Bike Vibration at about 60 km/h

shush007

I just bought a new Trek Emonda SL (about a month old) and everything has been going well. I've done about 250km on it just doing short loops around my house. However, on the weekend I had some time to venture a bit further away where there are larger hills. On this ride I noticed that once I reached approximately 60 km/h on the descents, the bike would vibrate as if I had ridden over the ripple strip on the side of the highway (that makes the tires really noise to wake you up). At first I thought I had ridden over a bad patch of road, but by the fifth time it happened I was certain it was not related to the road surface. The funny thing is, the vibration would only last for about one second at a time. However, it did happen about 5 times on two different descents.

I thought maybe it was related to be half holding the brakes, but I'm almost certain I wasn't braking at some of the occurrences. It may have occurred more when leaning in on turns, but I can't be certain because it hasn't happened enough and I'm a bit scared to go and try again at 60km/h down hill.

Does anyone have any ideas on what it could be?

I checked the quick releases on the wheels were secure, which they were.
I visually checked the wheels were aligned as they pass through the brake pads, which they were.
I have slick tyres on, so it shouldn't be the thread on the tyres.
I've ridden down this road on my old bike which did not vibrate.
On my normal rides (speeds up to about 50km/h) it hasn't happened.

Any help is appreciated!

topgunsteve

Was it a vibration or could you describe it as a wobble through the steering axis? You'll find quite a few articles on speed wobble.

Out of interest, what size frame is your emonda?

andcp

Have you checked the head bearings?

The Rookie

Sounds like a brake pad issue, you may need to tweak the toe angle slightly.
http://www.bikeradar.com/gear/article/w ... ing-22677/

compuwiz_uk

if all else fails & you still have the wobble then try removing the reflectors from the spokes - probably wont do diddly but hell, its worth a try lol

fenix

Pull the front brake on and rock the bike back and forth, any movement there ? If so tighten up.

So many vibrations is a bit odd. I don't think its the rare speed wobble.

shush007

Thanks for the responses everyone.

topgunsteve wrote:

Was it a vibration or could you describe it as a wobble through the steering axis? You'll find quite a few articles on speed wobble.

Out of interest, what size frame is your emonda?

I'm not sure if it was a wobble. I didn't feel like I would crash immediately. It was more like a high frequency vibration with really small amplitude if that makes sense. It really was as if I was driving on the ripple strip on the highway - unpleasant but I didn't feel like my body weight was shifting left/right because of it. It felt like the whole bike was vibrating. I couldn't tell if it was from the front or back or both.

Andcp wrote:

Have you checked the head bearings?

I haven't checked the head bearings themselves, but when I hold the front brake and rock the bike back and forwards it does not have any movement in the headset.

The Rookie wrote:

Sounds like a brake pad issue, you may need to tweak the toe angle slightly.
<span class="skimlinks-unlinked">http://www.bikeradar.com/gear/article/workshop-step-by-step-guide-to-quiet-rim-braking-22677</span>/

The brake pads already have a very slight toe in angle, and I don't think I was applying the brakes when it happened so I don't think it is brake related.

compuwiz_uk wrote:

if all else fails & you still have the wobble then try removing the reflectors from the spokes - probably wont do diddly but hell, its worth a try lol

Bike doesn't have reflectors on the spokes

fenix

Are you new to cycling ? I've seen it said that gripping the bars too hard can cause issues.

60Kmh is going some if you are new to cycling. Relaxing is said to help.

I've only ever had a speed wobble once and that was on a new bike in extreme cross winds. Never happened again.

shush007

Fenix wrote:

Are you new to cycling ? I've seen it said that gripping the bars too hard can cause issues.

60Kmh is going some if you are new to cycling. Relaxing is said to help.

I've only ever had a speed wobble once and that was on a new bike in extreme cross winds. Never happened again.

I've been riding for about 5 years. Don't think I was gripping the handlebars too hard. I'll have to try and replicate it and see when exactly it is happening. If I can replicate it consistently, I might put my old front wheel on (and possibly my old rear wheel, but it only has 10 speed cassette on it, not 11)

topgunsteve

Could it be a wheel balancing issue? its interesting that it seems to happen at a critical speed.

Secteur

Fenix wrote:

I've only ever had a speed wobble once and that was on a new bike in extreme cross winds. Never happened again.

Same here, as a new cyclist - same conditions - only ever happened the once but it was terrifying! On a fast, very busy road, going downhill, on a sweeping bend with strong side winds.

I had read about it on here a few days before it happened and I remember flashing back to the forum posts as it happened - I clamped my knees to the top tube and it settled.

But it was in my top 5 awful cycling moments!

jpf51

I had a similar issue on a fast descent though it was more of a wobble than a vibration. Traced it to a lose bottle cage on the downtube when carrying a full 1 litre bottle!

The Rookie

I can get a front wheel wobble (like a rapid oscillating steering input) on my commuter in a certain riding position (crouched right forward in the saddle), if I move move my weight EITHER more forward (sitting on the top tube a la Froome) or back it goes away. The oscillation is so rapid it feels like a vibration unless you look at the wheel. Headset is brand new and no play, it can just happen.