Could really use some help, please! 72 Chevelle, Wilwood kit, poor braking...

[Jeebus]

Hello, I have been working on my 72 Chevelle for a while now, and finally got to take it out for a spin for the first time this week. Among other things, i upgraded to a Wilwood Disc brake kit front and rear, for the car. We bled and bled the system, and the brakes work... but not well. I cant even lock the brakes up from 55, or any speed for that matter. They slow me down, but not fast enough.

The original equipment on my car when i started was disc front brakes, drum rear brakes, with a booster and master cylinder, with a small prop valve under the master cylinder.

When i bought the kit from CPP, it was a 4 wheel disc kit, with conversion brackets out back, and drop spindles for the front. It came with all 4 rotors, and calipers, as well as new hoses and what not.

My questions is, really what can be causing this poor brake response? Do i need a different proportioning valve? Do i need no proportioning valve? I assumed the kit was a complete kit, but i honestly dont know now. I sent an email out to CPP last week and have yet to get a reply.

Any advice?

Im so happy to finally have this car on the road, but its just not safe driving now, I really would love to figure this out.....

114046

[v8s only]

I had the same problem ( wilwood brakes) and after trying 3 different brake boosters and master cylinder i was not happy until i got a c6 corvette master and booster now its perfect. nice car btw

[TheJDMan]

Nice looking car! But from your OP it is unclear whether you replaced your original MC/booster or not. If you still have the original MC it is likely a mismatch to the calipers. You might contact Wilwood and ask them what MC they recommend with the calipers you have.

[raustinss]

What those fellas said.....look into MC and prop valve replacement....btw great looking car

[kevmurray]

Hello, I have been working on my 72 Chevelle for a while now, and finally got to take it out for a spin for the first time this week. Among other things, i upgraded to a Wilwood Disc brake kit front and rear, for the car. We bled and bled the system, and the brakes work... but not well. I cant even lock the brakes up from 55, or any speed for that matter. They slow me down, but not fast enough.

The original equipment on my car when i started was disc front brakes, drum rear brakes, with a booster and master cylinder, with a small prop valve under the master cylinder.

When i bought the kit from CPP, it was a 4 wheel disc kit, with conversion brackets out back, and drop spindles for the front. It came with all 4 rotors, and calipers, as well as new hoses and what not.

My questions is, really what can be causing this poor brake response? Do i need a different proportioning valve? Do i need no proportioning valve? I assumed the kit was a complete kit, but i honestly dont know now. I sent an email out to CPP last week and have yet to get a reply.

Any advice?

Im so happy to finally have this car on the road, but its just not safe driving now, I really would love to figure this out.....



This is a common complaint with performance brake kits. If you can provide more info someone here can tell you what is wrong.


Which kit did you buy? (P/N?)
What is your pedal ratio?
What master are you using? Do you know the piston size?
Are you using a booster? Which one? Engine vacuum reading?
Which proportioning valve are you using?
Which Wilwood calipers are you using? (Need piston sizes)
What are the rotor diameters?
What is your wheel rolling radius? (F&R)

[ChevelleNV]

How much vacuum does your engine make? if your got a radical cam and you don't make a lot of vacuum the brake booster cant do its job...

[Jeebus]

Okay, Im truly sorry for this taking so long to reply. I have had this in at the brake shop, and I have had several phone calls with wilwood now also....

I mis spoke earlier, there is no brake booster, it is the master cylinder directly to the firewall, with the proportioning valve bolted below it, this is all what came on the car when i got it... i do not believe its OEM, but it is what was installed with the disc front, drum rear brakes, and it worked great then, but after switching to 4 wheel disc from wilwood, im having the problems.

After speaking to wilwood, he is telling me that 110% he is positive the master cylinder has air in it, and that i need to bench bleed the master cylinder to make sure all the air is out of it, then start the bleeding process at each wheel again.

