Non- S Boxster brakes and 15” wheels - 986 calipers/986 rotors on Carrera 3.2?

Maxhouse97 · 01-10-2021, 11:48 AM

Currently have the Instant-G kit on my ‘87 with a full 996/Boxster S brake setup front and rear. The kit modifies the front hubs to accept stock 996 rotors, rears fit ok. I have a 23mm and have removed my proportioning valve. I also have my stock 3.2 system on the shelf. I am running 17” wheels for clearance.

I am pondering a backdate and want to run 15” wheels, and am therefore looking at modifying my brakes. (I think I can run 16” wheels but I really want to push for 15s for aesthetics and weight). A 930 setup is out of my budget. So I was looking at the standard Boxster brake setup on stock front Carrera rotors, but understand that this does not add anything to my stock Carrera setup in terms of heat sink capability (the original reason I went to the 996 setup is because of constant over heating/bleeding at the track).

So I started thinking about using stock non-S rotors instead of my Carrera rotors. This rotor is 298mm x 24mm, a little larger than the Carrera 282mm x 20mm. I think most do not try this because the stock rotors don’t fit the Carrera hubs, and therefore using Carrera rotors is both simpler and cheaper. But since I already have modified hubs I think I should be ok.

My question is has anyone else tried this, and what were the results? I assume I’ll have to modify my current caliper brackets, as they are spaced for 996 318mm rotors. Don’t know if I can get someone to make a new bracket or machine down my current brakes and calipers. Thoughts?

The advantages I see are better capability than stock Carrera, with lighter weight and relatively cheap rotors. Also with stock Carrera rears I think bias should be ok, with 23mm MC.

My only other worry is making sure this new setup can fit under 15” wheels, as the rotors are 8 mm larger than the rears. But it seems from the internet that Boxsters can fit 15” wheels.

Let me know what you think - thanks. If this is too complicated I could just go back to stock Carrera brakes but I love the additional capability I have now and want something close to it.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Maxhouse97

Currently have the Instant-G kit on my ‘87 with a full 996/Boxster S brake setup front and rear. The kit modifies the front hubs to accept stock 996 rotors, rears fit ok. I have a 23mm and have removed my proportioning valve. I also have my stock 3.2 system on the shelf. I am running 17” wheels for clearance.

I am pondering a backdate and want to run 15” wheels, and am therefore looking at modifying my brakes. (I think I can run 16” wheels but I really want to push for 15s for aesthetics and weight). A 930 setup is out of my budget. So I was looking at the standard Boxster brake setup on stock front Carrera rotors, but understand that this does not add anything to my stock Carrera setup in terms of heat sink capability (the original reason I went to the 996 setup is because of constant over heating/bleeding at the track).

So I started thinking about using stock non-S rotors instead of my Carrera rotors. This rotor is 298mm x 24mm, a little larger than the Carrera 282mm x 20mm. I think most do not try this because the stock rotors don’t fit the Carrera hubs, and therefore using Carrera rotors is both simpler and cheaper. But since I already have modified hubs I think I should be ok.

My question is has anyone else tried this, and what were the results? I assume I’ll have to modify my current caliper brackets, as they are spaced for 996 318mm rotors. Don’t know if I can get someone to make a new bracket or machine down my current brakes and calipers. Thoughts?

The advantages I see are better capability than stock Carrera, with lighter weight and relatively cheap rotors. Also with stock Carrera rears I think bias should be ok, with 23mm MC.

My only other worry is making sure this new setup can fit under 15” wheels, as the rotors are 8 mm larger than the rears. But it seems from the internet that Boxsters can fit 15” wheels.

Let me know what you think - thanks. If this is too complicated I could just go back to stock Carrera brakes but I love the additional capability I have now and want something close to it.

I've mentioned it a thousand times but it's worth repeating

Boxster brakes is not a performance improvement over 3.2 Carrera

Even what you have would be better w/ the stock 3.2 Carrera rears

If you must change and 930s are out
use 3.2 Carrera front, pre '83 rear, no p/v and you can even keep the 23.8mm m/c, though some will find the leg needed to be too much, it does give you much improved control

A really nice intermediate that isn't far from 7 & 8 x15 is 7 & 8 x16 w/ 205/50 & 225/45 tires, you'd only loose ~5.5lb-ft but gain in overall grip

Maxhouse97 · 01-10-2021, 12:36 PM

Thanks Bill I have the 16s you suggested on my list and very well go that way. Was just exploring the 15” wheel path. And was thinking the Boxster 298x24 rotor had to offer a larger heat sink than the Carrera 282x20.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Maxhouse97

Thanks Bill I have the 16s you suggested on my list and very well go that way. Was just exploring the 15” wheel path. And was thinking the Boxster 298x24 rotor had to offer a larger heat sink than the Carrera 282x20.

ok, that would be a plus

but you'd still be better off w/ 3.2C rears w/ those fronts