Why is the rear Q caliper drag­ging on my BMW?

Motorcycle News (UK) - - Garage -

The pads on my BMW RT ap­pear to be con­stantly in con­tact with the disc, even af­ter a full caliper strip and ser­vice. When it’s on the stand it is pos­si­ble to turn the wheel, but you can hear the pads rub­bing. If I then re­move the caliper from the bike the pis­tons slide back rea­son­ably eas­ily. The brake fluid level is roughly mid­way be­tween low/high and the brake pedal spring seems to be up to scratch, mov­ing the pedal back when re­leased. Ron Posse, Put­ney

An­swered by Tez, Mo­tor­work­suk We’ve found that the orig­i­nal BMW rub­ber brake hoses break down in­ter­nally af­ter 10 years and don’t al­low the fluid to re­turn fully. An­other pos­si­bil­ity is that if the brake pedal po­si­tion has been changed, it could be that when it re­turns to rest it is not al­low­ing the master cylin­der to re­lease com­pletely, there­fore pump­ing pres­sure up, but not re­leas­ing it. If nor­mal grease was ap­plied to the caliper slid­ing pins dur­ing the ser­vice, the rub­ber dust caps could also swell and re­strict move­ment.

A

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