Yet another speed wobble question.

roderick.inglis33Q7QOHdSD

Hi all.
I have read all the measures needed to stop speed wobble when it happens (knees on TT, light grip on drops, bent arms and slightly off saddle).
my question is this, can these measures be used to pre-empt and prevent it happening? Or are they only useful once it starts?

many thanks in advance

Roderick

MattFalle

are you getting a speed wobble?

also bear in mind mechanical preparation to stop them happening.

roderick.inglis33Q7QOHdSD

I have had two, at 28mph+

Can you elaborate at all? Thanks

MattFalle

mechanical can be either tyres, headset bearings, either wheel, unsuitable bike sizing, poor geometry for what you want, bent or broken frame, position wise can be gripping 'bars too much, too tense.....

amongst others.

roderick.inglis33Q7QOHdSD

Thanks. Yeah the bike is newly built, service and checked. I’m 6,7 and have a 60cm frame, so there is a lot for the wind to target, I have cut out 15mm of spacers and the same in seatpost drop after a recent bike fit, so hopefully that makes the overall package a bit stiffer- not sure if that helps me or not? Main question is really can it be pre-emoted or is it only useful as a reaction?

singleton

Can someone else ride your bike and see if it happens for them?
That might help you eliminate some potential causes or identify what is causing it.

hopkinb

FWIW, I had one at >70 kph, which is what, 44 mph, on a long straight wide, 7% or so, downhill stretch and since then, I just don't go that fast, made me absolutely sh!t myself, but I knew to try and relax, knees on the top tube, and eventually it stopped.

Thought I was a goner, or at least heading for a bust collarbone and 95% roadrash. To answer your question though - if I am on a downhill and likely to get >55 kph, I will pre-empt - low on the drops, butt in the air, lightly grip the bars, think loose, knees on the top tube - look far ahead, use the brakes to scrub off excess speed (edit: before any wobble - don't brake during one) - all that jazz, but I'm not racing, I'm getting old, I won't bounce, so there's no need for me to go that fast.

28 mph/45 kph sounds quite slow to be getting a speed wobble though - given a tailwind or a draft, I can ride at that pace on the flat, so maybe it's something with the bike that's setting off the oscillation.

slowmart

As the numerous personalities of the MF have already stated, there are numerous triggers for a speed wobble. bald spots , low tyre pressure , road surface , losing traction on the front wheel because it's left the ground and come back down again. Your position and loose grip are spot on which means the focus is on your bike. From what you've said your a large unit so the mechanics on the bike are fundamental.

Don't touch the brakes, lean forward and let your speed slow naturally.



Take comfort speed wobbles aren't a common occurrence in cycling or motorcycling, preparation is key and will help remove possible triggers for outcome that leads to your backside twitching like a rabbits nose.

On the other side coming out of this means everything tastes a little sweeter.

hopkinb

slowmart said:

bald spots ,

As my kids love to remind me - male pattern baldness is a thing, but how will this affect me ability to descend? How did Pantani manage it?

roderick.inglis33Q7QOHdSD

Thanks very much for all your comments and help. Very much appreciated.

MattFalle

I used to get mega speed wobbles on the S3 until a friend wrapped her delicate smooth fingers around the wheels and turned them from eggs to RAZOR SHARP RACING WHEELS OF DEATH

dartmoordude

hopkinb said:

FWIW, I had one at >70 kph, which is what, 44 mph, on a long straight wide, 7% or so, downhill stretch and since then, I just don't go that fast, made me absolutely sh!t myself, but I knew to try and relax, knees on the top tube, and eventually it stopped.

Thought I was a goner, or at least heading for a bust collarbone and 95% roadrash. To answer your question though - if I am on a downhill and likely to get >55 kph, I will pre-empt - low on the drops, butt in the air, lightly grip the bars, think loose, knees on the top tube - look far ahead, use the brakes to scrub off excess speed (edit: before any wobble - don't brake during one) - all that jazz, but I'm not racing, I'm getting old, I won't bounce, so there's no need for me to go that fast.

28 mph/45 kph sounds quite slow to be getting a speed wobble though - given a tailwind or a draft, I can ride at that pace on the flat, so maybe it's something with the bike that's setting off the oscillation.

Sounds identical to mine on a Cervelo C5. Seriously thought I was a goner on a 16% descent. Still have no idea how I stayed on but the gods must have been smiling on me!
Now I limit my speed lighten the grip with my hands and clamp the top tube with my knees. Does it make a difference, who knows, but it hasn't happened since (18 months).
Got the bike checked and discussed with Cervelo who denied any known problems. Stay safe

First.Aspect

I've only experienced it twice, and used the knee on the frame solution.

But there are lots of articles here https://www.velonews.com/tag/shimmy/

Lennard Zinn has a particularly large brain so reading a few might be time well spent.