and I'm tentative, that that's when I get it.

iampaulb

dw300 wrote:

iampaulb wrote:

davep123 wrote:

I'll try the knees on the top tube next time..

I do this a lot, when im coasting down a steep decline. I learnt this trick Downhilling in Morzine, grabbing my saddles with my thighs to control the back end. I find it helps a lot, stay one with the bike so to speak. :P

And of course relax and I try to avoid use of the front brake over 30 mph.

This is the most important thing i think, if you stay relaxed on the bike it will help. But i also found DH'in and on the road the front brake has the best stopping power.

dw300

iampaulb wrote:

dw300 wrote:

iampaulb wrote:

davep123 wrote:

I'll try the knees on the top tube next time..

I do this a lot, when im coasting down a steep decline. I learnt this trick Downhilling in Morzine, grabbing my saddles with my thighs to control the back end. I find it helps a lot, stay one with the bike so to speak. :P

And of course relax and I try to avoid use of the front brake over 30 mph.

This is the most important thing i think, if you stay relaxed on the bike it will help. But i also found DH'in and on the road the front brake has the best stopping power.

Yup it does .. but isn't that precisely why you don't want to use it too much at high speed. If you brake with the front you throw a load of weight onto the front wheel, which is simultaneously trying to slow you and steer you, which I'm presuming can be a contributing factor to starting a speed wobble.

If you're doing 50mph, you should be controlling your speed with the rear brake so that you don't have to brake hard. Just scrub enough off to slow down, then use the front to stop quickly once you're below 30 or whatever speed you're confortable with using it.

I'm not saying you can't improve your bike handling enough to use both front and rear and stop faster, but if you're having problems braking earlier with the rear is probably the safer option. Cars trail their rear end by toeing in the rear wheels, which increases stability at high speeds, and while you can't do that with one rear wheel, you can still trail it by getting weight back and braking from the rear.

davep123

Thanks for all the advice. it's reassuring it's not just me!! Hopefully the first and last time!!!!

ThatBikeGuy

Only happened once when i hit a cattle grid doing 50+ in the wet. Needless to say i watch out for the signs nowadays.

Speller78

I've had it once, was probably doing 35-40mph and went past a gap in the trees and a crosswind caught me. I tensed up trying to keep the bike in a straight line and started wobbling all over the place. Managed to remember to relax and it straightened back up on its own. Not an experience i would like to repeat.

astrazen

Very interesting topic guys.
As a beginner it's great to read up on stuff like this.

Drumlin

I've been riding for over 30 years and it's only happened to me once. I was only doing about 20 mph, and the bike was fine before and fine after. I've concluded its just a random thing, when a whole load of parameters happen to coincide at that particular moment.

HasselHough

This has happened to me 4 times out of 5 on the very same descent, http://app.strava.com/segments/1559561 and its getting to me a bit, I've checked the bike, all is well, although I'm pretty light weight 65kg and the section of descent always has a cross wind. My mates just breeze past me and I'm riding a bucking bronco! My mate actually thought I was coming off today, not sure how I held on but thank god I did.
Think my heart rate is higher on the down than the cat 3 climb to get to the top!!! Not sure what to do other than go easy.

Wobblehead

Happened to me once, knocking on 50 down Fleet Moss towards Hawes. Managed to stay on somehow, never been the same since going downhill, can't let go for fear of the wobbles coming back.

Absolutely terrifying.....

oldwelshman

I have had it a few times on different bikes at different speeds, sometimes caused by road conditions to start it, resurfaced, also wind, worst case was when my pedal came off pedal its axle thrwoing me forward when I was at 49mph according to garmin, here was the result, I did survive somehow though ;

The Little Onion

I suffer from this from time to time, particularly in cross winds. I live in the peak district so there are a lot of steep exposed roads - the problem is much greater at the top of a descent, where there is more wind, than towards the bottom, even if I am going faster. I found that standing up and gripping the top tube with my inner thighs helps (said the actress to the bishop!). Oddly, the biggest change has been to swap my crappy rear tyre (Ultremo R1) with my favourite tyre (Vrederstein Tricomp) - since then I have had no trouble.

peat

Think i may have just had one of these.

It started about 40mph and i did the worst possible thing by tensing up and grabbing the brakes. Managed to get it stopped, i was convinced i'd lost a spoke or the skewer had come loose.

I tentativley made it the rest of the way home. Checked everything was tight and there were no signs of cracks in the forks/headtube.

Reckon it was just a wobble. Brown lycra.

greasedscotsman

Peat wrote:

Reckon it was just a wobble. Brown lycra.

You'll be wanting some of these then...

overlord2

Wobblehead wrote:

Happened to me once, knocking on 50 down Fleet Moss towards Hawes. Managed to stay on somehow, never been the same since going downhill, can't let go for fear of the wobbles coming back.

Absolutely terrifying.....

Ive seen Strava there are people hitting over 60 mph. You have to have a screw loose to be hitting that kind of speed.

Its a nice decent though.

smoggysteve

I had this about a month ago doing around 40mph on a down hill stretch. I thought it was maybe the magnet for the speedo was making the wheel unbalanced but it never happened again. Does make your ar@e twitch a little though.

dmclite-3.0

Ive had this a few times and come to similar conclusions as other posters. mine I think is also to do with a very short headtube on my Litespeed siena. I also tended to get a front end shimmy when cold and descending, so now I damp the top tube with my knee, raise off the saddle a fraction, relax my grip and also put my tongue between my teeth ! sounds stupid but I know a coach who after giving me descending and cornering tips, he said if you get tense you will bite down on your tongue instinctively and is a good indicator of tension, so relaxing and anticipating on descending is the key.

Sounds stupid, but I have been doing this for 4 years now and it works as I am still a bit of a wuss descending.