gregl316

iTrader: (1)

I should say not locking up. I installed the complete system on my 91 RS. I installed brakes from a C5 in the front, Wilwood discs in the rear and just got done with the Wilwood 1 and 1/8th" mastar cylender and adj. combination/ prop valve. I blead the heck out of them. But the fronts don't seem to bleed to well. The peddle doesn't go to the floor as the do when I do the rears. (2 man bleed). Took it out to test and set prop valve and the brakes don't lock up. The car stops good the brakes don't lock up. Are they supposed to? I tink so I am worried about the fronts not bleeding well. I did get the rears to lock up alittle adjusting the prop valve closed but not the fronts.

I am lost

gregl316

iTrader: (1)

Thanks for all the help. I called Wilwood and got 2 different answers.
1 I need to bleed my front and rear brakes at the same time. There is a vapor lock not letting the fronts bleed correctly.
2' To take the front brakes off and sand them with 100 grit to get to new material and re-brake them in.

I have done #2 so far and the brakes work better but not like I expected. I will try number one once I get more help.

Has anyone else had this issue? My stock brakes would lock up if I stood on them but that was with stock tires.

Edwardgp

Does the complete system upgrade include new brake hoses to the front calipers.

gregl316

iTrader: (1)

Yes, braided SS. Both front brakes bleed and brake the same. No pull.

RBob

iTrader: (1)

The M/C bore is too large for the C5 calipers. The increase in rotor diameter helps, but not enough. Look at the stock set up:

M/C bore: 24 mm (about 0.95")
Caliper piston area: 4.9 SQ"
Rotor diameter: 10.5"

The C5 caliper piston area is smaller at 4 SQ", which reduces the clamping pressure. Then combined with the larger bore M/C the line pressure is reduced. So the overall caliper clamping force is reduced.

With the stock front discs and 100 pounds of force on the stop pedal, there is about 2182 ft/lb of front rotor torque.

Change this to the larger M/C, smaller caliper pistons, and the larger rotor, there is about 1602 ft/lb of front rotor torque.

That is with no other changes then the three I listed. A substantial loss in front braking power (27% less).

Just changing the M/C bore to get back to the original braking torque. A 0.96" diameter M/C bore gets close at 2199 ft/lb. Of course there is not a likely M/C in that bore dimension.

The stock 24 mm bore provides 2271 ft/lb of front rotor torque, better then stock.

RBob.

gregl316

iTrader: (1)

Way thanks. I only bought the 1 and 1/8th bore size cause Wilwood said. So should I just use the stock one? Or get a smaller one around 7/8s or so? Wilwood hasn't admitted the size problem yet. But I can see why after you explained it.
I knew you would come through Rbob now if I can only get it to run better. I am kind of getting the hang of it and my VE learns are coming together.

RBob

iTrader: (1)

If you have the stock M/C easy enough to swap in for a quick fix. Although, the C5 calipers don't require the quick take-up design of the stock M/C.

A 15/16" bore in a non-quick take-up would be perfect. The 7/8" is a bit on the small side, and would likely be a bit touchy.

Wilwood may have sized the M/C according to the rear disc set up. If you know the piston area for them it would be helpful.

RBob.

gregl316

iTrader: (1)

Thanks Dude;

I will find the piston area. They are 4 piston drag lites. What is the "quick Take-up" design you speak of? Is a Wilwood M/C a quick take-up? I have a Wilwood adjustable Prop valve too.

Should I get a 15/16th M/C from Wiwood? Now the issue is returning the old/new one and exchanging it. I got it for Summitt.

If I put the stock M/C from the Camaro on it and use the adj. prop valve will the work good? Up to their potential? I don't want to cut corners. This car is the best of the best,

Just tell me what to buy to get the best performance out of them.

RBob

iTrader: (1)

The Wilwod won't be a quick take-up (QT). Or, I would be very surprised if it were. Look at the size of the M/C where it mounts. A QT M/C will be fatter in that area.

There is an additional piston that is large in diameter (32 mm) to supply a large amount of fluid. This pushes the pads out to contact the rotor faster. Once the line pressure hits about 100 psi the M/C then switches to the main bore (24 mm).

The use of a QT M/C has to do with the design of the caliper. The stock iron pulls the pads back further to reduce drag.

