Brake Judder

[andyf]

Re: Brake Judder

I've used PAGID discs on my Focus and my wife's KA and they seem to be fine and have lasted longer than the original set.

When MOT inspectors advise stuff like that they are just trying to upsell you

[chris_cussen]

Re: Brake Judder

For MOT tests the examiner is not allowed to dismantle anything, so the inspection can only be for visible surfaces on the disks and pads, and he certainly could not remove the drums to inspect them for wear or the condition of the brake material.

[stevejgreen]

Re: Brake Judder

For MOT tests the examiner is not allowed to dismantle anything, so the inspection can only be for visible surfaces on the disks and pads, and he certainly could not remove the drums to inspect them for wear or the condition of the brake material.

I believe an MOT tester has the power to measure a disc and pad thickness if he thinks it is borderline, provided he uses no tools. It would end up as an advisory if he didn't. But checking the MOT inspection manual would answer that.
Certainly dismantling is prohibited.

[philcoyle]

Re: Brake Judder

I use a very creditable MOT chappy who actually goes on refresher courses, his version is that if your brakes pass the read outs required, then drilled , grooved or scored, your brakes have passed. Most modern day discs have a wear indicator cast into the disc or info on the perimeter. Although I must admit I would like to see someone measure the pads or discs on my 6.5j alloys. You could lose a finger or two if you don't look at what your doing when you spin the wheels by hand.
My reference is to the inequality to motorists who have visible braking parts and those who don't and could be hiding all sorts of nasties.
http://www.meyle.com/fileadmin/user_...12S_en_web.pdf interesting.

[ggrum]

Re: Brake Judder

So far I have checked the near side only with the following results: Disc run-out is 0.1mm compared with the 0.15mm max specified. The disc thickness is 23.92 +/-0.01mm so no significant variation there. I don't know what the minimum specified thickness is but there is hardly any lip on the edge so I think the wear is minimal. The discs are grooved but were on the car when I bought it 3 or 4 years ago. The pads are in good condition with even wear and about 6mm of friction material remaining and the piston is not sticking in the caliper. As far as I can see there is nothing wrong on that side but I'll take it out for a run round the block to see if taking it all apart has made any difference before looking at the off side.

[philcoyle]

Re: Brake Judder

Have you tried removing the discs and thoroughly cleaning the hub and disc mating surfaces.

[ggrum]

Re: Brake Judder

Phil, thanks but I did that. I checked the run-out before removing the disc then after having cleaned up the mating surfaces. The figure was the same. I'll do the same on the other side a bit later.

[philcoyle]

Re: Brake Judder

Keep at it, nil desperandum and all that.

[ggrum]

Re: Brake Judder

Checked the off side brakes today. Disc thickness is 23.98+/-0.01mm and run-out both before and after cleaning the disc/hub mating surfaces is 0.06mm (the lowest I've ever measured on any car). The caliper piston is not sticking although it was a little tighter than the near side. Pads are in good order with about 6mm of material. So as far as I'm concerned there is nothing obviously wrong with the brake components. Took the car out for a run and the judder is still there although maybe not quite as bad, unless that's wishful thinking on my part. It has been suggested that worn suspension joints or bushes can contribute to this problem but they all seem ok as far as I can tell. I'll find out for sure at the next MOT which isn't until March. In the meantime I'll think I'll just ignore it until something more obvious happens. Thanks to everybody for their input.

[greyV8pete]

Re: Brake Judder

Checked the off side brakes today. Disc thickness is 23.98+/-0.01mm and run-out both before and after cleaning the disc/hub mating surfaces is 0.06mm (the lowest I've ever measured on any car). The caliper piston is not sticking although it was a little tighter than the near side. Pads are in good order with about 6mm of material. So as far as I'm concerned there is nothing obviously wrong with the brake components. Took the car out for a run and the judder is still there although maybe not quite as bad, unless that's wishful thinking on my part. It has been suggested that worn suspension joints or bushes can contribute to this problem but they all seem ok as far as I can tell. I'll find out for sure at the next MOT which isn't until March. In the meantime I'll think I'll just ignore it until something more obvious happens. Thanks to everybody for their input.

Meantime maybe worth getting the wheels balanced, if only to eliminate that from the equation? Also handy to find a nice empty road and try a few really hard stops from 60 mph to purge any glaze build up from the discs. Peter.

[philcoyle]

Re: Brake Judder

How about a mad idea, like taking out the pads and clean up the backs of them and copper grease the shims, but swap them over side to side. Wondering if you altered the rotation difference on the pad surfaces will give you the same results. If it alters in any way then get some new pads, at 6mm and depending on the age of the materials if they were mine they would be in the recycle bin by now. Also take off any square edges on the pads with a fine file, just gently around the pad surface, or file a small groove across the pad surface.
If nothing changes, then its the petrol and a box of matches, ONLY JOKING. smiley face.
But anything is worth a try to find a solution.

Is your suspension of the ford sierra type? I seem to recall that the bottom ball joints on them were tested by putting a long bar under the track control arm and levering it up using the inside of the wheel. Besides the weather is miserable now and it's nice being in the garage all greasy instead of shopping with the other half.
If your bottom ball joint moves more than 20 thou, then replace, what's that in foreign.

[ggrum]

Re: Brake Judder

I don't think I have a wheel balance problem as front tyres changed not too long ago and there is no sign of wobble through the steering wheel at 60 - 70mph. Also tried the hard stops - didn't realise just how good the brakes on a Cabrio are! Regarding Phil's suggestions I might just put new pads in anyway although I resent chucking away perfectly good Mintex pads. I'll also check the bottom ball joints a bit later but right now the weather in this part of the country is good so I'm going to use the car and live with the judder. I'll just have to brake very hard! Thanks again.

[greyV8pete]

Re: Brake Judder

I think that the EBC Green Stuff pads have the abrasive bedding in coating. Opinions seem to be divided about those pads with, it seems, about a 50/50 love / hate rating!

Just a thought that worn front shock absorbers can result in judder. Hey! You could be joining the replacement coilover club!

Peter.

[ggrum]

Re: Brake Judder

Peter, thanks for that happy thought! At least I will know which ones to buy. I've got the EBC Green Stuff pads on my Roadster but couldn't honestly say if they are better than standard pads. Unless you do track days or some form of racing where you would have prolonged hard braking I imagine the standard pads are good enough but I'm sure someone will correct me.

[ggrum]

Re: Brake Judder

Without doing anything else at all the judder seems to have gone away overnight in much the same way as it appeared. I can't think what has changed but I'm sure there will be plenty of theories about what happened. I guess there is always the chance it will re-appear for no obvious reason but, as ever, I'll remain positive!

Thanks again for all the suggestions.