Front Wheel Deflection

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Posted: Oct 1, 2015 at 5:24 Quote
Hi there,

Please help a desperate rider,

When I'm slowing down from a reasonable speed with the front brake, the top of the front wheel deflects sideways toward the left leg of my fork (brake side). If I'm going downhill and I hit the brake hard, the tire even grinds the fork. This is causing several handling problems.

I already checked hub tension, spoke tension, QR skewer tension (9mm) and all of them seems to be fine. I ran out of ideas of what could be happening.

Any thoughts would be appreciated.

Posted: Oct 1, 2015 at 7:59 Quote
Have you tried tightening your hub

Posted: Oct 1, 2015 at 8:57 Quote
Probably either a really flexy wheel or the most knackered bearings of all time

Posted: Oct 1, 2015 at 15:31 Quote
VladMTBR wrote:
Hi there,

Please help a desperate rider,

When I'm slowing down from a reasonable speed with the front brake, the top of the front wheel deflects sideways toward the left leg of my fork (brake side). If I'm going downhill and I hit the brake hard, the tire even grinds the fork. This is causing several handling problems.

I already checked hub tension, spoke tension, QR skewer tension (9mm) and all of them seems to be fine. I ran out of ideas of what could be happening.

Any thoughts would be appreciated.

You said you checked spoke tension and it "seems to be fine". Did you use a tensiometer, or are you just going by feel? It really sounds like spoke tension to me.

Posted: Oct 1, 2015 at 18:33 Quote
That would scare the shit out of me!

Mod Plus
Posted: Oct 19, 2015 at 12:45 Quote
First off, I'd recommend against riding very far until you have this resolved. Those "handling problems" you mention could cause serious injury, especially if your tire rubs the fork hard enough to stop the wheel from spinning and tosses you over the bars. Depending on your mechanical abilities I'd recommend heading down to your local bike shop to have them assess the situation, but in the meantime here are a few suggestions you can try at home.

Although it sounds like you already spent some time checking over your wheel, my initial thought is that the front axle could be broken, something that's more common when combining a disc brake with a quick release axle. Take the wheel completely off the bike, and give one side of the axle a tug. If it's broken, you'll probably end up with a snapped piece of steel in your hand and a bunch of greasy bearings on the floor, but at least your problem will be solved.

Another possible reason for this problem is if the quick release is slipping in the dropouts, either due to a faulty quick release or from dropouts that have become worn and wallowed out. With the wheel still on the bike and the quick release secured, stand on the left side of the bike and give the wheel a firm tug towards yourself. Is there any movement? If the dropouts are worn, or if the knurled part of the quick release isn't gripping as firmly as it should, then the force generated when applying the front brake could be forcing the axle to shift downwards, which would cause behavior you described.

If the wheel's not to blame, then an issue with the fork, possible extremely worn bushings or even a cracked or broken arch would be my next guess, but in any event I'd imagine a trip to your local bike shop will still be in order, either for the parts or service necessary to get you safely riding again.

Posted: Oct 19, 2015 at 13:56 Quote
Nice to know what tomorrow's tech Tuesday is!

Posted: Oct 21, 2015 at 3:31 Quote
VladMTBR wrote:
Hi there,

Please help a desperate rider,

When I'm slowing down from a reasonable speed with the front brake, the top of the front wheel deflects sideways toward the left leg of my fork (brake side). If I'm going downhill and I hit the brake hard, the tire even grinds the fork. This is causing several handling problems.

I already checked hub tension, spoke tension, QR skewer tension (9mm) and all of them seems to be fine. I ran out of ideas of what could be happening.

Any thoughts would be appreciated.

You said it's a 9mm QR, but what type? If it is an external cam type, those can very often feel as though they are tensioned properly when they are not. When the external cam gets dry it requires a lot of force to close, giving the impression of proper tension. Try putting a couple of drops of chain lube on the cam and open/close it a few times. If it suddenly feels super easy to close it, there's your problem. I worked as a mechanic for 30+ years and saw this issue with that type of skewer all the time. If that does turn out to be the issue, either make certain to lube it occasionally, or better yet, replace it with a Shimano skewer. I hope it's as simple as that and that you don't have something more complicated/expensive going on. Good luck.

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