Hi,
Just got my '71 back from the shop. One of the things i asked him to do while he had the car was fix the parking brake (didn't work at all).

He said he the front and rear cables needed to be replaced...so he did that, but the brake still does not hold the car at all...even on a relatively flat surface the car rolls away with the brake on. He said to get into it much further would be expensive. Basically blamed it on the stainless steel brake calipers saying the pads have an arc to them causing it to not hold the car properly. he said the best thing to do is to wear in the brakes to make more of a flat surface and better grip.

what do you think my next step should be? want to diagnose myself since his fix did nothing.

 

take it to a shop that knows corvettes, they obviously dont. the parking brake has nothing to do with the calipers. The inside of the rotor acts as a drum and there are drum type brake shoes that apply the brake action to the inside of the rotor. they can be externally adjusted thru a slot unless the mechanism is rusted and that part can be expensive

 

Here is an instruction sheet from GM that is found in the AIM. I have on our site.

http://willcoxcorvette.com/repairand...lp.php?hID=141

The GM instructions were to put the car on rolls and apply the handle 10 - 12 notches until drag is felt. Operate it like this for 50-60 seconds and then release the handle. This with curve in the pads.

Hope this helps you.

Willcox

 

Wilcox:
I'm puzzled! I know you are highly knowlegeable about corvettes but the OP didnt have the shoes for the parking brake replaced. All they did is replace the cables and the shop that did the work is blaming the parking brake problem on the new caliper pads. The sheet you posted applies to the shoe brake in, not pads. Please clarify, thanks.

 

I guess I'm assuming that the pads were replaced since the calipers don't have anything to do with the parking brake and the brake pads are flat without arch. I'm thinking typo above and maybe the OP meant to say SS p/b shoes, not calipers.

The parking brake shoes may not be new, but it may be worth re-adjusting them and brandishing in again. Either way, he'll have the instructions on how to adjust the cables should he want to go back behind the shop that did the work.

Maybe he'll post again and clarify.

Willcox

 

yes, i meant SS shoes...not calipers. sorry. i'll have a look at the diagram. shop i brought it to was actually a corvette restoration shop....was surprised he could do any better

 

big difference, thanks for clarifying

 

Yep..that's what I thought!

You should follow the instructions for the adjustment page and then instead of putting the car on a dolly (which I don't think you'll have) try just pulling forward about thirty to forty feet with the brake 10-12 clicks pulled. It should deliver about the same results!

Just be careful you don't have it too tight when you do this you don't want to tear something up either... You'll know from the drag if you have it to tight. What you are trying to do is burn off the high spots on the shoes.

I'm pretty surprised the shop that installed the parking brake shoes did not know this! Well... I'll leave their skill level at "no comment".

Good luck.

 

If you do have new SS P/B shoes they may need to be chamfered at the ends of the linings to make proper contact with the inside of the rotor. We have run into that issue before, but it shouldn't cause the brake to not hold at all (usually causes some sort of noise rather than non-function)

Andrew
800-442-0335

 

i think he meant shoes and not caliper pads.. yes as wilcox said, wear in the shoes for a better contact arc.. and adjust the shoes up tighter against the inside of the drum. or an equally common problem.. if the shoes are 35+ years old, replace them and the hardware. then you will have new shoes , hardware, and cables. then the brakes should work as designed ( which is not very well.. they are a parking brake and not a emergency stopping brake).

 

my guess is your restoration shop didn't want to deal with it. look at it this way...at $120 an hr, they saved you maybe $1000 because it probably still wouldn't work.

 

i brought the car in with the brake not working at all. they said the cables were old and they could not do any more adjusting so first step was to replace those and hope for the best. he said if it did not work then from there it would get expensive because they'd have remove the calipers, rotors etc to adjust the shoes.

when i left the shop the brake hardly worked, but at least it worked a little. he told me best thing to do was wear in the brake by driving 50 mph and slowly engage the brake until I feel drag, and do that for about 1 min. he said he thought the shoes were probably relatively new but wasn't sure. I haven't done what he said yet as far as wearing in the shoes, but did try it a slower speed for only a few seconds to see if i felt any drag....which i didn't. It seems like after doing that the brake is worse....it basically has no effect at all.

I did some searching last night after reading the great advice in this thread, and it looks like i may be able to adjust the shoes without removing the calipers or rotors. i'm going to jack it up and give it a try. not sure if i'll have to adjust the cables again after that. not even sure i'll be able to make the adjustment to the shoes...but will give it a try. worth a try rather than 75 bucks an hour x 6 hours or so to have him do it.

 

Hopefully you will be able to adjust your parking brake. Take the rear wheels off and run the rotor until the hole is at the bottom and you see the adjuster. Use a screwdriver to turn the adjuster towards the floor.

What you will likely find if these have not been replaced is the adjuster is rusted and not moveable. You might be lucky and be able to remove the adjuster without breaking either the top or bottom spring...get it moveable and then re-install it.

On my '81 that I just did this past weekend I found the top spring broken on both left and right sides. Took me several hours to replace all the parts that I could...not able to replace all of them with the axle in place. Now I have a working parking brake....but then found the rear bearings are shot....see my other post.

Good luck

 

Not certain about this but most of the newer cars now have 4 wheel disc brakes and use a drum system for parking brake.

 

my '78 parking brake doesn't work worth sh*t and doesn't develop tension on the right side cable only. my mechanic said sometimes the old bonded shoes come off their backing plate. FWIW.

 

I disagree...when I bought my original condition 75 the emergency brake worked fine...I did some Bureau of Automotic Repair research some time ago and I recall that no car was allowed to roll onto California streets unless they can lock up the rear wheels at 25mph...my 75 was able to do just that until a corvette only repair shop replaced my spindles...and rebuilt my emergency brakes...and now they lock up going in reverse, but not forward...almost like they put them in backwards or upside down.

I'm starting to think that there's some common misinformation being passed around about the design and operation of the C3 emergency brake system that all the shops are going by which is causing all the C3's to have horrible emergency brakes. If you can't lock up the rear at 25mph then they are useless as a parking brake as well as an emergency brake...anything more than a 5% grade and the car will most likely roll away.

 

Pwsusi

I don’t know what info you have read re adjustment of the parking brake, but here’s a few things that have not been mentioned.

Jack up the car at the rear and put it on jack stands. Take off both rear wheels. Ensure that the cable has been adjusted out so that it loose! There is an adjuster at the quadrant where the cable from the leaver joins the crossover cables to the wheels. Get them loose so that there is no influence on the brake shoes.

As stated, the shoes are adjusted by turn screws that you access through holes in the rotor/ assembly. Have a good look at some diagrams so you know what you are looking for in the hole! With a bright flashlite (Maglite type) you should be able to see the turn screw and even the way it goers into the adjuster, so you’ll know which way to turn it. Tighten it right up so that the wheel is locked. Then, take it back about 8 “clicks”. Do both wheels. When happy, then adjust the cables at the “equaliser” to take up the slack, ensuring not to adjust them so much that they apply the brake. Once done the brake should lock the wheel at bout 14 clicks of the lever.

If the adjusters are stuck, you can see them (just!) by removing the callipers and rotors. A little WD40 type stuff will help, taking car not to contaminate the shoes! I wouldn’t be tempted to try and remove the shoes with the spindle in place! Despite what all the books say it’s a major pain!!

 

i don't know who put the SS shoes on, but the reputable shop that just had the car put the new cables in and said they could not get the brake to work with just cable adjustment alone. they said they'd have to adjust the pads and would be time consuming/expensive.

If i'm understanding you correctly it sounds like you are saying to just make the cable adjustment as described in the above diagram. at this point i was thinking of attempting adjusting the shoes. What do you think, cable adjustment, shoes, or both?

 

thanks Stephen for the info..we were posting at the same time. going to jack the car up today and see if can do it.

 

Have fun! Assuming the adjusters are free to turn, it's not hard, just fiddly! You need a thin but strong screwdriver, or one of those brake tools. Have a good mat to kneel on, or a creeper. All that bending and crouching to see into the adjuster holes gets tedious!