996 C2/C4 Brake Upgrade - 6 Pot
Discussion
Having done a quarter of a million miles on stock C4 calipers and standard'ish size discs I fancy a brake upgrade.
Obviously the difference in caliper fixing bolt distance precludes the use of Turbo or GT3 bits without swapping front uprights so having got the measuring tape out this afternoon it appears that Cayenne Turbo 6 pots will go on with a small adaptor along with either Cayenne Turbo or 997 Turbo discs (depending on if I want solid or drilled discs).
The discs are the same PCD and the offset relative to hub face is close enough. Adaptor for the caliper is pretty simple too as the Cayenne caliper is lug mount so to fit it's a case of make a set of studs that allow the adaptor (essentially a straight bit of billet) with a couple of holes to suit the Cayenne caliper lug mounts to be be bolted to the upright via a pair of K Nuts and a slight bit of machining on the caliper itself.
Cayenne Turbo brakes give a healthy 350mm X 32mm disc with a 6 Pot that's bigger than the GT3/Turbo setup with a pad size designed to stop 2 tonnes of 4X4 so ought to be pretty fade resistant on track stopping a 1300KG C4 even with a "cheap" pad material.
These calipers seem to be used by a lot of VW and Audi tuners with reasonable results. You can even buy them brand new from the states for 800 quid from JHM and the discs are only £200 a pair as a basic Brembo supplied plain disc.
Surely it's not that easy though or everyone would be doing it? Has anyone gone down this route further and has any feedback?
I can't see why it won't work but then that is why I have a shelf full of random stuff I've purchased off e-bay having not seen how it couldn't work
Obviously the difference in caliper fixing bolt distance precludes the use of Turbo or GT3 bits without swapping front uprights so having got the measuring tape out this afternoon it appears that Cayenne Turbo 6 pots will go on with a small adaptor along with either Cayenne Turbo or 997 Turbo discs (depending on if I want solid or drilled discs).
The discs are the same PCD and the offset relative to hub face is close enough. Adaptor for the caliper is pretty simple too as the Cayenne caliper is lug mount so to fit it's a case of make a set of studs that allow the adaptor (essentially a straight bit of billet) with a couple of holes to suit the Cayenne caliper lug mounts to be be bolted to the upright via a pair of K Nuts and a slight bit of machining on the caliper itself.
Cayenne Turbo brakes give a healthy 350mm X 32mm disc with a 6 Pot that's bigger than the GT3/Turbo setup with a pad size designed to stop 2 tonnes of 4X4 so ought to be pretty fade resistant on track stopping a 1300KG C4 even with a "cheap" pad material.
These calipers seem to be used by a lot of VW and Audi tuners with reasonable results. You can even buy them brand new from the states for 800 quid from JHM and the discs are only £200 a pair as a basic Brembo supplied plain disc.
Surely it's not that easy though or everyone would be doing it? Has anyone gone down this route further and has any feedback?
I can't see why it won't work but then that is why I have a shelf full of random stuff I've purchased off e-bay having not seen how it couldn't work
Edited by poppopbangbang on Saturday 23 May 00:11
Tony1963 said:
My first consideration would be the master cylinder. If that isn't matched to the calipers, it all goes very wrong with pedal travel/piston stroke/caliper piston travel.
GT3 25.4MM master cylinder is a bolt on or 27mm 997 master cylinder is nearly a bolt on so if the pedal travel is excessive that's an easy fix.rich83 said:
Has anyone got master cylinder size and caliper piston size info? It's easy to do a few sums to see if the matching will be an issue
Not for the Cayenne calipers but the internet says they are the same piston sizes as GT3/Turbo in which case the GT3 master cylinder will keep the fluid volume and movement relationships as intended. Whether the internet is correct or not we'll find out shortly as I ordered as set of Cayenne calipers to play with over the weekend!EGTE said:
These are a popular mod for Audi B5 RS4s and they work really well. Ferodo Premier pads work well with them, too (great bite) and very reasonable.
