Crazy idea for front brake setup w/ 996 calipers and 15" wheels

Maxhouse97 · 02-25-2017, 05:53 AM

I have a full 996 brake system (NB) on my 87. It requires 17" wheels, and I want to downsize (16" min, would love 15").

The fact that I just rebuilt my calipers with new OE seals ($$) and the cost of 930 calipers has driven me to look for a solution with my current calipers. So I need to go to a smaller front rotor and bring the caliper closer to the hub. I currently have the Instant-G 996 brake adapter kit with caliper adapters and new hubs to accommodate 996 OE front rotors that are 318mm x 28mm. Here's my idea:

- Buy base boxster caliper adapters (Rebel racing) to bring the caliper 10mm closer to the hub (I'm assuming the caliper mounts the same to the 2 adapters)
- Source Wilwood 11.75" x 1.25" rotors (~298mm x 32mm) with custom hat to fit my 911 hubs (I would probably sell the instant-G hubs).

Pros: this size rotor has good thermal capacity (930 size), is cheap (~$100). I would reduce my front bias from the stock 996 setup (by my rough calculation from ~1.8 to ~1.6).

Cons: I may have to widen the throats of the caliper a little (or source a slightly thinner rotor), there may be some pad overhang (not sure). I will also probably have to add some washers to the boxster caliper adapter to move the caliper 2-3mm outboard to line it up with the rotor. Still not sure if this will fit 15s - I've been told the boxster setup does, but the 996 caliper may be slightly taller.

What do you think? Any show stoppers? I ran the idea by Clint at Rebel Racing and he thought it was feasible (albeit with just a conversation over the phone).

Bill V. - would love your thoughts as the Pelican guru on brakes! Thanks.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Maxhouse97

I have a full 996 brake system (NB) on my 87. It requires 17" wheels, and I want to downsize (16" min, would love 15").

The fact that I just rebuilt my calipers with new OE seals ($$) and the cost of 930 calipers has driven me to look for a solution with my current calipers. So I need to go to a smaller front rotor and bring the caliper closer to the hub. I currently have the Instant-G 996 brake adapter kit with caliper adapters and new hubs to accommodate 996 OE front rotors that are 318mm x 28mm. Here's my idea:

- Buy base boxster caliper adapters (Rebel racing) to bring the caliper 10mm closer to the hub (I'm assuming the caliper mounts the same to the 2 adapters)
- Source Wilwood 11.75" x 1.25" rotors (~298mm x 32mm) with custom hat to fit my 911 hubs (I would probably sell the instant-G hubs).

Pros: this size rotor has good thermal capacity (930 size), is cheap (~$100). I would reduce my front bias from the stock 996 setup (by my rough calculation from ~1.8 to ~1.6).

Cons: I may have to widen the throats of the caliper a little (or source a slightly thinner rotor), there may be some pad overhang (not sure). I will also probably have to add some washers to the boxster caliper adapter to move the caliper 2-3mm outboard to line it up with the rotor. Still not sure if this will fit 15s - I've been told the boxster setup does, but the 996 caliper may be slightly taller.

What do you think? Any show stoppers? I ran the idea by Clint at Rebel Racing and he thought it was feasible (albeit with just a conversation over the phone).

Bill V. - would love your thoughts as the Pelican guru on brakes! Thanks.

First issue-base Boxster calipers are designed around 24mm thick rotors, I doubt that they can accept 32mm rotor, Boxster S uses the caliper as 996 they are designed around 28mm rotors, you may be able to get them on 32mm, though I never tried it.

W/ any of the Boxster calipers you are better off w/ 3.2 Carrera rears

Maxhouse97 · 02-25-2017, 08:00 AM

Thanks for the response Bill. Yes I'd use the 996 front calipers, so going to 32mm shouldn't be too hard.

On the rears, why do you suggest stock Carrera 3.2? Is it because the rotors are slightly larger to help with the bias? I was hoping to keep the current 996 rear caliper due to its weight savings and better design than the single piston ATE caliper. If that's the case maybe I can use a Carrera rear rotor with 996 rear caliper? Or is it the piston sizes?