pulling to the right

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shortmort37

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Recently I had my local shop install an MC36221 dual master cylinder (per the recommendation from this site), along with new front drums, shoes and wheel cylinders. The car stops great - until the brakes warm up a bit. Then, I notice there's some pulling to the right, especially on a hard stop. Occasionally, I've heard a screech. I don't seem to be leaking any brake fluid; is it likely I need to back the shoes off on the right a bit, or could there be another explanation?

Thanks
Dan
 
The shoes will auto adjust so backing them off will only last till they auto adjust back to their happy place.

Things that can cause pulling.
(No particular order)

  1. Wheel bearing lube leak
  2. Brake fluid leak
  3. Suspension parts warn out
  4. Backing plates worn where the shoes ride
  5. Drums turned to the max or more and not the same on both sides.
 
Another possibility is that the left side has a plugged or partially plugged/kinked hard line or hose. #5 above is a strong possibility too. Brake fade on the left side could certainly do it.
 
If you lift and spin wheels cold, I think you may find the left one dragging excessively, and what happens, - it gets hot and loses friction, and doesn't slow as efficiently.
If you have a temp gun, shooting the brake drum hot may give an indication.
If so, loosen left adjuster a tad . ( scientific measurement ).
Good luck
 
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Make sure the new lines are not touching the exhaust
 
Dana67Dart said:
The shoes will auto adjust so backing them off will only last till they auto adjust back to their happy place.

Things that can cause pulling.
(No particular order)

  1. Wheel bearing lube leak
  2. Brake fluid leak
  3. Suspension parts warn out
  4. Backing plates worn where the shoes ride
  5. Drums turned to the max or more and not the same on both sides.
Click to expand...
There's no evidence of (2), at least on the ground or a visual inspection of the new connections. When the weather improves, I'll pop the cover on the MC, but I doubt it. The front end was recently rebuilt, so I don't see (3) as a factor. If (4) were in play, wouldn't that affect cold stops, as well as warm? The drums have never been turned (5) - they're brand new.

(1)? Maybe. Excessive grease, liquifying under heat? I... dunno. Wouldn't that stop, after a while?

I think pulling the drums to see what's going on may be in order. But thanks for the very thoughtful list!

Dan
 
inertia said:
If you lift and spin wheels cold, I think you may find the left one dragging excessively, and what happens, - it gets hot and loses friction, and doesn't slow as efficiently.
If you have a temp gun, shooting the brake drum hot may give an indication.
If so, loosen left adjuster a tad . ( scientific measurement ).
Good luck
Click to expand...
I don't have a temp gun - but it may be worth the investment for my garage. But @Dana67Dart said:
The shoes will auto adjust so backing them off will only last till they auto adjust back to their happy place.
Click to expand...
I'd try backing off in my '59 Plymouth - but, it doesn't seem like it's indicated with auto-adjusters.
 
shortmort37 said:
I don't have a temp gun - but it may be worth the investment for my garage. But @Dana67Dart said:

I'd try backing off in my '59 Plymouth - but, it doesn't seem like it's indicated with auto-adjusters.
Click to expand...

What Dana didn't mention is they will not auto-unadjust, if they were accidentally tightened too much on renewal, - and they are a pain and time consuming to fiddle with 2 tools thru the adjuster hole to undo it.
Early in my career, I over-adjusted new brakes, thought they'd "wear in", some did, some didn't, my mechanics have done it trying to flat-rate, my apprentices did it.
Lift the front and spin the wheels, easy .
jmo.
P.S. .. one of those I messed up was my sister-in-law's, - she never missed a chance to rub it in at family events . . lol
 
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inertia said:
What Dana didn't mention is they will not auto-unadjust, if they were accidentally tightened too much on renewal
Click to expand...
Good point,

And they might work fine till they get super hot.

On a side note I was having issues with my rear drums on a 8 3/4 swap. WELL used drums - turned, used shoes, cleaned and lubed everything else.

I finally got it all worked out, but in the process I had the rear on stands and had the engine running and trans in reverse.

Had my wife stab at the brake pedal a few times and for the first time in my life got to watch the auto adjusters actually function.

Gave me goose bumps!
 
BTW one of the things I did to monitor whether my rear brakes were adjusted correctly I used a thermal temp gun to see that both sides were about the same temp
 
another thing I experienced is, if the drums have been turned, not getting turned all the way to the face of the drum on the inside, leaving a ridge. The shoes expand when hot and would ride that ridge once they got warmed up with brake use. I won't tell you how long it took to figure that one out...
 
Take the car for a drive until the brakes pull. stop & put your hand on each front drum. The 'pull' side [ the right ] will probably be hotter. That means the shoes are rubbing building up heat & changing the friction co-efficient. Could be adjustment, soft return springs, out of round drum, blockage in brake hose/line.
 
