The Triumph Dolomite Club - Discussion Forum

It looks a hell of a lot different now Mike, it's a credit to you First time i have been called a southerner I dont have a passport! Are you on the TSSC forum as well?

Tony,

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NOW A CLUB MEMBER 2017057

Thanks Tony. I enjoy the restoration work. I am on the TSSC forum as DollyMike but I rarely go there as the Dolomite isn't featured much. The only other Triumph I have owned was a 1967 Vitesse 2 litre saloon, which I owned in the early seventies. I wouldn't mind another one of those, but my classic car ownership has mostly been MGs, with a Lotus Elan Sprint thrown in for good measure. I wouldn't have the Dolomite 1850HL if it hadn't been given to me for nothing!

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

I also disliked the "expanding plastic plug" fixing method and used machine-screws, nuts & washers with a reinforcement plate inside the door.

My original offside TEX door mirror had started to pull away from the door-skin, allowing dirt and moisture to ingress into the gap between the mirror-plinth and the door-skin, resulting in rust!

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Regards.

Nigel A. Skeet

Independent tutor of mathematics, physics, technology & engineering, for secondary, tertiary, further & higher education.

https://www.linkedin.com/profile/view?id=308177758

Upgraded 1974 Triumph Toledo 1300 (Toledo / Dolomite HL / Sprint hybrid)

Onetime member + magazine editor & technical editor of Volkswagen Type 2 Owners' Club

Mine just wobbled when there was only the plastic peg fixing. The screws and nuts keep them nice and steady.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

My Toledo, first registered July 1975, has both a drivers side door mirror and a pair of wing mirrors. I believe that the door mirror was factory fitted but the first owner was more comfortable with wing mirrors so had a pair dealer fitted. Although the way I have them set up does work quite well I am not too keen on the visual appearance but as the paintwork is largely original I will be leaving as is.

I know they'll never be what a car with ABS has (and never should be), but the ones on my Sprint (which has an 1850 servo) are at very least adequate for an emergency stop.

If your's aren't, I'd ask if the servo is working properly: Its having failed is one of the more common reasons the TR7's brakes are called bad names. They may not be that great with it, but without it they're the same as the HA Viva's and, if you'll pardon my French, merde.

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).

My servo is a fully reconditioned unit from Wins, and the entire brake system has been renewed, pipes, flexibles, master, rear slaves, front calipers and new pads/shoes. In any case the servo doesn't make the brakes any more efficient, it just reduces the pressure needed to operate them. The brakes on my Dolly will stop the car quite well, but even with the servo the effort is more than I expect after driving modern cars, and the size of the discs is tiny considering the weight of the car. They don't inspire confidence in what is a hundred mph car. I can't imagine them surviving a long steep descent.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

I don't understand what you mean about the servo not making the brakes more efficient; it increases their effectiveness by, as you say, reducing the pressure [on the pedal] needed to operate them.

What aspect of efficiency do you mean? Are you implying that some of the force being applied to the pedal is being wasted some where?

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).

The amount of braking force that can be generated is purely a function of the size of the discs and pads, and the amount of clamping force that can be applied. You also have to be able to get rid of the heat generated. Without a servo the brakes will work just as well providing you can provide enough force to the pedal.

On a modern car, the servo assistance is high, so without the servo the pedal feels very solid and would need a very high pressure on the pedal, but providing you are able to supply enough force, the brakes will work just as well without as with the servo.

On an older design like the Triumphs and MGs the amount of servo boost is minimal. On the MGB, which I have the most experience with, the car started back in 1962 without a servo. A servo was added in about 1973 without altering the brake design at all. Having driven both cars with and without a servo, you are really hard pressed to tell which is which. In fact the non-servo car feels to have more powerful brakes because the pedal is firmer.

Similarly, the boost supplied by the Dolomite servo is low and the car would stop just as well without it as it does with. The real issue is the small size of the discs and pads. Compared with the MGB set up they are tiny, and yet the weight and performance of the two cars is very similar - in fact the Sprint is quite a lot faster without any improvement in braking. The bigger discs of the MGB also mean the heat can be lost more easily. In my opinion the Dolly was under-specified in the braking department.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

Interestingly, if you look at Amonton's 2nd law of friction, you'll see that the size of the pad has no effect on brake effort (torque). That's just the total force applied through the pistons, the dimensionless coefficient of friction for the two surfaces (giving the force of friction from Amonton's first law), and the distance of the hub centre from the centroid of the pad (which, from what I can find, should align with the centre of the piston in a two pot system). It may be interesting to note that Coulomb's Law says the rotor speed is not part of that equation either, except when it's zero.

I can't really comment on the MGB, but if the distance from the pad centroid to the hub is larger than for the Dolomite, that will give it a greater mechanical advantage (more nearly one). Whereas, a smaller system has advantages in terms of unsprung weight, and the knock-on effects that has on the suspension system. I suppose lightening the brake system is less of an issue where you don't have alloy wheels and nuts.

However, the Sprint's brakes are more than adequate for stopping a road car. It was, after all, designed and built to homologate a Group 1 race car; as which it had some successes in the BSCC in 74 to 78. And FIA rules (e.g. Appendix J 1971 Art. 257 clause i) did not allow different brakes in Group 1. They did for cars in Group 2 (which could also have different carbs and manifolds), but they were not allowed in the BSCC at that time.

And I'm still none the wiser about where efficiency came into the equation.

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).

Servos make no difference to braking. My toledo (TR7 engine) had no servo initially, but I added one as it was too much of a difference between our other cars (including my spitfire which uses GT6 calipers and vented discs and stops VERY well)

Indeed the toledo is still marginal in terms of braking, and does not feel re-assuring. The discs are tiny, smaller than a std spitfire. And therefore not as good...

The theoretical side of brakes is all well and good, and talking pad areas etc. But would you really want a pad the size of a 1p? things would go wrong very quickly as it is real world and not theory, and there are other factors that come into play (heat being a big one)

Brake weight is not something to skimp on. You can go buy alloy callipers, and mitigate weight by lightening elsewhere (alloy hubs, light alloy wheels, light tyres etc) but good brakes outweigh (no pun) handling advantages by some margin. Having watched cars come down Stelvio and lose there brakes makes you realise that theory is no match for real life...

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Clive Senior
Brighton

Hi Bumpa, I'm new to this thread and can't be ar$ed reading the theories....I've had my 1850 brakes totally redone and am pleasantly surprised how good they feel compared to my 2016 Skoda Superb.
I don't need to plan ahead. Of course if push comes to shove in an emergency stop.....
The brakes don't feel as good as my 2009 petrol Focus. Feel better in normal driving than my diesel Skoda. Feel infinitely more responsive and safer than my 2008 diesel Combo!!

Oh, I wasn't saying pad area is irrelevant, just that it isn't a factor in the torque the brakes give for a given foot pressure. Their significance is in fade performance and life.

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).

Well an MGB has 14" wheels, which allows a bigger disc to be fitted and therefore the brakes can be better!

This is a really old chestnut that has been dealt with at length in a number of other threads. We KNOW that Dolomites are underbraked, especially in Sprint form. This is not helped by, in my experience, many cars having brakes that are not performing as well as they might be, due mainly to lack of consistent use.

And I should think that, by now, we all know the cure! It's called a Trackerjack conversion! It's available, it works and I would recommend it to anyone who wishes to drive their Dolomite harder than an occaisional sunday afternoon ride to a show.

And none of this debate has anything to do with mirrors, which this thread is supposed to be about!

Steve

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'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.