TR2/3/3A TR3A Disk Brake Question

[TR3-Stu]

I fired up the TR and took it for it's first short test hop down the street (slightly illegal) . Had a good firm petal before I started off and the handbrake worked perfectly. After the first application of brakes, the front disks are firmly still on. The car will move, but will not coast at all. The calipers are brand new Moss units as are the pads; I drilled out the restrictor valve after I had trouble bleeding the brakes and finding an earlier post about problems with that valve; - why would the pressure at the disks remain high after I'm off the brake petal? Help
Stu

 

[bobhustead]

Freeplay in the master cyl push rod could be a problem. Also, new pads are often too thick. With wheels off, can you pry the pads back to where the rotors spin freely?
Bob

 

[CJD]

If you are sure the restrictor is disabled, then my thought is along with Bob...check that the master cylinder piston is returning fully to the stop. It could either be the rod is adjusted too long, or the new MC piston is "sticky". You will have to remove the rubber boot to make sure. The rod could be loose, but the piston still short of retracting. It must fully retract to vent the brake lines.

 

[bobhustead]

Two more thoughts. A mechanical bind keeping pedal or push rod from returning to original position. Or, the clevis pin somehow mispositioned (this latter seems unlikely, but possible).
Bob

 

[bobhustead]

I just went out and looked at my car. It looks like it could be possible for the pedal end of the pushrod to foul the right front bolt (or something trapped against it) that holds the pedal box to the firewall.
Bob

 

[Geo Hahn]

I drilled out the restrictor valve...

I never heard of drilling out the valve, most just open it and remove the spring thingy.

 

[Hamish Racing]

Often with the new calipers the piston dust “bellows” rubbers don’t allow the piston to fully “relax” thus preventing coasting due to the pads binding.

too thick pads are also an issue as previously mentioned
I sanded mine a little

 

[TR3-Stu]

John, Bob, Geo, and team Hamish
Thank you for all the useful suggestions and hints. I wasn't clear on my 'drilling out' the restrictor valve - as Geo said, I just removed the springy thing. As to the new pads, when I installed them they went in easily and each wheel rotated smoothly, so it seems to be pointed at the MC. I will be out there today checking the MC closely as it sounds like that is my problem. Thanks again for the quick responses - this forum and it's members are so valuable.
Stu

 

[TR3-Stu]

Brake MC update - thanks to all of your valuable advice, I checked the MC play/throw and, as several members suggested, my adjustment was not allowing the MC piston to fully retract. Simple fix with immediate good results.
Lesson learned - there's always more to learn. I started working on British cars when I was 16 (1st car was a '55 small-mouth TR, 2nd, a '56 MGA), then got away from British vehicles for quite a while, but still considered myself a decent mechanic. I'm always humbled by what I don't know, or have forgotten.
Thanks again for all the help.
Stu

 

[Joel Lester]

Excellent news! Glad you were able to get'r sorted out

 

[CJD]

Glad to hear...now enjoy driving inthe nice fall weather!