924Board.org

[Cedric]

[Raize]

I faded my brakes on about 5 miles on B-road with extremely aggressive driving once. Either on full throttle or full brake at all times so of course they got hot. Back when I had no-name EBay pads on it, TRW I think.

My thought process is that on track the speeds are higher, so you might at least be getting more airflow around the brake to cool them.

I've fitted EBC Yellow now and though it's nice when warmed up a little, it's not great when cold - you can push all you want but the friction just isn't there. They're about half worn after 8000 miles of driving.

There's not that many options for 4-bolt pads, it's like

1. EBay TRW
2. EBC coloured pads
3. Mintex 1144
4. Mintex 1155
5. Hawk of various types, probably HP+ (but hard to get, for me)
6. Carbon Lorraine of various types, probably RC5+

[safe]

Big brakes are easy on the pads, that a good thing for sure. With a more common caliper used on performance cars there is usually a bigger supply of premium pads.
On my 911's I use Performance Friction on turbo calipers (same as 924 Carrera GTS), they lasts for several seasons of track usage!


Back on track:
Peugeot 406 have solid rear rotors 290x10 mm with a height (wheel face to back of rotor) of 60mm. So that disk will space inward quite bit, I think that is a gootd thing. Golf 3 have calipers for 10mm disks with mechanical parking brake and it has 38mm pistons. I think that could be an OK match for my Volvo front calipers. With smaller front pistons the 406 calipers would be pretty ok.

Vented rotors in the size 290-300 x 20 mm with some height to them would have been ideal, but I haven't found any in 4x108. Golf 4 / Audi A3 have aluminum 1 piston (41 mm) calipers that could have been useful.
Maybe there are some Japanese stuff, but most a 5 lug.

All these calipers above are quite inexpensive.
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/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

[Cedric]

[safe]

Starting the front upgrade. Seems to fit at least.

Ford Focus ST 170 disks, Volvo V70 calipers.


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/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

[safe]

Original front rotors turned down to just hubs.


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/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

[Juho]

This is awesome! Did you do any machining on the new hub except cutting off the rotor? Or did you have to modify the center bore for new rotor?

[safe]

[!tom]

Awesome
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78 924 NA
5-lug

[Juho]

[Beartooth]

I can see what you guys are saying about the stock brakes - definitely adequate for street use, outside of very aggressive driving on very twisty (and empty) roads. One thing too, a stock 24 (125HP, or less...) will be easier on brakes in even the most aggressive driving: you start braking later and have less energy to dissipate if you're doing 100 at the end of a straight instead of 120. I'm amazed better pads would extend the life that much - I'd have figured smaller, solid rotors would be hard on anything on the track. In my case, I do most of my aggressive driving on unpaved roads. It's more fun not having to get flying to reach the grip limits (plus not many paved roads are twisty around here). The lack of grip also means it takes longer to put energy in, as well as take it out, so I doubt I'll ever see any issues there.

Anyway, that looks like a pretty significant brake upgrade you've got going, safe! One front rotor I've considered is from some 80's Fords (4-lug Mustangs, for one). It's 256MM, and looks like it's got enough height, or offset. I have no idea how hard it'd be to adapt the existing spindle to use the Mustang bearings, or adapt the hub to use the Porsche/VW bearings. It's the same bolt pattern though, although using studs. I'm also not sure there what the best solution would be - ditch the studs and drill and tap it for bolts, or find/make some nuts that'd work with the stock rims. Here's a pretty detailed view of the rotor/hub I'm talking about: https://www.rockauto.com/en/moreinfo.php?pk=2033432&cc=1133996&pt=1896&jsn=1438 You might even be able to use the stock caliper, but I imagine you'd have to somehow grind the pads down at least half-way to account for the thicker rotor. That might be a good place to use the VW calipers someone on here was experimenting with, especially since the original calipers are hard to find parts for.

On the rear, that Pugeot rotor sounds like a good choice. I'd come to a similar conclusion, that a taller (more offset) rotor would be desirable unless you were to make a completely new hub. I've done some digging through some vehicles I think might be a match and came across similar results: there aren't a lot of 4-lug disk brakes, and adding the high offset and ease of mounting to a drum machined down to make a hub cuts out many of those. Something like a Mercedes rear disk setup (which incorporates a small drum brake for the parking brake) would be nice, but all of those seem to be five-lug. So a caliper setup that incorporates the parking brake would probably be required. A custom-made hub would solve a lot of problems, but I can only guess that would cost hundreds of dollars, and it just doesn't make sense to spend much money there.

Ultimately, I think the goal would be to find vented disks for the front, just a solid disk in back is fine, and use all off-the-shelf parts other than caliper mounts and maybe a bushing or two (to adapt the rotor, like safe did, or to adapt different wheel bearings to the spindle). I can't say I need the extra brakes at this point, but I'd like to have them, and eliminating the brake shoe adjustment would be really nice too. I tightened the shoes once since I got mine going, and I can already discern a little drop in the pedal. I might just have to get in the habit of adding a click now and then.
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1980 931 diamond in the rough

[safe]

I have a set of Peugeot solid rear rotors, I will find a way to adapt them to the rear. I also have a rear caliper suiting the 10 mm rear rotors with 38mm pistons, should be near a good ratio for my front pistons.

I need to do something with the master cylinder and brake lines. I will try with a 23+ mm 931 MC.
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/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

[safe]

[Cedric]

Not even close
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1980 924 Turbo
www.instagram.com/garagecedric/

[safe]

I'll try 15s, but I don't have any here in Stockholm.
_________________
/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