Converting GT6 self-adjusting rear drum brakes to manually-adjusted brakes

[Roger K]

Has anyone actually done this conversion, and knows that it is possible?

I've been looking through the parts that I think may be needed, and without a parts book for the earlier cars it's very difficult to work out.

Comparing early non-roto GT6 with the late non-roto GT6 (swing spring):

Early car has shorter driveshafts, different back plates, different drums, shoes, cylinders and an adjuster.  The vertical link, rear hub and trunnion block are the same as far as I can tell.

The later car has drums that are l.5" wider.   If I fit the earlier drums and earlier backplate, I assume the backplate would sit in the same relationship to the trunnion block as the later backplate would.  This means that there would be a 0.5" gap between the inner edge of the early drum and the backplate.  Does this mean that you would have to fit the early, shorter driveshaft as well?  In which case, the spring would need changing also?

If there's someone out there who's actually done the job I'd be really interested for some feedback on this.  The more I look at it, the more I think it's not a feasible conversion and we're stuck with the self-adjusters.

[Clive]

The rear upright on you car is shared with all spitfires/heralds/non roto versions of GT6 and Vitesse. 

So yes, you can use early GT6 or Vitesse backplate/drum/shoes/adjuster etc as a complete setup, but no mixing. (spit used long and short driveshafts, but same spring -probably! but definitely the brakes were unchanged)

You could even use spit/herald rear brakes. I did on my 2.5 vitesse and they could still be locked up before the fronts, just.

[Roger K]

Thanks Clive - but I still don't understand how you can fit narrower drums to the longer driveshafts.  Surely the drum will still bolt to the face of the rear hub, which will sit further away from the backplate because of the longer shaft - or have I missed something?  If it didn't, the wider (self-adjusting) drum would be touching the backplate, hard.  Unless a different offset is built into the back plate.

The springs definitely are different.  When I bought my car, it had a Spitfire 1500 swing spring fitted (the invoice for it came with the paperwork), and the car had pronounced positive camber on the rear wheels.  I have bought a GT6-specific swing spring and it is noticeably shorter.  According to Rimmer's, both the 1500 and the late MkIII have the same 'long' driveshaft, but different springs.  I'm really not sure how much you have to change to get manually adjusted rear brakes.

So think my question is:  does anyone have a GT6 with a swing spring (non-roto), but manually adjusted brakes?

[dougbgt6]

43 minutes ago, Roger K said:

The later car has drums that are l.5" wider.

No it's not that much the earlier GT6 drums are 1.25", late 1.5" so that's 0.25" wider. Not much difference. 

But, the servo. Late GT6 has a servo operating on the front wheels only. This  is because the beefed up rear brakes, wider drums, bigger cylinders, would be too much with the

servo operating on them. However, when the servo was fitted as an option on earlier cars it went on all 4 wheels and you may have to do this if you convert.

Doug

[Clive]

1 hour ago, Roger K said:

Thanks Clive - but I still don't understand how you can fit narrower drums to the longer driveshafts.  Surely the drum will still bolt to the face of the rear hub, which will sit further away from the backplate because of the longer shaft - or have I missed something?  If it didn't, the wider (self-adjusting) drum would be touching the backplate, hard.  Unless a different offset is built into the back plate.

The springs definitely are different.  When I bought my car, it had a Spitfire 1500 swing spring fitted (the invoice for it came with the paperwork), and the car had pronounced positive camber on the rear wheels.  I have bought a GT6-specific swing spring and it is noticeably shorter.  According to Rimmer's, both the 1500 and the late MkIII have the same 'long' driveshaft, but different springs.  I'm really not sure how much you have to change to get manually adjusted rear brakes.

So think my question is:  does anyone have a GT6 with a swing spring (non-roto), but manually adjusted brakes?

Roger, all the extra shaft length is between diff and upright. But that 1/4" is taken up somehow, poss backplate is recessed or suchlike? Of the drum has a built in spacer?

spit mkIV is where the change from short to long shafts happened, probably the same time as the non-roto GT6 was released. But I think the spit didn't change the spring though aftermarket springs are often are listed under different numbers. And yes, GT6 is different. Is it just the bottom leaf is beefier?

