Australian Cycling Forums - Bicycles Network Australia

I had a terrible experience a few weeks ago where i was descending a very steep road (in excess of 20%) and thought i would tuck in and just cruise, and before i knew it i was sitting on 80km/hr (keeping in mind it was a rough road) i started to brake for an upcoming corner when i got the worst speed wobbles.

Everything slowed down and for a second i thought that was it, that i was hitting the deck. I managed to recover by riding it out, doing some off road and deploying my foot brakes in the gravel. I gotta say it scared the crap out of me, and i hit the same hill yesterday and i was so gun shy that i was riding the brakes all the way down, not letting myself get over 55. I actually then was getting nervous about blowing a tyre from overheating brakes.

Anyway, how the hell do the pros descend in excess of 100, any tips?
Happened to anyone else?

They only do that when its a straight steep well surfaced decent. Dont worry about hitting those speeds, descend safely naturally you will get a bit faster as you get the confidence.

if i am doing 55 with the brakes on, I am going to stop and walk down ....

ozstriker wrote: Happened to anyone else?

Yep.




Very similar to what you described, in my case the speed was 95 and i came off the bike and collected a sharp rock. Ever since then i've been understandably very nervous going downhill, however i've found that nervousness is counter-productive. It seems to me that when i tuck down and let it rip, i'm more stable than when i sit up and try to keep the speed down, weight distribution, aerodynamics i don't know. I now just avoid very steep descents wherever possible.

Stiff arms and body will make the bike handle a lot differently than if you are relaxed.

You just need to put weight over the front wheel...its the lack of weight that causes it to wobble. I can get my bike to do it easily just by riding no hands and slapping the stem sidways and the front wheel just wobbles like crazy...there is a youtube vid of it somewhere. But as ldrcycles says...what happens is it starts to wobble and people sit up trying to slow down and in reality it makes it worse.

Sam

Here is the info..

http://www.cyclingtips.com.au/2011/03/s ... -its-head/" onclick="window.open(this.href);return false;

and the video is half way down.

I can do what he does in the video...get it to wobble...and then grab the top tube just behind the stem...and it will still continue to wobble. But if I lean forward and take weight off the seat and put it onto my hands on the top tube (which in turn puts weight onto the front wheel) the wobble stops straight away.

Sam

Strange Rover wrote:You just need to put weight over the front wheel...its the lack of weight that causes it to wobble. I can get my bike to do it easily just by riding no hands and slapping the stem sidways and the front wheel just wobbles like crazy...there is a youtube vid of it somewhere. But as ldrcycles says...what happens is it starts to wobble and people sit up trying to slow down and in reality it makes it worse.

Sam

not doubting you, but on a motor bike when you get into a tank slapper you accelerate hard to lighten the front wheel. I have never had a speed wobble on a vélo but my natural reaction would be to hang my bum off the back.

Close your eyes on the scary bits.

Holy heck that video is frightening!

I like this comment on that article too "we always said speed wobbles was like a dog: It could smell your fear".

toolonglegs wrote:

Strange Rover wrote:You just need to put weight over the front wheel...its the lack of weight that causes it to wobble. I can get my bike to do it easily just by riding no hands and slapping the stem sidways and the front wheel just wobbles like crazy...there is a youtube vid of it somewhere. But as ldrcycles says...what happens is it starts to wobble and people sit up trying to slow down and in reality it makes it worse.

Sam

not doubting you, but on a motor bike when you get into a tank slapper you accelerate hard to lighten the front wheel. I have never had a speed wobble on a vélo but my natural reaction would be to hang my bum off the back.

If I take my hands off the bars and sit up whilst decending at anything over about 50kmh both my Cinelli and Colnago start to speed wobble, so I don't know that this is the answer TLL.

Any combo of bicycle, wheels, and rider can develop wobble, and it is highly unpredictable. It is generally presumed to be dependent on weight distribution, and is more common with taller riders, and higher placed saddles.
Many say unload the saddle, load the pedals, get the bum back, squeeze the knees in against the top tube.
IME it is more likely to happen when you are banking through a long curved descent.

ft_critical wrote:

toolonglegs wrote:

Strange Rover wrote:You just need to put weight over the front wheel...its the lack of weight that causes it to wobble. I can get my bike to do it easily just by riding no hands and slapping the stem sidways and the front wheel just wobbles like crazy...there is a youtube vid of it somewhere. But as ldrcycles says...what happens is it starts to wobble and people sit up trying to slow down and in reality it makes it worse.

