Yun's rear brake upgrade - Part 1

[secondchance]

Before I ran into head gasket issue I have been working on big brake solution since this April.
I contemplated Speed Shop solution which is grafting on of C5 drum type parking brake. Tempting but I thought this to be overly complex. While surfing the web looking for a solution I ran into Revolution Brake website which advertised C4 rear big brake conversion using mechanical e-brakes. After a few telephone discussion with their rep, Kevin, I took a plunge.

This kit showed up with following major components:

http://i658.photobucket.com/albums/uu303/byongyun/2013-04-29201225_zps8fadd3bb.jpg (http://s658.photobucket.com/user/byongyun/media/2013-04-29201225_zps8fadd3bb.jpg.html)
http://i658.photobucket.com/albums/uu303/byongyun/2013-04-29201301_zps41e8325e.jpg (http://s658.photobucket.com/user/byongyun/media/2013-04-29201301_zps41e8325e.jpg.html)
http://i658.photobucket.com/albums/uu303/byongyun/2013-04-29201552_zps2200fd28.jpg (http://s658.photobucket.com/user/byongyun/media/2013-04-29201552_zps2200fd28.jpg.html)
http://i658.photobucket.com/albums/uu303/byongyun/2013-05-10183330_zpsd661c8bc.jpg (http://s658.photobucket.com/user/byongyun/media/2013-05-10183330_zpsd661c8bc.jpg.html)

As usual this did not turn out to be a straight bolt up conversion due to a few engineering issues.

Once the bracket is located to clear rotor (this dictates where the main caliper and e-brake caliper is located in in-out relative locations) main caliper was installed with no major issue. However, e-brake caliper was offset inboard by 3/16" and outer pad could not be installed.
http://i658.photobucket.com/albums/uu303/byongyun/2013-05-12120523_zpsdea9e0ac.jpg (http://s658.photobucket.com/user/byongyun/media/2013-05-12120523_zpsdea9e0ac.jpg.html)
http://i658.photobucket.com/albums/uu303/byongyun/2013-05-12152958_zps40c2e7e2.jpg (http://s658.photobucket.com/user/byongyun/media/2013-05-12152958_zps40c2e7e2.jpg.html)

Solution was to shave outboard shoes by 3/16" and have a shim cut out of 3/16" aluminum to be used as shims for the inboard.

Problem: Factory cable sheathing was too short due to new sheathing mounting on the bracket.
Solution: "L" shaped brackets under the car where the other end of sheathings clip to was cut and shortened by 1-1/4".

Problem: Factory e-parking cable at the wheel side is a rectangular casting with a rectagular hole designed to slip over parking brake lever. New e-brake caliper is actuated via lever with a hole designed to accept clevis.
Solution: Bought 2 additional clevises and using M6 thread clevises were attached back to back so that one end would connect to e-brake lever and the other end would connect to rectangular cable termination.

This conversion took a while and some sorting out but final result works like a charm!

Ans "yes!" this set up with 13" rotor will clear factory A molds - Jim and I confirmed it by mounting a factory A molds.

Once my motor rebuild is complete I will convert the front to 14" Wilwood 2 piece rotors and 6 piston Superlites.

After that I will replace rear rotors also with 2 piece 13" Wilwood rotors.

[POWERBRAKEBOB]

I am sure you will need a larger bore master to feed all those caliper pistons. Unfortunately, larger masters will not bolt on to the original vacuum booster.
I recommend my Hydroboost system, which will have unbelievable stopping power, AND clean up the engine compartment.
The computer and wiring harness can be rerouted UNDER the Hydroboost, and the battery relocated to the rear compartment.
HUGE improvement in stopping power, a better master, and cleaned up engine compartment

[secondchance]

Thanks for the info.
So far OEM set up seems to work fine. My front conversion is on hold until my 380 build is completed.
After I convert the front I'll be able to asses if I need larger master. Another option is to graft on Tahoe master - we shall see.

[ZZZZZR1]

I have C6 Z06 front / rear calipers with a stock master and no issues

But I'd consider an upgrade there if here is a benefit!

:cheers:

David

[Daniel_Mc]

I have C6 Z06 front / rear calipers with a stock master and no issues

But I'd consider an upgrade there if here is a benefit!

:cheers:

David


David,

The F body MC is a great alternative and will give you much better petal feel.

-Daniel

http://imageshack.us/a/img594/4807/gruo.jpg

http://imageshack.us/a/img547/8162/93a0.jpg

http://www.corvetteguruforum.com/modules/newbb/viewtopic.php?post_id=194228

[batchman]

Good luck with the full conversion Yun (and the rest of the build).

Daniel, thanks for the excellent link. Are the pics of your car, if so what brakes are you using and how did the rear bias work out?

I really need a 1" master if I'm staying with the PBRs, which should be adequate for my racing. Same stuff stopped my Cobra on a dime.

Thanks,
- Jeff

[Daniel_Mc]

...Are the pics of your car, if so what brakes are you using and how did the rear bias work out?

I really need a 1" master if I'm staying with the PBRs, which should be adequate for my racing. Same stuff stopped my Cobra on a dime.

Thanks,
- Jeff

Jeff, no these were on a 85 running 6 piston Wilwoods up front and 4 Piston Wilwoods out back the GN III design. I've had the F body master in the attic for a year or so and never put it on my 89. The 89 is running the Wilwood GN III's as well. I purchased the set up I am running now from the Rippies and Randy has been telling me I need to do the F-Body MC to get the full benefit on the system. I need to find the time and do this mod. One thing the article does not mention and I have heard mixed reviews about is you have to drill out the hole in the MC for the Corvette rod to fit. The rod is a slightly different diameter on the Corvette than it is on the Camaro. I ditched the J55's when they failed on me at TWS running CCW going into turn one (pucker factor :censored:). Depending on what racing you are doing getting a set of good brakes will be great not to mention much safer (or could change the class be careful and read your class rules).

Our ZR-1 has AP Racing brakes and the Camaro master with a bias valve however I cannot comment on the install the builder of the car did this but works great on the street (I do not track this car). However I can get you pictures if you are interested.
-Daniel

[batchman]

Depending on what racing you are doing getting a set of good brakes will be great not to mention much safer (or could change the class be careful and read your class rules).

Our ZR-1 has AP Racing brakes and the Camaro master with a bias valve however I cannot comment on the install the builder of the car did this but works great on the street (I do not track this car). However I can get you pictures if you are interested.
-Daniel

Not to steal Yun's thread completely, but for autocross the J55s with appropriate pads and braided lines should be just fine (my 99 Cobra had essentially the same caliper and braking was excellent with 250 lbs more weight and a lot less tire). Runs are usually under a minute and only 2-3 real braking points, then 20 minutes to next run. In fact I sometimes think of swapping to 12"s to reduce weight.

My concern with the F-body MC is rear bias. No way to increase the rear bias, adjusters only work as limiters. I have significant understeer under braking, meaning I need more rear bias. Since I really need a firmer/faster pedal (ie 1" master bore) I'm hoping to hear from someone with j55s had to limit rear braking with the F-body MC.

Looking forward to Yun's next chapter!

Cheers,
- Jeff

[XfireZ51]

Would be great if we could adapt the 4 piston Brembo from the F body.

[-=Jeff=-]

Yun,

Since you have a 4 piston caliper in the rear, What are your plans for the front?

[secondchance]

Yun,

Since you have a 4 piston caliper in the rear, What are your plans for the front?

6 piston Wilwoods with 14" 2 piece rotors. I'll be replacing rear with 13" 2 piece rotors also.