Pads Changed, Wheel Stuck

[essay]

Hi guys,

Thought I'd change pads on my front brakes. Set up is 8 piston unassisted. Outside pads went in fine, however inside pair needed to be helped with a rubber mallet as the pistons would not retract sufficiently. Consequently wheel now does not rotate. Would draining brake fluid and releasing pressure enabling pistons to retract to release pads off disc. Any help appreciated!

[Duncan]

well...is the disc exactly in the centre between the 2 sides of the caliper? even 1/2mm can make a big difference, so most likely either the wrong offset disc or inaccurate caliper brackets. The good news is, inside too tight can be corrected using shims or washers between the hub and the caliper to space the caliper inwards a little. The G4/D2/Ksport 8 piston brake kits come with shims for this exact purpose because they know not to trust the factory's "tolerances"

2nd....some pads are simply bigger than others new. You can always grid a little off.

3rd....if it is actually a piston not retracting ie if you pull the caliper off and you can't get the piston to sit flush....then you have a seized piston and this will stuff your braking performance. In this case remove the caliper and get it rebuilt, may be expensive if the brake piston or bore are damaged.

[essay]

well...is the disc exactly in the centre between the 2 sides of the caliper? even 1/2mm can make a big difference, so most likely either the wrong offset disc or inaccurate caliper brackets. The good news is, inside too tight can be corrected using shims or washers between the hub and the caliper to space the caliper inwards a little. The G4/D2/Ksport 8 piston brake kits come with shims for this exact purpose because they know not to trust the factory's "tolerances"

2nd....some pads are simply bigger than others new. You can always grid a little off.

3rd....if it is actually a piston not retracting ie if you pull the caliper off and you can't get the piston to sit flush....then you have a seized piston and this will stuff your braking performance. In this case remove the caliper and get it rebuilt, may be expensive if the brake piston or bore are damaged.

Ok thanks for info, so you suggest i remove caliper? How do I release the pads hold on disc i.e tight as.

[Duncan]

That's where i would start, you need the pads back out to have a good look. Wheel back off, undo the 2 big bolts that hold the caliper onto the hub. If it does not come free easily lever it off the disc.

then take the pads back out, and have a good look at the caliper pistons (be sure not to let the caliper dangle on the brakeline - support it).

can you push the pistons back so they are level with the caliper (or at least even on both sides)? If not get the caliper rebuilt (or a new one if it is a G4/D2/Ksport one lol)

if so push them right back, and put the caliper back on the disc.

is the disc exactly in the centre of the caliper? If not, do you have the correct offset disc? O if it is close to centred you can use a washer or shim to space the caliper inwards a little - put the washer between the hub and the caliper.

[essay]

That's where i would start, you need the pads back out to have a good look. Wheel back off, undo the 2 big bolts that hold the caliper onto the hub. If it does not come free easily lever it off the disc.

then take the pads back out, and have a good look at the caliper pistons (be sure not to let the caliper dangle on the brakeline - support it).

can you push the pistons back so they are level with the caliper (or at least even on both sides)? If not get the caliper rebuilt (or a new one if it is a G4/D2/Ksport one lol)

if so push them right back, and put the caliper back on the disc.

is the disc exactly in the centre of the caliper? If not, do you have the correct offset disc? O if it is close to centred you can use a washer or shim to space the caliper inwards a little - put the washer between the hub and the caliper.

Thanks for the info!