Mountain Bike Reviews Forum banner

Front wheel bends towards the disc on hard braking- whats causing it?

9K views 20 replies 12 participants last post by  copylatte 
#1 ·
When braking hard the top of the front wheel gets pulled towards the side of the disc brake.

I have tried different QR axles- no difference
I have tried an entirely different wheel- no difference

I am wondering if the bottom of my forks where the wheel engages onto them may be faulty?

Help please.

slow-motion video demonstrating the problem:
 
#4 ·
I'm trying to imagine what happens to the wheel when you try to slow the hub while the tire/rim is driven forward by inertia. What's in between them? Spokes, held by the hub flange and rim, with the hub on an axle held by the fork. The stopping force on the rotor is on one side of the hub only, so I expect it would tend to cause twisting of the hub/axle/fork. So as mentioned, a beefier axle/fork would resist the twisting better. The hub/axle is also held by the spokes. Spoke count, hub width, rim stoutness and proper tensioning also contribute to the wheels ability to resist deforming forces, whatever the source.

So if you want a wheel that deforms less, get a beefier, wider hub/axle/fork with a stouter rim from a quality builder. Short of that, you might try taking the wheel to a wheel builder to have the spoke tension checked and adjusted.

Edit: And per Harold, the shop can check for any other problems, so bring the whole bike :thumbsup:
 
#5 ·
Thanks for your reply. The spokes have been checked and they were fine. I actually put a different wheel on (from a different bike where this problem does not happen), and the same thing happened on my bike! Makes me wonder if the fork has worn out and is no longer the right size for wheel?
 
#7 ·
Are you properly installing the wheel and putting enough tension on the QR handle? For road bikes, general rule of thumb is to lock the QR lever to the point where your palm turns white. It shouldn't be overly difficult to close the lever but it should be tight enough to where your palm will turn white when locking it. Also are you installing the wheel with the bike while it's upside down?
 
#9 ·
Hmm it could be a fork problem like you mentioned. You swapped wheels around from another bike and the problem persisted. Maybe it's just me but when i watch the video, the right fork stanchion (left from our view) almost looks like it bends when you brake. I could just be going crazy but that's what it looks like!

Maybe you should inspect the fork crown for cracks. Look on the outside and inside of the crown where the tire passes between it.
 
#10 ·
That's an odd one. Could be broken axle in the hub. The QR isn't the axle. The QR pinches the dropouts against the axle stubs that stick out from the hub. What happens when you grab the tire near the fork crown and push it side to side? Any looseness or grinding?
 
#21 ·
You can get a QR adapter that will allow you to use a QR fork with a 15mm wheel (it slides into the 15mm hub). Try the 15mm wheel or try with a friend's wheel and see if the adapter fixed it. from my own experience my front wheel would consistently move to the disc brake side over time until it sat crooked in the frame no matter what I did with the QR until I got the adapter and a 15mm hub. QR's are too weak on their own...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top