How do I fix sticking/tight hydraulic brake calipers? I took my wheel off my front forks to repair a puncture.  I had the bike upside down when I removed the wheel.  When I came to replace the wheel back into the fork slots, the hydraulic disk calipers were too tight to accept the brake disc. I had to use something to prize open the calipers so the gap was wide enough.  When I span the wheel it's still to tight and the calipers still make contact with the disc. Is there any reason why the calipers are now tighter and how do I fix the problem?

Thanks.
Most likely, while you had the wheel out, the brake lever was pulled, and the piston position was reset too close to the disc. 

You need to remove the brake pads, and very gently push the pistons all the way back into the caliper. 

Then replace the wheel, and pump the brake lever. It should take 2 or 3 pumps to feel normal again. 

Hope that helps.