Pulsing Brakes

[Hamster31]

My C30 has what can only be described as pulsing brakes, which though legal from an MOT perspective, do feel as though one or more of the disks are not of constant thickness. The rear ones were changed 2 years / 17K miles ago and look almost new. The fronts are not seriously worn, but the age is unknown.
I've not had this on any other car before. Obviously, I could just go for a complete disk / pad change all round, but would prefer not to spend the money if there's a simpler solution.
Any ideas out there?
Many thanks,
Hamster31

[wilbydoughboy]

Maybe the brake discs are to thin. I had a similar problem with an Escort van and new discs solved the problem.

[Hamster31]

Thinking about it; the brake pedal doesn't move, but the braking effect seems to vary, a bit like part of the disk is creating less friction than the rest. Could this be from corrosion caused by prolonged standing with the pads in contact with the disk, creating a localised area of corrosion?

[big_yin]

That should normally clear after braking a couple of times.

Another possibility is that the discs are maybe warped?

[domhart10]

first idea would be to have a look at your breaks, the most vital part to stopping your car. Its pretty important you keep these in good condition. If they are looking old / worn out, I would get them changed as soon as possible.

Check the discs / pads and change them if they are low. If you have changed that and the issue still persists, your brake line hoses might be the culprit or your brake fluid might need a change as well.

[iantowil]

Pretty sure you have disc thickness variation. If you google "brake judder", there are some great explanations. I've gone through three sets of discs and still had the problem return after a few months. I can only think I have disc runout probably because the hub is out slightly - both front wheel bearings have been changed.
My latest remedy is to for on car disc skimming. If you google that, again you'll see some great explanations. I'm hoping this should sort the problem as it cuts the disc where the brake pads sit, so by definition the disc should be perfect at that point in its rotation.
If there is a problem with the rear brakes, try braking with just the handbrake and see if you can feel anything.
Hope this helps.

[iantowil]

Another quick point, try a dti clock on the disc if possible. The literature says anything over 50micron will give symptoms. Mine were way out.

[dingov70]

A simple solution , go to your local MOT place & ask very nicely if they will perform a brake check . tell them you have a fluctuation problem . We do it all the time for customers & usually don't charge as a goodwill gesture . Takes less than 5 minutes .

Last one I did turned out to be a bulging tyre & worn track rod end !

[Rusty1]

Originally Posted by Hamster31

The rear ones were changed 2 years / 17K miles ago and look almost new. The fronts are not seriously worn, but the age is unknown.

Try to isolate whether it’s the front or rear brakes by pulling up on the handbrake while moving, you may feel the lever pulsing. I suggest this because I had rear brakes replaced with Brembo discs & pads, within 10k miles they’d warped enough for me to feel it and the MOT picked it up - not bad enough to fail though. They were replaced under warranty but I was surprised that aftermarket parts could warp that quickly, if I change them again I’ll go with OEM parts.

[AndrasL]

Sadly the disks can warp at any time. I had to replace my half year old TRW disks because of this.