Stoptech 14" 6 piston and 13" 4 piston rear kit?
 

I've been running the Brembo 13" front Gran Turismo kit with the Racing Brake rear kit this season on our Rx7 road race car. Unfortunately it has proven to not be enough brake for the speeds our car is going.

I'm thinking of having a 14" Stoptech (355x32mm) and 13" Stoptech (332x32) rear kit custom made.

I've priced it out and I think I can get it done for for around $2250 front and $1850 rear.

Anyone else have a kit like this already out? I'd rather buy it than make it if I can, but I couldn't find one, especially in the price range.

Anyone else interested?

I would not use Stoptech if they gave me the product for free.

What exactly are the issues you are having, what is your specific setup (car weight, class, etc) and which tracks are you running?

The Gran Turismo kit is not an actaull race kit, so my first thought would be to upgrade the kit you have. Running a 14" rotor is good if you have the wheel clearance and do not mind the extra weight. Can make more specific recommendations once I know more about your setup.

I have always heard good things about stop tech, has that changed? For a long time I have heard that willwood makes not so good brakes at the low end of their product line, but they make ok stuff at the top of their line up of brakes.

Not sure what the specific issue is with StopTech. It's a fairly proven package.

I'd be interested to hear what sort of speeds you're running and details on your car that are making the existing kit not enough, and what ST might do w/ regard to a 14" kit. There would be the issue of what to do with the master cylinder with that much piston, and what you might do about an e-brake if you use ST rear calipers.

I have had issues with StopTech and thier "engineers", going back a few years that I will not get into on a public forum. I am aware some things have changed there but I still consider thier product standard at best if not substandard.

In order I choose to use:

AP
Brembo
Wilwood

I have a set of FSL 6-pistons here for my car, but may never use them, as a set of AP calipers may have come available.
When racing Porsches in the past I have noted:

Brembo - Race calipers vs street calipers are very different, although most street calipers can be upgraded.
Wilwood- work well, only issues I have ever had has been with the older Dynalite style calipers using serious slicks (10"wheel fnt, 12 or 13" rear) after a season or two the caliper would have flexed to the point we replaced them out of hand. At 110 or so a caliper at the time, it was almost as cheap as replacing pads. The newer calipers are much improved and have used several sets of FSL calipers and they also work well.

I think too much emphasis gets placed on the caliper or brand of caliper or size of rotor and not the actual job the brakes need to do, so most brake systems are less than optimal.
I have a friend who is using the D2 purple 6-piston calipers, which are clones of AP Racing calipers (co much in fact the D2 parts can be uses in the AP calipers and vice versa) and other than the anodizing turning brown from the heat they have worked flawlessly despite being a "lesser" caliper.

Stoptech has been used in a lot of forms of racing. http://www.stoptech.com/proven_techn..._success.shtml While I agree Brembo Race and AP are good calipers I think Stoptech is as well. Individuals can have issues with any of the manufacturers. AP is owned by Brembo FYI. The big issue with Brembo and AP is the cost of consumables (rotors, etc...). Figure about $1000 a set for new rotors. Stoptech can be done for half that. We'll size the pistons to be used with the 15/16" Mazda 6 master cylinder.

Our car is a bit extreme. It's LS V8 powered (about 460 at the wheels - soon to be close to 600) and weighs about 2600. We run 12" wheels all four corners with 315 fronts and 335 rears. We can reach about 150 at Thunderhill, 145 at Laguna, and 130 at Infineon.

We're running SCCA ITE this season and have won 6 of the first 8 races. Only races we haven't won are one where we had an electrical gremlin while leading and the season opener which we blew up the stock diff before putting in the Ford 8.8.


http://www.norotors.com/index.php?ac...ach=1497;image

http://www.norotors.com/index.php?ac...ach=1499;image

Rotor costs are what you are willing to pay I suppose. I tend to use Coleman or PFC rotors. Last I checked Coleman 12 1.1 rotors were 140 per corner, fairly economical really. Not sure about Brembo rotors BUT they are likely to become insanely hard to come by now that Brembo has turned pissy and are only shipping containerloads. I use PFC pads, and while not cheap, tend to last very very well.
As always YMMV, but I would think your streetcar Brembo Calipers with drilled SS pistons, TI heat sheilds, PFC 97 or 01 pads and Coleman or PFC 1.1 rotors with adequate cooling should do you very well. On the SWC C5R Vette running 500whp, 2800+lbs, using PBR (OEM Vette) rear brakes and 13" 1.1 rotors with AP calipers worked perfectly.

Have you got any from Coleman lately? I've tried e-mail and phone call and can't get anyone.

Actually no I havent, but maybe I should call over there and see whats what

So what about the brakes isn't working?

