TECH..............have you found that since Volvo switched to single piston floating calipers that you are either rebuilding or replacing them more often? I'm on my second frozen caliper in 30,000 miles. The old Girling's never had issues as I recall. I change my brake fluid yearly with BMW DOT IV or Ate Super Blue............by rotating those two fluids you can tell when the system is totaly flushed to each caliper.

r.

 

Never had to replace one on the 70 series.

 

70 series is the same as the 850........... Strange that I would have both of them freeze up at about a 10,000 interval...........

r.

 

Yes very strange.

 

i wonder if there is another brake set-up that would just bolt on to the C70 like the dual piston calipers and rotorsfrom the volvoSUV. more than likely you would need the hub inorder to mount the caliper with the rotor.

has anyone looked into this minus the porshe big brake upgrade?

 

don't know. What is interesting is that in both instances the rubber 'boot' separates from the caliper allowing water to rust the piston. Fortunately it is cost effective to simply purchase rebuilt units at less than $50.00 (NAPA) than rebuilding them. Rebuilding them is inexpensive unless you have the rusted pistons such as what I experience. Of course the dragging caliper screws the heck out of your rotors!!!!

r.

 

Yes it must be the climate difference on why I don't see them.

 

I'll bet you're right TECH. When it is below freezing and the auto sits at the airport all week, I'll bet the rubber seal hardens and when you start driving and the piston expands on the first stop, the rubber seal pulls off the rim of the caliper allowing water to enter and eventually rust.

r.

 

Sounds like a good diag!!! LOL

 

I am assuming that the boot in question is the main boot around the main brake piston. One weak point about floating caliper designs is that the piston has to travel twice as far, to cover the wearing of the pads on both sides - this means that the boot has to allow for twice as much movement as in a two-piston, non-floating design.

The other "boot" that exists in a floating caliper is the one that protects the sliding pin that the whole caliper moves on. I have seen these let water into/onto the pin, so that it starts to rust. Then the caliper doesn't move as freely as it should, leading to uneven wear.

 

Nope...........not the first issue you bring up. New rotors and new pads last summer. The pins have the appropriate grease and the seals are intact. I fly every week and leave my Volvo in the lot. It gets c o l d in the frozen tundra where I reside and I truly believe that when I get back each week-end to the lot and start driving, the rubber boot pulls off the lip of the cylinder which allows the water and salt to enter and rust the heck out of the cylinder causing the piston to not be able to withdraw.................the rest is history.