payton

Hello all,

I was wondering what most are running for a dual purpose car. I presently have a 69 Camaro with a C5 front suspension, LS1/T56.

I am running Wilwood SLA6's on front and SLA4's on the rear with 13 inch 2 piece rotors. I had a NASCAR guy fab up a manual twin master set-up with a balance bar. With the limited room that we had to work with, the pedal ratio is 5.5:1 instead of the reccommended 6.2:1. Pedal effort seems pretty high. I was running the BP-10's and have since purchased a set of their new BP-30's that I will be installing this weekend. If this next move does not improve the effort I am considering going back to a power assist set-up or back to the drawing board on the manual brakes.

So I guess the question would be for those running track days, auto cross and HPDE's. Are most, if not all, running the stock power booster from the factory?

Any problems with lots of wide open sprints where not much vaccum is generated causing loss of effectiveness or feel?

What type of pressure are you generating at the caliper?

Thanks for your help

Payton

0Todd TCE

Two things:

1. The pad change will be significant but only if it's really the compound you are looking for. A change to a higher Cf for the sake of pedal feedback is not ideal. You'll still have to push hard, you'll just get a bit more bang for the buck when hot. 10s are for the street and should not have been used on the track, whereas 30s are more a track pad and not suitable for the street.

2. You didn't say anything about the mc bores chosen for this conversion. I'd say this is where your change needs to be. What bores are being used now? How did you arrive at them?

gkmccready

I agree with Todd. The MC sizes are the magic in getting a manual brake set up to really work. I removed the power brakes from my RX7 to gain much needed room in the engine compartment.

payton

I have worked my way down to a 5/8 on the front and 3/4 on the rear. Basically sized these down the get the pressure up. I am generating close to 900 lbs on the front and 700 lbs on the rear with about 100 lbs of leg pressure. I probably need to adjust the balance bar and get more like 1000 in front and 600 in the rear, but I will still be pushing with the same amount of leg effort. I can really stand on them and generate more, but I think that I would fatigue in 20 minute track session. I cannot find a calculator to see what kind of pressure difference a 6.2:1 ratio would make with everything else held constant.

What pressures are normal?

My thought on the pad swap was more bite for the same amount of pressure. I considered running the BP-30's on the street as I am not putting 3000 to 4000 miles a year on the car, but I am sure they would eat up my rotors with light braking on the street. They are still in the box, so I may just switch them in for track use.

Maybe I have gotten spoiled with power brakes all of these years, but I feel my car should really stop with the set-up I have and it just does not meet my expectations.

gkmccready

Somebody more familiar than me should be able to help you out if you provide piston sizes, as well. Going too small on the MC to get the pressure up may put you in a situation where you can't displace enough fluid to push the caliper pistons far enough, right?

http://www.markwilliams.com/braketech.aspx

0Todd TCE

I'd be surprised if you're putting in 100lbs of leg. 60-70 is pretty common.

Regardless, here's what I came up with based on 70lbs (my normal value)

70 leg
5.5 ratio
.625 bore
1259 psi

70 leg
6.2 ratio
.625 bore
2026 psi

Pretty much what you thought; a longer pedal would sure help. In both cases however you're probably also correct that the value of a pad change would be very good also.

Moving from an estimated Cf of .45 street pad to a .62 track pad alone will increase rotor tq by about 30%. I guess perhaps your plan to do the pads first is simple enough. The only down side I see there is that they won't work for the street real well as you know and will take some warming up to be real effective.

payton

get the piston to the pad. I am not bottoming out the master, so I do not think I am running out of volume. I had thought the same thing as I was sizing down. Thanks for the link

On your calculations, should the pressure number be split because force exerted from pedal is applied to both masters? So I should see 600 or so lbs of force to the front with 5.5 ratio and 1000 lbs with the 6.2? That seems more in line with what I am seeing on my pressure gauges.

The cf starts higher cold, per the chart at Wilwood, for the BP-30 than the BP-10's but that is at 100 degrees. I am still concerned with cold braking and light pressure removing the pad material from the rotor and the coarse pad causing premature rotor wear.

For me to go to the 6.2 ratio it would take a complete new pedal box as my custom pedal are at max length and ratio for the confines of the area.

Are most running a power assisted brakes?

gkmccready

Most folks seem to run the newer Corvettes (C4/5/6) not only with the stock power brakes, but they keep the stock ABS, too. You might try posting in the SCCA or NASA forums, especially in the production or gt classes.

0Todd TCE

Yup, sorry I was only showing you how the pedal ratio changed the final numbers.

A quick re plug of some info shows me 633psi front and 440 rear with .625/.750 bores and the balance bar in the center. Move the pivot it changes of course.

Bill Dearborn

Can't talk to your pedal effort issues but I think you will be disappointed in the BP-30s. Last year there was a shortage of the 7420H pads and Wilwood suggested a comparable replacement for them, the BP-30s. No where near comparable. They just couldn't perform like the Hs at Watkins Glen. It was not noticeable when braking for most turns but when braking for Turn 1 or Turn 5 into the bus stop they just couldn't slow the car. First time I went up the back straight and tried to slow with them I ended up going through the run off area as I was going to fast to make the turn.

The H pads may be a better fit for you. Although, I have power brakes the H pads took less effort for more braking than the BP30s did.

Bill

payton

Thank you both for the help and information.

I know is seems silly to post on the corvette forum with a 69 Camaro, but the weight and handling is almost identical to the C5 and I have found what works on C5's works on my car.

0Todd TCE

Don't recall the shortage but yes I'll agree on the pads. There are some others (A and B) that I'd have suggested first.

payton

on jumping on the BP-30's. I took the rec of another guy running a first gen camaro. I will send them back and get a different set.

So the H compound is the one to get or would either A or B?

0Todd TCE

Depends on experience level and how durable you want things. Personally I'd put B pads in for a novice driver or track that does not require quite so much brake. Cost effective and reliable.

For the more hard core user the H pads are the ticket. A harder pad that will last long but has a slightly higher Cf over B. Costly pads.

Only the most extreme conditions (small circle track) where temps are sustained would I suggest A pads. Very hard on rotors, very metallic and moderately priced.

payton

Good advice.

Todd, you have earned a new customer on future purchases.