I don't know why nobody makes a silicone dust boot for racing calipers, it should hold up to the heat better and less dust in your pistons is a good thing.

Yeah, or viton or something.

I think it has been tried, but I havent run across much of anything that wont burn into dust (even silicone) under race conditions. This is not too much of an issue with race cars because racer are (or should be) fanatical about claning/inspecting thier brakes. I had some 996 GT3R Cup calipers that were literally cooked in less than three World Challenge races. Huge monoblock calipers and the paint was turned from Porsche red to 60's Vega maroon. All of the rubber bits were toasted and crispy, and it was cheaper to just buy new calipers than rebuild them...

And on that note...

Here is a link to Damian's dual master, balance bar setup:
https://www.rx7club.com/forum/showthread.php?t=723283


And another to Max Cooper's site using the Wilwood rear caliper:
http://www.maxcooper.com/rx7/how-to/...ear/index.html

Here are a coulple of pictures of my tilton dual MC brake set up:
https://i211.photobucket.com/albums/...D/LS1FD004.jpg
https://i211.photobucket.com/albums/...D/LS1FD018.jpg
https://i211.photobucket.com/albums/...D/LS1FD168.jpg

I'd prefer to do it the way Bill is doing it and keep ABS. Unfortunately, the cage that was in my car when I purchased it did not afford me that luxury. I guess I could look into placing it somewhere inside the compartment and building another bulkhead for it

So you do you heel and toe with the pedals way over there? That's the big reason I see about not using a Tilton pedal box.

That picture is kind of deceiving. It's not as far as it looks(though it is farther than a stock configuration). I added the widefoot accelerator pedal extension from David B. and have no issues heel toe downshifting. It feels just like my other track FD's distance wise. I roll with the ball of my foot for reference. I'll see if I can't get new pictures in the next few weeks that show the finished product. I still need to play with the master cylinder sizes some more to get it dialed in a little more.

http://www.petting-zoo.net/photos/RX...IMG_2154-l.jpg

I haven't driven this configuration yet, but I'm actually a touch nervous that the brake is too close to the gas. :-) (All the tar and crap is gone now...)

Very interesting thread and something to think about. What is interesting is the effect of the track you race on. At Mosport I struggle to keep enough brake temp in the pads and rotors. I am running PFC 81's in the front of my ex Speed WC Cougar with no brake ducts and I never can get them to a sustained 700+ degree reading. I am looking at going to softer pads, just to get some braking effect for the first 3 laps.

With my RX7, I run stock a set up with unvented rears and with Hawk Blues I can get about 4 weekends out of a set of fronts. If I go to a tighter track, I can melt the seals out of a set of calipers in less than an hour and turn the same Hawk Blues into crumbly sandstone with bent backing plates, LOL. I really need to upgrade and I am running about 280 hp and a 2450 lb NA car.

Eric

Update: After the first event with my new brake set up (see post #22) at Infineon, I am very pleased. I ran Hawk DTC 70s front and rear.

Guy

Well, I fried my rear brake piston seals last weak at WGI (actually probably at Summit Point last month)—only five days on what were almost new calipers, so I've got feelers out to StopTech on a rear kit with more pad volume. Looks like the rear RX8 kit might adapt well.

Anyone have a calculator or spreadsheet or something to help figure out matching rear piston sizes... I'd like to match my front kit, but there are variables such as 2 or 4 piston rears, and larger rear rotor, and different shaped/size pads that will factor in. I'd like to keep ABS and OE (or 929) MC.

Here is one from GooRoo / Andy:
https://www.rx7club.com/showpost.php...&postcount=168

Yep the one problem with any BBK and leaving the rears stock or w/ 99s is front bias which if you're not racing or trying to set lap records it's actually a safe way to set up the car.

Sounds to me like fingerlock and shipnout have the simlple race application answer so if I was racing that's likely the route I'd take. If money was no object I'd run a wheel and tire setup like blackey and some sort of crazy PFC custom brake setup with manual dual master cylinders etc... so if I needed to lock em down in the blink of an eye it could be done. On a lot of high dollar very fast cars I see PFC setups and I think they also make the best pads hands down which really says something in such a competitive market.

PFC calipers are bad ass, but they are horrendously expensive.

The StopTech front kit doesn't have a bias problem so much, because instead of the stock four 36mm pistons, they actually use two 36mm, and two 30mm to compensate for the larger rotor and bigger pads. Most people on stock setups used a lower torque pad in the rear, whereas I try to run them even because of how it's balanced.

Big reds are 36/44, and ST's for the '99 rears are 34/36. I'm poking around to find the Brembo and AP 5200 sizes.

Yep typically 500 to 1k more than brembos kits.

After many ride alongs I can say you have the same front bias problem I do :) Piston size is important but what's killing us is the pad and rotor size up front vs rear not so much the piston size.

Peter,

The Brembo GT1 calipers use 40/44 mm pistons and the Wilwood 4 pot calipers have 1.12 in (28.5 mm) pistons. As mentioned above I use the 929 MC (1 in) and a Tilton bias valve installed in the rear circuit.

I'll post up a short video clip which shows the result of too much rear bias...:eek:

Guy

The Wilwoods NDL's I thought had 1.12 and .810 pistons, which would be massively front-biased with those Brembos, 74/26, vs. the stock 68/32, but if you've got them w/ all 1.12 it should be about 69/31.

This based on Howard Coleman's spreadsheet tool (which factors rotor diameter but not pad surface area) and not factoring your bias valve.

Yes,

The Wilwood NDL #120-5074 calipers have four 1.12 in pistons. I'm not sure to what dimension the 0.810 refers. (usable piston depth in inches perhaps?)

Guy

I started doing some preliminary measurements, and a possible problem in the rear may be clearance for ST calipers. You can't really move the rotor too far inboard, because the forward portion of the hub carrier where the toe link mounts is a limiting factor, and even with the new "mini 4-piston" (ST-41), you'll need about 3.375" at the minimum from the backside rotor face to the outside face of the caliper.

Blackey,
Let me know if you've made any progress with StopTech. My source hasn't responded yet.

As promised, a video showing the result of too much rear brake bias :eek:

I'm just glad this happened in T2 and not T10...

Guy

^^^^

If the stock bias is about 68/32 and most big brake kits are too front biased, about 67/33 to 71/29 most of them, then what does everyone see as mostly ideal if you don't have adjustment? 65/35?

I run the Wilwood Superlight SL-6 thermolock caliper. It basically has a stainless can that fits inside the piston and reflects the heat back to the pad. I've run the brakes for three years now without any deterioration on the rubber. (400 rwhp 2300 lbs FC with yokohama slicks) Previous to that I built stainless heat shields that fit between the stock calipers and the brake pad by clamping to the back of the brake pad. Worked OK, but the stockers still burned up after about a year.

-Trent

Brembo caliper is 36mm / 40mm FYI

Wilwood makes two calipers with 1.12"x4 pistons which is about perfect for balance. The Forged Superlite

http://www.wilwood.com/Calipers/Cali...emno=120-11125

Can be fitted up to the Racing Brake rear with very little work. I had a local shop make a set of brackets and they made a jig so they can make more (Ian Gordan Racing)

Can you provide me with any info on the rear Wilwood stuff? Maybe a part # for the caliper and bracket?

I assume you are using the larger "99 spec" Mazda rotor.

Hey Nath, responded to your PM on norotors.