I can see his point, as my brakes were disconnected for nearly a year while the car was worked on, and air for sure got into the system.

This is the next thing my shop is going to be checking on, to see about solving the problem. Im hoping this takes care of it! I will post back later today!

[Apogee]

It would help if you described the pedal feel in addition to providing the component and system information requested above. Is your pedal high and hard, low and mushy, or something else?

Tobin
KORE3

[Jeebus]

Tobin,

I do not know the full details off hand, so I will try my best to provide some info that will be of help.

This is the kit i bought from CPP http://www.ebay.com/itm/CHEVELLE-NOVA-CAMARO-FRONT-REAR-WILWOOD-DISC-BRAKE-/380370340158?pt=Vintage_Car_Truck_Parts_Accessorie s&fits=Model%3AChevelle&hash=item588fd6c93e&vxp=mtr

The picture im attaching, is the master cylinder and prop valve that is on my car. When the car had Disc front, and Drum rear, this setup worked find. After switching to this disc brake package that i sent the link to above, my brakes have been very poor.

I do know know my pedal ratio off hand, everything appears to mount in the stock location on the chevelle, so i have to assume its the oem ratio?

I do not know the master cylinder bore size either, i can ask the shop to measure next time its off.


The pedal is able to be pushed all the way to the floor, with moderate resistance, but at 40mph with the pedal slammed to the floor, the brakes are not locking up, and its slowing me very gradually. to me the pedal feels soft, but if i pump it a few times, it gets stiffer but seems to stop no better each time.

the shop just bench bleed the master cylinder now, and air did come out, so we were hopeful. put everything back together, and took it out for a drive, and even tho it is stopping better, its not right yet, its still a gradual stop, no ability to lock the brakes up at all.

The shop i have this at is telling me i need to change the master cylinder most likely, to one that is setup for dual piston calipers on all 4 corners. Is that my next logical step?

My bill with these guys just keeps getting larger, and i trust they are doing everything they can, and not milking the job at all, but i just dont know what else to do...

All the help is greatly appreciated!114447

[Jeebus]

Was able to obtain this information.

Pedal radio is roughly 6:1 and the current master cylinder bore is 1"

[Apogee]

Your CPP Ebay link is ended, so there's a tiny picture with no information regarding the kit. That said, it looks like you have a Wilwood D52 front kit (possibly just a caliper "upgrade") paired with what I would assume is a D154 rear kit since you mentioned dual-piston calipers at all four corners. That said, your master cylinder bore size should be sized relative to the effective caliper piston area, the number of pistons is irrelevant. Wilwood lists the caliper piston areas of their calipers on their website, or you can just measure the piston diameters and calculate the A=pi*r^2, noting that you only calculate the area of one side of fixed-mount calipers. The D52 (http://www.wilwood.com/Calipers/CaliperList.aspx?subname=GM%20D52%20Dual%20Piston) 's should have a 6.28 square inch piston area, and the D154 (http://www.wilwood.com/Calipers/CaliperList.aspx?subname=D154%20Single%20and%20Dua l%20Piston%20Floater)'s should have 1.98 square inches.

Most people would run a 15/16" to 1" bore MC in a manual brake application with 6:1 pedal ratio and D52/Wilwood kits. If the master cylinder were the cause for a low brake torque symptom, then you would expect a high and firm pedal. Since you say that the pedal feels low and "pumps up", that generally indicates that there is still air in the system. When you bench bleed the mast cylinder, what method did you use, recirculation or plugged-port? The issue with the recirculation method is that you get no positive feedback as to when you're done...just because bubbles stop coming out does not mean that there isn't any more air in the unit, whereas with the plugged-port method, the pistons will hydraulically lock when it's fully bleed, telling you when you're done.

While I think air is your main problem, pad compound could also be a factor in your low brake torque scenario, so even if/when you get the system fully bleed, you may find that the pedal effort required to achieve lockup is excessive. Changing to a higher CoF pad will increase the brake torque for any given pedal effort and may make the brakes more to your liking.

