unbalanced wheel lock up

[steven polaski]

I recently installed all new rotors and brakes on a 86 cab. The problem is the front right grabs earlier than the front left giving me premature lock up on the right side . I was wondering if there is a proportioning valve any ideas ?

[Goth]

It is common to have old brake hoses cause this after a brake job. Inside of hose starts restricting fluid flow.

[coloradoporsche]

Did you bleed the brakes? If not, this would be the first step. If it does not fix the problem, do it again

[steven polaski]

All new stainless lines complete bleed down and used the blue high performance fluid.

[steven polaski]

This is what they look like

[Nostril Cheese]

sticking piston?

[steven polaski]

I lift the car and the wheels spin free hit the brakes and release no problem . The front right just locks up a tad earlier then the rest. I mean this is hard braking not just tapping the brakes . I run goodyear f1 245-40-17's all new so it's not the tires

[Dave 86 930 Fl]

Steven,

I'm having a similar problem with my 86 930. I've ordered rebuild kits from Pelican for both front calipers, hopefully this will resolve the problem. I'll follow up after the parts arrive and I've done the rebuild.

Regards, Dave

[madmmac]

Double check tire pressures....drive the car for a while and rebleed the brakes.

If still a problem, go for an alignment and corner balance.

[porsche930dude]

mine does this as well. i blame it on uneven pavement traction side to side in most situations but sometimes it apears as if they should lock up at the same time

[jorian]

I think the proportioning valve only controls front to rear bias. My left front wheel locks up sooner than the right and I believe it is the caliper. I have rebuild kits waiting to be installed.

[911pcars]

Originally posted by steven polaski
I recently installed all new rotors and brakes on a 86 cab. The problem is the front right grabs earlier than the front left giving me premature lock up on the right side . I was wondering if there is a proportioning valve any ideas ?

There is a proportioning valve between the front and rear calipers, not side-to-side.

Did you bed the pads before? If you didn't, could be different coefficients of friction between wheels.

Sherwood

[steven polaski]

The calipers are new as well , I think tire pressure and corner balance may be the issue . I did heat cycle the pads but maybe it's just a quirk .

[javadog]

Usually a corner balance will help. You'll probably find that the wheel that locks up first is carrying less weight than the other one on that axle. With a driver in the car, to get the front wheel weights eqaul, you usually have to accept too much weight on the left rear wheel.

Either that, or carry a heavy passenger with you at all times.

JR

[NY65912]

Ditto on the corner balance, it did a world of good on my SC with 930 brakes. I was having a hell of a time with front lock up.

[Gunter]

I found at times that the calipers are not centered on the rotors and require shimming.
With pads removed, look down and check that there is equal distance/space between rotor and caliper.
It's something that is normally not checked when new rotors and calipers are installed.
It can be out quite a bit. I have seen more than 1/8" discrepancy at times.