924Board.org

[-nick]

ok, now you guys are just getting silly. i don't think the 924 needs much more than vented discs can give. i am checking into the 951 rear bias valve however. it's use is just to keep the rears from locking up under severe braking.

also- i don't know what i was so worried about with the brake lines. it's really very simple to change over to the front/rear split that the later 944's use. i'm going to use the T adapter that is already there to tie the rears together and i have a female/female adapter to pull the right front lines together. what a snap!

thanks for posting Tom's website. he's a regular rennlist.org guy and i've never had a chance to check out what he's been up to.

regards,
-nick

[Cbass]

He's an invaluable source of info. I think a set of 928 GTS brakes or 911 Turbo S brakes will do quite well on my little car.

[John H]

the 928 S4 calipers are alright if you want to pay the dollars for them and also as I mentioned you need to change rims.
The vented disc's for the 924 are ok for road and track work as long as you don't exceed about 200hp after that they come a bit of a liabilty.
One thing you have to remember is the S4 has thicker discs than the 931 5 bolt. The 5 bolt is about 20mm thich and the S4 is 32 mm so this has a bearing on the mounting points etc.

Personally I don't think it's worth the effort to put S4's on - easier to go for an after market like AP racing, Wilwood or such like.

[-nick]

oy! the weight!! this is rotating mass we're talking!

i'm going to weigh the 5lug parts to the 4lug parts when i do the swap (this weekend if the weather holds out). just the 944 brakes seem tons heavier than the 4 bolt. the s4's aren't going to help you any in this department.

200hp is not much. 924S's were touching 160hp (plus much heavier) and i've never heard any of those owners mention anything about brakes. i would think the way to go is to just use real track pads with the 944 brakes. i really can't imagine getting brake fade with a good .55 coefficient and 1400 degrees track pad to play with. use drilled rotors and duct some air in if you're getting that much fade.

even on the street you can use a substantially better pad than stock and avoid the extra weight.

is this really happening to you?! i'm really curious.
-nick

[John H]

When I was racing the GT replica I had boost at about 1 bar and on a good day we got 260hp. Initially brakes started to fade after about 4 laps. I experimented with different pads and I now run a Carbon Metallic compound - good when cold and doesn't fade when hot. As the car is a GT lookalike I run scoops in the front spoiler with ducting taking air to the centre of the hubs thus cooling the brakes. With the carbon pads and the ducting braking is OK but the next mod for the race car is a 4 pot caliper at the front and 2 pot rear.
On the weight front you have to remember the standard 924 dics are about 13mm thick and 257 mm dia (10 inch) the 5 lug untis are 282.5 mmm and 289 mm dia (11.1 inch front/11.3 inch rear) and 20.5mm thick. just on thickness there is a 50% increase - mid you they're vented so some of the thickness is used in the vents.

[ This Message was edited by: John H on 2002-03-27 13:06 ]

[Cbass]

I don't think it's really possible to have brakes that are too good. A 200hp car with great handling doesn't deserve great brakes any less than a 400 hp car with great handling.

Hence the Turbo S Brembos or Big Reds, or Big Blacks. Besides, it's another incentive to add more power.

[John H]

[-nick]

wow! i'm really surprised. the '86 951's used the same rears as the early 944's and 931's. the front's are bigger, but not by that much. i figured if that was enough for the much heavier 951 then the plain 5 lugs would be plenty for the anemic 924. of course 260hp is really getting up there.

i'm not saying that anyone should skimp on braking power, but big reds on a stock 924 is a little silly. would you put brembos on a fiesta? i doubt it! i just don't see a reason to add the extra weight if you'll never use it. John's case aside, i don't think many 924's would ever benefit. especially on the street.

interesting thread though. btw- did i mention how heavy 16" wheels are? my 205/55 tires are 13lbs each and the C2 wheels are probably at least the same, i'd roughly say this is twice the weight at each corner than the 924 alloys. and this is just the wheel/tire weight! i'm going to need a lot more power to get this thing rolling!

regards,
-nick

[Cbass]

If you're using a stock motor, maybe.

Most good alloys weigh about 20 lbs each. If you have really good tires, brake fade might be an issue. If you have a 275 hp intercooled motor, then it might just get you killed.

BTW, in Canada the brake swap is still really expensive, I just mentioned it because I have nothing better to spend money on.