If they carry it in that size, or the 24 mm size. Not knowing if you have changed the line to M/C flairs, the '98 - '02 Camaro M/C is a 1" bore and bolts up to a stock set up. Will lose a little braking over the smaller bores.

May be able to make up for some of that with better pads.

I don't like the QT design. From a post on here the poster stated that when he applied the brakes firmly the car stopped well. When he as quickly as possible stood on the brakes the car barely stopped.

So I tried it out myself. Sure enough, with the stock QT M/C when I did what is called a 'panic stop', there was very little braking. Yet when I firmly apply the pedal and stood on it, the brakes work very well (C4 fronts and drum rears).

Pads are the most important aspect. Be sure to use a good street performance pad. Such as the StopTech Street Performance or the STILLEN Metal Matrix High Performance pad.

RBob.

gregl316

iTrader: (1)

wildwood only seems to make an 7/8, 1, 1&1/8th, As far as QT desighn I don't know either. So should I waist my money and get an 1" one or just save the $200 and keep my stock M/C off my 91? Maybe get one from a Vette? I upgraded my brakes thinking that they should work 100% better then stock. Well I never really had an issue with the stock brakes. But to late. I think they should lock up if I press them hard enough.

A panic stop they just go away. But if I slowly like normal press on the brake they work good. I put an adj. prop valve in cause of the swap to discs in the rear.

Am I expecting to much?

RBob

iTrader: (1)

Here are the front brake torque figures for various M/C bores. First, stock front brakes with a 24 mm bore:

2182 ft/lb

Now with the C5 front brakes:

1-1/8" bore: 1601 ft/lb
1" bore: 2026 ft/lb
24mm bore: 2269 ft/lb
15/16" bore: 2305 ft/lb
7/8" bore: 2647 ft/lb

Using a 1" bore M/C with good pads should do the trick. The 7/8" bore M/C are typically used in a manual braking system (no booster). As you can see the brake torque really goes up with it, but so will pedal travel.

With the C4 brakes on the front of my car I lost braking torque. This is due to the smaller caliper pistons. The larger diameter rotors made up for some of that loss. The rest of the loss I made up for by using StopTech high performance street pads.

They are rated FF, but they are at the top of the FF rating for friction. If you plan on some canyon carving or such can go to better pads such as CarboTech AX6, or Porterfield R-4S.

Changing from a mid-range FF pad (used in the brake torque figures above), to the CarboTech AX6, which is near the top of the G range, and we have this:

1-1/8" bore: 2081 ft/lb
1" bore: 2634 ft/lb
24mm bore: 2950 ft/lb

Shows the difference pads can make, a 1-1/8" M/C doesn't look too bad now.

RBob.

gregl316

iTrader: (1)

That is great but I am really just using the car as a seldom driver I will never really test the brakes and don't think I need that good of pads. I am running just the stock pads that came with the set up.

So tell me where and what to buy for just every day driving. But I do want to take advantage of my brakes. Basically new car.

RBob

iTrader: (1)

If the lines that connect to the M/C still have the OEM bubble flair, install the stock M/C and see how it is.

You mention stock pads, are these GM stock? Check the edges of the pads for a 2 letter code. Will be something like EE, FE, FF, or none at all. The higher the letter the higher the friction. The first letter is for a cold pad, the second for when the pad is hot.

RBob.

gregl316

iTrader: (1)

N0pe I referred them. I doubt think there's any letters

gregl316

iTrader: (1)

I already put new fittings on. I will check the letters when I get home

gregl316

iTrader: (1)

I contacted Summit and they aren't giving me a problem returning the M/C. But do I want the 1" and just upgrade the pads? Or can I get away with upgrading the pads and keeping the 1&1/8th M/C? Why would Wilwood tell me to get the biggest M/C they sell. I just want my brakes to work good.

Where do I buy the good pads? I want the car to STOP when I stand on it. Rite now the thing isn't nose diving at all and I pretty much have the prop valve closed.

I just read about the CarboTech AX6 I think that's way to much pad for me. This is mainly a street driven car.

RBob

iTrader: (1)

You want both, check the rotor torque values that I've posted.

