Rear Brake imbalance TR4

[MikeF]

HI Got a surprise advisory on brake balance my MOT.

 

The rear off side is down on foot pedal to just acceptable, but hand brake is 100% equal and works well.

The cylinders, rubbers shoes etc were all replaced both sides 5? years ago.

Everywhere is dry, no leaks or splits and everything slides about OK.

The brake shoes are barely worn but there is there is some slight what I would call "cratering". You can see them in surface and just feel with a fingernail some pits or craters about 4-5 mm long 2-3 mm wide. Lots of black dust.

The car stops in a straight line and there is no pedal sponginess or pump up.

Handbrake being OK suggests some sort of hydraulics problem but what?

Would appreciate suggested "to do" list

 

Mike

Edited August 19, 2016 by MikeF

[RogerH]

Hi Mike,

rubber flexible hose partially blocked maybe.

 

Roger

[RobH]

On a live-axle 4 there is only one flexible hose which feeds both sides so I doubt its going to be that Roger. I did have a similar issue with my 3 once and that was due to the to the brake pipe being crimped nearly flat - I had obviously hit a very big pot-hole at some point and the pipe had been trapped between the axle and something on the chassis. The PO had replaced the pipes and obviously not run them in a sensible route.

[BlueTR3A-5EKT]

Start with the easy stuff. Visual inspection of pipe work, (as RobH mentions) adjustment and bleeding of both sides. Bleeding sequence - LH side rear then RH side rear. Get an assistant you trust unless you have an useful one man bleeding kit. Be sure to use the correct fluid to match what is in the system now.

Peter W

[Motorsport Mickey]

Working it out from the description, despite what you may think the brake cylinder is not sliding correctly on the back plate.

 

When you use the handbrake the leverage of the handbrake pulling mechanism frees it up and so you get a 100%, when the hydraulics are used only the piston gives any leverage for expansion of the brake shoes...not enough. Strip the rear brake drums down side by side, examine the brake cylinder movement with the brake drums off, careful you don't pump the brake pistons out. Clean off the back plates lubricate ( I'd use copperslip) so that that the cylinders move easily on the backplate and rebuild and see if that cures.

 

Mick Richards

Edited August 19, 2016 by Motorsport Mickey

[boxofbits]

I agree with Mick on the wheel cylinder not sliding properly. Also the age of the cylinders may not be a factor, as it could depend on how often the car is used.

 

You might find the Pistons have got a bit tight through lack of any real movement and will need freeing up.

 

Kevin

[Lebro]

+2

Bob,

[MikeF]

OK thanks very much everyonel, I'll do it all and see if I can get it back on the tester.

[stuart]

Also while you have the cylinders out examine the back plates around the slot where the cylinder sits for a worn depression where the handbrake lever sits as the pins on the lever can and do wear a dip in the back plate which can impeded the sliding of the cylinder. If there is a depression then weld it up and grind back smooth. Also paint being scraped off the back plate can stop the cylinder moving freely.

Stuart.