c4 brake upgrades in second gen Fcar - Lateral-g Forums

jamesinark · #1 01-14-2010, 01:01 AM

As some of you know I'm putting c4 front and rear suspension in my '71 RS and I've been looking at my corvette donor car and was thinking that the factory brakes could use an upgrade.What options would some of you guys suggest I have as far as bigger rotors and better calipers?Keep in mind I am willing to do some fabricating to make it work and keeping overall expense down is important ,but not so much so that I'd be willing to sacrifice safety for a few hundred dollars.I feel I need to add that I would like to use use manual brakes with two master cylinders and a bias bar and in-car adjuster along with adjustable prop. valve for the best brake balance.I have some c5 deep dish wheels (18x9frt/18x10rear)so I have room for 13" rotors in front and rear ,but would deem 12" rear sufficient.Any suggestions ,anyone?

**WSSix** · #2 01-14-2010, 08:46 AM

What year C4 and is your C4 donor car a J55 car? C4s could come with 13" front brakes. That is the J55 option. The 13" C4 front brakes are good brakes but the C5 13" front brakes use a larger pad and wider surface area on the rotor. You get more clamping force with C5 brakes. This is not to say the the C4 brakes are inadequit though. You could stay with them and be happy I bet. If you want larger than 13", there are plenty of kits out there that adapt C6 front brakes to C4s. Check with Tobin at Kore3 and see if he has anything for the vettes.

jamesinark · #3 01-17-2010, 11:13 PM

My donor car is not a J55 optioned car.I'm not sure that that the front rotors are 12" (I think they are a tiny bit less than 12",something like 11.8 or so),but I think they are considered 12".If I could find some J55 rotors what would I need to put them on my spindles?I'm not real familiar with corvette options so I was wondering if the J55 option used a modified spindle or a whole different type with a different part#.As far as Kore3 upgrades I scanned through the site and didn't see any c4 to c5 upgrades.I could have missed it as it was rather late,but Vette Brakes and Products does have a c4 to c5 upgrade ,but it only uses c5 components on the front spindles and production c4 on the rear.Would that be adequate for pretty serious road racing?Also you know if the dual master cylinder setup would work with these combos?I would rather run manual brakes with bias bar and adj. proportioning valve.I was thinking that i could juggle m/c bore sizes as well as the different rotor sizes and number of pistons front to rear to get the brakes balanced out rather well.Any suggestions?

**WSSix** · #4 01-18-2010, 07:50 PM

I need to know what year the donor car is. It sounds like it is a 88+ car. If that is the case, you only need J55 brake rotor and pad abutment brackets. The caliper wasn't different. I'd recommend a new one anyway just to be safe. Aside from those pieces, the spindle doesn't change. Everything that is different is in the pad abutment bracket. If you;re pre 88, you'll need adapter brackets and modified pad abutment brackets

If you're going to get serious about road racing the car, step up to better brakes. The J55 brakes where on the ZR1 cars. The rear brakes were the same regardless of model so the rears are fine. However, as good as this stuff was there is better now. I say do it right the first time and be done with it. I'd go C5 minimum if not look into a C6 Z51 setup or C5/6 hybrid setup. (My TA is C5/6 hybrid on the front. C5 rotors and C6 Z51 calipers which are stronger than C5 calipers). You could go C6Z06 but that's getting very expensive.

Manual or not, I honestly don't know. I would be talking out my butt if I was to answer. I would say talk to Tobin at Kore3 as he knows brakes. Maybe also contact Wilwood. You may even want to take a look at what Wilwood has to offer for brakes but it won't be cheap.

One thing I can tell you about the C4 master cylinder is that it is very biased towards the front of the car. One of the common mods people do that track these cars is to change the bias spring in the MC so that the rear brakes work more. This helps to prevent the nose drive the C4s are famous for. My solution also in tells changing the suspension but that's not going to help you in this case since you're not a C4. If you go manual, you're going to be changing the MC anyway so this is a mute point.

jamesinark · #5 01-20-2010, 10:32 AM

WSSix,I read your reply and found two different c4 to c5 conversions(one from kore and one from VBP).The kit from Kore uses the hybrid version on the front like you have on your car or I may go ahead and go with their six piston front and four piston rear caliper conversion.That is if they will clear my wheels .I saved their schematics for both the front and rear and will check clearance soon as I put my wheels on after I put the '71 body on temporarily.The VBP kit uses the hybrid version on the front and rear(c5/c6)or the c5 alone so tell me where you got your c5/c6 hybrid setup for your Formula,cuz my wifes WS6 is undergoing some suspension mods very soon as soon as I get all the parts together.

**WSSix** · #6 01-20-2010, 12:07 PM

My front setup for my TA came from Kore3. I went with his billet hubs using 1/2" screw in studs, C5 rotor, and Z51 caliper. Not sure whose parts I am going with just yet on the back but I will be mounting a complete C5 rear setup.

jamesinark · #7 01-21-2010, 03:15 PM

I've got c4 calipers in front and rear and baer eradispeed slotted and drilled rotors in front and the same in rear on my wifes '02 TA.They work pretty d*** well. Where we live the roads are really curvy with plenty of hills and we make plenty of 300 and more mile trips.At least once and sometimes twice a month we get to go to our doctor who is in Little Rock and there is a 90 or so mile stretch of really well maintained road that is pretty well devoid of cops so we use the hell out of the brakes and lots of acceleration in between.I am working on exhaust upgrades (already using flowmaster catback) with a true dual system because it needs a little more flow with a little less sound.Reason I wanted to know about your brakes setup is when i'm done with the suspension I'd like a little more brake for some track time.My wife really would like to try a fullout run on a track and she is really pretty good behind the wheel so I'd like to upgrade the brakes for her when the rest is done.I'll look into a setup like yours.Thanks for the info.Really appreciate it!

**WSSix** · #8 01-21-2010, 06:05 PM

You're welcome. The same type setup is available for fourth gens as what I have on my TA. You can even go bigger. I believe all the kits for your wife's car will be cheaper than what I paid simply because her car already has a sealed hub setup instead of a rotor and hub combination like the 2nd gens.

jamesinark · #9 01-21-2010, 06:23 PM

I'm not sure that I want bigger than yours as I'm just running 17" wheels and I don't really get the purpose of wheels bigger than 18" for actual performance advantages.The extra weight and inertial mass more than outweighs any larger contact patch advantages in my opinion,but like I said it's just an opinion.I agree that looks plays a part in the whole package ,but I'll never put looks over performance anyday.I will look into a similar setup to yours for her TA , because I think the 13" rotors will fit and the c5 calipers are a superior product as far as I have heard.Thanks for the info.

**WSSix** · #10 01-22-2010, 08:14 AM

C5 front brakes will fit inside all the factory 17" wheels found on the 4th gens. I believe you can get C6 calipers on there as well. They are slightly bigger than C5 calipers.

One thing to pay attention to when decided 17" or 18" is tire selection. I can't see it becoming a problem any time soon that tire selection would be limited on a 17" rim but it's something to keep in mind. Other than that, it's mainly a looks thing.