 

But as before, the drum/backplate and innards need to be changed. Shafts/spring/upright/hub etc need no change.

Top tip, if you want a better handbrake, get Dolomite handbrake cable arms. They are longer so better pull-ability. 

[Rabbit]

I may be wrong on this but had the problem of NON self adjusting on my Dolomite 1500TC. Fitted new cylinders but not happy with amount of handbrake play despite adjusting cables etc. In the end I drilled 5/8in holes opposite the auto adjuster (non), where the lever located on the adjuster wheel and simply adjusted up with screwdriver through hole until slight rubbing then removed drum and backed off 1 'click'. Been absolutely OK now for 2 years. I know it SHOULD work but in my case it didn't so reverted to normal adjustment. It worked for me. I believe the self adjust drums  on later GT6 are  larger but cannot see why what I did should not work on them. 

[Roger K]

I like that as a fix, Rabbit - I have an aversion to changing components from standard because a) they're not standard, and there can be knock-on effects, and b) I'm fed up with scratching my head 5 years later trying to remember what parts I used!

At the moment the issue is 'solved', in that I can't find GT6 backplates of either type for sale anywhere so am stuck with the self-adjust type.

[Peter Truman]

I like the Rabbit solution, one car I've owned in the past had a hole in the drum face to do just that maybe a Sprite? bit of a fiddle but worked well

Would the Hart style Stag aftermarket lever adjusters help application leverage' 

I know my Sprint has self adjusters they appear OK but I seldom use a handbrake anyway even in a modern (had stretched cables on a car once) and after brake overhaul I think its a drive it backwards and apply brakes hard!

[poppyman]

The Rabbit solution does work as i have done the same on a Dolomite. Also disconnect handbrake cables either side before doing it. Said Dolomite can now lock the back wheels and leave rubber on the road. 

Tony.

[Clive]

I still have self adjusters on my Toledo (Sprint axle)

Converting to manual adjusters would have required TR4 stuff, and that gets expensive.

New cylinders, and a good clean up etc of teh mechanism/backplates etc, and then, just in case, a 5/8 hole drilled in the drum for access. They adjust up OK, but I worry about getting the drums off...

[NonMember]

33 minutes ago, clive said:

I still have self adjusters on my Toledo (Sprint axle)

I believe the Sprint axle uses the self-adjusters from the 2000 saloon / Stag / TR7 which are completely different to the late GT6 & 1850 ones. The Sprint ones work.

[poppyman]

2 hours ago, clive said:

I still have self adjusters on my Toledo (Sprint axle)

Converting to manual adjusters would have required TR4 stuff, and that gets expensive.

New cylinders, and a good clean up etc of teh mechanism/backplates etc, and then, just in case, a 5/8 hole drilled in the drum for access. They adjust up OK, but I worry about getting the drums off...

They will undo Clive with a bit of extra force if you struggle to get the drums off.

Tony.

[Pete Lewis]

a tip if you make a decent hole in the drum nave for access you should make two  both opposites to keep the drum  in  balance 

i have a pair of new  2000 thruppenny bit crap machined drums from a reputable supplier which now have some spare holes 

but unless you can skim the drums on a mandrill and make em round they woulds make a nice door stop 

they were cheap and seemed a good must have,,,, just had to  put the old ones back on 

the holes are free  !!!

Pete

[Roger K]

Has anyone any first-hand experience of drilling GT6 drums to access the adjusters?  All the above seems to relate to Dolomites... I'd be grateful to hear from someone who's actually done it on a GT6!

[Pete Lewis]

i just used a cone /step drill   the drums  are cast  so machine well  

 

my new wonky drums had been  I suggest gripped in a 3 /4 jaw lathe chuck  giving the same hopeless lobbing as some synchro rings on sale 

Pete

 

 

[Roger K]

Thanks Pete, yes, definitely use a step drill.  What I really meant was, does this method work OK with the GT6 adjusters - can you get to them OK, etc.  I'm a bit confused over the different Dolomite setups described above in the thread, and just wanted reassuring that holes in the GT6 drums, with the specific GT6 auto adjust mechanism, will work OK.

