DIY race brakes?

[A Quiet Boom]

OK I've got a complete machine shop at my disposal with a CNC mill and a lathe large enough to make my own wheels if need be. Let's say I want to put the ultimate set of brakes on my car for track use and occasional spirited street driving. Assume I would make my own rotor adapters, caliper adapters, and even 17-18" wheels if need be. Also assume I'd like to source the calipers from Brembo and the rotors from Wilwood or similar. What is the optimum front/rear bias for rotor size and piston sizes? I've got front and rear suspension sitting on a bench in the shop, I had originally intended to use a complete 996 setup I bought at a swap meet but figured I could do better. Since I bought the large lathe it's been my intention to make a custom set of wheels using BBS rim halves and a machined center so rims are already in the picture. Lastly, just doing a project like this is half the fun for me, machining is my other hobby and I need something to occupy my time while the CNC cranks out exhaust tools and the new water-shields I'm working on.

My brother showed my gigantic Brembo calipers he wants to adapt to his 700HP Ranger Splash, he told me they where part of a kit for an Expedition or some other behemoth, made my 996 calipers look like go-cart binders!

[JeremyD]

The 993 brakes work pretty well.



Bill is the authority on brakes

http://home.nycap.rr.com/wmv/generalbrmd.htm

[A Quiet Boom]

Originally posted by JeremyD
The 993 brakes work pretty well.

So I've heard I'm thinking something much bigger. 993's are actually larger than the 996 brakes. I'm thinking something like 6-8 piston calipers and 14" or larger rotors. I suppose I could measure the front and rear pistons and rotors to figure out a good starting point for brake bias. Rear rotor hats would include provisions for stock E-brake setup.

[Wil Ferch]

Be creative.... if you're starting from scratch, locate the calipers on the ID of the disc...and put in a REALLY big diameter disc...

Audi experimented with such a design, but the "spider" that holds the caliper in an "inboard" ( rather than "outboard") location ,made it complicated , costly and unwieldy.

- Wil

[A Quiet Boom]

OK Wil, not THAT big LOL! Besides I'm looking for off the shelf calipers.

How about these 8 piston bad boys, 28/32mm pistons, 4 pads per caliper. Made for an Escalade. Radial mount makes adapters easy to design.

[JeremyD]

those would be bigger - but the 993 brakes stop my fat a$$ cabriolet on a fast track - so unless you are building a rocket powered 3500 lb gorilla, why>

[A Quiet Boom]

Originally posted by JeremyD
those would be bigger - but the 993 brakes stop my fat a$$ cabriolet on a fast track - so unless you are building a rocket powered 3500 lb gorilla, why>

Is there a better reason than it will be a fun project for me? Same reason I wanna make my own wheels. I wonder what Porsche runs on the GT1?

[JeremyD]

no more reason that that - If you are going to do that - how about some custom billet hubs that would allow you to use big wilwood or brembo rotors without custom hats...

There might even be a market for something like that...

[Jack Olsen]

The best brakes are just big enough to prevent overheating and fade. Anything beyond that adds unsprung weight, the enemy of good handling.

That said, I'd like someone to start making billet centers for 18-inch Fuchs-style 3-piece wheels. I'll promise to not rain on your big brake parade if you'll agree to start making wheel centers.

[Bill Verburg]

The objective is and always will be to get the smallest , lightest system that works for the duration of the longest event participated in. Anything else is a waste and only slows you down.

Full replacement should be expected at the completion of each event.

Don't want to buy a new set of brakes every weekend?

Then put together the smallest lightest system that holds together and does the job for whatever length of time you choose. The longer the time frame the bigger the design needs to be. Bigger means cooler means longevity. Bigger rotors are the heart of the matter not bigger calipers.

Not bigger calipers per se, though that often comes w/ the territory, the true need is bigger or more efficient thermally rotors.

for most 911's 930 brakes fill the bill for most people most of the time, 993 brakes use the same rotors and are only a variant on that theme.

next step up is 993RS. If you toast those in short order you are truly flying in a 911.

Next up is 996t and 996cup/evo, you would never approach the capability of these in a 911. They are designed for much heavier much faster cars. The massive brakes on these cars are needed because of their combination of weight and speed.

The factory realizes that the performance cost of the very large brakes can be minimized by increasing their thermal efficiency, hence all the effort to get the PCCB ceramics to work.

the massive brakes used on sedans and SUVs are needed because of their massive weight.

