what is the torque setting for...

ButterFingers

ButterFingers

Active Member
hi there,
My calipers are separated, in two half's, there is no torque value for tightening the 4 bolts that join the 2 half's back together again. I have found 60 ft/lbs for the pillar swivel nuts and the link strut that are having new boots, that's quite a load on a unf thread of that size, the 4 bolts are a bit smaller and possibly 60 ft/lbs would suit that area too, or not? 2 of the 4 bolts are a bit smaller .....
Peter
 
Over the weekend , I finally assembled the front brake calipers.
This is what happened in the shed....
The most difficult job was deciding in what order to reassemble the parts, trial and error was the order of the day, the workshop manual giving no help.
It can only be done if the two parts of the caliper body are separated, despite what the W/M says.
First, the piston rubber seal is inserted into the bore of the caliper, being lubed with brake fluid and a small paint brush.
Then the outer dust seal is fitted to the groove in the top of the bore, then the new piston is placed into the outer seal , being well lubed again with brake fluid.
It was then placed into the vice with a timber spacer on the piston and vice jaw, and gently tightened up, pushing the piston into the bore , through the rubber outer seal.
This operation can only be done with a vice , the inner bore seal and piston are an incredibly tight tolerance fit , and cannot be pushed by hands, no-matter how big or strong they are!
The next thing that happened was almost magical to watch....
As the piston was pushed into the bore, the top outer dust seal lip, just slid up and into the top grove on the piston, with no input from me...wonderful.
I carefully checked that the seal was indeed located in the piston groove and it was job done,
The other side of the caliper with the single large piston was next, and this job only took less than 10 mins, the first caliper with 2 pistons , a steep learning curve and patience, took over one hour!
Bolted the two halves together with new O ring washers, torqued big bolt to 50 lbs and smaller on to 30, fitted a new pad assembly kit of 2 new bars and spring clips that hold the pads in, making sure that
the shims on the rear of the pads were located in the direction of disc rotation, and the caliper assembly was done.

Question: after bleeding the front calipers and a test drive the car still pulls to the left a bit, it did the same thing before the caliper refit!
Do you think that it needs bleeding more, being that he line from the master is longer to the left hand side than the right?

end of rant,
its 45 deg C outside , so I'm inside for the day, aircon on, keeping cool..... :cool:

Peter
 
Hi had the brake pulling problem before and was caused by the rubber brake hoses collapsing internally making the brakes coming on /off unevenly.
Have you ever changed the hoses?
Regards.
Clive.
 
Hi there Clive,
No I have not changed the hoses, they looked OK on the outside.
One thing that has always worried me is that when working on brakes with rubber hoses, I have used the plastic hose clamps, and afterwards always used them to
re-pinch the hose back into shape, having left an oval shaped dent in the lines.
I wonder if this action damaged the internals of the rubber hoses?

Another thought : some like to fit the hoses with the outer casing made from woven S/S mesh, having never used this type of fitting, can they still be clamped for overhauling work on the brakes, and if so,
will the S/S mesh spring back into shape afterwards?

Peter
 
Have used both types of hoses on p6s but found the braded type didn't age very well / on a daily used car the metal ferral part corroded quickly.
On a normal road car I would use the standard rubber type but do not use old stock ones , order new ones from Wins ETC
Clive.
 
In my opinion if you cannot push the pistons into the bores by hand then they are too tight and may hold the pads onto the disc. If one caliper is tighter than the other then the car will pull.
One cause of this is the dust seal holding the piston tight and not letting it relax away when the brake is released. I have found that the lip at the very top of the piston bore that see's the weather grows in diameter with rust, this reduction in diameter makes the dust seal grip the piston tight.
When rebuilding calipers I always emery this area back to bright metal - making sure not to touch the bore.
This done the piston will be able to be pushed through the dust seal and on into the bore by hand, any tighter and it will bind on the car.
 
I had the seals being too tight on my Rover P4, so rather than using mechanical means to remove the rust build up, I used one of chemical strippers to do it, which worked well.
 
You don't have to worry about sanding the bore of the caliper to bare metal, as it has no sealing to do. The hydraulic seal is between the piston surface, the square rubber ring and the groove that the rubber ring sits in.

Yours
Vern
 
hi there,
what Vern says is very true. The piston does not touch the walls of the bores at all.
I noted that the old bore seals were very worn and Thin, the new ones a perfect fit but thicker, because they were New.
They were a tight fit on the new S/S pistons from the word go, but fitted perfectly into the bore groove.
I did clean out the grooves as well as I could, and tested the fit before going ahead with the real thing.
The dust seals are very flexible and have considerable slack built into their design, so when fitted had a good bulge at the edges, not tight at all.
I have ordered new front hoses from Scotts autorubber and after fitting will see how it brakes and let this thread now the result.
At least the car now stops reasonably, even if it wants to turn left all the time, but I wont let it get the upper hand, just my left foot...

Peter
 
Vern Klukas said:
You don't have to worry about sanding the bore of the caliper to bare metal, as it has no sealing to do. The hydraulic seal is between the piston surface, the square rubber ring and the groove that the rubber ring sits in.

Yours
Vern
Click to expand...
Sorry, you have missed my point on this, I am NOT suggesting any sanding of the piston bore.
The area above the dust seal is the problem making the dust seal tighter on the piston.
Nothing at all to do with the main seal or bore.
 
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