Oracle 36 Wheel FLex

My Oracle 36" wheel is flexing and rubbing on the disk brake when I slow down and speed up with a lot of force. I am concerned that my wheel has been poorly built and that the flexing may be reducing the overall power that is going into my pedals. Has anybody else had a similar issue? Is my disk brake adjusted to close to the rotor? Or is the wheel just flexing more than it should?

Please respond with insight.

Take it to a bike shop to get it trued and tightened?

Since the rotor is attached to the hub the wheel build won’t come into it. It may be bearing play. See if you can feel any movement in the bearings when moving the wheel by hand.

If it’s not bearing play then it may be frame flex. I can make my rotor touch the brake pads by forcing the frame and wheel in opposite directions (never actually noticed it while riding), but my frame is the old Nightrider style with the small diameter tubing. The Oracle frame should be stiffer but maybe there’s still enough flexibility for it to touch sometimes.

Have you changed brake pads recently? If you’ve just put new pads in then you may need to push the pistons back into the caliper to create a bit of extra clearance.

Are you using spacers between your bearing and your crank? As others have pointed out the wheel build won’t be a factor. There is some movement somewhere between the hub and the caliper mount. The bearing is the most likely culprit.

I had a similar issue when I first switched to disk brakes. The bearing was sliding a tiny amount on the spindle.

Another thing to check: If the rotor is out of true and already running very close to one of the pads then any flex which might otherwise go unnoticed might result in rubbing.

Flip the uni upside down and sight down the caliper so that you can see daylight between each pad and the rotor. Rotate the wheel through a full revolution. Does the rotor stay centered between the pads the whole way around?

If the rotor is looking out of true you can bend it back using your fingers. Just go slowly, a bit at a time, and be careful about touching the braking surface (if you do touch it, clean it with isopropyl alcohol before letting it touch the pads).

You can also adjust the lateral position of the whole caliper if the rotor is consistently closer to one pad than the other.

A loose bearing cap is a common problem and could causes movement between the frame and caliper. This is especially likely if the caliper is mounted on a Nimbus D’Brake disc brake mount. Of course this presents a problem because the bolts attaching the brake mount or bearing cap to the frame can not be tightened too tight because that will deform the bearing and cause other problems.


Hi Richard I have a qu-ax and have a similar noise only under high load I am pretty sure my noise is brake pad knock off ,as someone has said I tightened my bearing holders after centralising the rotor and only get the noise occasionally give it a go.