jzsoup

Can anyone explain why I get front wheel wobble at speeds above 45mph? Of course I'm rarely anywhere near that speed, but my last road bike and current road bike both had/have that problem. The first bike was a Scattante and the current one is a Giant TCR C2.

What gives? By the way, it scares the living **** out of me.

Grumpy McTrumpy

checked your headset recently?

jzsoup

Yep, several times. Both bikes were always tight.

brianappleby

grab your top tube with your knees.

also play with your fore-aft balance.

firereign

Hold on tight!!!

Bontrager

Is your speed sensor magnet opposite the presta valve? Have you not removed the reflector? Checked the bead of the tire. Loosened your death grip on your handlebars? Checked your tube to make sure it's not twisted? Removed the squirrel from your spokes?

jzsoup

I've done both those things and it does help. Now I just try to ride further forward with more weight on the bar. I've also heard that if you're heavier it doesn't happen as much-but that defeats part of the purpose of my riding.

What causes it?

Grumpy McTrumpy

if it is a wheel balance issue then spinning the wheel at a high speed while the bike is in a repair stand will cause the bike to bounce up and down on the stand slightly.

jzsoup

I'll try those other things, but the squirrel stays as a warning to the rest of his cute and fuzzy friends.

asgelle

https://www.faqs.org/faqs/bicycles-fa...ection-23.html

Wanderer

Headshake is a common problem on two wheelers. The oscillations are usually damped by your hands and arms on the handlebars, but not always. Ball bearings, especially if too loose or too tight seem to make it worse.

In the motorcycle world, roller bearings, tightened more than specs, usually resolve it. In the bicycle world, properly tightened headsets, and thicker grease sometimes help.

It can also be caused by a defective or improperly installed tire, but it's usually in the headset.

roshea

When I read the subject line I was going to ask which model of TCR it was. I thought they had gotten rid of that trait in recent years - maybe not.

bob the nailer

it is called wheel shimmy and it is scary, i have experienced it a couple of times going downhill, unfortunately your first instinct to grab the bars more firmly seems to make it worse. i also find that a knee against the top tube helps.

JoelS

Sit back a little and take some weight off the front wheel. If you're over the front wheel and have to brake, you're much more likely to go over the front. Also, being over the front wheel introduces more stress into the fork/front end of the bike. Weight farther back.

TandemGeek

Good articles on Front Wheel Shimmy:

https://www.sheldonbrown.com/brandt/shimmy.html
https://www.calfeedesign.com/forksymmetry.htm
https://search.bikelist.org/getmsg.as....9703.0148.eml

TarmacAG

Make sure the fork is tightened.

DannoXYZ 

These sympathetic vibrations can be scary. Whatever you can do to change the frequency of the oscillations will shift the speed at which it occurs. Usually I find changing to a stiffer fork really helps. So does speeding up or down out of the range of speeds where the vibration occurs is the fastest way out. On one of my early bikes, a small-tube aluminium bike similar to a Vitus 979, it would pretty much always shimmy at 42-44mph. So as I come close to 42mph on a downhill, I'd just get up and sprint up to 45mph and it may wag its head once at most.

flatlander_48

Here is an interesting article on "Speed Wobble" by Craig Calfee...

carpediemracing 

I don't know the Scattante but I know that all three of my Giants get wobbly at 45 mph or more. They don't have the dreaded speed wobble (i.e. violent side to side shaking, hard to hold onto bars), but the front end gets a bit loose. I found this to be the case with my TCR carbon (1 1/8" slimmer fork) as well as my TCR aluminums ("aero" forks standard on Giants for a while, 1 1/8" and 1", the 1" in both aluminum and carbon steerers).

The more flexible the fork, the worse it seemed (1" carbon steerer, the third TCR fork I had in one frame, was so bad I decided not to ride it outside).

When I upgraded the 1" to a Reynolds Ouzo fork (carbon steerer) the bike felt much better. I upgraded the 1 1/8" fork to an Ouzo as well. The TCR carbon I left with its original carbon fork, but I keep my top speed under 50 mph on it.

Based on my experience with my TCRs I would guess that upgrading to a much stiffer fork would help immensely, at least on the TCR.

cdr

jzsoup

Good to hear I'm not the only one. Thanks everyone for the explanations and especially the links to articles on the matter. I may consider a stiffer fork; but I'm not sure it's warranted as I live in a relatively flat area and rarely hit speeds over 40mph. Hell, I rarely hit anything considered "speed."

hrt4me

Thanks for the informative post about wheel wobble/shimmy; I experienced this recently at a race clinic.

Grumpy McTrumpy

I'm going with my first answer Regis. Tighten headset bearing pre-load.

Porter20

Should it be? Does this help balance the wheel or hurt it?

jnlabay

I am curious what the pro's do when they are screaming down the alps in frnace and on the tour what they do for this problem

uke

I think they have real (as opposed to armchair) engineers who make sure this problem doesn't occur.

Personally, if I regularly experienced this at 45 mph, I'd probably slow down until I figured out how to stop it completely.

That said, the fastest I've gone is 36 mph, and I'm not in much of a hurry to go any faster. The roads here just aren't that good.