[DogMeister]

1967 GTO with power drum brakes on all four. Saturday to and from a show they were pulling to the left. Jacked it up today and the left shoes on the front were dragging pretty heavy. Backed off the shoes, did a test drive, it started pulling again. Jack it up again, the left shoes are dragging. Back them off until the wheel is free spinning, while leaving a little drag on the right. Another test drive, pulling to the left again. Checked and the left shoes were dragging heavily again.

On Friday I re-packed the wheel bearings and replaced the wheel seals. All the hardware, springs, wheel cylinders, drums, bearings, and shoes are relatively new. The adjusters appear to be working properly except those damned left ones are working TOO well.

This is starting to piss me off. Anybody got any ideas? I have another '67 at the paint shop right now that'll have front discs so I don't want to do a conversion on this car.

[stevep]

Are all of the self adjusters working properly??

[70gtojosh]

Possible brake hose collapsed, acting like a check valve not allowing the wheel cylinder to be able to back off?

[DogMeister]

Adjusters are working, if anything the front left is working too well. I'm going to check the return springs and wheel cylinder tomorrow. Hoses are recently replaced.

[Geoff]

Sounds like the piston[s] in the wheel cyl not retracting after brake activation. And/or weak return springs. Buy new wheel cyls & a spring kit, not expensive.

[Sirrotica]

Are you sure you have the correct adjuster on that side? the correct adjuster will only adjust as the brakes are applied in reverse, not going forward. If you have the wrong one on the left side it will adjust as it's being driven forward, causing the problem you're having.

The star wheel should be going down on the outside of the wheel to lengthen the adjuster, and up on the backing plate side. I've seen a few times when people have done a brake job and cleaned the hardware up from both sides, the ended up with the adjusters swapped causing this problem of the adjusters working as the car is driven forward. Also I've seen the parts books incorrect and the customer was given the wrong part for the wrong side. Then there is mislabeling from the manufacturer that is also a problem sometimes.

Just another thing to check for improper self adjuster operation problems.

[mgarblik]

Originally Posted by Sirrotica

Are you sure you have the correct adjuster on that side? the correct adjuster will only adjust as the brakes are applied in reverse, not going forward. If you have the wrong one on the left side it will adjust as it's being driven forward, causing the problem you're having.

The star wheel should be going down on the outside of the wheel to lengthen the adjuster, and up on the backing plate side. I've seen a few times when people have done a brake job and cleaned the hardware up from both sides, the ended up with the adjusters swapped causing this problem of the adjusters working as the car is driven forward. Also I've seen the parts books incorrect and the customer was given the wrong part for the wrong side. Then there is mislabeling from the manufacturer that is also a problem sometimes.

Just another thing to check for improper self adjuster operation problems.

X2! This is the most likely problem. I have seen this 100 times or more, generally from "professional" brake shops like Midas. Also as a secondary check, make sure the primary and secondary shoes are in the correct position. The short friction lining on all four wheels should be facing the front bumper. The long friction shoe to the rear. On the rear the parking brake lever attaches to the secondary shoe. Wheel cylinders, flex hoses residual pressure check valves in the master cylinder are far less likely causes.

[DogMeister]

Star wheel and shoe placement are correct. This morning the wheel was free-spinning, indicating the wheel cylinder is not retracting correctly, Replacing the cylinder, return springs, and flex hose tomorrow. Also going to clean the rub pads on the backing plate.

[mgarblik]

Thanks for the reply. There is almost no chance the problem is the wheel cylinder. The wheel cylinder has no physical parts in it to make the shoes retract. There is a spring in the center but it pushes out gently, does not retract anything. Actually, it's primary duty is to keep the sealing cups standing vertically and sealing the fluid. If the metal pistons were extremely rusty in the wheel cylinder, they could be sticking, but typically would never release. If everything is assembled correctly like you say it is, the flex hose to the wheel cylinder is your most likely culprit. There is a test you can do if you want to verify. Drive the car until the brake drags pretty hard again. Jack the car up while it is dragging and crack open the bleeder screw. If it immediately loosens up, the flex hose has collapsed internally. Good luck.

[Geoff]

If there is rust in the wheel cyl, not uncommon for older cars, the piston may not retract after brake activation because the piston gets jammed on the rust. This scenario fits the symptoms described.

[GT182]

A suggestion only IF you aren't worried about having factory brakes up front. Convert to disc brakes up front, you'll be glad you did. I don't miss drum brakes up front on my 66.... not one bit. The car stops so much better and you don't have to worry one bit about correct adjusters or pulling to the left or right.

[DogMeister]

Originally Posted by GT182

A suggestion only IF you aren't worried about having factory brakes up front. Convert to disc brakes up front, you'll be glad you did. I don't miss drum brakes up front on my 66.... not one bit. The car stops so much better and you don't have to worry one bit about correct adjusters or pulling to the left or right.

As I stated in my original post I am not gong to convert this car to discs because the one I'm currently having painted will have discs on it.

[389]

Oil on the linings? Once you contaminate the linings they need replaced, especially fronts.. Are you sure its not the back brakes causing the pull..

Porterfield makes excellent brake shoes for the GM A body..

[ZeGermanHam]

Originally Posted by DogMeister

As I stated in my original post I am not gong to convert this car to discs because the one I'm currently having painted will have discs on it.

Seems like you have some ideas for moving forward, and that's good. But in the end, this isn't isn't much of an excuse. Front disc swap kits are cheap and effective, and much safer.

[TCSGTO]

Make sure wheel bearings are adjusted correctly on the offending wheel. Stock sized 11” discs won’t decrease stopping distance over a drum system with the right shoes and in proper shape. Like stated above Porterfield, or MCR shoes will reduce fade. Discs are easier to modulate near the lock-up point though.
If you want to stop faster larger diameter discs with larger diameter wheels and better tires are needed. The brakes only stop the tire, the tire stops the car.

[DogMeister]

Replacing the flex hose, wheel cylinder, and return springs fixed the problem. To answer some earlier questions, the wheel bearings were torqued properly and there was no grease or oil on the shoes or drums. At this point I didn't care which piece in the system it was (pretty sure it wasn't the return springs). I was under a time crunch, and again, a disc brake conversion was not in the cards for reasons expressed earlier. BTW, the first parts I obtained were NAPA parts. The flex hose would not seal to the wheel cylinder. The mating surface on the wheel cylinder was not machined properly and no amount of torque would crush the copper washer enough to seal. AC Delco parts worked right out of the box, even though they're made in China.