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Re: Brake grab



> I'm breaking my car in before I go to the Classic, and things are going 
> pretty well, but I've got one little weirdness I hope y'all can help 
> with. On braking it pulls to one side. I've had the alignment checked 
> out, and the alignment guys traced it to the brakes. They tried bleeding 
> the caliper oon the slow side, but it came up good, no air in there. 
> What are the other possible causes of this?

One thing that I have found is that the rubber hoses can become 
"frayed" internally such that the MC can push fluid past the clog, 
but the fluid won't flow back on its own.  This causes that wheel to 
pump up and drag even when the caliper is fine.

The way to diagnose this is to just open the bleed valve and see if 
fluid will drip out under the force of gravity.  With good hoses and 
a clean bleeder valve the fluid should drip out readily.  It is often 
easy to distinguish a difference between sides of a car when doing 
this.

Once you suspect this, remove the caliper and disconnect the hose 
from the caliper.  You will notice that you still do not get a 
significant leak.  Finally remove the hose and you will be surprised 
how fast fluid pours out the end of the steel line!  It will be the 
same from a new hose.

I usually find this on fronts where mechanics abuse the brake 
hoses when removing calipers, but I have seen it at the rear also.  
As our cars become older, it becomes more and more common.

> These are old VW guys, and one thought he remembered there should be a 
> shim between the caliper and the backing plate, but I didn't have them 
> before and it all worked fine. Ideas?

There should be a special plate that holds the piston in the proper 
angular position (20 deg from the bottom.)  The pistons don't 
really tend to rotate in use, but most people don't have the right 
gauge to get them set up right in the first place so this plate does 
it for you.  Getting the angle right IS important to prevent 
grabbing and noise, so this might be your problem too.

This rotation thing is covered in the Bentley Manual.

I have the gauge and the plates.  If you want the calipers set up 
correctly you could send them to me, or just buy a set (4) of the 
plates.  

Jim
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*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
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