Front Brake Judder Fixed

[Pukmeister]

Hi All, thought I would share my fix for front brake judder in case anyone else has the same snag.

'04 GS with the anti-squeal mod on the front disk mounting bolts (ptfe washers). Recently started juddering under braking, so I decided to mount a DTI (clock gauge) and measure the runouts. I struggled to find a decent mounting point for the DTI, the realised I could remove the brake pad retaining pin, reverse it and screw it back in so that it stuck out from the caliper like a stud.

With the DTI my RHS disk was running at 4thou throw (0.1mm, max limit 0.13mm) within about 70 degrees of disk rotation. LHS disk was almost zero runout.

I unbolted the disk and removed the mounting screws/bobbins/washers and lo and behold, there was light furry corrosion of the alloy disk mounting faces on the front wheel where the disk mounting screws/bobbins locate. A bit of a cleanup and I refitted the disk in the same position to the correct torque in stages, and the runout is now down to 1 thou (0.02mm) and the judder has gone completely.

Hope this helps for anyone else with the same problem.

 

[(RIP) Kaister]

Not saying you're wrong about runout, but........................

with a twin opposed piston caliper the runout can be massive before you'd feel it.
- its varying disc thickness around the overall diameter that causes 'pulsing'.

i had an old guzzi lemon2 - it had a massive 1/4" ding in the rear disc - total runout.
BUT - cos the pistons 'floated' - ie they went in and out with each other - the pressure in the system stayed the same.

Couldn't feel a thing - only noticed it when cleaning it.

I'd wager you cleaned a bit of grease from the disc face and fixed the problem. .

just my experience - and the situation might be different

 

[Pukmeister]

I used a micrometer to check the disk thickness at varying positions to check for wear Phil, it was definitely the way the disk was mounted to the wheel (or rather, the expanding corrosion beneath the mounting bobbins allowing the disk to flex away from the wheel by a few thou). No grease on my disks either, I use an aerosol brake solvent cleaner to regularly strip, inspect and clean around the pistons and disk face. I understand what you mean about the hydraulic fluid equalising between pistons though.

How's the winter down under by the way, been out riding much ??

(Heatwave here, but Thunderstorms due tonight.)