Are you looking for more brake torque/stopping power, or are you having trouble with rotors lasting? You're making a lot of power w/ a lot of tire for sure, but those aren't insanely high speeds (maybe they are for those tracks)—But It's not uncommon to see 150-160 at VIR, WGI, and SPR in a street car.

This photo of clearly shows the limitations of Bill's current brake setup.

http://grandrants.files.wordpress.co...rubble-car.jpg

So Bill, what's in the works for the motor? Turbo, turbine, supercharger a V-12 swap from a P-51? Will you be achieving escape velocity before T1 at Thunderhill?

Sarcasm Saturday...

Guy

No the motor is ten years old and it time for a refresh. We'll probably put an LS3 in it for next season.

That along with a Racing ABS system and bigger brakes should put us in good shape for the NASA Nationals.

Bill, I look forward to seeing how the new brakes work out for you. I've ran all of the current rear set up's(99+, racing brake) and the results are negligible at best from the stock rears as I'm sure you already know. BTW, how is the S2000 ABS working for you?

Pete, you should check out Bill's car. You would really appreciate his set up. It's similiar to my car, but 10x nicer and about 150 more rwhp. He is also running JRZ's, so you might hit him up for some realworld feedback. His car is def. a sub 2's car at VIR.

Awesome video of Bill's car from Laguna Seca: http://www.norotors.com/index.php/to....html#msg14063

Brent

Bill,
You have a PM :-)

Is this the blue FD? Scott/2mchpwer's car from NJ?

FWIW, Chris/Hyperion, another very fast LSx powered FD in the Bay Area, has had challenges getting his car slowed down in an acceptable manner at track days. He is on the RacingBrake kit.

It seems that once you get to those power levels on the FD chassis on a road course, the regular off the shelf stuff doesn't seem to be sufficient. I pitted next door to Jack Mardikian a couple of years at a NASA event/race when he was running his Civic in H1. He is a very fast driver and has a very nicely setup turbo rotary FD that is very fast. The build thread is on here somewhere in the Twins Turbo thread. He advised me that none of the "street car" big brake kits would work well enough once you reach a certain level of speed and talent. He recommended AP Racing Brakes.

Hope that helps.

Guess I'm wondering how everyone is making the distinction between "racing" brakes, and "Street" big brakes, and what sort of speeds (not power levels) are dictating what need (is it cooling/heat resistance, actual stopping power?)

Most of the calipers and rotors used in "street" big brake kits are racing calipers and rotors with dust shields and anti-rattle hardware.

I think the Brembo kit I have would be fine for 90% of the guys out there. The problem I think I have is balance. The rears have very small pistons. This pushes the balance to the front. I think what is happening in my case is just the rears are not up to the task. We upgraded the rear rotors to the "Racing Brake" (Racing brake is an actual company FYI) version, but the caliper is just too small to do anything. We went as far as to remove the proportioning valve to get more rear brake, but it really doesn't matter. Now we are no where near stock, so take what we have almost as a different car. In order to balance the rear brakes I need a bigger rear caliper. Since the Brembo's are just marginal in the front (rotor cost / replacement - not braking force) it seems like a good idea to design a good front and rear kit complete. I'm setting the rear brakes at about 58% of the total braking force which will be a bit high. I can then dial them down with a proportioning valve.

Bill

At the level you're talking about it's time to consider dual masters with a balance bar, not a factory master with prop valve.

Yea, agreed. I'm hoping Howard is going to start making them, otherwise over the winter we're going to do a pedal box. I'll still have them set up about the same though with 58-60% on the front and 40-42% on the back to start with.

And rubber dust boots and "solid" pistons. Usually easily upgraded to no dust boots and drilled/vented pistons.

This all makes more sense.

Agreed, the stock rear calipers have their limitations, not the least of which being tiny pads (particularly compared to upgraded fronts), and the availability of those pads in good compounds (no PFC's). Usually the reason everyone sticks with them is to retain e-brake function, which may not be a concern for you guys with pure race cars.

I'd love to upgrade my rears to even a 2-piston StopTech, with bigger pads, easier to change, more torque, etc. Wondering if some sort of hydraulic e-brake would be easy to adapt and solve that issue once and for all.

I'm running the Brembo GT BBK up front (thanks Fritz!) and I just upgraded my rears to four pot Wilwood calipers and the 1" bore 929 master brake cylinder. This is the same rear set up that Shpnout runs. These calipers work with a Widefoot bracket and the 99' rotors. Finally, I'll have a decent selection of pads available!

Now you tell me Guy. Where did you get them? How did they work? Did you run the Brembo's without the bigger rear kit first? Did it make a difference?

Bill,

I sent you a PM with my contact information.

Guy

Gee whiz Guy, your giving away all the secrets!!!.......... I'll never catch Bill now!

:-)

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.