Brake disc run out

[Stagdad]

Can someone tell me what the limit for run out is on the stag disc.I've checked mine and they are both within 5 thou total run out but i'm still getting brake judder,I think it may be my caliper pistons getting stuck on one side so the other piston is bouncing off the run out.I fitted new seals a couple of days ago but they are still doing it,may be my calipers are shot but the pistons are perfect with no wear marks.

Cheers Steve

[Kevin Garrod]

ROM says 0.1524mm or 0.006in. max.

[StagnJag]

Have your pads got the shims on the back? and are they copper greased? (Also on the back!!!)

Rgds

Dave

[Stagdad]

Have your pads got the shims on the back? and are they copper greased? (Also on the back!!!)

Rgds

Dave

No and no ,could it be that simple Dave?Thought the shims and grease were for squeal which I don't get.

Worth a try cheers Steve

[stagmuffin]

its probably just something serious steve!!!! talk to mr willwood lol.
steve

[Stagdad]

its probably just something serious steve!!!! talk to mr willwood lol.
steve

Have already mailed Chris witor about said wilwood kit but at over £700 i need to find a cheaper solution else my other project will stall for too long.

Cheers Steve

[V Mad]

Steve, are your wheel bearings tight enough? Also check tyres and wheel balance; maybe swap them around see if anything improves.

[Stagdad]

Steve, are your wheel bearings tight enough? Also check tyres and wheel balance; maybe swap them around see if anything improves.

Thanks Chris ,wheel bearings are tight with no play and I can't swap wheels because the front and backs are different size tyres and they are directional but they are all new and i had it with my old tyres.Wheel balance seems fine at any speed.

I would be interested in what run out others have if anyone has a wheel off at the moment and has a DTI

Cheers Steve

[Andrew S]

Steve, is there a possibility that you have a small amount of air behind one of the pistons?

[V Mad]

I wonder if a change of pad type (material) would be an easy fix? ie put EBC green stuff in or vice cersa, switch back to normal?

[Stagdad]

Steve, is there a possibility that you have a small amount of air behind one of the pistons?

Always possible Andrew but wouldn't that just give a spongy peddle,sub 50 mph the peddle is solid.I'm going to try the muffin mans calipers and see if it improvesCheers Steve

[Duncan Skye]

Dear Steve,

If your judder is coming from one side only, then that is that side you need to pay attention to. As per the previous comments, eliminating them one by one narrows the options remaining, but a judder (say) on one wheel has already narrowed it down to that side. Try looking at the rubbing surfaces of the disc. Has an oil seal failed perhaps at the bearing? If not and the piston seals are OK, then try a good squirt from an aerosol of Brake Cleaner and wipe dry with a clean rag. It may be worth taking the pads out and giving them a rub with some rough 'Wet and Dry' on a flat surface to get rid of the 'rubbing glaze'. If you're going that far though, you should do the same to both sides for balance.

The disc itself, though running true, may have corrosion starting from the rim inwards, or from the hub side of the swept surface which (as rust expands) will cause high spots. The disc should be inspected on the inside as well, particularly behind the splash guard as that surface is more exposed to road splash and not very visible .

Although the judder is cyclic and in sync with the rotation of the wheel, in a tight, well maintained system, an out-of-balance force may not be able to manifest itself. Wear in any part such as a ball-joint can allow freedoms of movement that, when constrained by the limits of the wear, can manifest itself as an out-of-control vibration. You'd need to check everything that can move - ball joints, bearings, bushes - even the anti-roll bar ones and nuts and bolts as well.

I hope that is of some help.

With best wishes,
Duncan, Skye

[Stagdad]

I wonder if a change of pad type (material) would be an easy fix? ie put EBC green stuff in or vice cersa, switch back to normal?

Got green stuff with drilled rossini discs all new 6 months ago,so i'm hopeing its the calipers and trying stagmuffins ones should give me the answer.

Cheers Steve

[european voyager]

Are the steering U/Js ok where it comes out of the bulkhead ? Are the bolts tight ? Are the wheels balanced ?
Mine judderd when the wheel bearing was needing adjusted.

[Stagdad]

Dear Steve,

If your judder is coming from one side only, then that is that side you need to pay attention to. As per the previous comments, eliminating them one by one narrows the options remaining, but a judder (say) on one wheel has already narrowed it down to that side. Try looking at the rubbing surfaces of the disc. Has an oil seal failed perhaps at the bearing? If not and the piston seals are OK, then try a good squirt from an aerosol of Brake Cleaner and wipe dry with a clean rag. It may be worth taking the pads out and giving them a rub with some rough 'Wet and Dry' on a flat surface to get rid of the 'rubbing glaze'. If you're going that far though, you should do the same to both sides for balance.

The disc itself, though running true, may have corrosion starting from the rim inwards, or from the hub side of the swept surface which (as rust expands) will cause high spots. The disc should be inspected on the inside as well, particularly behind the splash guard as that surface is more exposed to road splash and not very visible .

Although the judder is cyclic and in sync with the rotation of the wheel, in a tight, well maintained system, an out-of-balance force may not be able to manifest itself. Wear in any part such as a ball-joint can allow freedoms of movement that, when constrained by the limits of the wear, can manifest itself as an out-of-control vibration. You'd need to check everything that can move - ball joints, bearings, bushes - even the anti-roll bar ones and nuts and bolts as well.

I hope that is of some help.

With best wishes,
Duncan, Skye

Thanks for your ideas Duncan ,discs and pads are 6 months old and look like new and all the bushes have been done recently but as i have found with many stag spares that doesn't mean they are still ok 6 months later so i will have to go through all the joints again.

Cheers Steve