[Pete Lewis]

ok  sorry i get that  , cant say as  never drilled a self adjuster hole on a mk3  set up

the later sprints etc  used the lockheed brake same as 2000 /2500   has a system of levers  and a rachet advanced spreader bar 

Pete 

sure you can eye up just where to drill , just do one as a test ???so long as it get you ro be able to twiddle the knorched wheel it will work 

 who said that ???

Pete

 

[Colin Lindsay]

14 hours ago, Roger K said:

Has anyone any first-hand experience of drilling GT6 drums to access the adjusters?  All the above seems to relate to Dolomites... I'd be grateful to hear from someone who's actually done it on a GT6!

Measure out from the centre of the axle to where the adjuster sits against the backplate; replace the drum and measure the same distance outwards; mark, and drill. You need a very small hole, just enough to admit the end of a small screwdriver that will lever the adjuster. 

[Roger K]

1 minute ago, Colin Lindsay said:

Measure out from the centre of the axle to where the adjuster sits against the backplate; replace the drum and measure the same distance outwards; mark, and drill. You need a very small hole, just enough to admit the end of a small screwdriver that will lever the adjuster. 

 

[Roger K]

My memory may be playing tricks, but I seem to remember my old Frogeye (or something else I had ages ago) had quite a large hole, maybe 3/4", which allowed two small screwdrivers in - one to lift the ratchet spring lever and the other to turn the adjuster wheel.  I also seem to remember that you could actually put the wheel on in a way that left the hole exposed, so you had to watch how you aligned them to avoid this.  Probably completely wrong...

[Pete Lewis]

all my  Old Hillmans had a wheel hole to align with the drum easy to insert a screwdriver and turn the snail cam you could do it roadside 

just get the hole lined with the cam head and twiddle on the spot ......since then we have had ....Progress!!!!

Pete

[poppyman]

1 hour ago, Roger K said:

Thanks Pete, yes, definitely use a step drill.  What I really meant was, does this method work OK with the GT6 adjusters - can you get to them OK, etc.  I'm a bit confused over the different Dolomite setups described above in the thread, and just wanted reassuring that holes in the GT6 drums, with the specific GT6 auto adjust mechanism, will work OK.

It will work Roger as the set up is the same. I have a couple of mates with GT6's who always moaned about their handbrakes, both can now lock the rear wheels even on a dry road. The main thing is to disconnect the cables when adjusting the foot brake or you will be wasting your time. There is room to drill a hole but measure up, both mates have it on their "to do" list.  

Tony. 

[Roger K]

Thanks Tony, I've just refitted the diff so have the rear axles and brakes to do this week (nothing else to do....), so I will measure up and drill the drums when I get to that stage.

Whilst refitting the diff, I've learnt the hard way that the new rear diff mounting bushes Rimmers sell are 1mm wider than the originals.... metric approximations of 1.5", I guess.

[Colin Lindsay]

17 hours ago, Roger K said:

Whilst refitting the diff, I've learnt the hard way that the new rear diff mounting bushes Rimmers sell are 1mm wider than the originals.... metric approximations of 1.5", I guess.

What's the oft-quoted Ulster phrase I use about that sort of thing? "Aye, sure it'll do..." Thankfully there are plenty of alternatives that are a good fit, but sadly maybe too late for you now, Roger.

[Roger K]

7 minutes ago, Colin Lindsay said:

What's the oft-quoted Ulster phrase I use about that sort of thing? "Aye, sure it'll do..." Thankfully there are plenty of alternatives that are a good fit, but sadly maybe too late for you now, Roger.

Worked on them with a file and they slotted right in.  Could have saved myself half an hour of pointless shoving and levering, though, if I'd taken my calipers to the bushes first.