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tldr; Budget big brakes for early NA with off the shelf parts and minimum machining...and it fits inside 15" wheels.
Caliper is 2lbs lighter than stock NA caliper; rotor is 5.5lbs heavier - net gain of only 3.5 lbs for about 26% more brake torque.
For a given brake line pressure this combo should make more brake torque than 951 brakes and be comparable to "Big Reds".
2009+ Dodge Caravan 302mm brake rotor modified to fit the back of the early 944 NA hub (open up center hole and drill 5x126 pattern). 28mm thick vs 20 for stock NA.
2004 Pontiac GTO brake caliper, already has the 76mm bolt spacing to bolt up to the 944 spindle. Need to elongate the holes less than 1/8" to pull the caliper radially inwards to clear the wheel barrel. Needs 1mm spacer washer between caliper and spindle to center over the rotor. Twin 42mm piston floating caliper.
C5 Corvette brake pads fit the GTO calipers and perfectly match the radius of the rotors
This GTO caliper will work on a late NA as well with an 87+ 951 rotor but you might need to machine the caliper more to adjust the caliper centerline over the rotor.
So far I have only got one side mocked up, but will order the other side's parts and get them machined in the next week or 2 before getting driving impressions. Will update later.
Once the front is sorted I do intend to figure an upgrade for the rear as well to fix the F/R bias, hoping to find another near-bolt-on caliper for that too. Have some options noted but I haven't bought any of them yet to check.
Just to reiterate what was discussed at length in the 928 thread I linked above, the venturi/eductor is in the middle of line that goes from ambient pressure upstream of the throttle plate to the manifold downstream of the throttle plate, which is at engine vacuum. With such a large hose, this by itself would be a massive vacuum leak. I have never really looked into it but the correct stock configuration controls the vacuum leak to manigable levels so that the engine operation is not affected. This seems to work for the vast majority of cars. l don't profess to know exactly what the correct parts are but suffice it to say that a stock configuration is the best way to go. But yes, hooking temporarily up to a source of engine vacuum would at least prove the booster is working.
Just to reiterate what was discussed at length in the 928 thread I linked above, the venturi/eductor is in the middle of line that goes from ambient pressure upstream of the throttle plate to the manifold downstream of the throttle plate, which is at engine vacuum. With such a large hose, this by itself would be a massive vacuum leak. I have never really looked into it but the correct stock configuration controls the vacuum leak to manigable levels so that the engine operation is not affected. This seems to work for the vast majority of cars. l don't profess to know exactly what the correct parts are but suffice it to say that a stock configuration is the best way to go. But yes, hooking temporarily up to a source of engine vacuum would at least prove the booster is working.
So V2 if you have the 16” manhole wheels could you mount the caliper with out working on the holes?
Yes, no hole slotting needed for 16" wheels.
If you have 16" manhole wheels then I assume you have a late offset car, which means you would pair the GTO caliper with an 87+ 951 rotor. You might need to mill or space the caliper inboard/outboard somewhat to center the caliper over the 951 rotor. I don't have that parts combo so I don't know how far it might need to move.
It a 87 924S with the 16” manhole covers, I did just did the Volvo 240 front calipers, I know that is more of an aesthetic change and not really a great change in performance. Your latest project sounds like it might be an improvement in braking. That’s a good thing!
Dan
can just see them poking through the mesh...perspective is off in the photo, but looking straight on, the rotors fill the whole "open" area of these 15" wheels
V2,
so do you think the bigger two puck caliper will out perform the four puck Volvo caliper? Granted it will have it will have 302mm vs 282mm rotors but will four pucks clamp better than two? Although size usually matters!
the twin 42s have 22% more piston area than the 4-pot 38s, so for a given line pressure the 42s will clamp 22% harder.
the bigger rotor adds another 6% or so.
believe it or not a 4-pot 38mm actually has LESS total piston area than a 944 NA's stock 54mm single-pot front caliper. but since the radius on the rotor is greater with the 4 pot (approx. 122mm radius for the 38s vs 114mm for the 54) it does make about 6% more brake torque.
number of pistons in a caliper is (mostly) irrelevant. a 4-pot fixed (opposed piston) caliper with 38mm pistons will squeeze the same as a 2-pot floating caliper with 38mm pistons.
how in the world did you ever figure out all the different combinations of parts from different cars that worked?
you can find anything with enough time on the internet...
there was actually a RL post from a guy about 10 years back saying he "thought that just maybe" GTO calipers would fit.
i tried it out, sure enough they do.
the US GTO was derived from an Australian Holden car which itself was derived from a German Opel car which a few years prior to that was also sold in the US as a Cadillac Catera. I bought a caliper and checked, the Cadillac Catera single-piston 57mm calipers also bolt up to the 944 spindle. i was intending to use the Catera caliper originally but the bracket just slightly fouls on the 944 wheel hub. Catera guys upgrade to 2004 GTO calipers...and the GTO caliper does not foul the hub.
GTO guys use Corvette C5/C6 brake pads on their cars since it is a direct fit into the bracket and there are better, bigger pads available for those cars.
for the rotor i found a catalog online that lets you search rotors by size (OD, thickness, overall height). i needed a 28mm thick rotor for the GTO caliper, and wanted a rotor around 300mm OD, (like a 951 uses).
to line up on the 944 hub it needed to be around 25mm from rotor face to rotor centerline.
the Caravan is the right thickness, right OD and 26mm from face to rotor centerline, hence the 1mm spacer moving the caliper inboard.
you can find anything with enough time on the internet...
there was actually a RL post from a guy about 10 years back saying he "thought that just maybe" GTO calipers would fit.
i tried it out, sure enough they do.
the US GTO was derived from an Australian Holden car which itself was derived from a German Opel car which a few years prior to that was also sold in the US as a Cadillac Catera. I bought a caliper and checked, the Cadillac Catera single-piston 57mm calipers also bolt up to the 944 spindle. i was intending to use the Catera caliper originally but the bracket just slightly fouls on the 944 wheel hub. Catera guys upgrade to 2004 GTO calipers...and the GTO caliper does not foul the hub.
GTO guys use Corvette C5/C6 brake pads on their cars since it is a direct fit into the bracket and there are better, bigger pads available for those cars.
for the rotor i found a catalog online that lets you search rotors by size (OD, thickness, overall height). i needed a 28mm thick rotor for the GTO caliper, and wanted a rotor around 300mm OD, (like a 951 uses).
to line up on the 944 hub it needed to be around 25mm from rotor face to rotor centerline.
the Caravan is the right thickness, right OD and 26mm from face to rotor centerline, hence the 1mm spacer moving the caliper inboard.
Spencer what’s your thought on the GTO calipers vs using the wilwood 120-6816 with the wagenswest brackets?
Spencer what’s your thought on the GTO calipers vs using the wilwood 120-6816 with the wagenswest brackets?
Should be comparable in brake torque for a given line pressure which is nice. Those have really big pistons so even using a stock 944 NA brake rotor will make a lot of clamping force.
Downside is you would most likely need a bigger master cylinder to move enough fluid - which means the pedal will be harder. Not a big deal on a 944 with power brakes though.
Cost works out about the same as what I have here. I don't know if the Wilwoods will fit under a 15" wheel though?
07-23-2022, 08:31 PM
944 NA budget brake upgrade option
