Nigel fits new parts to stop the GT6 cooking its brakes
Afew months ago, I reported on fixing a few MOT advisory issues on the GT6, including a rear brake imbalance. A thorough clean of the brake shoes and drums and careful adjustment seemed to do the trick – but it turns out I crossed this job of the list too soon, because under sharp braking the car began pulling to the left again. Back in the garage I jacked up the back of the GT6, got the wheels off and set to work stripping the brakes. There wasn’t an obvious reason for the problem – it had all been assembled correctly last time, the slave cylinders were sliding in their slots on the backplates as intended, so what was wrong? The rear brake shoes didn’t have much lining thickness remaining, so I got a new set from the Triumph Sports Six Club’s shop and fitted them, as it was about time for new shoes anyway.
I cleaned the drums again with 240 grit wet and dry then started to refit them. In hindsight, at this stage I got a little clue that the problem might lie deeper. Naturally the brake adjusters needed backing off to allow the drums to fit over the new, unworn brake shoes. The odd thing was that the right side needed adjusting out much further than the left. I adjusted the brakes, checked the handbrake’s operation and then put the wheels back on. Off for a short test drive, it was soon obvious the brakes still pulled left when I tried stopping sharply. More alarmingly, the right rear brake was heating up very quickly, much more than its opposite number. Test drive cut short, I limped home.
The heat is on
Once safely back on the driveway, I grabbed my digital thermometer from the garage and measured the temperatures of the rear brake drums. The left side showed a reasonable 48° Centigrade, but on the right it was an alarming 112°C. This technology is great – the digital gauge gives precise figures and saves you getting burnt fingertips trying to judge temperature by feel!
Clearly the right rear brake was binding badly – so badly it would quickly cook the new shoes. Once it had cooled down, I stripped off the drum but could see nothing obviously amiss. The return springs were in their correct places and the handbrake cable seemed to be free-moving and properly adjusted. After backing off the brake adjuster further, I took another test drive. The result was the same; a spell of head-scratching
followed. One thought was that perhaps the return springs had gone weak with age and were failing to adequately pull the new shoes back from the drum surface. Worth a try, and it would leave the hydraulic slave cylinders as the only rear brake components I hadn’t replaced, so I visited Rimmer Brothers’ website and ordered new return springs and a pair of slave cylinders.
Breaking the bind
The postie soon delivered the goodies, so it was back to the garage. I stripped out both rear brakes in record time – by now I could do it blindfolded! Before disconnecting the hydraulic pipes from each slave cylinder, I went to the brake master cylinder, removed the top and covered the reservoir with cling film – an old trick that stops too much fluid leaking when opening up the hydraulic circuit.
The new slave cylinders were fitted, with a smear of copper grease to help them slide freely on the backplates. The spring retaining clips went back into place behind the back plates, the hydraulic pipes were reconnected, and I rebuilt the rear brakes complete with brand new springs. After adjusting the brakes once more, it was time to bleed the system.
Everyone seems to have their own personal weapon of choice when it comes to bleeding brakes and I must have tried them all over the years, with varying degrees of success. My current favourite is a vacuum bleeder that runs off compressed air to generate vacuum and suck the fluid through the system from each bleed nipple. This method is working well for me, though my small under-the-bench compressor struggles to supply air at an adequate rate, making bleeding a bit slow. Anyway, with the brakes bled all felt well with the system, so it was time for another test drive.
This time everything was fine. The car pulled up straight and the rear drums both showed temperatures around 50°C after repeated use. Problem solved, but what was the cause, after all? Well, I examined the old slave cylinders on the bench. The left cylinder was fine; I was able to ease the piston out, finding both piston and bore looking clean. The right side slave cylinder was a different matter, though – the piston was seized in its bore, though after much persuasion it came out, revealing some nasty corrosion.
That’s reassuring – now I know what the real problem had been. I’m just a bit embarrassed it took so long to track down. But it’s fixed, the GT6 now drives as it should, and I’m happy about that. In celebration, I treated the little Triumph to an oil and filter change, then lubed its trunnions!
‘The left-hand side showed 48°C, but on the right it was an alarming 112°C’
Nigel’s so familiar with the rear brakes, he can work on them with his eyes shut.
Adjusting the new rear brake shoes. New shoes and return springs didn’t solve the problem.
Nigel’s handy little bleeder.