Brake bias issue? (1 Viewer)

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Joined
Apr 28, 2022
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Location
Montana
First post. I've read brake related several threads and reviewed the service manual for the 200 Series to the best of my ability.
My 2016 200 Series ~104,000 miles is dragging the rear brakes enough to generate heat while driving. The first thing that came to mind was a stuck caliper.
Both calipers retract/move freely when I open the bleed screws. I reset the parking brakes per the Factor Service manual as well.

Front brakes will be cold to the touch after a drive, rears are warm. If a caliper were sticking I'd expect one side to be noticeably warmer, but both are within a few degrees of each other so either they are failing the same way or the issue is that pressure is remaining applied. I plan to replace the rear calipers, pads, rotors next week but I will be surprised if this resolves the issue.

When I review the FSM I see that with the booster functioning properly the system should generate more force at the rear. I was under the mistaken assumption that the vehicle would be biased toward the front brakes. Ass|u|me I was wrong.

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Given the apparent rear bias could my problem be brake pedal free play adjustment or it a problem with the master cylinder?

Apologies if I've missed something obvious in the FAQs or forum. I did find cases of faster wear on rear pads but didn't see anything quite like what I'm experiencing.
 
How hot are they getting? And are you getting excessive wear on the rears?
 
Given your location, I'd suspect rust could be a concern for the parking brake. I know you said you adjusted it but does the mechanism move freely when you loosen it al upl?

M/C free play can also be the problem. If the M/C piston does not fully retract, the brakes can drag.
 
Given your location, I'd suspect rust could be a concern for the parking brake. I know you said you adjusted it but does the mechanism move freely when you loosen it al upl?

M/C free play can also be the problem. If the M/C piston does not fully retract, the brakes can drag.
This particular vehicle is very clean rust wise. Aside from a bit of rust forming on frame welds it is very clean.

I did remove both rotors and observed the parking brake travel the other day. I did several pulls of the lever and observed the return spring on both sides after performing the adjustment. When the brake lever is ~7 clicks there is a visible gap in the shoe ends and part between them (anchor block?) at the highlighted area. I didnt measure but the gaps looked equivalent and were probably 3/16" per side. I may be exagerating. When the parking lever is down (disengaged) there is no gap between the shoe ends and part sitting between them. I've also noticed the heat is being generated in the rotor disc area and not at the hub where the shoes make contact.

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I'll take a look at pedal play and adjustment. Perhaps both calipers/pistons have enough wear they are sticking just enough to drag equally.

Appreciate the replies.
 
Maybe the rear caliper slider pins are sticking and binding a little?
 
Related note: when I installed a new booster assembly in my 100, the rear brakes dragged. I had to re-bleed the brakes and that fixed it. Did you have some brake work done recently?
 
Stock height or lift?
Stock height, no brake work. Recent tire balance and alignment, no issues following the work. I swapped to winter wheels/tires and noticed the truck pulls slight right after install which triggered the inspection.

Maybe the rear caliper slider pins are sticking and binding a little?
I removed the calipers and inspected the pins. Regreased, no signs of pitting or dragging I could detect. The calipers move freely in brackets.
Related note: when I installed a new booster assembly in my 100, the rear brakes dragged. I had to re-bleed the brakes and that fixed it. Did you have some brake work done recently?


I did bleed both rears when I noticed the issue. I'll check back once I inspect the pedal free play and replace the rear brakes.

New rotors and partial hardware have arrived, the rest will be delivered on 1/9. Regardless of if they are the issue it is time for brake maintenance.

I just wanted to ensure there wasn't some known issue I had failed to locate on the forum. I appreciate all the suggestions.
 
Sorry for the long delay.

Summary of work back in January
All new OEM rear:
Rotors
Calipers
Pads
Reset parking brake
Bled system per service manual

System was still maintaining slight pressure and generating heat due to pads dragging slightly on rotors.

Asked several folks who do brakes for a living and got shrugs.

Ordered all new OEM parts for front.
Installed
Rotors
Calipers
Pads
Anti rattle and squeal plates and springs
Thoroughly bled all four calipers per service manual

Rears no longer dragging.
 

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