Which rear brakes for Coupe?

[HPmuirt]

OK guys, my rear calipers have had it and the MOT is at the end of the month, so it is time to give my rear brakes some attention.

I have the Porsche 996 upgrades at the front so the obvious route might be to do 'Paul's rear brake upgrade' but I have new OEM rear disks and braided hoses so replacement calipers is the cheaper option.

I seem to have 4 options, all of which have both pros and cons, which as I see it include: -

1. OEM replacement calipers
simple, mid price, OEM, good pad availability, no hassle with disk machining, but no performance improvement

2. Rear brake up grade kit from Quattro Corner
Expensive option, non standard disks which need machining every time, best performance, pad availability?

3. Replacement Aluminium calipers from Custom Auto Craft
Cheapest option but non standard calipers = pads not always available in chosen material (e.g. Ferodo 2500) and potential for pad availability issues in future.

4. BK020 302mm conversion from Ultimot.de
Most expensive option if new calipers required but uses OEM calipers spaced further out so should give better breaking from same swept area.

We all know that both Paul at Custom Auto Craftand Pete Reeve at Quattro Corner are great suppliers so this is not a thread about the suppliers, just the options. What I (and others who read this thread later) need therefore is feedback from people who have been through this and what they think about their chosen route in terms of value for money vs convenience vs performance.

Comments and recommendations please?

Cheers n

Si

[rj scotty]

Firstly let me start with

I would go standard OEM. The front do most of the work.

Spend the extra cash elsewhere

cheers

rich

[AndyP]

I'm almost certain the C.A.C calipers will take a std Audi fitment pad. check with Paul, but this is the way I'd go.

[Error404]

I'd go with the 280mm vented upgrade, the stock rears are pathetic by modern standards.

[s2_wot]

There is another option.

If you look at kit number BK020 on ultimot.de it shows a 302mm x 11mm disc and a bracket that locates your existing caliper at a larger diameter.

The ultimot site is a bit of a disaster so I can't put up a link.

[S2central.net]

I wouldn't worry about the simple mods to the B7 300x22 discs. I did mine 5yrs ago and they are still great. In fairness I do small miles. The A8/S8 carrier is the most expensive aspect of that choice but I don't regret doing it.

[andy10v]

2. Rear brake up grade kit from Quattro Corner
Most expensive option, non standard disks which need machining every time, best performance, pad availability?

I went this way and love it, however I needed to replace pretty much everything so it was a no brainer, if I just needed calipers it would have depended on the cash flow at the time. More leverage means there is more chance of the handbrake working

Turning the discs is not really a hastle as long as you plan in advance, and have a friendly machine shop.

[HPmuirt]

There is another option.

If you look at kit number BK020 on ultimot.de it shows a 302mm x 11mm disc and a bracket that locates your existing caliper at a larger diameter.

The ultimot site is a bit of a disaster so I can't put up a link.

Interesting, thanks for that - I have updated the first post to include the option for future readers. IMHO a damn expensive option - in fact nearly as much as the full upgrade from Pete and then I still need to buy calipers on top

Any more rear brake upgraders out there care to comment?

Cheers n

Si

[s2_wot]

Interesting, thanks for that - I have updated the first post to include the option for future readers. IMHO a damn expensive option - in fact nearly as much as the full upgrade from Pete and then I still need to buy calipers on top

Any more rear brake upgraders out there care to comment?

Cheers n

Si

It's too expensive IMO but performance would be good me thinks and it'd look good. The unusual shaped bracket could be made locally I'm sure (bambridge?). I'd love to know what the rear disc is off. It looks like a porsche item.

While we're on about rear calipers biggred.co.uk do repair kits and the likes of GSF sell refurbished calipers on exchange.

[Fat Audi 80]

Do bigger rear discs "feel" any different, does the car dive less? Just wondering. I always assumed the fronts did 80% of the work so a rear upgrade is hardly worth it.

However, if you already have 996 fronts or equivalent, I would imagine a rear upgrade would provide more balance again....

[s2_wot]

Dive will be the same and even with a rally car anti dive suspension maximum braking force that can be applied without locking up on any axle will be the same. CofG / weight distribution are the key factors.

If you think about it the moment around the CofG under braking will be constant irrespective of suspension travel up to the limit of traction.

[Error404]

Just upgrading the front I think does affect dive, since larger diamter discs have more "leverage" for the same pedal effort, the larger diameter discs enable the braking force to be applied more efficiently. so when you upgrade the front brakes an not the rear proportionately the brake balance effectively changes as the upgraded axle is able to make better use of the brake force applied.

[s2_wot]

The driver could well be feeling effortless braking and the result being the nose of the car is taking a dive with upgraded fronts only.

But the degree to which the nose will dive in an emergency stop is a function of the weight distribution and the CofG while the friction between the tyre and the ground is the limiting factor. (assuming like for like comparission with the same suspension setup before someone says the car will dive less with a stiffer suspension).

It can be argued that with upgraded front brakes only that the front tyres only are being brought to the limit of traction more often. Then the back tyres are not getting close to the limit of traction.

In this case the overall braking effort of the car could actually be reduced because the rear brakes are doing very little while the fronts are pushing the limits of traction.

It doesn't matter if the car dives more or less, the key is to try to get maximum braking force to each wheel without losing traction on any wheel so the brake pressure can stay constantly applied rather than being switched on and off via the ABS valve. The front axle should lose traction 1st but we all know that anyway.

To add to the rear brake upgrade question, all that's needed at the rear is a slightly bigger piston on the same disc to increase the brake effort. Or a marginally larger diameter disc and the same caliper. The latter being better in respect of pedal travel.

Even venting the rears is overkill I think. I never managed to get standard rears to go on fire, so heat isn't a problem. Overcooling could be an issue though.

[HPmuirt]

I agree that we are not running the rear brakes to the limit of traction whether using standard or 996 front brakes and so there is room for improvement.

In theory an S2 should be able to apply a greater braking force to the rear wheels before they lock as they are driven, compared to the FWD Coupe, so again a rear brake upgrade looks like a good thing.

Therefore from my original list of 4 options, I guess I should discount option 1 (new OEM calipers) and option 3 (new Custom Auto Craft calipers) as neither provide improved rear braking.

Therefore, I again ask, who has the rear brake upgrade and how does it feel?

Cheers n

Si

[S2central.net]

Got to say I noticed an improved 'feel' with the 280 vented rears - much of that is probably cos it replaced really old & tired original calipers and crusty discs. I am still on stock fronts - incredible I know but that is life.