Speed Wobble

[Paul on the Pearson]

I wouldnt quite say my life flashed before me but the immanence of something involving of a lot of pain, blood and the emergency services having to be called certainly did. Coming down into Brighton on that fast decent yesterday I had some serious speed wobble, which, to put it mildly is a little unerving as in "Oh no I'm about to die!" sort of unerving. Admitedly Im not exactly what you'd call a demon decender and generally prefer fighting against gravity in the opposite direction. I managed to slow down enough for the wobble to stop, in fact I did eventually stop, but having never experienced it before didnt really know what to do to avoid ending up on the tarmac and in hospital ( I didnt actually end in either but it was close). Any advice? I'm sure ancient cycling wisdom says something like dont touch the brakes, but thats like saying if you come face to face with a grizzly (fairly unlikely on the London to Brighton ride) to stay still and not run.
So what should you do if it happens again ? Does rider position make a difference? There was quite a strong crosswind and I tend to get blown about a fair bit and I'm also not that confidant on decents so I dont just go with it and probarly brake too much.

[John the old'un]

I have read that as far as motorcycling goes the standard action in the event of a speed wobble is to put as much weight as possible onto the front end.
Never experienced it myself.

[Marek]

I think if you are on the drops, feet at quarter past nine and knees/thighs holding the top bar it should be fine. I think lack of confidence can actually lead to wobble, so just go with it, unless there is something wrong with your bike it should be fine. Mind you I have a lot more weight than you which could be the difference but not sure.

Cheers

Marek....

[Andrew G]

I nearly always descend on the drops as I think it's easier to control the bike, and you also lower your centre of gravity.

As Marek says if you brace your knee(s) against the top tube it'll help sort out a wobble, and can help prevent one occurring - Works well when it's cold too as a shiver can cause a wobble. You also want to stay relaxed (easier said than done if you are a nervous descender) as this will help prevent the wobble occurring and also assist correcting. If you go tense and rigid ( ) then it will make things worse. Try and keep your arms and legs "soft" as they'll dampen out the bumps which are probably a cause of the wobble in the first place.

[Will]

stand up

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

[mrP(Boonen)VT]

[quote="Marek"] I think lack of confidence can actually lead to wobble, so just go with it, unless there is something wrong with your bike it should be fine.
Marek....

[tel]

Paul, I have a similar problem to you (we have the same bikes), but only on rather steep descents. I remember Sean Yates writing an article about this but can`t remember what he said. I`ll try and Google it later.

Althougth it frightens the crap out of you I don`t think you`ll actually crash.

Terry

[mrP(Boonen)VT]

Wonder if it is a similar principle to the way a caravan "snakes" at a certain speed if not loaded correctly?

[Andrew G]

Just a though but what fork are you guys running Tel and Paul otP? I know PVT has an Ambrosio which I also have on a bike and it's very stable, quite deep and sort of aero shaped (like a wing, round front pointy back). My fixed from Pearson's has a Pro fork which is narrower and rounder and a lot more twitchy, never had a speed wobble but it's not as stable as the deeper profiled forks on other bikes.

[Steve W]

Hi Paul,

I had the same thing on Saturday coming off ditchling I sloowed a bit because of the severe side winds and the sail effect of deep rim wheels was starting to worry me, then it happened 43 mph and the front wheel started to shake violently. I just about hung on as my mind was doing a quick damage assessment of the impact of being thrown off on that decent.

I slowed a bit more and it settled down. Totally freaked me out though so I did some research in case the bike set up had anything to do with it.

One piece of advise I dug up was to take your backside off the saddle for a bit as this removes the base point of the ocillation and apparently it should stop.

The other one was as Andrew and Marek have said to grip the top tube with your legs.

I can't help but think a combination of factors such as nervousness and bad side wind had a lot to do with it, and nothing to do with the bike thankfully.

[mrP(Boonen)VT]

I have noticed that when I use my Planet X 101 deep (very deep!!) front wheel (combined with rear disc) that above 40 mph I get a sort of rhythmic sail effect in that it starts to sway slightly from side to side, which was a bit un-nerving at first, but is fine now I know it happens, although totally different from a wobble which it does not do.

Using a Bora front, which is deep, but not as deep has no efect whatsoever.

[Paul on the Pearson]

Cheers thanks for that chaps. Andrew the forks are unbranded and came with the bike but there fairly deep. To be honest I think the main problem is lack of condfidance and the fact that that was the first time I'd been on the bike for two months didnt exactly help. Also I dont always ride in the drops on fast decents. Basically I just need to stop being a big girls blouse, throw caution to the wind, get in the drops and get on with it!
Cheers.
PS its good to be back in the saddle!

[Marky Mark]

Please don't try this at home people.

My advice to myself is 'go faster, much faster'

A certain speeds 'Harmonics' will play a part in every machine, you either back off from it or go through it.....

[Andrew G]

[quote]Also I dont always ride in the drops on fast decents. Basically I just need to stop being a big girls blouse, throw caution to the wind, get in the drops and get on with it!
Cheers.
PS its good to be back in the saddle!

[mrP(Boonen)VT]

[quote]also to reach the brakes