Cheapo BBK....

[GaryS]

I did some googling and found there are at least two 996 calipers. One has 36mm and 40mm pistons. Another one has 36mm and 44mm pistons.

Assuming I didn't mess up the calculations, the bigger one has slightly more clamping power than 135i calipers and would provide torque equal to 135i brakes if 325mm rotors are used. The smaller one has slightly less clamping power than 135i calipers and would need 360mm rotors to provide equal torque.

[pixelblue]

Gary,
you totally went geek on us that was some impressive calculations!

[DriveHard]

Ok.. im game..you have me interested..

There is also a consideration to Brake master/booster size as it relates to calipers and there piston size. ( i will have to search for where i saw that. I think it was on miata.net forum where they were putting late model masters on early model cars for auto x and BB upgrades)

Whats the 996 weigh ??

That pad is small.. The clamping force may be equal or better as a stand alone figure, but how does the larger surface area of "our" 135 pad play into that.. there has to be a benefit to = clamping force spread out over more brake pad surface area.

ill look for that calculation

[Focusedintntions]

Well Gary the m3 rotor I'm using is a 360mm rotor . Another nice benefit of the Porsche caliper is its easier to change pads and they are cheaper. Got the micrometer today but I'm not at home to measure tonight.

[GaryS]

If you end up with too much torque in front, you can use DTC60 front and back.

[Focusedintntions]

Lots of pad compounds availible. First need to make work.

[pixelblue]

how big can I go with 17" wheels? I mean rotors

[Focusedintntions]

Kori I think you'd be hard pressed to go much bigger. I'd guess 345 max.

Also just did a quick measure and I have the 36 and 32mm pistons

[SkinnyVT]

Originally Posted by DriveHard

Ok.. im game..you have me interested..

There is also a consideration to Brake master/booster size as it relates to calipers and there piston size. ( i will have to search for where i saw that. I think it was on miata.net forum where they were putting late model masters on early model cars for auto x and BB upgrades)

Whats the 996 weigh ??

That pad is small.. The clamping force may be equal or better as a stand alone figure, but how does the larger surface area of "our" 135 pad play into that.. there has to be a benefit to = clamping force spread out over more brake pad surface area.

ill look for that calculation

Pad size has no effect on friction, only effects the heat capacity of the pad.

I highly suggest OP reads some of the whitepapers on the Stoptech site http://www.stoptech.com/technical-su...l-white-papers

[GaryS]

Originally Posted by DriveHard

There is also a consideration to Brake master/booster size as it relates to calipers and there piston size.

That's true, but only if you're considering changing one of them. The variables in play are piston surface area x effective rotor radius x pad friction.

Originally Posted by DriveHard

That pad is small.. The clamping force may be equal or better as a stand alone figure, but how does the larger surface area of "our" 135 pad play into that.. there has to be a benefit to = clamping force spread out over more brake pad surface area.

Bigger pads spread the friction so they last longer. But it's the piston size that affects clamping power.

[Focusedintntions]

Skinny I've read those white papers a few times before This is a fun exercise with hopefully some good results. I'm going to try and pick up the rotors this evening and try to start this weekend.

[Focusedintntions]

So I picked up the M3 rotor and when compared to the RB rotor is significantly heavier...easy 6 to 8lbs by my arm scale haha. Size wise it's about a 1/4 bigger around on all edge. In all honesty we could probably use the 135 caliper with this rotor. It's the same thickness as the RB rotor. Depending on how everything goes I may also try to develop a bracket to run the M3 rotors with our calipers too.

In all honesty when studying the porsche caliper vs ours, I think the biggest flaw in ours is the fact you can only bleed on one bank of the caliper. I believe no matter what we do some air is getting trapped in there and leading to unequal piston pressure.

Another idea i've noted to help protect the interior of the caliper from heat that I got from the stoptech white papers is to get some titanium shim "buttons" to drop into the pistons. These should be fairly cheap when compared to full titanium pistons that race teams use and according to Stoptech is 70% as effective.

[BiscottiGelato]

I did go to eBay to check out those 996 calipers, they can indeed run pretty cheap (< $300 a pair).

Ti buttons are still going to cause issues with narrow pad and rotor clearance, isn't it? I thought the limitation with the stock calipers is because the rotor/pad is not clearing the pistons? Or am I completely off base here?

I think whatever you get working Porsche caliper vs OEM caliper or otherwise, and assuming that the adaptor can be made reasonably available (more available than those Dieselboost ones anyways...), a lot of people are going to dive into this!

Were you comparing the M3 rotors to the 135i RB rotors? There's a big size discrepency isn't there? The RB 135i rotors are at 16.5lb, the RB M3 rotors are at 18lb. How heavy are the M3 OEM rotors?

Thanks for all your effort in spearheading this effort. So far this is sounding awesome!

[Day Laborer]

Updated pics?

[Focusedintntions]

No updates as ended up having to go to VaTech Saturday. Still haven't even gotten to install my stud kit

[eric@helix]

This is an ambitious project--big thumbs-up on attempting it. My advise is to be VERY thorough in testing the kit that you end up with, meaning driving it very carefully to an auto x and see how the car behaves with the non-factory bits on. Remember that the manufacturer engineers the brakes for your specific car's weight and distribution, and that the master cylinder and bias splitting is engineered for the stock brakes. Just keep an eye toward safety.

Also, remember that the limiting factor in braking is not pad-to-rotor friction, but tire-to-road friction (that's why we have ABS), so the real performance increase of a BBK is heat dissipation, which isn't a factor on street cars. I know, I get it, it's more the look and the challenge of coming up with something unique, which is great, but just be sure that you're safe in doing so.

[pixelblue]

Originally Posted by eric@helix

I know, I get it, it's more the look and the challenge of coming up with something unique, which is great, but just be sure that you're safe in doing so.

I don't think he's doing it for looks. he has come up with an alternative less expensive solution to improve braking for the track.

[Focusedintntions]

This definitely isn't for looks but for heat management of the brakes.

[BiscottiGelato]

Despite Eric having not read bulk of the threads leading up to his comment... I do share his concern on adding random adapters to the brake system, and what does the additional torque sustained on the caliper/caliper bracket means... Changing caliper all together raises even more concerns...

[pixelblue]

Originally Posted by BiscottiGelato

Despite Eric having not read bulk of the threads leading up to his comment... I do share his concern on adding random adapters to the brake system, and what does the additional torque sustained on the caliper/caliper bracket means... Changing caliper all together raises even more concerns...

same concept as buying a BBK except custom

[Focusedintntions]

Originally Posted by BiscottiGelato

Despite Eric having not read bulk of the threads leading up to his comment... I do share his concern on adding random adapters to the brake system, and what does the additional torque sustained on the caliper/caliper bracket means... Changing caliper all together raises even more concerns...

Well its not like i'm downgrading in caliper quality. Its definitely an upgrade over ours. As far as additional torque onto the bracket I can see where there would be a concern on this. I'm having an entirely new bracket to be made and milled out of aluminum once complete. The caliper really will only be getting pushed out about 1/4 inch further out. The biggest movement of it will be in a lateral fashion due to the new offset of the rotor. As Kori said there, this would be no different than installing a bbk which would come with a new bracket also. My biggest concern isn't a failure of the bracket, but getting the measurements correctly as to get perfect fitment of the caliper.

[S54dan]

I knew you would go this route!!!