Sam

not doubting you, but on a motor bike when you get into a tank slapper you accelerate hard to lighten the front wheel. I have never had a speed wobble on a vélo but my natural reaction would be to hang my bum off the back.

If I take my hands off the bars and sit up whilst decending at anything over about 50kmh both my Cinelli and Colnago start to speed wobble, so I don't know that this is the answer TLL.

True, like I said I have never experienced it ... and I am 194cm with long legs ( saddle to peddle is 1011mm ).
I change clothes at fast descending speeds and don't seem to get it with hands off the bars either... oh well, i will count myself lucky.

It's fine with 3 wheels on a recumbent with your bum 100mm off the bitumen !

I thought you roadies were tough ;-p


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Holy smokes, that video is crazy

makes sense what they say, thanks for the link ill definitely keep it in mind

Normally, i just push both sides of the handlebar to get rid of speedwobble

That video is scary, and here is another good one demonstrating it:

[youtube]http://www.youtube.com/watch?v=VfngbsIU ... r_embedded[/youtube]

I thought the poor rider was going to crash as he wobbled to the edge of the road quite quickly. I haven't had it in ages. Some reckon they experience it at 55km/h or so, I've not experienced that - not recently anyhow. The last time it did happen I ended up off the bike for a long time and with grazes and a bad back. I was new to it all then.

Perhaps I'm getting a bit better with my bike handling these days. I tend to keep my knees against the top-tube when I'm descending, unless I'm pedalling. I find it keeps things more steady.

I don't do the hands off the bars thing at high speeds however - I'm realistic about my abilities.

that video above - classic scenario i reckon. it's cold, he looks like he's gripping the bars too hard (probably can't feel how hard) -> wobble.

20% grade descent and cruising? Where did you find roads like that here in Oz?

Cycling Tips had a good post on descending technique. Main things I do are: hands in drops to weight front wheel; weight the outside foot on corners; look ahead to where you want to be; slow down if I have any doubts.

sogood wrote:20% grade descent and cruising? Where did you find roads like that here in Oz?

Toowoomba, there's heaps of bitumen walls to climb around here.

Know your brakes & how fast your bike will stop safely, go practice somewhere, pick a telegraph pole or something on an open bit of road (on a slight downhill slope would be great), do gradually faster speeds & practice 'panic' stops.


Once you know how hard & fast you can stop, then you have a good skill set for descending, the trick is, just do it, over & over again, the more times you do it, the more you become comfortable with it.

I don't move my weight forward, I lift off the seat, clamp the seat with my thighs, for straights, pedals level, weighted on the outside pedals for corners.

I exceed 50kph 4 times a day, every day on my commute ride, normally most of them are over 55 usually nudging 60kph, it's like anything, the more you do it, the more comfortable you get with it.


Good descenders are usually just very comfortable & confident descending, it's an easy skill to practice & can really make you a fair whack of time gains (especially if you climb as badly as I do).

toolonglegs wrote:

Strange Rover wrote:You just need to put weight over the front wheel...its the lack of weight that causes it to wobble. I can get my bike to do it easily just by riding no hands and slapping the stem sidways and the front wheel just wobbles like crazy...there is a youtube vid of it somewhere. But as ldrcycles says...what happens is it starts to wobble and people sit up trying to slow down and in reality it makes it worse.

Sam

not doubting you, but on a motor bike when you get into a tank slapper you accelerate hard to lighten the front wheel. I have never had a speed wobble on a vélo but my natural reaction would be to hang my bum off the back.

My Giant Defy/American Classic 420 combo used to get the wobbles on more occasions than not descending down my own street. I can reach 70km in a tuck easy.

I found the best way to stop it was to start peddling, would settle the whole frame down and you could get on the brakes, so sort of similar to TLL's motorbike experience.

Can't say I'v ever had speed wobbles. Is it the conditions/speed/bike? Or combination of all?

Yes