need more info on the brake bias, how would one shim/modify it to put more rear bias? My setup currently has too much front and shows little wear on the rear, i may tinker with an adjustable one...
Oteck, you need bigger pistons in the back. That's the only way. The prop valve can't increase pressure to the rears, only decrease it. If you're low on clamping force there to begin with, you're kind of SOL.
- You could have the rear calipers bored out to fit a larger piston (LS430 rears are 43mm).
- You could have the front calipers sleeved to run smaller pistons (the LS430 pistons are 43mm and are massive compared to the stock 36mm pistons).
- You could find another caliper that uses larger pistons, though there aren't many on the market that run large enough rear pistons. Even porsche's rear calipers are slightly undersized. I can't think of any fixed calipers at all that have big enough pistons. GM uses some decent sliding calipers of about the right size though. I use 88 Fiero calipers (48mm piston, but I'm using smaller rav4 rotors in back, 302mm diameter)
- Running a larger rear rotor would help, but piston area is an exponential increase, while the lever arm is not, so you'd need really huge rear rotors to get the right balance.
- You could try significantly higher ? pads in the rear than the front, but you'd need a pretty big differential to get the balance back to stock.
- You could build a dual master cylinder setup with a balance bar. Honestly, this might be the best option, since it would give you better control over the brake bias than any of the others, and knowing your fab abilities, probably wouldn't cost much more than having the calipers custom machined. I have a pic somewhere of a DMC on an SW20 chassis, and it doesn't look very complicated at all.
Oteck, are you concerned about street or track braking? What modifications have you made? (wider tires, lost weight) OEM braking is really quite good on these cars, so unless you have done major mods, I would look into into maintenance issues like the slide pins on the calipers, condition of the pads/rotors before changing anything.
With heavy use, the front pads typically wear out twice as fast as the rears. If you're getting 3 sets of front pads to one set of rear pads then that might indicate there is a problem. Are there any other symptoms that would indicate that the rears aren't working right? Have you tried using a cheap laser thermometer to see what the temperatures are on all 4 corners? Its a really easy diagnostic. Harborfrieght has them for about $35 on sale.
My car also has a little too much front brake compared to the rear and always locks the front left first. I plan to change to a higher friction rear pad next season to correct that for racetrack use.
I disagree with ScareCrowX somewhat - I bet you can solve your issue without paying big bucks for bigger calipers/rotors in the rear :thumbup
Phat, he's no longer on stock brakes. He's running LS430 calipers front and back, with I *believe* either LS400 or supra front rotors in front with supra rear rotors and a custom drum style E-brake. My comments were in reference to his front to rear piston area ratio, but I know he didn't mention that in his post (I only know because I've followed his brake threads on the other board ).
I'm not sure how wolfkatz got his hydraulic balance the same with the LS430 and OE rear calipers. I'm assuming he sleeved them for smaller pistons, because in stock form the LS430 calipers are monstrous- 42% more area- compared to the stock calipers. They're the same size as EVO/STi/350Z calipers, which is why I've said in the past that those wouldn't work well for our cars, because it's so hard to source a rear caliper that's big enough to balance them out. An equivalent rear caliper would have a 51mm bore or so- much bigger than the 43mm pistons in the LS430. That's another reason I went with the porsche 996C4 calipers- they're 38mm pistons, which is only 11% more than stock, and much easier to balance.
I wish manufacturers would list calipers by piston area rather than bore diameter. Then I wouldn't have to do as much math..
for now i bought an adjuster which i'll put in the front until i can finalize how i'll deal with it. Gutting the prop valve is an idea but not safe since you can lock up the rears easily
My understanding is that there were very few North American non-turbo cars with the ABS option. So it follows that there would be very few replacement parts available for those cars.
What a great info thread! Now I'm trying to bring it back to life.
So my situation is: got a 1993 turbo, both rear calipers' bleeder valve snapped off. There are no reman calipers for turbo (22V-L and 22V-R) available. Can i buy the NA calipers (16V-L and 16V-R) and fit turbo rear rotors? Or I need to use the old brackets in order to fit the bigger rotors?
Dead thread, but I too need some help... so Ill try it. 1995 NA trying to replace rear calipers and I've purchased to different sets for complete calipers. On both sets (different caliper re-manufacturers) the area in the bracket where the pad is suposed to fit is too snug. Basically it's 3mm shorter than the old ones. all six calipers (old set and two new sets) are 16V-L and 16V-R and both the old and new pads fit in the old brackets correctly, but neither the old or new pads fit in the new brackets. Am I missing something dumb or should I reuse old brackets with new calipers until I can get new brackets machined down 3mm in both places?
Well, my experience was that all the brackets were 1.5mm to 2mm too short where the inside brake pad is supposed to fit, and 2.5mm to 3mm too short where the outside pad is supposed to fit. I took apart the old calipers cleaned the slide pins, and reassembled new calipers and old brackets, and then everything went back together perfectly.
The only thing I noticed was the old brackets had “4309X” on them, and the new ones didn’t. Google didn’t turn anything helpful up.
New bracket brands (that all didn’t fit the same way) were
Nugeon (Rock auto)
BrakeBest (O’reilly’s)
Duralast (AutoZone)
Very Odd, but thanks for the advice, and maybe this info can help someone else out.
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