Tobin
KORE3

[Jeebus]

Tobin,

I apologize, the link was supposed to be to the actual auction, not my completed auction page.You are right, they are the D52 calipers. The auction description states this about the calipers:

Rear - The rear calipers with 1.25” piston provide 2.46 cubic inches of piston area per caliper, to maintain the original front to rear brake bias and use of the OE master cylinder
Front - Left and Right calipers ar new wilwood D52 dual piston floating calipers. Forged billet aluminum bodies, stainless steel pistons, and competition style-high temperature seals put an end to rust and bore pitting. The calipers have a 2.00" piston and provide 6.28 cubic inches of piston area per caliper. Calipers contained the hardened slide pins and high friction pads

Does this info change anything?

When we bleed the master, it was with a re-circulation method, yes, I would say we did 5 sessions of about 20 or so pumps, with 3 min breaks between. We saw some visual air come out at first, and after it came out, we kept going for a while, but like you mentioned... i have no idea if all the air was gone.

I am going to try to find some plugs and use the method you suggest, and see what i can figure out tomorrow again.

Thanks a lot for the help!

[Apogee]

...Rear - The rear calipers with 1.25” piston provide 2.46 cubic inches of piston area per caliper, to maintain the original front to rear brake bias and use of the OE master cylinder
Front - Left and Right calipers ar new wilwood D52 dual piston floating calipers. Forged billet aluminum bodies, stainless steel pistons, and competition style-high temperature seals put an end to rust and bore pitting. The calipers have a 2.00" piston and provide 6.28 cubic inches of piston area per caliper. Calipers contained the hardened slide pins and high friction pads

Does this info change anything?

Nope, that info doesn't change a thing, but let us know how your plugged port bleed goes.

[Twentyover]

Tobin,

I apologize, the link was supposed to be to the actual auction, not my completed auction page.You are right, they are the D52 calipers. The auction description states this about the calipers:

Rear - The rear calipers with 1.25” piston provide 2.46 cubic inches of piston area per caliper, to maintain the original front to rear brake bias and use of the OE master cylinder
Front - Left and Right calipers ar new wilwood D52 dual piston floating calipers. Forged billet aluminum bodies, stainless steel pistons, and competition style-high temperature seals put an end to rust and bore pitting. The calipers have a 2.00" piston and provide 6.28 cubic inches of piston area per caliper. Calipers contained the hardened slide pins and high friction pads

Does this info change anything?

....


Only my opinion of the guy's math skills who wrote the copy for the ebay ad

[Apogee]

Only my opinion of the guy's math skills who wrote the copy for the ebay ad

C'mon...if squared is good, then cubed must be extra special. That's funny, I didn't even register the units snafu, too busy looking at the numbers...and I'm usually a unit-Nazi.

[Hydratech®]

Here are a couple of quotes but from one of our many Pro Touring / Race customers over the years:

"Thank you soooo much for helping me out - my manual brakes truly sucked on my heavily modified twin turbo race Mustang despite all of the conventional wisdoms no matter what I did - it felt like trying to stop a dump truck" Now it stops the way I had spent years trying to get it to, and my lap times are MUCH improved as a result...

"I installed your hydraulic brake assist as a last ditch effort in my quest for proper braking and now the car feels like I had always hoped that it should, now it stops better then my '07 CTS-V !!!"

We have 15 years worth of these testimonials upon request over the years we have been in existence. Yes, in spirit a manual brake system *should* work... but...

IF you have properly functioning power steering, and have done "what all the conventional wisdoms and P/T 'gods' have told you to do", and still can't stop the way the want = we will make your Chevelle stop so damn hard that it will leave you in surreal disbelief: http://www.hydratechbraking.com/GM_A_Body.html

Sigh... There will be a bunch of people that may / will jump in here and tell you it is overboosted, though the reality is that everyone that has experienced the difference of (sh*t for brakes to OH YEAH) can attest to why we exist... Spoken the other way around - stopping too hard? Hmmm - Sort of like too much horsepower in the little pedal on the right? Well, don't press it so hard then LOL (call me crazy).

