Experimental rear brakes

[MD]

Anybody done anything different to the transaxle rear brake set up for racing applications that works really well?

Inboard/outboard-doesn't matter.

What calipers, rotors, pads ??

[hammer]

MD,

My Joolie runs vented Ford Courier rear rotors, 105 calipers and DS3000 pads in the traditional inboard configuration. Combined with the big 4 pot RX7 fronts it stops beautifully. The only pain in the proverbial is changing the rear pads and accessing those goddamn bleed nipples.

Cheers,

Brent

[Cool Jesus]

Hah, I've just been writing that ive not come across any threads on an alternate rear set up. Although, not a track set up, I'm looking at retro fitting 147 rear calipers on the transaxle. A mock up indicates its possible with a made up bracket. May even be able to lower them at the back for better access a la auto delta style?
Hammer, was there any fabrication required with your setup?

[MD]

Hammer,

The 105 caliper. Is this an original rear or front caliper?
The DS 3000 pads come in a thousand  formulations. Which one?

Access to the original caliper location can be improved upon by creating a removable inspection panel over each one in the boot floor. Best way to fix the inspection panel is to use say 6mm "nutserts" in the flooring and use some 6mm socket head bolts to fix in place. Worked well on the "Brick"

Mr Cool 

I have heard (but not seen evidence) of front Sud calipers being used. Would you say the 147 caliper idea is the same?

[Cool Jesus]

It's only early days for this calliper swap, the idea was only born when I was cleaning up my daughters brakes for paint this week. I like the inspection hole idea, brilliant. 

[Mick A]

For my race car, I took my GTV6 rotors and callipers off the front and moved them to the back and outboard. And put 305mm GTA rotors and callipers on the front. Together with a pedal box and balance bar, it's fantastic.

[MD]

Aha that sounds like we're cooking with gas..
Obviously no mechanical hand brake left or do you use a hydraulic replacement?

So those rotor diameters and pad areas appear to work well in combination with a balance bar. I don't use a balance bar as two cylinders would foul my front end bracing set up so I might have to trim the rear pad area if it is over braking the rear.

Fortunately I have a couple of sets of the GTV6 Brembos so that's no hassle and my rear brakes are already outboard so it should be a simple enough modification.

What pad formulation are you using please?

[Mick A]

Correct, no handbrake needed for a race car.

I use QFM A1RM pads front and rear because I can afford them and they perform well, and without trying to sound up myself or anything, I brake bloody hard, and late, and they stop the car beautifully every time and also the compound isn't too hard, so they don't fuck the rotors as quickly. I've gone through maybe 5 sets of pads and still haven't had to change rotors.

Great pads for the price, half what you pay for a set of EBC's.

I've got some old pics somewhere on my hard drive of the fabrication process, I'll try find them.

[MD]

Well that's great news. I use the same pads at the moment and also find them good. I don't use any extra cooling of the rotors at present but I think I need to use some heat recording paint to see just what temps my brakes are running at as ideally I would like to keep the pads operating in within their heat range. Without this info,  I could be cooling them down too much or not enough so I guess that has to be my next step.

I am convinced however that the rear brakes on the transaxle are typically very much underutilised and yet this is such a huge asset over any front engined/box car and I am determined to fine tune this pat of my car. Even on my road going GTV6, I have dispensed with the in-line rear brake bias unit and the car brakes much better-rain or shine.

Thanks for sharing.

[Mick A]

Do you get brake fade with your current setup?

[MD]

No.

[Mick A]

Probably not worth worrying about all that R&D until you are braking a bit harder and cooking the brakes in the current setup?

[Duk]

Why not add a bit more rotor and a lot more caliper to the rear, MD???
If you've got R32 GTR front brakes, why not use the slightly smaller R32 GTS-t front brakes at the back? You may have to play with master cylinder sizes and fiddle with you bias, but if the rears can be better utilised, I say do it.

[MD]

A little background.

Last season, spent most of that time bedding in the suspension set up and getting braking feel under the belt with a street engine and some gearing tweeks. At the same time getting some track time and all that it teaches you including how tyre walls feel ! 

Call it training.

Now with a bit more bravado and thicker underwear, I have revised the power plant and put in a supercharged new motor. The car now hauls arse. The corners arrive a lot quicker and the brakes need a review to be up to the task. You could say judging by the white knuckles that I am braking harder.  Hence why I put the hand up for some feedback.

My full Nissan conversion works very well but I do like the idea of using the GTV6 Brembos at the rear for just a bit more bite and I am pleased to have been advised by Choderboy that this set up works well. Always good to know one is headed in the right direction. I use a tandem master and for reasons explained before, I can't use a balance bar. All I can do is start off with perhaps a larger pad area in the rear and if it is over breaking, either change pad formulation or just reduce the area incrementally until a balance is arrived at ( bit of stuffing around for sure). I have used in-line balance adjusters for the rear brakes in exactly the same configuration before and it makes little difference so I  think formulation or area is the way to go with larger rear calipers for the experiment.

The other factor that is different to your set up Choderboy is my rotor diameters which are 298 front and 300 rear and so the rear leverage is more than the GTV6/Ford Courier rotors already. However the rear pads are typically street area of around a matchbox size which is what started me thinking...

Thanks for the discussion fellas.Not all people are willing to divulge racing set ups and and so your contributions are all the more appreciated.

[105gta]

Hi MD, just to put my 2 cents in, as you know I'm building my gtv6 and my intended (well I have all the parts just have to get around to it) rear brake set up is bmw e46 m3 rear discs 328mm with the factory front brembo caliper.  Outboard of course! My fronts are Evo 9 brembo calipers with Audi B7 RS4 front discs 365mm (full floating discs) which some will say are way too much but my car will never be as light as yours with the supercharged v6 in it. Mind you this requires 18 inch wheels to clear the fronts.
The BMW rear discs are cross drilled so although slightly bigger in diameter I will lose a little in contact area..
As for pads that will be experiential as you plan to do. I'll probably start with pagid's and see where it ends up.. But with keeping with these calipers, the pad choice is huge and reasonably priced considering their importance