# Speed Wobble??



## jeff84065 (Apr 8, 2013)

I am still new to this great sport and I have a reoccuring problem.
I like to climb and everytime on the way down, once I hit 45 to 50 mph I develope a nasty speed wobble. This last time it took 2 lanes to recover.

What causes speed wobble on a bike?

My background information
I ride a Specialized Roubaix Apex, stock wheels
I am 6'0 and 225 lbs.

Any help would be great, Thanks


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## bikerjulio (Jan 19, 2010)

This has been an exhaustively debated subject for many years. I'd suggest some more online research. 

I too have suffered from this and it's been the most scary thing I've encountered on a bike. 

There can be mechanical problems, which need to be ruled out, but I'm tending towards the "rider induced" theory. On my last cycling trip, and on descents where I'd had trouble in the past, I made a very conscious effort to relax my hands and shoulders, put most of my weight on the pedals, and had no problems.


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## Bumpstop (Mar 9, 2010)

Back in the day, the Suzuki 750 would wobble above about 145 kph. In most cases, motorcycle (and there's no reason to believe a bicycle is any different) is due to imbalanced wheels, the front wheel being the more likely culprit. Put your bike on a stand and spin the front wheel numerous times to see if it always stops in the same position, indicating a heavy spot. Is you speedometer magnet on the front wheel? That would be sufficient mass to induce a wobble at those kinds of speeds.
I don't think balancing a bike wheel would be very easy, owing to its light weight and difficulty in determining how much weight to add to balance it, and where. But its a place to start, and it isn't very difficult to spin the wheel a few times! 
Another thing to look at is if your tires are mounted properly - are there high and low spots if you spin the wheels, viewing the profile of the tire from the side? This too would contribute to wobble. I find it quite a challenge to mount a tire without high/low spots. When you're going 45 - 50 mph, otherwise trivial imbalances or out-of-round tires will really add a substantial force.


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## Srode (Aug 19, 2012)

Bumpstop said:


> Back in the day, the Suzuki 750 would wobble above about 145 kph. In most cases, motorcycle (and there's no reason to believe a bicycle is any different) is due to imbalanced wheels, the front wheel being the more likely culprit.


If it was a Suzuki with the 16 inch front wheel I think the problem was more geometry than wheel balance. A friend I used to race with had the same problem on his Suzuki over about 130mph, my Honda interceptor did not. When we were on the track, the use of a steering damper (required later by WERA and AMA) eliminated the issue completely. Had the same issue on my ZX7 when hitting a hard bump at speed (made quite a scary pit road exhibition one time hitting a pot hole half way down pit lane at what was probably higher than prudent speed) and the steering damper fixed that too. Net I think it's likely more geometry and something that induces the wobble. A bicycle doesn't have the mass a motorcycle does to self dampen a wobble.


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## lbagley (Apr 9, 2013)

Jeff
Would you by any chance have a short ish stem on your bike 90mm or below ?

As mentioned i would check the whole bike over and if you unsure on how to check get into your local bike shop 

When you say stock wheels would you know what they are ? 

You might want to try putting more weight on the front of bike to stablise the bike.





jeff84065 said:


> I am still new to this great sport and I have a reoccuring problem.
> I like to climb and everytime on the way down, once I hit 45 to 50 mph I develope a nasty speed wobble. This last time it took 2 lanes to recover.
> 
> What causes speed wobble on a bike?
> ...


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## jsedlak (Jun 17, 2008)

Have a trusted mechanic check the fork & the headset. If that does not fix it, try a different wheelset. If that does not fix it, have someone else ride the bike and see if it happens for them.


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## JasonB176 (Aug 18, 2011)

I have found that by not having a "death grip" on the handlebars, my bike is much more stable at high speeds. It can take a while to build confidence and just learn to relax your upper body but it really seems to make a difference in stability.


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## jeff84065 (Apr 8, 2013)

Thanks for the input!!

I do try and relax when I down hill. Light grip but I try to balance equally with weight on the seat, pedals and bars. When it happens I slow till it stops and then get back on it and try a different postion to see if it helps. Still get it. 

I will try to pull my knees up to the bar and see if that helps.

I am also looking for a new set of wheels for this season as well.
My current ones are Dt Swiss 2.0

I will take my bike in and have them check the forks. The bike store seems to think it the rider. Which it very well could be.

Once again thank you for your input.

It sucks to work hard to get up the hill not to get the reward of going down it.


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## r.shoemaker78 (Feb 23, 2012)

I would experience this on my old bike at about 43-45 mph. On my newer bike it has been as smooth as glass on decents over 55 mph and thats using the same wheelset and handlebars. The geometry is definatly different and more agressive on the my Cervelo and it begs me to go faster. I know I wasn't as confident on the old bike, especially if there were corners, so I had a much more rigid grip and posture where I find my confidence keeps me loose and balanced on the new bike. 

Just thought I would post my experience in this area as I think it was all me creating the issue.


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## Peter P. (Dec 30, 2006)

If you have a friend that can test ride the bike at the same speeds, you'll be able to determine whether it's the bike or the rider.

Isolate the problem to the bike and then I can suggest methods to locate the source of the wobble.


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## tom_h (May 6, 2008)

Calfee Design thinks an asymmetrical fork can cause wobble, and thier explanation seems plausible:
Fork Symmetry | Calfee Design

It requires specialized fixturing to check, I doubt a bike shop could do this.


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## jeff84065 (Apr 8, 2013)

Thanks again for the input.
Update
I rode the hill again and once again it got me.
So I went to buy some new wheels and ended with a new SL4 with the disc brakes.
Hopefully my speed wobble is a thing of the past.


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## tom_h (May 6, 2008)

jeff84065 said:


> ... So I went to buy some new wheels and ended with a new SL4 with the disc brakes..


Your local dealer must love you!


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## Mooney (Apr 20, 2013)

Congrats!! Lets see some pics.... Any wobble with this one?


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