Speed Wobble

[samson99]

when mountain biking, i hit 50km/h on a tar road. decided to ride free hand. got a speed wobble. any reason why i would get a speed wobble?

[Yang]

Latest Ride Magazine, August edition p.49 has an excellent article on speed wobbles, why they happen, and what you can do to prevent/ stop them. I've never had one, but maybe that's because my extreme shaking from fright going downhill at speed offsets the oscillations of the frame. 

[linnega]

sitting up probably messed with the balance a bit.  You could probably have controlled it by putting a knee on the top tube.

 

[Veloce]

Very interesting read that...got to do with resonances in the frame and constructive interference causing the oscillations to build up until a noticable "wobble" is achieved. You can counter this by damping the resonant frequency or by changing it by squeezing your knees on the top tube. I've tried this and it does work.. 

Your hands on the bars were obviously damping any resonances in the fork and the removal thereof released the demon within!!!!! 

 

Cars have the same issue when they experience valve bounce: the valve springs oscillate at high frequencies (high revs) and then all timing is lost and you run out of revs and damage the valves at the same time

Proper cars like the older Alfa Romeos counter this with 2 springs that have different resonant frequencies so they cancel each other out, the result, a much higher revving, race winning engine   

Veloce2008-08-17 13:40:39

[Racer X]

Bikes have handle bars for a reason. That said I go handless quite often and see how fast i can go, then I am under 21 and thus frontal lobe has not fully developed yet. Therefore I do not properly perceive danger.

[Yang]

I've never had a speed wobble because of hands free. Mainly because I can't ride hands free. Has there been a poll on this?

[Racer X]

Not that I know of.

[Dirtbreath]

when mountain biking' date=' i hit 50km/h on a tar road. decided to ride free hand. got a speed wobble. any reason why i would get a speed wobble?[/quote']

 

Take heed, it's a warning from God to get off the tar. Has nothing whatsoever to do with having your hands off the handlebars.

[Johan Bornman]

Every bicycle and rider combination has a critical speed at which a speed wobble develops. Riding no-hands brings on the wobble quicker. You can alter the critical speed by:

 

1) loosing weight

2) Changing your body shape

3) Fitting different wheels

4) Fitting different bars

5) Moving yor weight around

6) Shivering in cold weather.

 

Some bike/rider combinations are lucky enough never to enter the critical speed range, mostly because we just cannot reach it.

 

A speed wobble is an oscillation through the length of the bike, with your body as one of the nodes. The whole thing becomes a vibrating guitar string, but below audible frequency.

 

If you are very brave, you can stop the wobble by destroying the offending node. You do this by standing up or as some people suggest, putting your knee against the top tube.

 

In my view, the best way to deal with speed wobble is to practice getting out of them. I do this by pedaling no-hands down a long straight stretch of downhill. As soon as the wobble comes on, I stand up and kill it in the but. I do this as often as the stretch of road develops. Eventually, dealing with this becomes instinctive.

 

It also makes for developing a great party trick - riding no-hands standing up.

 

So far I still have all my teeth.

 

 

[PhilipV]

 

Bikes have handle bars for a reason. That said I go handless quite often and see how fast i can go' date=' then I am under 21 and thus frontal lobe has not fully developed yet. Therefore I do not properly perceive danger.

[/quote']

 

I also had this problem with percieving danger, until I misjudged the height on a 5m freeclimbing rock(read: utter stupidity and carelessness.) Needless to say, I didn't make it, and the earth decided it had enough of me bouncing on it, and promptly knocked the fear of heights and a sense of danger into my head. Problem solved, I promise to now only free climb over water. No promises on the mtb though...

 

[Canaris]

mtb at 50km on tar, it was the bike shivering and shaking in shame, get off the road.....