Oct 26

BRAKE SHUDDER ISSUES – HUB TYPE ROTORS

THE ENQUIRY/PROBLEM:

Customer is complaining of severe brake shudder almost lurching when brakes applied. Having noted that the customer has only had the rotors fitted for a few weeks/months and that the shudder is getting worse.

THE CAUSE:

If a hub type rotor is fitted with the hub filled with grease, the grease will expand with use (heat) and be forced out the back of the hub past the seal.

The grease is then thrown outward and eventually finds its way to the rear face of the rotor. Once the grease is on the face it causes contamination of the pad and rotor surfaces resulting in an uneven coefficient of friction.

Due to the changing friction on the face the driver of the vehicle will start to feel the symptoms of brake shudder. Over a short period of time the rotor develops DTV (Disc Thickness Variation) which results in pedal pulsation.

The obvious signs of this problem is that the back of the rotor is covered in grease, also the face of the rotor will possibly have dark brown to black partial rings of a burnt looking substance on it (refer above photos). In some cases the grease is also forced out of the front grease cap (refer photo below).

SOLUTION:

When fitting hub type rotors only pack the wheel bearings with grease and lubricate the seal leaving the center of the hub free of grease.

 

Technical Support
Disc Brakes Australia.