A nice sunny day in the mountains so I thought that I'd take a ride on my new bike down Victoria Pass.

All went well until I hit about 60 km/h and the bike suddenly began to violently shudder. A rhythmic shaking possibly in time with wheel rotation and as if I had a really badly unbalanced wheel. It really felt like I was about to be dumped off onto the road, but managed to pull over and stop with the wobbling continuing down to quite a slow speed. There was nothing I could find wrong with the bike and it rode nicely, afterwards, but not as fast :-)

I've done Vic Pass before on my other bike with narrow light wheels instead of big heavy mountain bike tyres going faster with no problems.

So, any suggestions as to how I can stop this happening or what's causing it? Is it just an unfortunate characteristic of the frame itself? Gotta say I'm a bit reluctant to test it again although at least this time the only vehicle behind me was ironically, an ambulance.

Views: 587

Reply to This

Replies to This Discussion

I'm pretty sure you are talking about side to side shaking with the front of the bike wobbling like crazy - AKA speed wobble also AKA death wobble.

Watch this poor guy at about 0:29 onwards ...

It's a resonance thing - the bike, your weight, the loading of the bike all contribute.

I've had it a few times and the way I've fixed it is by pushing one of my knees into the top tube - that changes the dynamics of the bike and changes the resonant point - the wobble stops immediately.

Huh, I normally just put more weight over the front wheel.

Normally? You get this with a frequency Timothy?

The knee to the top tube seems to be consensus based on the WWW oracles.
I think if I experienced it once it'll be the last time I'll ride that bike.
I've had it plenty of times on my Litespeed - usually 40kmh or so, downhill, no hands, carrying a tray of coffees on the short roll from Lane Cove shops to home. Knee on the top tube fixes it, without even needing to put a hand back on the bars :-)
Are you sure it's not the caffeine-withdrawal shakes?
29er does it too when it has the big 2" tyres on. It does it in slo-mo, maybe at 25-30kmh with the bars waggling in big wide slow wobbles!

As said previously though, I would be seriously freaked out if this ever happened at high speed with hands on the bars! But I'm sure the knee thing would fix it ......

Had it happen a few times when I tried a shorter stem. Ended up going back to the longer one as the bike was more stable through the corners. Only a centimetre difference on the stem length but made a huge difference in handling.

and a skewer just about to do a quick release can give a nasty wheel wobble. Easy to stop, push down on your frame and re tighten. Hubs with loose bearings can sometimes give you shimmy issues.

Sounds a bit frightening, i've not experienced it (so far....).

Is there any association between the wobbles and applying the brakes? I notice in the video that it started at the entry to a bend, at a point where one might lightly tap on the brakes. 

Watching the video it looks like the wobble stops as soon as he unclips.

https://en.wikipedia.org/wiki/Speed_wobble

I've experienced it on the electric bike, going about 50kph down a hill. Just gripping the bars and bracing myself against the wobble was enough to stop it.

My Dutch bike does it at 67km/h. A small bump will set it off. Maybe geometry a bit steep.

RSS

© 2019   Created by DamianM.   Powered by

Badges  |  Report an Issue  |  Terms of Service