[A Quiet Boom]

Jack, don't think it's not something I haven't thought of. My only problems right now are the CNC mill is limited to 12"x18" work envelop so the largest center I could make is 12". The other problem is I haven't upgraded my controls yet so I can't put in enough code to make something that complex yet, this is one of the reasons I haven't finished my water-shields. Once I have the controls upgraded the sky is the limit on part complexity. My plan for wheels was to rough the centers on my 22" lathe and then cut a Fuch's style center in the blank. Trouble is I don't have any Fuchs at the moment so I'd have to buy a scrap wheel to copy. I'll have to pay a friend a visit and take some measurments. BTW, billet is a generic term, I'd probably select a good aircraft grade aluminum like 7075 but it's way pricey. I've got a machinist buddy in NC who has a similar mill to mine, he put a digitizer on it, I could send him a wheel and he could digitize the center for me so I could stretch it out to my max size.

Aside from that I promised RoninLB water-shields so I gotta make those first. I'm just looking for winter projects since I can't get the cars in the shop until spring.

Edit: by complex I mean all those curved surfaces as well as the dimples for the lug nuts, internal groove for the center cap etc. This will all be easy with my new controls.

[A Quiet Boom]

Thanks Bill, any idea the rotor, piston, and pad sizes on 993RS and 996T setups? Say I wanted to use a 993 front in the rear with appropriate rotors, what would be a good match for the front?

Jeremy, I thought about the hub when I realzed I'd have to modify it to fit the 996 rotors over it. Even then the rotor is about 1 inch farther out board which would likely cause fitment issues. I've seen the Wilwood's with hats up close and they are much better than the 996 rotor IMHO. As far a a custom hub/hat, not a bad idea but much more expensive than the 1/4" aluminum adapter hats. I can't see a good reason to justify the price difference, there is a lot more metal and machining involved in making a new hub. What's a hat cost anyway? Figure a hub would be at least $200, perhaps much more as it's at least a 3 op machining job. Then you gotta buy and press in studs etc.

[masraum]

There's a moderate show on Speed called something like Sports Car Revolution or something like that. It claims to be a show about/for real car enthusiasts, you know, no parts that don't make the car faster, light is good, etc.... It does some good work, but the people in the show and the production is moderate. Anyway, they've dyno'd cars after brake upgrades and light weight clutch/flywheel upgrades to note the differences. So don't forget, having to spin all of that mass up eats power as well as screwing weight and unsprung weight at that.

[Bill Verburg]

any idea the rotor, piston, and pad sizes on 993RS and 996T setups

Oh I guess I have a vague idea



Semi full disclosure here

[Jack Olsen]

Christian, I'll take second position to RoninLB.

The finished center would be a 17" disk less than two inches thick. We'd just need a donor model from some Pelicanite who's spotted cracks in his original Fuchs.

And I would make a great test pilot.

Didn't someone once post a picture of a brake caliper made as a continuous (as in 360-degree) piece enclosing the rotor? I don't know how many pistons it had, but the entire rotor was used at the same instant.

[A Quiet Boom]

Thanks Bill. So it looks like Big Reds in front and S4's in the back would be plenty of brake. Now the question is can I find calipers with those dimensions that aren't called Big Reds? I noticed in the V8 thread that ks911 had 6 piston calipers in front, gonna have to find out what those where.

Jack, 17" sounds a bit big for an 18" wheel. I figure more like 16" Then take away 1" on the radius for a bolt flange and I'm down to 14", still bigger than my mills capacity. One option would be a rotary table (new controls have 4 axis capability and cut the wheel in "fifths" but that's a ways off. I can get 7075 in 2" thick from a local supplier though. I measured my 17" cup knockoff and they are 16" from inside to inside of course they don't have a flange for bolting the rim halves on either. Wonder what the ID and bolt circle of an 18" rim half is? See I could cut the flange of the center on the lathe and drill the bolt pattern on the manual mill then move to the CNC for the "petals" and other work.

[Jeff Alton]

If it helps you out at all, my kinesis 17 inch wheels have centers that measure approx. 15.5 inches......

I like the idea of a hub that will take an off the shelf factory rotor. Not sure why I like it the idea but...........

Cheers

[A Quiet Boom]

In order to run a 996 factory rotor with a custom hub it would have to be two piece so the rotor could be set back to the correct depth for most wheels (I think, looks like they would work fine with my cup knockoffs). Used hubs are pricey, I know I wanted to buy a set to modify. I suppose a short hub could be made with long studs and a spacer but that brings up a safety issue on the track doesn't it?

I gotta admit though I really like the Wilwood rotor and hat setup, much more beefy than the 996 rotors I have and the rotor sits back where it's supposed to. I'd like to find an off the shelf large rotor like a truck rotor that would replace the factory rotor yet be thicker and larger diameter or a rotor that would slip over the hub like the 996 does and be the correct depth, suppose I could bribe the manager at the local NAPA LOL?

[MichiganMat]

have you checked with:

http://www.colemanracing.com/

They have all kinds of brake related goodies available for customization.

[hmd]

I have seen a setup using GT3 rotors and calipers. The hubs were custom machined down so the rotors can just slip on. I don't know if this would be big enough for you.