This is partly a driver here too. I'm fed up of buying RS29's at £250 a go every 10K miles or so (10K miles for me is two or three months) so the huge pad size in the Cayenne caliper should mean equal braking performance for much less pad cost and much greater pad life!arcticGT said:
The only way pad cost is going to go down, is to switch to a cheaper pad. RS29s for the 6 pots are ~ £400.
Exactly the plan. Larger pad = more friction material on the disc surface = ability to use a pad with a per sq-cm friction producing ability that is less and still maintain the same over all braking torque. Also larger pad = more thermal mass in the pad = no need for a friction material capable of operating at very high temps.fioran0 said:
The discs are only £200 a pair because they weigh ~8 tons each. Those cayenne rotors are seriously heavy. There was a splurge of track guys running them as a cheap option on the 6GT3 for a while. No idea what they were thinking.
As a standard C4 disc is a single piece disc the weight difference is essentially only the material making up the extra diameter. It's possible to use a standard 997 Turbo disc as well, which are just as heavy as the Cayenne discs (minus the weight in the drillings ). If the weight is a concern 350mm discs are easy to buy from AP/Alcon/Brembo and a bell is very easy to draw up to suit, I could even do floating ones if I want to make the bobbins.fioran0 said:
Regarding the planned upgrade. I am a big fan of projects but I'm not sure how this one will go. I have the same calipers on my Q7, I have a 996 Cup with the normal 6 pots and my dad has a C4. The mounting holes on the GT3 and indeed the C4 calipers comes down through the area where the mounting flange is on the calipers you are looking at. Those cayenne calipers are quite a different shape on the inboard side because of the different mounting and I am not certain that there will sufficient flexibility to mount them using an adapter. I would expect that to get that mounting face to simply clear the wheel carrier will move the whole caliper itself so far inboard that it won't line up with the disc etc. This isn't something that an adapter would cure. You would be into machining of the wheel carrier etc.
Caveat is of course that I have never looked at this going that way so hopefully you figure something out.
What you are talking about is the difference between a radial mount and lug mount caliper. There is a metric sCaveat is of course that I have never looked at this going that way so hopefully you figure something out.
t load of room to do whatever you like with regards caliper mounting due to the original being radial mount and the planned new disc being 30mm larger diameter than the original :-) Adaptor carries the Cayenne caliper on the outboard face so it is no issue getting the caliper on the centre line. It may be neccesary to flat some faces on the Cayenne caliper or similar but nothing beyond what can be accomplished with ten minutes on a mill. The Cayenne lug mounts are within the length of the original caliper radial mountings so it is very easy to offset them as required as you are not trying to get two fasteners into the same space.This is why I can't work out why no one has done it. We'll find out if there is some major reason why shortly as I have all the bits on the way! Thing is with the C2/C4 upright you can't easily fit the GT3/Turbo brakes as the centres of the caliper mounts are different on the 6 Pot. It's actually more machining effort to fit these as you'd need to reduce the height of the mounting bosses on the caliper and machine some offset studs with a locking plate or similar to account for the difference.
fioran0 said:
One other point. Those calipers use a strange shaped pad. It isn't the same as the GT3/Cup pad shape. I know because I tried to use a bunch of RS29 I had for the Cup in them and it wasn't even a close thing. Something to keep in mind if you get to that stage.
The Cayenne caliper carries a larger pad than the GT3/Turbo caliper. I think the piston locations may be silimar within the caliper but the shoulders of the pad are far bigger. With a pad size designed to accomodate the heat generated stopping 2.2 Tonnes of 4X4 repeatedly you don't need expensive/exotic pad materials when you use the same pad on a 1.3 Tonne vehicle 
One all the bits arrive and I've had an accurate measure I'll quickly spin some brackets up and we'll see how close it all is. If it does work I need another set of front 4 pots to put on the back with a 330mm disc..... then all I've got to do is see how the ABS deals with it!
Escy said:
Did you ever finish this?
Yep many 10's of thousands of miles covered on them. They will always need to be mounted via a bracket to adapt the hole spacing and offset. Lug mount simply won't work due to the offset required for the 997 Turbo or Cayenne disc. Plus it is a far, far nicer way of doing it!
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