Inequal braking

[Big T]

‘99 k2500 Suburban. GMT-800 front brake conversion with TSB proportioning valve. Rear drum brakes are new as of 4,000 miles ago. Rear brake pistons are the larger units from the 1 ton. ABS brakes generally do not work 99% of the time.

Left rear wheel will lock up before all the other wheels at mid-level stopping force. Brake pedal is firm. This has occurred since before redoing the rear brakes. On the rare occasion that the ABS works, this is not an issue. What should I be looking for and addressing.

 

[ak diesel driver]

Assuming the axle seal isn't leaking causing the issue, I would look at the spots on the backing plate where the shoes ride. Could have a groove worn into it causing the shoes to jump when moving.

 

[DieselAmateur]

Did you put on new drums or re use the old ones without turning them down? A very out of round drum could potentially hang/ lock up quicker where it's more oval/ flat

Have you tried just backing out the adjuster a tad to see if that side is tighter than the other?

 

[Big T]

Did you put on new drums or re use the old ones without turning them down? A very out of round drum could potentially hang/ lock up quicker where it's more oval/ flat

Have you tried just backing out the adjuster a tad to see if that side is tighter than the other?

New drums.

Adjusters are on the list. Working on replacing window regulator today.

 

[Big T]

Assuming the axle seal isn't leaking causing the issue, I would look at the spots on the backing plate where the shoes ride. Could have a groove worn into it causing the shoes to jump when moving.

No leaks.

 

[jrsavoie]

New drums.

Adjusters are on the list. Working on replacing window regulator today.

New drums doesn't = round drums

 

[Big T]

New drums doesn't = round drums

I would have felt that rolling to a stop.

 

[jrsavoie]

I would have felt that rolling to a stop.

The only way I would say for sure is to have them turned.
Where'd the drums come from?

If they're Chinese, I'd bet heavily on not round. It doesn't always take a lot.

 

[Big T]

The only way I would say for sure is to have them turned.
Where'd the drums come from?

If they're Chinese, I'd bet heavily on not round. It doesn't always take a lot.

Brake Drums came from Napa, but everychink is Chinese today.

 

[jrsavoie]

Drums came from Napa, but everychink is Chinese today.

Truthfully, I've never seen round chink drums.

Do you have anybody around the still turns them?

 

[Big T]

Truthfully, I've never seen round chink drums.

Do you have anybody around the still turns them?

Would have to work hard at it to get a drum out of round. Maybe it does need round eyes to do the job properly.

Seriously, this is more of inequal pressure than out of round drums. I will back off the adjuster tomorrow, after installing starter relay on the ‘94.

 

[Will L.]

Last time you flushed & bled brake fluid?

Yes, drums warp out of round and cheap ones come out of round. Seems impossible but they do.
Put the drum on backwards so you can check runout by spinning axle.
Block front wheels, jack stands under rear axle, flip drums around. Start and put in reverse. WITHOUT hitting brakes. Check runout both sides & and if ok- just turn off engine. If out of round- have cut.

 

[Big T]

Last time you flushed & bled brake fluid?

Yes, drums warp out of round and cheap ones come out of round. Seems impossible but they do.
Put the drum on backwards so you can check runout by spinning axle.
Block front wheels, jack stands under rear axle, flip drums around. Start and put in reverse. WITHOUT hitting brakes. Check runout both sides & and if ok- just turn off engine. If out of round- have cut.

Flushed and bled when I changed the brakes and drums two years ago or about 4K miles. It was doing the same thing before I changed out the brakes.

 

[WarWagon]

Just saying my 1995 had a new out of round, no, off center drum. One of the things I don’t miss.

The backing plate also had wear groves on the passenger side.

I have also been known to install a set of shoues “backwards” on one side.

 

[Big T]

Well it’s not serious, therefore not urgent. I will methodically go through all suggestions as time avails.

 

[Big T]

Point one, new fluid and system has been bled. Pedal is rock hard.

 

[Will L.]

Many pictures. Videos are good too.
Make two circles of plumbers tape, one for each side. Give a bit of slack so we can see the shoes move about 1/8”- but do not hit the pedal without something to restrain the movement.

Unequal park cable adjustment is possible.

When you flushed the lines- are you 100% there is nothing in the line restricting flow? I have removed lines from slaves to let it push out high volume low pressure and measured volume that comes out in 4 pumps to compare the two sides. Examine the hard line from T to slave cylinder for dents.

 

[MrMarty51]

I’m dealing with a brake fluid flow problem today too.
Brand new rotors, hubs, calipers and pads.
Left both front bleeder screws open and refilled the reservoir.
Didnt take long for fluid to flow from the left bleed screw/hose.
Right side never did flow after a couple of hours.
Step son stopped over.
He pump up the pedal, I crack open the bleeder, repeat many times.
Pretty soon got a puff of air, then more and more air. Pretty soon some fluid.
Not a good healthy gusher, just a piddling each time.
Finally told Nick, thats enough.
Then I tried to turn the left side rotor, turned nicely.
Tried the right side rotor, it was stiff and bound.
Pried back the piston slightly.
Rotor turns free.
Fire the brake hose parts cannon at it tomorrow, if the parts store has one.
I am sure that the hose has internally collapsed and is not allowing fluid to flow either direction.
Time will tell.