tt9714

I recently removed the front calipers from my '86 951. Like virtually everything else on the car they are stock and ~original~.

I had a very difficult time retracting the brake pads while the calipers were still on the car. It felt like there was a lot of resistance to piston movement. The spring plates were not corroded, so I don't think that they were causing problems.

Once I finally got the pads out and calipers off the spindle, I wanted to check the pistons. Again, I had a ~very~ difficult time getting any motion out of the pistons (in or out).

Can someone provide some perspective on how new and recently rebuild calipers "feel?" Specifically, how much force is required to depress a piston when the caliper is disconnected from the brake system?

Danno

How worn were the pads? How far out did the pistons push? Did you push on the 2nd pad to retract the pistons with the other side empty?



That's because the hydraulics could over-extend one set of pistons (push it out completely) opposite the one you're pushing in. Then the pistons don't line up with their cylinders any more and you have to wiggle and rotate them as you try to push them back.

Scott at Team Harco

With no hydraulic connection (hoses off) you should be able to push the piston in by hand with only steady but firm force. If the piston is already bottomed out you can use compressed air to bring it back out. It should move out easily and smoothly with a strong continuous blast of air. I would recommend using enough air pressure to force the piston out all the way(use a rag to help catch the piston and reduce risk of damage to parts). This will allow for a proper inspection of the piston and piston bore.

A rebuild kit (seals, grease, etc.) is very inexpensive ($15 - $20 from several suppliers). Inspect all metal parts and replace any that are questionable. Pay special attention to guide pins and their bores, pistons and their bores. Any scoring, pitting or rust damage indicate a replacement is due. I replace anchor bolts if they are not in near perfect condition. Also inspect the brake hoses and replace any that show signs of wear or damage.

Sorry for the excessive detail - but brakes are one of most overlooked areas of the vehicle and tend to be one of the most important.

Horsepower is so much more glamorous and exciting. Try hauling your butt down from 100+ mph into a 30 mph turn without effective brakes! I've learned that brakes are as important as the engine and suspension hopefully I can rub some of that insight off.

Scott
Former brake engineer (for Teves (or ATE)) <img src="graemlins/c.gif" border="0" alt="[ouch]" />
<a href="http://www.teamharco.com" target="_blank">www.teamharco.com</a> <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
getting better all the time <img src="graemlins/yltype.gif" border="0" alt="[typing]" />

Hans

[quote] I've learned that brakes are as important as the engine and suspension <hr></blockquote>
Thanks Scott
- Engine power makes you go fast,
- Tires make you go fast around the corner,
- Brakes make you go fast tomorrow.
You can die in these machines called automobiles...

Bottom line: Brakes are the one (and if realy desperate even the only) area of a car that is NEVER to be neglected.
Someones future could be depending on it.
So if in doubd go to see a dealer / specialist, have him do the repair and pay the bill!

Take Care

billybones

Well My first Q, is did you remove the resivoir cap? This is a hydraulic system that is designed to follow the fluid level dropping. in very small increaments. the vent above the rubber seal on your cap is very small. not prone to large movements. keeps the dirt out. This goes for both in and out movement.