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Does anyone know of any 4 piston front calipers that would fit the stock Rx8 rotors? The rotors that go with the sport suspension to be specific. So i think larger than the base rotors.
yup .... wilwood superlite ... you will need to make an adapter plate to fit them. Can't remember which piston dia. I have sorry but they are slightly bigger in combined area than stock . Don't go for smaller than stock !
yup .... wilwood superlite ... you will need to make an adapter plate to fit them. Can't remember which piston dia. I have sorry but they are slightly bigger in combined area than stock . Don't go for smaller than stock !
Idk if its truely worth it for us in terms of performance, look the weight of the caliper I suppose but in reality, not gaining any surface area from a larger rotor.
It's massively not worth it to upgrade the brakes unless you like the look. Stock brakes with good pads still set laptime records in the right hands.
Can't remember which piston dia. I have sorry but they are slightly bigger in combined area than stock
EDITED FOR CORRECT OE CALIPER PISTON SIZE; thank you Brettus
Stock front piston dia. is 54.0mm (2.126in)
- area is 2,290.2mm^2 (3.55in^2)
- equivalent 4-piston dia. is 38.2mm (1.502in)
RacingBrake RB4045 caliper on RX8 kit is 38mm (1.496in) pistons; about equal to OE
I thought Wilwood may have had a 1.50” piston option for the Superlight, but not listed
Closest Wilwood Superlight piston size is 41.1mm (1.62in) piston
- area is 2,659.6mm^2 (4.12in^2); ~14% increase over OE, should be fine
and then for the rear; Stock rear piston dia. is 43.0mm (1.693in) - area is 1,452.2mm^2 (2.25 in^2) - equivalent 4-piston dia. is 30.4mm (1.197in), will likely need to use a 1.25” caliper piston size; ~4.4% increase over OE
Stock front piston dia. is 50.0mm (1.967in)
- area is 1,963.5mm^2 (3.04 in^2)
- equivalent 4-piston dia. is 35.4mm (1.392in)
closest Superlight 4-piston caliper piston size is 35.05mm (1.38in) and 1,935.5mm^2 (3.00in^2) area
just barely smaller than OE and honestly you won’t even notice that difference with the electronic EBD (ABS rear brake bias controller).
The next Superlight 4-caliper piston size up is 41.15mm (1.62”) and 2,658.06mm (4.12 in^2) area
that’s a pretty substantial jump in piston area; 37.3%
I thought they may have had a 1.50” piston, but not listed; that‘s 3.53in^2 area, or 17.8% piston area increase. Might be more workable except it’s not available.
RacingBrake RB4045 caliper on RX8 kit is 38mm (1.496in) pistons; 3.52in^2 area = 17.2% increase
Not saying the 1.62in pistons won’t work, but they will take more pedal travel to engage. Think I’d recommend staying with the 1.38” dia. pistons.
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Just found my calcs on this :
I have the stock caliper diameter at 52mm, which changes things ....
I originally had the 1.38" calipers and found them to be a poor choice (rear brakes overheated on track)
I now have the 1.62" calipers and they do the reverse (front brakes run hot) but work a lot better than the 1.38".
So ...neither is perfect but of the 2 sizes the 1.62" works way better.
you were right that my initial post had the wrong size, except I’m fairly certain it’s actually 54mm because I found my previous post searching that dimension and also listed on eBay, but neither 50mm or 52mm comes up anywhere on the forum; only 54mm, for caliper piston size, so I corrected the info using that number. Was probably just sloppy and crossed up the proper dimensions:
TeamRX8 mentioned Wilwood Superlite 4R 1.25” pistons would be sufficient for rear to match/slightly exceed OEM. Does anyone know of any suppliers who sell that caliper with necessary adapter brackets/hardware to work with OEM rotor specs? What about a suitable MC4 parking brake option as well with brake line that reaches? I’d like to change calipers to reduce weight, not directly to increase braking power (because with good pads and rotors the car is already very good). I don’t want to go the whole big brake/two piece rotor route as I want to keep the cost more reasonable and don’t want recurring cost of two piece rotors.
I haven’t necessarily checked into the weight of everything in the rear. Perhaps the MC4 parking brake negates or minimizes those improvements anyway. Then I suppose it’s more for consistent look of the car from wheel to wheel.
Feel free to offer any insight into whether this is even a worthwhile endeavor with regard to the rear.
UPDATE: I did some further research and MC4 weight is 3.3lbs it looks like and Superlite 4R 1.25” piston is 5.3lbs. So 8.6lbs for that setup vs OEM rear caliper which is 9lbs. So little to no benefit it looks like.
Last edited by schm1347; Dec 16, 2024 at 11:21 PM.
I looked into these BBkits a while back since I was coding an Rx8 for Assetto Corsa racing sim. For the most part The sakebomb BBkit really doesnt have much additional torque, but is like 12lb lighter per front wheel I think.
When I looked up rears they didnt offer a much of a benefit unless you got rid of your parking brake. I planned out a 19in wheel setup to get roughly 20% more torque which basically just used 1.62 Aero4s and the stock rear calipers but on 14in and 13in rotors up from the 12.7 and 11.9in rotors on the stock rx8. Basically I combo'd it to maintain the same brake bias for abs..... thinking through it now a few years later I would probably go aftermarket abs and a haltech, which opens alot of doors.
Here is a link I used to a torque and bias calculator. LINK
Here were the inputs for OEM brakes with Hawk 5.0 pads (I vaguely remember having to do some moment arm calculations for the leg input)
