Brake Diving and flash update Update

[ricford]

My complaint was the bike nudging ( sort of like diving only not as severe) to the left when braking. I just had the brakes replaced last week. One pad was worn more than the others (long story short, I didn't need to replace the brakes and the dealer just did what I asked and didn't tell me it wasn't needed) The upshot of replacing the pads was that the bike no longer dives and brakes straight. I'm averaging 33 mpg on the flash.

 

[PinkRosePetal]

Have you given the new pads time to bed in correctly and fully?

When a pad is worn far more than the others it's almost always a pad sticking in the caliper so not releasing braking pressure OR the piston behind that pad is stiff in its cylinder so not retracting sufficiently to release pressure on the pad OR both of these.

A sticking pad obviously needs the caliper surfaces, where the pad slides, cleaned up to allow free movement of the pad. A touch of protective lubricant on the pad slide area is no bad thing.

The piston must be very free to move because it is only retracted by the rubber fluid seal which flexes very slightly as the piston moves outwards. When its flex returns to the relaxed state it draws the piston back slightly. Any stiffness clearly will prevent proper release of pressure on the pad. Good practice is to exercise the piston a number of times by pumping it forward using the brake pedal and squeeze it home afterwards before replacing the pads. Conversely, if a vehicle is pulling to the side under braking, the opposite side brake is the one which is sticking sufficiently to limit the actuation pressure of the brake pad. Since your brake pads are newly fitted, it's not so likely that the resistance to movement is the brake pad so that leads to the conclusion that there is probably a seriously sticking piston (or pistons) in one caliper.

A possible fix, but not an ideal fix, is to brake very hard a number of times in order to exercise all the pistons in all the calipers, you may find this sufficient to overcome the present issue. Only do this when you are sure the pads are fully bedded to the brake disc and only do it on a road where it is safe to do so.