#4
4. Backing plates worn where the shoes ride

...is insidious. Everything looks OK, backing plates might show wear, but the shoes bind against the backing plate. This happens even if the 'pads' where the shoes rub are lubricated.

It took me a LONG time to figure this out.
Symptoms include: works sort of OK, until you brake hard and you hear a 'clunk' sound.. The shoes move against the backing plate and then the brake gets grabby and won't release as well as it should. Once the shoes move around a bit the grabbiness goes away. This happens because where the shoe rubs against the backing plate, there is a small notch worn into the backing plate.

I finally took a sander and 100 grit paper to smooth out the 'pads' (raised portions on the backing plate). Now that side works nicely. Must do it to the other side.

I believe the effect is worst on the "leading shoe", as that is the one which moves out more and self-energizes. (Self-energizes means, the shoe moves out, and the friction against the drum causes it to pivot a bit and force itself harder into the drum.)

When the wheel cylinder is at the top as on these cars, it is the shoe facing the front of the car that is the "leading shoe", the one that uses that leverage to add braking force.

Drum brakes are subtle, amazing feats of engineering.
 
Swap the drums side to side.
You might be pleasantly surprised.
 
Dana67Dart said:
The shoes will auto adjust so backing them off will only last till they auto adjust back to their happy place.

Things that can cause pulling.
(No particular order)

  1. Wheel bearing lube leak
  2. Brake fluid leak
  3. Suspension parts warn out
  4. Backing plates worn where the shoes ride
  5. Drums turned to the max or more and not the same on both sides.
Click to expand...
Or shoes installed wrong. Primary shoe to the front. (short lining)
 
An update... and a question.

After the car sat overnight, I jacked up the front and tested the spin on the wheels; at first, I thought the tires weren't off the ground. But no, they were that tight! I took the car back to the mechanic, with a printout from the manual on how the brakes should be adjusted. Still... the car pulled to the right.

He suggested that perhaps a proportioning valve was needed, since I had him install a dual M/C... I pointed out, a proportioning valve affects the balance between the front and back, not front to left - and besides, it's needed when you have discs on the front and drums in the back, not drums all around as I have. I pointed him to this thread... And something clicked.

He put the car up on the lift, and checked the dimensions of the wheel cylinders (which the shop had ordered) - they appear the same on the outside, but the insides were different diameters! One side is getting more drag that the other, which accounts for the pulling.

New cylinders have arrived, and Tuesday I drop the car off for the installation. But, here's the question:

After the car warms, I still get a screech on a hard stop. Could that be explained by the difference in drag? Or do I still have a (different) problem?
 
shortmort37 said:
He put the car up on the lift, and checked the dimensions of the wheel cylinders (which the shop had ordered) - they appear the same on the outside, but the insides were different diameters! One side is getting more drag that the other, which accounts for the pulling.

New cylinders have arrived, and Tuesday I drop the car off for the installation. But, here's the question:

After the car warms, I still get a screech on a hard stop. Could that be explained by the difference in drag? Or do I still have a (different) problem?
Click to expand...
Did you mean one of the wheel cylinders has a different diameter inner piston? Sure that can make a difference! The larger diameter inner piston will exert more force than the wheel cylinder with the smaller piston. Once the cylinders are changed to be the same you should have equal braking (assuming the shoes are adjusted similarly). The screech is likely that one side locking the wheel up while the other one is still rolling, thus the pull you notice.
 
Ricks70Duster340 said:
Did you mean one of the wheel cylinders has a different diameter inner piston? Sure that can make a difference! The larger diameter inner piston will exert more force than the wheel cylinder with the smaller piston. Once the cylinders are changed to be the same you should have equal braking (assuming the shoes are adjusted similarly). The screech is likely that one side locking the wheel up while the other one is still rolling, thus the pull you notice.
Click to expand...
Yes! A different diameter inner piston. I thought the difference would create the pull, but it didn't occur to me that the one side might be locking up. Thank you - hoping for the best!
 
Throw one more on the pile. Using a '69 up adjuster with a '68 down system, or vis-a-versa.

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Grease or oil. Any grease or oil on the lining can cause lock up. Has sent me into a 180 while autocrossing on several occassions - which is what clued us into an axle leak. Depending on the extent of contamination sometimes brake cleaner can be used to remove it. Once its really in the lining and spread over a critical area I've always assumed the lining is ruined.
 
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the linings may have been glazed or damaged from all the heat generated while they were draging.

a posable remedy is to take some 120 grit sandpaper and go over the shoes to cut any glaze. if that does not do it I would replace the shoes and be sure there is correct lube in the correct locations on the shoes / backing plates
 
Had the same problem with my brother’s car years ago, when he snapped a bleeder off. I think the 9” and 10” front drum brakes take very similar looking wheel cylinders, but the 9” have a smaller diameter piston and cup. Didn’t find the reason for the brake pull until I changed to disk brakes.
 
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