RS3/TTRS Calipers on S2 Coupe

[quattrodave]

Hi Guys, would like some opinions on front brake upgrade using RS3/TTRS 4 piston brembo calipers rather than the popular 996 calipers.

Reason as follows:


1. Can get a fully reconditioned pair of calipers in red with brembo script for £350, 996 calipers are around the same price on ebay but not reconditioned.

2. RS3 piston sizes are supposed to be 40/44 so larger than 996 calipers and very similar to the original G60 twin caliper (40/45) so pedal feel will be the same.

3. Caliper brackets are available for around £150 shipped to UK from Epytec in Germany.

4. The brackets allow use of the a8 323mm disc (cheap).

5. Pads are available for £35 a set.

Thought its something a bit different to the 996 route and effectively uses an oe Audi caliper and I don't need or want to go to 18in wheels it will fit under my 17s or maybe even 16s in the winter (if not I also have a cheap and cheerful A3/TT 312 caliper adapter, A6 314 disc and 57mm piston A6 calipers, again keeps pedal feel similar to riginal g60).

All in with calipers/discs/adapters/pads the RS3/TTRS conversion comes in at about £625, I could do the 996 route for maybe £600 with non recon calipers.

Not worried about the reputation of TTRS calipers, all the problems were I believe pad related not with the calipers themselves hence the glut of 2nd calipers around a few years ago.

I also believe RS3 calipers are similar to the Aston DB9 calipers, anyone done this conversion before with the DB9 parts ? or with the TTRS upgrade ?.

Note I do not want to go to Zr17 or 18 (sorry Albert) 6 pots and according to 2 wheel folk law radial mount calipers are better than axial mount (can anyone explain).

Opinions please.

[Error404]

Don't forget the RS3 calipers have twice as many pistons as the G60s
I don't think it's been a common conversion due to cost and availability. The 996s are a proven setup, the reported RS3 brake problems might have scared people off. I'm sure they're perfectly fine calipers.

[Big Lee M]

I don't think the disk you want to use will be big enough as the standard RS3/TT RS use a 370mm. I've been looking at them for my Leon cupra, I know they can be run with the standard 345mm cupra/s3 disk.

[quattrodave]

Pistons,
Hmm well after much research on various technical sites the concensus is that on a fixed caliper you only count 1/2 of the piston area so a 4 piston setup only counts as 2, the wisdom being that on a sliding caliper the fixed side of the caliper (where the piston(s) is/are) does double the work as it also pulls the sliding part across. (effectively the fixed caliper pistons only move 1/2 the distance of those in a sliding caliper so pedal feel should be the same)
Believe me I have seen many posts (some on this forum) on this being the way it works. There was a post some time back on this very subject on this forum concerning rear 996 calipers being used on the front of a UR and the pedal feel being quite numb (as in hard) and the car brakes not working very well due to the small pistons meaning that you only needed 1/2 the travel on the pedal to compress them the same distance as normal with a G60 caliper (and if you do the maths 4 small pistons area on a 28/30 rear 996 caliper is pretty close in area (2644 sq mm per side) to 2 std G60 pistons (2847 sq mm per side) so if only 1/2 counts then its 1322 verses 2847 per side which explains why the pedal feels numb, OK back calipers also count in the maths but you get the general idea.
Discs
Hmm, the actual Epytec conversion is made for the 323 disc but I do understand what you mean see here
http://www.ebay.co.uk/itm/3217916270...%3AMEBIDX%3AIT

Think about it Audi fit the same single piston calipers/pads to discs that vary in size from 288 up to around 345 and if you look at the multi piston calipers from a 996 they have a very wide disc size spectrum.
One good thing is that with a spacer between the caliper/adapter different (as in larger) discs could be used if you wanted to go bigger at a later date, whats the biggest disc that the 996's have been used on ?

[Error404]

Not everything you read on the internet is right! Brake line pressure still acts on all the pistons so for the same line pressure the larger piston area exerts more force, simple as that.

[quattrodave]

All parts now purchased for the conversion which may take some time as the S2 is currently lanquishing on my drive awaiting my 90 quattro 20v engine rebuild completion.

However costs were:

Calipers £350 (reconditioned TTRS brembo's 40/44 mill pistons) Core supplies Ossett (advertised on ebay)
Pads (borg and beck) £33.04 - ebay
Caliper pin/fitting kit £14.95 - ebay but from brakes international Rochdale
Discs pair Bendex £40.59 (A8 323mm 30mm vented) - ebay
Caliper adapters £144.38 - german ebay epytec shop

Total cost for conversion £582.96 final thing is to get suitable brake lines when I do install so not too bad a price for effectively all new parts.