Brake judder- specific question

Can you help? I have a brake judder through the peddle and not the steering wheel in a Jspec NA.

Both front wheels off and I have a rubbing noise on about a quarter of the passenger side when spun. I’m guessing a warped disc. Also the pad seems to be wearing more towards the outside of the disc, and less towards the centre.

On the same wheel I also have a brake pad impression on the disc- pic below.

Firstly, would these symptoms suggest a warped disc, but also what could have caused the pad impression?

Thanks in advance.

S

Do you have access to a run out gauge?

I would check the sliders, undo the two 14mm bolts facing the wheel arch, leave the bottom one in and pivot the calliper away from the pads. The top slider pin has a 17mm head but should be turntable by your fingers and should easily move in and out (same with the one still holding the calliper on). If they are ok then check the piston, large adjustable grips are best, but you can use a block of wood and spanners to lever them back, it shouldn't be too difficult. If all these are moving freely then I'd move on to looking at the disks.

Do you have access to a run out gauge?

 

I would check the sliders, undo the two 14mm bolts facing the wheel arch, leave the bottom one in and pivot the calliper away from the pads. The top slider pin has a 17mm head but should be turntable by your fingers and should easily move in and out (same with the one still holding the calliper on). If they are ok then check the piston, large adjustable grips are best, but you can use a block of wood and spanners to lever them back, it shouldn't be too difficult. If all these are moving freely then I'd move on to looking at the disks.

Thanks for that- I don’t have a run out gauge unfortunately.

When you say pivot the caliper away from the pads; does the piston section come out first? I thought the pads were in the callipers?

Sorry if I’m being thick.

It's fine! you'll see if you loosen those 14mm nuts. The pads are clipped into the 'carrier' see your pic, and the larger red piece is part of the piston piece of the calliper.

With the top bolt out and the bottom one loose, looking down from above you can lever (screwdriver) the calliper off the pads, the pads will remain in the carrier.

Makes sense- Thanks for that.

Do you have any idea why there would be the pronounced pad mark on the disc?

Well if you have a sticky calliper, worse case its been dragging and getting very hot, then you stopped and its sort of clamped on a little and perhaps left that residue 'ghost' pad!

If it has been dragging then the disk could well be warped by the heat and then uneven cooling on the pad section?

So checking those two sliders and the piston for normal movement is the first and easiest thing to check.

Re the run out gauge, if you can rig up something with a clamp and some sort of pointer (think old needle on a record setup) and then get it very close to the disk, pop the wheel nuts on the disk and rotate and look for the opening/closing of the gap.

yes as scooter has said

The calipers are prone to seizing

im sure you can get a seal kit or get tghem reconditioned from the likes of http://biggred.co.uk/

Thanks both. Great advice!!

I’m having a look at them this weekend.

Thanks for all the help on this thread guys!!!

Just changed the pads and discs- one completely seized slider pin. With the look of the disc- clearly the cause... eventually came loose, and a lot of work later, now completely free.

Btw- comline discs were pretty cheap, but very nice quality.

The rears next!!!!!