TR2/3/3A TR3A Girling 9" Rear Brake Initial Adjustment

[Joel M]

I'm currently performing the initial rear brake adjustment on the rolling chassis, and would like some feedback. Per the service manual, I engaged the wedge into the adjuster housing until the drum could no longer turn, and then backed out 1 notch. At this setting, the drums appear to spin freely; however, when I engage the hand brake and release, there is some drag that doesn't go away when spinning the drum by hand. During assembly, I did check to ensure the cylinder moves inside the backing plate, but I wouldn't say it easily slides back and forth. My best guess is that when I engage the handbrake, the cylinder doesn't completely move back to the location where there is no drag. Is this normal behavior for a rebuild with new brake pads? I'm thinking this may be a non-issue after going through a normal break-in period.

 

[Hamish Racing]

Sounds like it should bed in.
Is the plate grooved from years of wearing? As this is quite common and can be welded and ground back.
or is the plate painted/ powder coated as this can restrict movement. But bedding in should sort this too.
great to be at rolling chassis stage though

 

[CJD]

If the drag is so little that when you take the drum/wheel and try to spin it...it still turns a little after you let go, then you are good. If you try to spin it and it stops instantly after you let go, then that is likely too much drag. Of course, that is just a technique.

A second check is, when you release the brake, the horizontal handbrake cables at the rear of the axle should be loose enough to feel a bit of play...no tension at all. If there is still any tension at all, back off the adjustment just enough to get minimum play with the brake released. Again...a technique, but it should be the last handbrake adjustment you ever make until you change something in the system. Adjusting the shoes in the drums also re-adjusts the handbrake.

If you check these points and you still think you have too much drag, then we need to look closer at your assembly.

 

[sp53]

Imho, the cylinder should not move at all or come back to a spot. “The cylinder doesn't completely move back to the location” There should 3 keepers and a rubber seal holding the assembly tight. The 3rd retainer holds the assembly tight. In addition, a long square box end is helpful to get the last click when everything is correct. Plus be careful not to get stuck on a high spot on the cam when adjusting--- that is where the longer wrench helps

steve

 

[ckeithjordan]

I found this to be helpful:

Bedding-In Your Brakes

Tech

mossmotoring.com

 

[bobhustead]

I have a great inexpensive tool that is still sold. You can find it by googling "drum brake adjustment caliper". It has an inside caliper with pointed contact tips to measure the drum and an outside flat caliper for the shoes. Just adjust the shoes, drum off, to touch the max diameter of the shoes, slide on the drum and you are set. Drum, of course, can't have a wear ridge on the edge or it won't clear the shoes.
Bob

 

[Joel M]

The backing plate on the passenger side did have some very minor groves which I dressed up and smoothed lightly with some sandpaper. It's not perfect, but seems to be a fairly good surface to accommodate movement by the cylinder. This may have improved the drag condition a little, and the drum does continue to spin a bit after I release it. The driver side has a bit more drag after I release the parking brake, so I will try to clean up that side next.

 

[Joel M]

So I worked on the driver side this weekend. There were no grooves in the backing plate from movement of the cylinder, but there were small grooves created by the small lever that manually actuates when the handbrake is used. I was able to repair this, and also remove some light pitting. Once installed, I noticed the cylinder movement in the backing plate was very smooth. Having said that, I still noticed some drag when actuating the handbrake lever and releasing. The drum does not stop spinning immediately upon release, but it probably only spins 1/2 to 1 revolution (this is with the passenger side wedge backed out and that drum spinning the opposite direction through the differential). If I back the wedge out of the adjuster housing two notches instead of one, the drag is almost completely gone. Is there any concern backing out two notches from locked drum during rear brake setup? I know the manual says one notch, but it seems like the the pads and drum would eventually get to an equivalent condition as the pads wear down during normal use.

 

[CJD]

One notch should not make a difference, unless the pedal is uncomfortably low. After a few miles the linings will bed and adjusting should be easier.

 

[Joel M]

Thanks for the feedback John. I will back off 2 notches on both sides for the initial setup, and then readjust/re-evaluate after proper brake burnishing.