Inexpensive 13" and 14" brake upgrade for 951's

MarkRobinson · 05-27-2010, 01:45 PM

I've been working on a big brake kit for a few months now on the 951's/928's equipped with 4-piston brembo's up front.

Testing on my cars, the upgrade will consist of a new over-engineered 2-pc Brembo brake rotor setup featuring a custom billet aluminum hat, where you can purchase either a 13" or 14" rotor, spacer, & bolts: where I retained my expensive and re-painted S4 (or Big Black) Brembo brake calipers, but they're spaced to allow the new rotor to fit.

Preliminary testing on the 13" rotor shows no weight added over the stock 12" rotor. Rotors are available either slotted or cross-drilled.

I'll have the 14" setup on my 928, my 928 race car, & the 13" setup on my 951S (as it's a daily driver) within about 2 weeks.

Neat huh?

Comparison: 13" 2pc setup vs stock S4 (cross-drilled in this picture) 12" rotor.

wild man · 03:10 PM

Are you saying you can just slap on a set of of 13", or even 14" rotors, using the same calipers & Pads, without any mods, other than changing the mounting location of the calipers? & what about the rears?

piperporsche180 · piperporsche180's Garage

More info!!!

333pg333 · 333pg333's Garage

The Dog on the left looks like he may have more unsprung weight though?

Actually the difference between the two rotors looks noticeably bigger than 1" too but perhaps that's an optical illusion.

Also the S4 calipers are not the Big Blacks, they're the Medium Blacks. The BBs which are 99.9% identical to the BReds are off the 928 GTS.

Mark Kibbort did something similar to what I think you're describing. Like to see the finished version though. Sounds interesting.

MarkRobinson · 05-28-2010, 06:14 AM

333pg333: I wrote S4s (or big blacks), knowing that there's a difference. I have big reds and S4's on my cars; I'm familiar.

Yes, you'll be able to reuse your pads & calipers (recommend a fresh pad set probably) for the new rotors. If I choose to kit this, you'll be able to purchase the new 2pc rotors, longer caliper bolts, caliper spacers (solid 6061 aluminim). This way you retain your calipers and brake lines, making the kit very affordable.

If I kit it, I think I can offer the 14" setup for possibly under $1k

Rears: working on that too, but since the calipers are not radially mounted, it's not as easy.

wild man · 05-28-2010, 06:17 AM

Quote:

Originally Posted by 333pg333

BBs which are 99.9% identical to the BReds

What what makes up that 0.1% difference, the color of the paint?? Since upgrading to bigger rotors seems to involve simply relocating the calipers, that makes it appear to be an easily do-able option. But that would only be true if it is already spelled out EXACTLY were they need to mount on the spindles, as in having already drilled and tapped holes in the correct locations. Otherwise I won't, and don't believe many that many others would either, try to make custom brake caliper mounts.

MarkRobinson · 05-28-2010, 11:26 AM

Custom mounts? Not needed: only a spacer bracket with longer high-grade bolts.

BR, BB, & S4 calipers are all radially mounted with the same bolt spacing/size (not length, but size diameter, which is why the BR's bolt up to S4 spindles). I'm merely spacing the caliper out & using an exact-dimension spacer.

wild man · 05-31-2010, 06:36 AM

Are you saying that they only need to be spaced out laterally, from the axis of the spindle, and NOT need to move out radially, from the axis? It's hard to make sense of how that would work, it the rotor diameter is larger. But if so, that definitely makes it a viable option. But as I already asked, is it same gig for the rears also? In order to maintain optimal braking balance, I would only consider up-sizing the fronts, if the rears are also up-sized.

wild man · 05-31-2010, 06:43 AM

Wait, are you saying that you have to up-size to BB's also, if you go up-sized on the rotors? In other words, I can't use my stock S4 MB's?

MarkRobinson · 06-03-2010, 06:35 AM

you'll be able to reuse your stock S4 or BB's (assuming you've upgraded to BB's & 13" rotors already) for the new 13 or 14" rotor set.

Rear up-sizing is difficult because the calipers are not radially mounted to the hubs.

Mark

wild man · 06-03-2010, 07:13 AM

Since my calipers are only S4 MB's, it looks like I'm out of the game.

MarkRobinson · 06-03-2010, 07:15 AM

S4 calipers and BB (big black or big red) calipers all work with the conversion. Only the smaller 4-piston tab-mount brembo's are out of the game so far, as I've not worked on adapters/rotors yet, but I plan to.

Mark.

MarkRobinson · 06-03-2010, 07:22 AM

Photo of a radially mounted Brembo bolts: includes S4 and Big Red/Big Black front calipers: Bolts bolt down toward the axis of the front splindle

wild man · 06-03-2010, 06:18 PM

I see what you mean now. Looks like the MB/MR's ARE still in the game, along with the BB/BR's. It is only the SB/SR's that are definitely out. So if I go out and grab myself a set of 13 inchers, I only need to add 1/2" spacers onto the studs, and my MB's will work perfectly? Where can I find 13" discs that'll fit 951 spindles??

MarkRobinson · 06-04-2010, 05:21 AM

the 965 '91-94 discs will fit your spindles and work with Big reds or Big blacks already. You'll need 1/2" longer caliper bolts too.

If I kit this, I'll offer everything necessary: longer bolts, spacer, 2pc rotor.

Mark

wild man · 06-04-2010, 05:24 AM

So you are saying that the 965 discs will NOT work with MEDIUM blacks/reds?

MarkRobinson · 06-04-2010, 05:30 AM

I placed big reds on my 951S back in '98, but cannot remember if I changed rotors or not. You do need the 10mm longer bolts for the BB & BR calipers. YOu could always try it, or heck I'll try it this weekend if my schedule clears up.

I have all the cars/components to test all these theories

wild man · 06-04-2010, 05:30 AM

Also, what advantage do the 2-piece rotors have over the 1-piece 965 rotors? The only thing I'm seeing is more $ required.

MarkRobinson · 06-04-2010, 05:33 AM

I've been using 965 rotors on my 965 for 12 years: They're very soft & very heavy. When your pads are done, so are your rotors. Pricing for the 965 rotors has doubled in the last 10 years from $125/rotor to nearly $250/rotor.

The 2pc will be stronger, last longer, and should be a bit lighter too. It might be a toss up: 2x the rotor life for 2x the price? But a true Brembo racing rotor that's radially slotted or cross-drilled.

wild man · 06-06-2010, 10:44 AM

It does make sense, if the stock 965 rotors are that crappy. But I am still unclear as to whether my stock 951S MB's (same as stock 928 S4) will work or not, with larger rotors. At first you seemed to be saying yes, then it seems like you flipped to no, in regard to the mediums.