Big Brake Upgrade

[Lee S]

Hi.

My D3 4.2 TDI has the 360mm front and 310mm rear brakes. I sometimes find the brakes a little lacking. They're not bad. They're just not good either. I want something a bit better but without breaking the bank on ceramics or things like Brembo/AP after-market kits.

Now, I was recently told by Audi (whilst having some other work carried out) that the rear discs were "fairly well lipped" and that the rear pads were 80% worn. In other words they need replacement sooner rather than later. So I thought I could do an "S8" brake upgrade starting with the rears.

As well as the new discs and pads I'd need anyway, I could just buy the larger 335mm S8 rear discs and associated pads and then I'd just need new backing shields and new calliper carriers to space the "universal" rear callipers out to fit the bigger discs. Then when the front discs and pads need doing, I can replace them with the bigger 385mm S8 discs and pads and again new calliper carriers, etc.

a) Has anyone done this kind of upgrade before and is it worth it, or would I be better off ploughing the money into better discs and pads at the current size?

b) Would having bigger, better, newer rear brakes screw up the braking balance badly if I left the fronts as the 360mm standards until they needed replacement?

c) Do I need bigger/different front callipers or is the different part number just down to the colour/coating on the S8 callipers? Part numbers for the callipers seem to be as follows:

• 4.2 TDI 360mm disc (PR-1LL,LM) - 4E0615123 (only one part number listed but with quantity 2 off)
• S8 385mm disc (+PR-1LK) - 4E0615123D (left black) & 4E0615124D (right black) - why are these handed, yet the above aren't?
• W12 385mm disc (PR-1LJ) - 4E0615123E (left) & 4E0615124E (right) - again, why are these handed, yet the first aren't?

The part numbers for the guide bushes, retaining springs (albeit with an S8 printed on them), pistons and seals all seem to be the same so is the only difference the larger disc and the different calliper carrier? If so that would make life a hell of a lot easier. Even the backing plate for the 360mm and 385mm seem to be the same part number on the front.

Any other comments?

[mattylondon]

I have the 360mm setup and have the same thoughts as you regarding the brakes are a little lacking.

Waiting at home to be fitted are a set of W12 front calipers and carriers, it's a straight swap. Not yet bought new 385x36 discs.

A few forum members have done the W12 caliper upgrade.
http://forum.a8parts.co.uk/showthread.php?t=8840

[Lee S]

But do you need different calipers or just the caliper carrier brackets? What's the difference with the part numbers? Have you checked the physical size of the W12 calipers against your original 360mm spec calipers to see if there is any difference?

As you can see, I'm trying as hard as possible t do this without having to change the calipers... If the pistons and guide pins are the same, but the caliper carriers are different, is that not enough to cater for the extra 12.5mm diameter?

[mattylondon]

I have checked and the 385mm caliper is subtlety larger than the 360mm. So caliper, carrier and discs are needed for the swap.

[Lee S]

Baaah !!! What a nuisance.

The rear callipers are all the same regardless of disc size... even the massive 356mm armoured car rear discs use the same calliper. Might even go for those instead of the "puny" 335mm on the back.

Not sure I understand why they'd build a whole different calliper using the same size pistons AND different mounting with the different calliper carrier just for 12.5mm. Doesn't seem to add up. If the calliper was bigger why didn't they just incorporate the 12.5mm in the actual calliper and use the same calliper carriers?

Matty, do they actually measure differently or are you saying they just look subtly different? Has anyone else measured the difference with a tape measure?

Would the addition of a letter at the end of the same part number make for a whole new part or just a variant of the same part (such as black lacquer on the S8 calipers)?

If they're deffo different then I will have to start looking for some of the bigger calipers I guess.... Meh !!

[mattylondon]

If I could jack the car up a measure the 360's I would

But best I can do for now is show the visual difference by photos off the net. Left is an S8 385mm, right 360mm. I'll make my own side by side photo when they eventually go on.



The addition of the letter at the end can make for a completely different part, (as I found out matching ABS units) But the difference between the S8 and W12 is probably the black lacquer only.

Hope that helps a bit