how to center rear ultegra brake calipers?

[Naixed]

My left brake pad is closer to the rims braking surface than the right. I have attempted to adjust and center the caliper by loosening the allen bolt, centering and retightening. I went out for a ride and noticed it was off center again.

Is there a proper way of doing this?

[cxwrench]

just what you're doing, but make sure it's tight. or, make sure it's tight, then move it by hand...that's what every bike mechanic in the world does.

[brucew]

Actually, there's a centering screw that makes the adjustment.

Park Tool Co. » ParkTool Blog » Dual Pivot Brake Service

[Seagoon]

+1&2 on what they say above,also make sure the wheel is dished correctly and is centered in the frame.

[Kerry Irons]

My left brake pad is closer to the rims braking surface than the right. I have attempted to adjust and center the caliper by loosening the allen bolt, centering and retightening. I went out for a ride and noticed it was off center again.

Is there a proper way of doing this?

As others have noted, center it by hand if the brake body can be twisted with hand force. And then squeeze the brakes a few times to let them find their "natural center." It may be that you are not moving the brake body but rather just moving the arms, which does not serve to center the brake. The likely thing that happened with your attempt was that when you tightened the nut, it put a twisting force on the bolt and therefore on the brake body, which threw it off center again. You most often need to firmly hold the brake body centered as you tighten the nut to prevent this.