Here is a TOP TEN to TOP FIVE move:

http://www.lateral-g.net/forums/showthread.php4?t=36692

Despite what the PT 'gods' will tell you about how 'real' race cars have manual brakes, right? So go ahead and remove all of your existing brakes, install $$$ larger class brakes, pads that brake dust the whee out of your fancy wheels every time you hit the brakes, jump through all of the flaming hoops the cognosante shall have you do, right?

Summary? When you have run out of time / effort / energy in getting your Chevelle to stop, give us a call.

:spam: ??? Ah - Nope... Been here since well since well before www.pro-touring.com came into existence...

[JustJohn]

Or...you could just order a vacuum booster and install it behind the master cylinder.

[Jeebus]

Here is where I am at now.

Purchased a new master cylinder, bench bleed the master cylinder. Got all the air out, took several hours, but i was able to hydraulic bleed it like suggested for a while, and it was extremely hard to push in by hand past .250.

Installed bled master cylinder onto car, then re-bled the brakes at each corner.

My brakes are better, in the sense that, i can press the brake lightly in a parking lot and I will stop fine. However, i still cannot lock my brakes up at any speed over 25mph, it slows it down, but it seems like not fast enough.

When i hit the brakes, it pulls hard to the left now, so i checked the right side for air again to see if there was a bit left in it that I had missed, and there was none.

I may be expecting too much i guess...idk, but idk what to go with next. I feel like manual 4 wheel disc brakes should stop better then this? Should i try pads next?

[rrelco]

it sounds like the same set up i have in my Elco, wilwood 1.0 tandem bore, 6 piston with 14 rotors, 4 piston 13 rotors rear. my pads need to heat up before they stop well and i cant get it to skid or lock up, but when i am at an autox on the straights then turn hard left this thing stops i have had a lot of guys tell me that my car stops. so if you cant get it to skid i wouldn't worry about that... plus when it skids your not in control.

[TheJDMan]

It sounds like you still have air in the system. Bleed, bleed, bleed and bleed some more. I had a hell of a time when I first bled my new brake system, I used a pressure bleeder, a vacuum bleeder and old fashoned pumping and nearly a gallon of brake fluid to finally get my system to work. Did I mention that you need to bleed some more.

[Hydratech®]

Interestingly, it may be good news for your scenario that your car is now pulling hard left upon heavier brake apply. Why? Short of having other mechanical issues (like steering and suspension problems, possible sludge / debris blockages of your brake lines), you may actually be starting to see the left front brake starting to actuate a proper amount of brake torque for the line pressures being applied to it (and now the other three corners need to catch up).

Are your rotors possibly zinc washed? If so, this can cause havoc in bedding in the brake pads initially. Zinc wash makes them look real good, but hinders the pads from bedding in until the zinc wash is worn off of the friction areas. The zinc gets into the pads and changes the pad bedding dynamic. If your rotors are not zinc plated, then the pads themselves may be having a hard time bedding in. How many miles do you have on these brakes? I'm guessing less than 200-300?

Soooo, assuming my theory that your left front brake is providing more brake torque than the other three brakes, the Rx here would be to take it out and just run it through it paces a few times over the next few days. If my hunch is correct, you will find the right front brake should catch up to the amount of brake torque / action that the left front is currently producing, which will manifest itself as the vehicle pulling less and less over the next 100 miles or so until equalized brake torque occurs (between the left and right side).

http://www.stoptech.com/technical-support/technical-white-papers/bed-in-theory-definitions-and-procedures/stock-brake-system-bed-in

Summary? Sounds like you've just about got it, simply only needing further actual road use, and maybe one more good brake bleeding session...

:6gears: