I'm replacing the FR caliper later today- As long as I plug the hose as soon as I remove it and prevent much air from going back up the system, do I have to bleed the entire system (front and rear) or, can I only bleed the fronts after this install?
TIA!
Chris

 

Wellllll...others may have another opinion, but if it was me, I'd bleed the whole system, just to be safe...

 

If it were mine, I would bleed the whole system.

 

if you did'nt open the rear brake lines . then you only have to do the fronts. you only invited air on the front with the replacement of the FR.

 

If you opened the system then you have to bleed it. Now if you just opened on section, the front then you could just bleed the front BUT I would do the entire system. This will give you good brakes( if the runout it ok) and get rid of all the old BF. This should be done every 2 years if you store the car during the winter. Even better make it a Spring start up job. Use a Motive bleeder as well and you'll be ok. DO check all the rotors for runout. It should be under .005 but I set them to under .002"

 

Here's a dumb Noob question... How do I do this and why? I always thought runout was the min thickness of the rotor before they have to be replaced. How do you set runout?

 

Not a dumb question, I haven't met anyone yet who was born with this information!

The vette used 4 piston calipers from 65-82. The early 65-66 caliper was a little different but same operation.
The rotors were assembled to the rear spindles and front hubs with rivets and then turned to 1.250" +/- .002"(this is a guessitmate for those of you with a 40 year old spec book in front of you!LOL) The finished surface was perpendicular to the centerline of the axle or hub so the rotor spun through 360* without much,if any, wobble or RUN OUT. The seal on the caliper pistons are lip seal design and have a max tolerence of .010".

So what happened when, lets say in 1973 a new vette stopped on a dime and then 50k miles later the owner notices the brake pedal starts to fade? The owner doesn't know, he just paid $800 to have the local vette expert or dealership do a brake job? He was told the shop turned the rotors as part of the job. Well they could run the fronts on a brake lathe IF they knew how to use a micrometer it could be turned and as long as they didn't under cut it (1.215") it would be ok. For the rears they had to drill out those rivets the factory used to hold them together in order to get them in a lathe. Well they turned then beautiful and then placed them on and used the lug nuts to hold the rotor on and finish the job. Then the trouble starts. A day, week, month later there is air in the system and the brake pedal is kissing the floor. The rotors were not turned on center with axle and now the RUN OUT is .007, .009, or more out and the 4 pistons in the caliper have become air pumps. They may not leak but they will draw air into the system.
The owner brings the car back, gets hit for new rotors, calipers, labor,etc and still has a problem. Vettes get a bad rap for having brakes "you can't bleed"

Sounds crazy, but I've witnessed it for 30 year now. I've seen the band aid approaches to correct this, some work others don't.

Bottom line- check the runout with an indicator, check the endplay in the bearings, correct if out and bleed the system. Lip seals will stop on a dime-just like they did in 1973, or 68, 75,etc. Now fixing the endplay and runout can be a job so do some research and your eye will be opened. Good luck, vette brake system 101 is over.LOL

 

OK, while I'm here, let me ask....are the modern calipers ammune to this runout problem, I mean, they obviously know it's happening, do the modern calipers stop the air pump action? I've seen guys talk of S/S something or other....is this the "new" fix?

 

As for the "new" SS calipers for c2-c3's no you still need to correct runout. The SS is just a sleeve pressed in the old caliper and honed to size to maintain the original dimension.The iron bores pitted from brake fluid and condensation mixing and then sitting for months of storage. The cars that were driven weekly did not have this problem for thousands of miles of driving.

Now if you are referring to new cars,beyond the 82's I don't know.

 

Yes, I meant new replacement cals for our C3's....my driver rear gets air when it gets cold out, but a bleed on that cal in the spring will last all summer and then the brakes start to fade as the cold weather comes in....very strange.....I was gonna replace that cal...doesn't leak, but gets air....very strange.....

 

GTR1999 thank you very much for the explanation about the brake run out. i never knew this and didnt know about this problem and sense i just installed a whole new brake system from the booster all the way to the calipers and rotors i will have the shop that i am bringing the vette to check the run out on mine and adjust as needed. nobody ever seemed to be able to explain the this to me but after reading your explanation it seems very logical. also do the S/S o-ring calipers from VB&P still have this problem? would a set of the Force 10 4-Piston Aluminum Caliper Disc Brake Kit from stainless steel brakes (SSBC) fix this problem? link to the SSBC caliper kits thanks