Front Disc conversion. Rear Drum brakes locking up

[nailz77]

Hi,

Have a front disc brake kit installed on a 57 chev.
Rear brake cylinders were seized and now replaced. Now rear drum brakes are locking up first.
Any suggestions?
How do I adjust the proportioning valve if it is that?

Dave

[CPPAaron]

Good Morning,

On the proportional valve there is not an adjustment. I would say most likely loosing up the adjuster on the rears would help. sounds like they might be on the tight side.

[nailz77]

Good Morning,

On the proportional valve there is not an adjustment. I would say most likely loosing up the adjuster on the rears would help. sounds like they might be on the tight side.

Hi aaron,

I am assured the drums are adjusted correctly.
Front disc were working fine with seized rear drum cylinders, now replaced cylinders back drums are locking up when brakes pressed.
Either wrong cylinders installed or faulty proportioning valve?
Do the proportioning valves stick/fail often?

Dave

[CPPAaron]

No issues with the valves on these really... I would double check you have the correct wheel cylinders. If the bore is too large this could happen.

[nailz77]

No issues with the valves on these really... I would double check you have the correct wheel cylinders. If the bore is too large this could happen.

Hi Aaron,

Have 1" cylinders fitted to the rear.
Is it possible to have the wrong proportioning valve? Would a disc/disc valve cause this?

Thanks,
Dave

[CPPAaron]

Only if it had a 4 wheel disc prop valve. There should be a "2" stamped on the bottom of it and a rubber cap in the front.

[FIFTYFIVE210]

Hi,

Have a front disc brake kit installed on a 57 chev.
Rear brake cylinders were seized and now replaced. Now rear drum brakes are locking up first.
Any suggestions?
How do I adjust the proportioning valve if it is that?

Dave

I know this is an old thread, but I was wondering if you found a solution to this. I have the same problem with my '55 chevy. Disc front, stock drums in rear. Thanks

[Dcastle]

This is exactly the crappy advice CPP will give you after they send U the wrong parts. Of course the proportioning valve could be defective or incorrect !!!!!

[80 Elcamino]

If you have not fixed yor problem yet, you might have to much pressure to the rear brakes. One possible solution is to install a adjustable proportioning
valve and decrease pressure to rear brakes