Without knowing the current pad rating I can't say. Although, looking at the above values, even a decent mid-range FF pad isn't going to provide as much braking torque as the stock setup.

Without knowing the rear caliper piston size/area I have no idea why they recommended that size. It may match their rear calipers, if so, that is why. You may need to take this into account once the smaller M/C is in place.

You'll know once you tune in the brake balance.

Summit carries the StopTech Street Performance Brake Pads. Get a set of those for the front along with the 1" M/C and enjoy brakes that will stop the car.

Yes, if not pushing the car a bit then not worth the $$'s for those pads.

RBob.

gregl316

iTrader: (1)

Thanks RBob is there no end to you expertise. I'll get that done and work on the tune at the same time.

I just ordered them. What's another 250 into this money pit.

The rear brakes specs are;

Calipers: Info / Part Number:
Left Hand - Part No: 120-12160
Right Hand - Part No: 120-12160
Type: Forged Dynapro Low Profile
Finish Color: Black Anodize
Piston Count: 4
Piston Area (In²): 1.98
Piston Type: Stainless
Mount Type: Lug
Brake Pad Plate: 4812
Brake Pad Area (In²): 5.1
Brake Pad Volume (In³): 1.71
Pad Compound: BP-10

Does this throw a wrench into the works?

RBob

iTrader: (1)

The total piston area of 1.98 sq" is less then the stock C5 brakes (2.47 sq"). So no over-braking here. Don't need a lot of rear brake on our cars. However, if more is needed then step up to the BP-20 pads.

Be sure to properly bed the new front pads. Also, it would be a good idea to use 120 - 180 grit emery cloth and remove the current build up of pad material from the rotors.

RBob.

gregl316

iTrader: (1)

tell me how to bed the pads in correctly. should I redo the backs too?

RBob

iTrader: (1)

Bedding is a series of slow-downs (no stopping) from decent speed with a fair level of pedal pressure:

http://www.stoptech.com/technical-su...-system-bed-in

Shouldn't need to do any additional work on the rears.

RBob.

gregl316

iTrader: (1)

OK I put the new M/C on with a 1" bore. Now it brakes completely different. Like a car, spongy in the beginning and goes from there. I am going to put the pads on today and see if that makes a difference.

Now I have an axil seal leak. Does it ever end?

gregl316

iTrader: (1)

Got the new pads on. I sanded the front rotors to get the glazing off. They were bad should have turned them. The brakes are good now except... I have no brakes going in reverse.

RBob

iTrader: (1)

Just need to use them more.

RBob.

mmadden55

What is needed for a c5 conversion?

gregl316

iTrader: (1)

Hi again I am back.
After replacing the Booster my brake system is all new. But I am still having the issue. Every once in a while I hit the brakes and the peddle is hard actually harder then normal and the thing doesn't stop. It is working a little but not all the way. Take your foot off the peddle and some times it is better sometimes not. But change something as in rpm's and the breaks are back.
Anyone have any clues? I will take it out again and see if it happens again and when it does for sure. There are only 2 parts that haven't been replaced. The hard lines and the filter in the vacuum lines to the booster.
Oh I have a vacuum gage and I do have vacuum during these issues.

THANKS

gregl316

iTrader: (1)

Well yes the rear brakes are solid mounted and there is a little movement in the rear axles. When the brakes are on there great but sometimes it takes a pump or two.
I hook up the sensor on the prop xalve now everytime I hit the brakes the lite comes on.
I also can't get the rears to lock up. I adjusted the prop valve and still nothing.
Are the back brakes worth what they are or are they the problem?

Thanks for the help.

gregl316

iTrader: (1)

Well... The breaks are great with the exception of "break check". I think it is the axle pushing the breaks out in a turn, The guys at Wilwood said to plug the hole between the two areas in he master cylinder cause it is at an angle. Well that didn't work.

I still have brake check and the brake light when I hit the brakes.

Anyone know why?

87350IROC

iTrader: (2)

Does you differential use c-clip axles? That could be your source of pad knockback in the rear.

As far as the brake light. Is it always on when your foot is on the brake? Or does it only stay on when you first press the pedal?

gregl316

iTrader: (1)

Yes they are "C"clips and They were brand new.

the brake light comes on and stays on when the brakes applied. But goes away when my foot is off the pedal.