Tri­umph GT6

Nigel fits new parts to stop the GT6 cook­ing its brakes

Practical Classics (UK) - - CONTENTS -

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!

prac­ti­cal­clas­sics@bauer­me­dia.co.uk

‘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.

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