Potential front brake upgrade for A4 B5's

[Foxmeister]

Having now invested in more power for the V6, ive been looking into upgrading to maybe the usual 312mm route that most do. In my search ive came across a company that has put together aftermaket/oem kits and started talks with them regarding the actual kit and possible bulk orders to negotiate a price fior it.

Original kit i saw had Brembo four pots(something mentioned about Renault, not sure if its a standard caliper on Sports etc?) with fabricated alloy mounts, set of 321x30mm Audi S4/S6 brake disks and bolts etc to mount it.

Since making contact and asking of kits he has mentioned using brand new Wilwood Superlite 4 pots and also a choice of the 312x25 or the 321x30mm discs. Has anybody any experience of the Wilwood calipers? Are they any good etc? Would people want the Wilwoods or Brembo's ideally?(More expense i'd think)

Looking for some general feedback lads on anybody with genuine interest and any opinions or alternative ideas that may help, then i can make contact with them again and discuss more options, pricing etc.

 

[a4-rob]

Wilwoods are a good brand, alot of the cossie boys use them. Plenty of bite

 

[Jason.s]

The renault calipers would be the Megane R25/6 brembo`s. One or two S3 people run them looking at sigs.

 

[aragorn]

If your going to the effort of an aftermarket kit, i'd look at using the 345mm B6 S4 disk, as even the 320mm B5 S4 stuff is a bit lacking for a high power car.

Whats important when using random calipers is getting the piston sizes correct. Even the commonly used Porsche 996 calipers have pistons that are too small for an A4 master cylinder. The 996 Turbo ones are ok however.

 

[Foxmeister]

If your going to the effort of an aftermarket kit, i'd look at using the 345mm B6 S4 disk, as even the 320mm B5 S4 stuff is a bit lacking for a high power car.

Whats important when using random calipers is getting the piston sizes correct. Even the commonly used Porsche 996 calipers have pistons that are too small for an A4 master cylinder. The 996 Turbo ones are ok however.

Yes Kev, thats my next queries for him. What is the suggested piston area thats needed for the A4 then, do you know of the top of your head? Will check which offering of calipers can match if they do even.

Also, as said i think hes happy to tweek thinks to suit, so if the B6 S4 discs were the prefered then this can be the route we go.

 

[ScottD3]

Just passing through and having a read.

I have a passing interest but nothing set in stone.
Interested in what you come up with.

 

[docurley]

This might give you something to thing about.

http://www.audi-sport.net/vb/a4-s4-forum-b5-chassis/54871-s4-rs4-brakes-a4.html

 

[jcb]

Even the commonly used Porsche 996 calipers have pistons that are too small for an A4 master cylinder. The 996 Turbo ones are ok however.

why?

 

[aragorn]

Because 996 Turbo calipers have larger pistons...

 

[jcb]

http://www.audi-sport.net/vb/a4-s4-forum-b5-chassis/62789-more-anchors-pull-your-teeth-out.html

get some!!

 

[jcb]

yes I know the turbos have bigger pistons
let me rephrase that....

Even the commonly used Porsche 996 calipers have pistons that are too small for an A4 master cylinder.

Why? how do they compare to the stock ones when they have four pistons and the stock A4 ones have one. That one piston would have to be the size of a dinner plate to make 4 pot monoblock brembos TOO SMALL for the stock MC

 

[aragorn]

Well due to some physics that are beyond me, when comparing sliding calipers with 4 pots (or any rigid caliper) you only compare one side of the four pot caliper against the piston in the sliding unit.

I suspect that the sliding piston in effect applies its force in two directions simultaneously (towards the disk, and into the sliding mechanism) whereas the rigid one only applies it in one (towards the disk). As a result a 57mm sliding piston provides the same clamping force as a two pot rigid caliper with two 57mm pistons.

As a result, your comparing a single 57mm piston in the A4 caliper with one 40 and one 36mm piston in the porsche caliper, rather than a single 57mm with two 40's and two 36's as you might at first assume.

the 40 and 36 from the porsche caliper gives a 9% reduction in piston area over the single 57mm piston slider, meaning 9% less clamping force for a given line pressure (ie pedal input). This also results in the pedal beginning to feel a bit wooden.

 

[Foxmeister]

Hmmm, intersting discussion here, always considered more pots(pistons) better than sliding single pots naturally! Some maths needed here!

Anyway, getting back to the original topic, the reply came back more than i was expecting, here it is;

I've been looking at the specs, and numbers to see what sort of price and
kit I could put together.

I think the most realistic kit would be one that uses 312mm discs from
either the A4 or the TT. It would be combined with the Wilwood 4 pot
Superlite calipers and fast road pads. As the A4 has some strange hose
connection, it would need a pair of front HEL braided hoses to be supplied
with it.

For a one off kit, the price would be around £650 plus delivery. This could
come down closer to £600 for an order of 5 or more sets.

The kit could also be made with the 321 discs from either the B5 S4 or the
04> A6 (similar spec/price) for the same sort of price.

The Brembo kit, which would use brand new Brembo 4 pot calipers, along with
a set of Hawk HP Plus pads would be around £50 more.

All the kits use brand new parts and high quality custom designed brackets,
and come with the correct fixings to fit to the car.

I understand this is probably a little more than the second hand Porsche
kits, but the difference, like I mentioned is these come with brand new
parts rather than used calipers which would probably need servicing before
installing anyway.

I was hoping nearer the £500 mark but i dont know if he'll come back with any better. We'll see!

I've currently dug up some Porsche brakes local to me so will be looking into these now. If anybody is interested in the above kits and prices let me know and i can either sort this out or put someone else in touch if people want this deal.