924Board.org

[Dutch924-racer]

I want to fit bigger front calipers on my 931. Easyest is to fit Boxster calipers on standard rotors.

But I want to use the bigger calipers like 993/996. Has anybody done this, and what rotors did you use ?

Problem is the 931 rotors are verry narrow (35mm). All other brake discs have a higher hub.
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[AppleBit]

I am interested in this as well...
_________________
Classic British Sports Car Restoration v6 + v8 Engine Conversion Swaps

Porsche 924 Wide Body LS1 Corvette 500 Horsepower Engine

[BionicBalls]

I seem to remember hearing from somebody that the 951 calipers are the biggest for the rear and that the rear calipers from the boxter are the biggest for the front.

I could be completely off-base but like I said, I seem to remember.
_________________
1980 924 NA
1982 931

[Rasta Monsta]

86 951: spindles, struts, front and rear rotors and calipers.




_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Dutch924-racer]

944 turbo calipers are the same size as Boxster calipers.

I know raceboy has 993 T (big reds) on his car. But what kind of rotors did he use ? And will this fit with 16inch wheels.



[/list]
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[morghen]

[Dutch924-racer]

[Dutch924-racer]

The Boxster discs are 24mm thick, so the will only fit on the original 931 discs. So that will be the easyest conversion. The Boxert S requiers 28mm discs, so you can use the 951 discs.
For the 'big reds' 993T calipers you need 32mm thick dics. So the 911 wil be good for that.

For the 931 you need discs with a narrow hub. The question is will these 911 or 951 discs fit the 931 spindels ???

Original discs:



944 turbo up to 8-1986



911 3.3 turbo 1983-1989


_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[ic932]

[ic932]

I think in the end, Raceboy just went for 951 hubs and spindles.

In those pics, it looks like he just bought a radial caliper mount for the later 951 hubs and spindles (non-M030).. and used big reds. i DOUBT he continued with this set-up, it must of weighed alot especially with those spacers.

[Dutch924-racer]

I just discovered a difference between the 931 and the 951 hubs.

The rotor on the 931 is mounted on the back of the hub and the 951 rotor is going over the hub. That is why the 931 hub is so narrow.

You have early and late ofsett (ET23 or 52). But what makes the difference ? Is it the hight of the hub ?
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[Rasta Monsta]

[ideola]

I believe all 5-lug 924/944 hubs through the end of the 86 model year used the rotor-behind-hub configuration, including the unique 86 951 setup, which Rasta is running on Shaggy, and which I am also running on the UWB.

As far as I know, all of these setups used "early offset" A-arms; the offset is determined by the A-arm, not the hub. In 1987, the "late offset" A-arms extended the hub by an add'l ~20mm or so (don't know the exact figure off the top of my head). As a result, the angle of the strut housing had to change, and so the strut housing attachment changed to accommodate the more aggressive angle required for the wider offset. Also, from 87-onward, the spindle diameter was increased to from the ~31.7mm diameter used on the early cars (including the 86 951) to ~35mm. The larger spindle obviously improves strength while necessitating a larger hub, I presume to allow larger brake discs (although I don't know offhand what impact this might have had on the hub bore for the brake disc).

Regardless of the hub size, AFAIK, all late offset hubs utilize a disc with a hat the fit OVER the hub, making servicing of the brake disc much easier. Early offset setups require the hub to be removed.

It's also worth noting that you CAN use late offset spindles and hubs on an early offset A-arm as long as you use an adjustable camber plate to dial out the camber introduced by the more extreme angle noted above. It also helps to use the Ground Control strut housings (which do not have the eccentric adjustment of the OEM strut housings, and REQUIRE adjustable camber plates).

Here are three combinations that I know work:

1. On the UWB, I have late offset alu A-arms with '86 951 spindles+hubs+Brembos+discs, with Ground Control strut housings and adjustable camber plates.
   
2. On the club sport project, I have early offset alu A-arms with '93 968 spindles+hubs+Brembos+discs, with Sachs Sporting strut housings and an off brand adjustable camber plate that looks identical to the Ground Control units.
   
3. I believe on Shaggy, Rasta is using '86 951 spindles+hubs+Brembos+discs+strut housings (not sure on his upper strut mount)

I believe the ONLY all-OEM configuration that will work on a narrow body car is to source everything from an early offset '86 951. You need the whole corner assembly: spindles+hubs+calipers+discs+strut housings.
_________________
erstwhile owner of just about every 924 variant ever made

[Dutch924-racer]

Ok,

I can do 4 things:

1) go for Boxster calipers (2x36mm, 2x40mm), on the orignal rotors. Only thing you need is the brackets and a modification to the brakeline.

2) go for Volvo 245 calipers (4x38mm) on standard rotors. Very cheap. Only need a brakline modification.

3) go for 951 setup (2x36mm, 2x38mm) will need to buy spindels, hubs, discs and calipers

4) go for 928 S4 calipers (2x36mm, 2x44mm), big problems finding the right hubs and discs. and you need 17 inch

I don't really see the benefit of the 951 calipers compared to the Boxtser The only thing is that the 951 discs 16mm larger.

The steel Volvo calipers are cheap but to heavy for my racer.

I will forget about the S4 calipers, to much work and they won't fit with my 16" wheels
_________________
937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[Rasta Monsta]

951 disc is also much thicker, with larger vents, therefore presumably better thermal management.
_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3