TR2/3/3A Sticking front brakes?

[karls59tr]

Driving my TR3 the other day on a bit of a long distance run and I got the distinct impression that the front brakes were partially on when they shouldn't be! Under what circumsatnces would this happen? The brake hoses were upgraded to the stainless ones years ago. Removed the restrictor valve this year. Apparently this valve was installed to keep the brake pads closer to the disc according to what I have read. (Those who have removed the restrictor said that it made little or no difference in actual braking.) Any thoughts on why the front brakes would tend to stay on?

 

[Sarastro]

There are lots of possible reasons; we'd just be guessing. Usually it is some corrosion in the caliper. I'm told that a plugged flex line can do it too, but I've never seen that, myself.

In a disk brake, the piston seal distorts when you brake, and then relaxes when you release the brake. That relaxation is what withdraws the piston. It doesn't take much to keep that from happening. A little rust or a little crud is plenty.

 

[karls59tr]

There are lots of possible reasons; we'd just be guessing. Usually it is some corrosion in the caliper. I'm told that a plugged flex line can do it too, but I've never seen that, myself.

In a disk brake, the piston seal distorts when you brake, and then relaxes when you release the brake. That relaxation is what withdraws the piston. It doesn't take much to keep that from happening. A little rust or a little crud is plenty.

Thanks I'll have to take a look to see if the pistons are sticking in the bore. I'm wondering if some type of light lubrication on the piston might might be beneficial or would that interfere with what the seal does?

 

[bobhustead]

How new are your pads? I have a belief, without empirical evidence, that new pads are sometimes too thick and drag when thoroughly warmed up.
Bob

 

[karls59tr]

How new are your pads? I have a belief, without empirical evidence, that new pads are sometimes too thick and drag when thoroughly warmed up.
Bob

Pads are fairly new. I agree with your assessment.

 

[Sarastro]

The thing is, if they are sticking, you need to take them apart, remove the rust or dirt or whatever is doing it, and then put them together with new seals and, if necessary, pistons. When you do that, it's good to lubricate the piston lightly with brake fluid, but nothing else.

 

[MK3HumberSceptre]

Like Many have stated there are lots of possible reasons.1: Pads to tight in Caliper ( due to rust build up and or if the paint/coating is to thick)
2: Caliper Pistons not retracting due to ..hydraulic pressure not being fully released (due to brake hoses, internal or external proportional valve / piston, Brake Pedal adjustment i.e.: not enough free play between pedal push rod and master cylinder ( have seen misadjusted brake switched not allowing pedal to release properly, caliper piston sticking due to corrosion or piston seals over heated and hard or just old.
plus many other possibilities.
Questions are.... Is it both or just one front brake dragging or is it possible it's a rear brake issue !!! Not sure how easy it is for the issue to be duplicated, But if it can be, stop the vehicle and feel / measure to temp of each road wheel to determine if its on or more wheel are warmer that they should be, then maybe then it can be narrowed down to which Axle / wheel the issue is affecting.

 

[karls59tr]

Like Many have stated there are lots of possible reasons.1: Pads to tight in Caliper ( due to rust build up and or if the paint/coating is to thick)
2: Caliper Pistons not retracting due to ..hydraulic pressure not being fully released (due to brake hoses, internal or external proportional valve / piston, Brake Pedal adjustment i.e.: not enough free play between pedal push rod and master cylinder ( have seen misadjusted brake switched not allowing pedal to release properly, caliper piston sticking due to corrosion or piston seals over heated and hard or just old.
plus many other possibilities.
Questions are.... Is it both or just one front brake dragging or is it possible it's a rear brake issue !!! Not sure how easy it is for the issue to be duplicated, But if it can be, stop the vehicle and feel / measure to temp of each road wheel to determine if its on or more wheel are warmer that they should be, then maybe then it can be narrowed down to which Axle / wheel the issue is affecting.

I'm thinking that I may have installed the spacers incorrectly at the caliper mounts on the right wheel causing the brake pad to constantly rub? Going to have a look tomorrow. I deactivated the proportioning valve some time ago and the brake hoses are the stainless type. Going to have a look at the caliper piston and seals as well

 

[MK3HumberSceptre]

that cold possible be the cause if the Caliper is not centered on the Rotor/Disc especially if the pad are still at new thickness.

 

[Snowkilts]

Rusty caliper pistons are common and will cause this. New stainless steel ones are available. Magically, my car doesn't pull any more when step on the brakes!