The Triumph Dolomite Club - Discussion Forum

'Evening all, I'm hoping you guys can provide me with some information regarding the Sprint rear axle. Long story short I'm doing the research for when I start rebuilding my Dolly, which will have ballpark 250bhp and 250lb-ft (turbo MX-5 lump in all probability) and want to make sure the axle is strong enough to handle this and do some track\hillclimb work reliably.

From the research I've done on these forums so far I understand that the diff will probably just about handle this sort of power, but I may well have to swap it for an LSD. Also I saw that it's possible to install a different inner halfshaft oil seal (the gearbox input one) to help prevent leaks. I'll probably be swapping the car over to a 4x108 pcd as well for better wheel and brake discs choice (subject of a future subject).

Given the fact that the axle is said to flex under heavy cornering, is there any mileage in trying to make a brace for the rear axle like they do with the Atlas (see below)? This would also give me somewhere to mount a Watts linkage. What other mods could I do to strengthen the axle? Aren't the halfshafts meant to be a bit puny?



I'd like to keep the sprint rear axle for weight purposes if nothing else, but I'm not sentimentally attached

Also I once taking time into account as well as money, should I just scrub the axle and install a volvo\atlas\TR7 axle?

Aye, that's a group 4 escort axle - nothing to do with me I'm afraid, just pinched the picture for illustration purposes

Why are you thinking of rear discs when the Sprint axle is already over braked for the car? What brakes are you using for the front?

Yes. This is from the homologation docs for the Dolomite Sprint

I have no more info that that picture.
Pop over to the motorsport section and ask. Among the items of dolomite rocking horse poo I believe there were tougher halfshafts. If I'm not dreaming somewhere I think I picked up that an alternative to those is an additional bearing on the halfshaft but I have no idea how that is achieved.

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1978 Pageant Sprint - the rustomite, 1972 Spitfire IV - sprintfire project, 1968 Valencia GT6 II - little Blue, 1980 Vermillion 1500HL - resting. 1974 Sienna 1500TC, Mrs Weevils big brown.

Still on drums and shoes...

Thanks for the replies guys - looks like the brace idea has been put into use before! Looks simple enough to do at first glance. I had heard about installing extra bearings, but that it would need expensive machining - being deep inside the casing I'd imagine it's quite difficult. Looks like the halfshafts are the remaining major weak point then... not sure what to do about that as I figure I'll be unlikely to get my hands on the tougher originals :/

The reasons for switching to discs on the rear aren't to do with braking effort - as you say the current drums are OK in that respect. The main reasons would be future availability of cheap parts, ease of servicing them and I'm more familiar with discs than drums. There may be a little weight saving, though I'm not too worried about that, and I think they look nicer - again not too worried about that as you can't really see anything with 13's on! From my point of view if I'm going to be changing the PCD of the car (which I am for wheel choice and hopefully front brake discs which don't need machining prior to fitment) then I may as well go the whole hog

Front brake discs are liable to be vented escort from the research I've done so far, mounted on escort ally hubs and a new stub axle. Currently got Trackerjack ones, but you need to machine the discs for those and I wouldn't be able to change the PCD. I would like a system where the hub doesn't need to be removed to change the discs, but I can't think of a decent solution short of swapping the uprights which I'd rather avoid... I have a tendency for scope creep if I'm not careful and would probably end up redesigning the whole front suspension