924Board.org

[gorillabiscuit]

I know the usual way to go rear disc on an early (1977) 924 is to upgrade from a 4 lug to 5 lug setup, but I was just curious - is there a compatible 4 lug rear disc brake setup that would work on a 1977 924? Maybe something from a similar era Audi? I know, probably not, because it is a transaxle rear end. Thanks

[Shurick]

You can turn old rear brake drums on lathe to make a pair of hubs:



If you need to balance stock 924 front brakes you can use some brake disks from ford 253x10.5mm and vw golf calipers with 34mm pistons :



Another thing needed is custom caliper bracket:


_________________
WBR, Shurick
'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
https://www.instagram.com/ru_pacecar/

[safe]

Exactly what Ford disks and golf calipers are you using?
_________________
/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Juho]

[MikeJinCO]

The quick answer is easiest way is to get to make a 5 lug conversion, all the parts are available form the pre 1985.5 944. I might be less expensive to find a wrecked 944 than to buy all the parts, 944 parts have a pretty good aftermarket.

Unfortunately due to the dual diagonal brake system the 924 has a long pedal travel and uncomfortable feel. I took my 77t to HPDE drivers school and it was hang on for dear life, but it always stopped. The brake system has a bunch of variables in it and changing any one thing leads you down a path for multiple other changes. To me the best thing to do is maximize what is there. Change all the flexible lines to the stainless steel wrapped ones which eliminates all the expansion of the rubber lines and upgrade and adjust the rear drums. I changed to Porterfield RS4 rear shoes figuring any aftermarket stock shoes would be Chinese junk for a Super Beetle, Hawk probably has some similar brake shoes. Cost x3 0r 4 of the cheap ones.

This is not the ideal solution, but a small fraction of the cost and it does work.
_________________
Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)

[safe]

[Juho]

where i live scrapped 944 are rare ive been looking perfect donor car for 3 years and havent found. 944 were sold lot less here and people here tend to keep much better care of their cars. Thats why im intrested in this. If i could get donor car from craigslist for cheap i would do that but not rly an option here......

[Juho]

[safe]

[Raize]

Rear brakes only do a quarter of the braking anyway at maximum effort. Even less if you're on track tires.


Better to focus on cooling the front brakes with some ducts I think. It's not stopping power the 924 lacks, it can lock the front wheels quite nicely (once or twice) -- it's stopping endurance and the best way to get that is from active cooling.

[safe]

Well, about 30%, but that's not insignificant.
The big issue, as you say is heat capacity. That goes for both the front and the rear.
The larger 300 mm front rotors will take care of a lot, I would really like thicker that 24 mm. But you can't get everything while keeping to standard parts.
In the rear I would like something close to 300 too, maybe the same disks as in the front is an option, but a little more height to the hats would be preferable.
I have some options on rear calipers, 38 mm pistons are common, that could work, 40 mm would be ideal! I have found that VW golf and Audi A3 has aluminum calipers with 41 mm pistons, the issue is that they are for quite thick rotors and a bit more expensive.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Beartooth]

I'd say upgraded front brakes is more of a priority than rears, but I'd agree with safe - I think under sustained aggressive driving, rear brake fade is going to set in quick with the drums. Of course, solid disks in front wouldn't be far behind, but either way, to much demand on the drums means driving around with almost no rear brakes after a certain point. My first car had all drum brakes, and a couple times I got up around 100 MPH and got on the brakes hard to see how it'd do: after a couple seconds you could literally feel the brakes dropping off no matter how hard you pushed. I'd guess it was down to around 50% braking action by the time you stopped. I've found the stock brakes on my 931 (4-lug brake setup) work well, but I'm not doing anything to task them much so far. I'm not sure how much of a priority a brake upgrade is for me; that said, if there's a cheap and relatively easy way to go to vented disks up front and disks in the rear, I'd be interested. If I come across a parts car with the later setup, or find the right deal on all the parts, I'd probably go with that. As I see it though, the requirement to replace the rims, plus the dwindling supply of donors make the later brake swap less of a no-brainer if there's another reasonably cheap alternative.
_________________
1980 931 diamond in the rough

[safe]

Stock brakes are good enough for stock power, even track duty, depending on the track.

But for a little hooning they start to fade for me even thou they manage to slow me down from 130+ mph to a more legal 60 (once). One hard stop is esier to handle than a bunch of lighter with some riding the brakes.

Going with the 5-lug setup would be the sensible thing, I have most of the parts to do it.
But I'm not doing that!! Nothing is sensible about my 924.
_________________
/Magnus, Stockholm Sweden
=======================
Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Cedric]

With std brakes on a std 125hp car you can run pretty much how many hours you want on a race track with the correct pad choice. I dont think you would overheat them on the road to the point of brake fade with race pads, but racier pads would bring along other "fun" stuff as some squeeling, lots of dust and warm up time, with the massive volvo brakes you could probably runt whatever pad you like without heat issues, thats nice. And when you get rid of the drums you also get rid of the sponginess.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Raize]

It's true that hooning is actually harder on the brakes than actual track driving as you have to massively over-brake every corner due to lack of sight.

I'm planning on doing a brake duct solution on my 4-bolt 924 in combination with "mid-range" brake pads like Mintex 1144 that work well cold and warm but not race-hot.

I hope that with the active cooling the front brakes can stay happy and that the rear drums, due to weight transfer, don't have to do much anyway. Every time I've felt the wheels after some hoony driving the rears are always luke warm and the fronts painful to touch.