New disks and pads

[Clifford Pope]

The brakes have been juddering a bit at speed, and I knew the disks were worn out and rusty, so finally got round to fitting the new pair from Chris Witor, and new pads.

The first problem was it was clearly impossible to get the pads in with the anti-rattle shims attached, so I discarded them. I have never had them before when buying pads. Even so, the pads are a tight fit in the caliper slot, despite pressing the piston right back into the caliper.
I tried the car, and it seemed fine for a while, but massive juddering set in after a while. The cause was clearly the disks getting hot.
I've taken the pads out, rubbed down any high spots, chamferred the edges a bit, and refitted. The brakes are slightly better, but still get too hot, I think. On each side, the inner pad is the culprit - they just seem to be very slightly too thick.

So I am now thinking of grinding the pads, to take about 1/2 mm off. Is that OK?

It is a Mk 1, with the earlier thinner disks, so it can't be wrong pads I don't think.

[johnnydog]

A thought (not meant to insult your intelligence!), what age of Mk1 have you got? The very last Mk1's were fitted with thicker Mk2 discs and calipers. The pads are also bigger - Mk2. Have you been supplied with Mk2 discs in error - assuming they would actually fit in the early caliper?
You say that the discs were very corroded etc; is there a build up rusty deposits on the caliper where the pads sit which is preventing the pad from seating correctly?
I would look into the problem more thoroughly - you should avoid having to file the pads down to get them to fit. The face of the piston should be flat again the pad recess on the caliper. If there is a lip of corrosion in the chrome on the outer edge of the piston, it could stop the piston from being pushed fully back, resulting in the tight fitting. Or the pistons have seized slightly?
I am certain it will be something simple!

[Clifford Pope]

It's a 1967 Mk 1, with the thinner disks. I measured them so I know they are as described, not the thicker kind. Allowing for reduced thickness from wear and rust, they are clearly the same size as the old ones. The Mk2s are I think substantially thicker.
The calipers are in good condition, not rusty, the pistons move freely and press right back into the caliper so that they are flush with the edge.

I have compared the sizes of the disks and calipers with old ones from my scrapped 1964 car, and they are the same. So the problem seems to be simply that brand-new components are just a bit too tight in their specifications. The pads are the more likely culprit I'd have thought, hence my question regarding shaving them a little.

[TedTaylor]

I have machined down later discs on my '64 Mk1 saloon to get the benefit of the beefier centre then used standard pads - all worked well.

Personally I wonder whether your pads are a bit thick for some reason. If facing them down be very careful as to the material of the pad because NOS may have been asbestos - I can give advice on this if you need it because I worked in asbestos surveying/testing before I retired.

If you are breaking an early Mk1 do you have good dash padding and gutter trims spare for sale please?

MUT

[johnnydog]

You don't say what make of pads they are; I have always fitted genuine old stock Lockheed or new Unipart and never had any issues at all.
On daily drivers, I have found that 'cheap' pads do occasionally require the metal backing to be filed to actually get them in the caliper (never had to re profile the pad face however...); a problem which has never occurred with 'decent' pads. I would try a different make of pad rather than re profile the existing ones.
Regarding the brake judder you referred to - there are a lot of questions regarding so called warped discs - many qualified people 'in the know' say that brake discs don't warp and judder is when there has been a build of brake material on the surface of the disc which is not visible to the eye, occurring when the brakes are hot and the transfer of material from the pad to the disc face when the pads are tightly 'clamped' onto the disc face, generally associated with sitting with your foot on the foot brake whilst stationary or applying the handbrake after a period of heavy braking, but in your case possibly because the brakes have been binding and the problem occurred when you became stationary as the pads were tight on the disc face.
I'm not an expert, but have previously gone through extensive problems with brake judder on a high performance Audi fitted with front discs costing £1000 a pair for the discs alone, which incidentally eventually resulted in the fitting of ceramics which cured the problem (which is another story).
In your case, once you get suitable pads to fit, and they are bedded in but the judder is still apparent, you may be able to eliminate it by a succession of short heavy braking with a cooling off period between them.
There is plenty of information about this and brake judder available from brake manufacturers and ways to eliminate it which makes very interesting and informative reading!

[Clifford Pope]

Many thanks - some interesting stuff on disk surfaces etc there.
As I've got the pads now (not sure which make, but CW genuine I thought) I might as well try grinding a bit off the surface. I've trued-up pads in the past with a sheet of coarse sandpaper on a flat surface. Precautions in case of asbestos, or any dust, of course.

i just wondered whether anyone else had ever encountered this problem. I've tried a Google search and the problem seems not unknown. Several car forums discuss similar poblems, and the advice generally seemed to be check carefully for rust etc, then grind down the pads if all else failed.

No comments on the anti-rattle shims, which obviously won't fit until a lot more pad has worn down.
The metal profile of the pads is correct, the same as the old ones, a good fit, after I remembered that the two are not identical, having a cut-away on one side.

Ted - re dashboard. Sorry, disposed of the old car some while ago. Somebody took all the seats and interior. I tried to extract the dash padding but found it bonded to the car structure, not a bolted-on dashboard. It was impossible to remove, it just shredded.

[johnnydog]

Sorry, Clifford, didn't mention the anti rattle shims, or anti squeal shims as they are sometimes called. I would obviously try to fit them as their purpose is to reduce movement of the pad in the caliper, which also causes noise (hence the reference to squeal). However, brake manufacturers are increasingly fitting a shim which is part of the pad and can't be removed, and are also fitting a 'crinkly' / rubberised substance instead of a shim. The other method (which has been used for years) is to put copper slip on the back of the pad where the piston contacts, which has the same effect.
As your pads are tight, if you can't fit the stainless shims, then I would use copper slip or the manufacturers own lubrication for this purpose ( I know Mintex make their own). I wouldn't fit them dry if possible.

[Clifford Pope]

The pads are Lockheed ref LDB 736. For what it's worth, the box that the last set I bought came in is marked ref LDB 735.

Yes, I always use copper slip on the back - a little smear on the steel eges too where they bear on the caliper.

[Dave B]

The pads are Lockheed ref LDB 736.

I think you've solved your own problem. CW lists Lockheed LDB 735 as the correct pads for an earlier mk1.
http://www.chriswitor.com/proddetail.ph ... 35&cat=248

[Clifford Pope]

Yes, that's obviously it. I never thought of checking the number, just asked disks + pads for an earlier Mk1, and assumed they would be correct.
I wonder what the 736 fits - they are identical in profile, just a fraction thicker.