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PostPosted: Sat Feb 13, 2021 10:01 pm 
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It's the ABS, or lack of, that's the big thing there.

With that, you can have more or less whatever ratio between pedal pressure and brake effect you want. I don't see that there's near as much reason to worry about brake balance either. Without it, there's yet another balance to be considered, between making it easy enough to get to the limit but not so easy it bites you in the gluteus maximus all the time.

Now that, as a reasonably priced retrofit, together with some reasonable increase in brake force, would interest me. Not so sure I've any need for vented discs, with or without ABS, though.

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).


Last edited by GrahamFountain on Sat Feb 13, 2021 10:10 pm, edited 1 time in total.

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PostPosted: Sat Feb 13, 2021 10:09 pm 
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One somewhat counter intuitive thing i've done, is to replace the Sprint servo on the Carledo with a smaller version from an early 1850. Whilst I did this initially from operational necessity (the Sprint servo I had failed and I couldn't get another quickly) It has remained in this state the last 5 years or so because I found it felt and worked better that way! Admittedly the Carledo is VERY light but I found it a tad TOO easy to lock it up with the Sprint servo, the smaller 1850 offering gave more feel under my foot (a personal taste thing as Graham so rightly says) but it works for me. It's only just possible to lock it up in the dry (by seriously ignoring the car's warnings) and when it does, only the fronts lock. Which is as it should be!

Steve
Oddly enough, I too am running with an 1850 servo. I fitted that while the Sprint one was being reconditioned, and I still haven't got round to swapping back. But I'm still happy that the brakes work well enough for my needs - with or without the increasing weight of kids. It's certainly better with a working 1850 servo than a none-working Sprint one. That were a bit hard on the foot.

I must go check the load sensing valve at some point though.

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).


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PostPosted: Sun Feb 14, 2021 12:14 am 
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i think this braking lark,all depends if your a bumper hogger or not! if you are a bumper hogger get another newer car and leave dolomites alone....dolomite are ment for cruising not scrap or breakers yards :D

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Dolomite 1300,1980`V`reg in british racing brown(russet),3.63 diff with 21t speedo pinion,95%poly`d,HL clocks,standard wheels with SE covers wrapt in 175 70 13,mot`d 19-09-2014,been off the since 1990,(july2017) stainless steel exhaust 3-piece,(xmas2018) wooden mountney steering wheel,(june2020) new monroe shock(radial front,gas-matic rears) with -1" lower`d springs all round.


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 Post subject: Hmm.....
PostPosted: Sun Feb 14, 2021 1:40 pm 
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I am very very reluctant to post in this thread,
but did the late Jon Tilson not revise his thinking on brakes after trying a TJ conversion?


If it was not possible to upgrade the brakes on one, I wouldn't own a Dolomite.
Triumph did upgrade Sprints to vented discs......



Ian

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 Post subject: Re: Hmm.....
PostPosted: Sun Feb 14, 2021 4:30 pm 
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If it was not possible to upgrade the brakes on one, I wouldn't own a Dolomite.
Triumph did upgrade Sprints to vented discs......

Ian
I take it then that you'd not like the Herald/Spitfire cross we have, which has type 14 front calipers (upgraded by me from type 12s) and no servo. But even the wife said they are good enough. Though it may help that it's hard to get more than 90 from it on the flat - and that with a fortnight's run-up - and I'd just said they could be better.

Interestingly, because vented disks get less hot, and the CoF between pad and disk is roughly proportional to temperature (up to the point of fade), if you only replaced solid ones with vented ones, you'd get less braking effort for a given pedal pressure: though it'd last longer if you used it lots. But I admit, I've never seen an upgrade that just swapped solid for vented disks.

Was the vented disk conversion from Triumph an ST option? Possibly Jeroen can say what the Group 1B (Group 1-1/2) race cars had fitted.

Graham

_________________
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).


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 Post subject: Re: Hmm.....
PostPosted: Sun Feb 14, 2021 5:40 pm 
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Quote:


If it was not possible to upgrade the brakes on one, I wouldn't own a Dolomite.
Triumph did upgrade Sprints to vented discs......



Ian
I quite agree. I had a Sprint 30 years ago and the brakes weren't great. That was with decent pads and everything up to scratch.

The Sprint had the same solid discs right the way through the production run.


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PostPosted: Sun Feb 14, 2021 6:45 pm 
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I believe the ST vented discs still used the type 14 callipers suitably spaced to accommodate the width, so same sized pads, swept area etc.


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PostPosted: Sun Feb 14, 2021 7:25 pm 
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I wonder if that some see the brakes on the Sprint as underwhelming is a lot about expectation, i.e. in comparison with modern cars?

As one who has almost exclusively driven TR7s with TR8 or SD1 brakes, Dolomite Sprints, and the Herald with (now) type 14s, for probably too many years, the Sprint's brakes seem fine to me. But then I'm entirely used to pressing hard to get the car to stop sharply (with a bit of cadence if the surface is slippy), and using the broad range of brake options that I get from that. If I only drove the Triumphs of a Sunday, I expect I'd miss the sharpness of modern car brakes when I did. I nearly hesitate to use expressions like spoiled. But without the safety-net of ABS, after all these years of stamping on the pedal (with some loud comment or other) in an emergency, I'm not sure any significant upgrade would make me a safer driver.

However, I acknowledge it would be possible to get used to them being, by my lights, too easy to lock-up. I still think Steve's comments about upgrading the brakes, and then having to wind them back with an 1850 servo is mildly amusing. Though I accept the change to vented discs is still valid for some.

But I still stand by the comments on modifications to the rear brakes without understanding the possible consequences.

As to the comment earlier about fade from brakes in hilly country being a reason to upgrade: during one afternoon spent mostly going up and down Blue Bank above Slights in a TR7 Sprint, I came to very much appreciate how the gearbox should be used on the down-hill legs.

Though, thinking about it, there's a "where the hell's the road gone" bit at the top of Rosedale head that's more scary. There's an interesting bit at the top of Bishopdale that used to have a sign for cyclists saying, in effect, those who wish to live are strongly recommended to get off and walk down.

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).


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PostPosted: Sun Feb 14, 2021 7:31 pm 
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I believe the ST vented discs still used the type 14 callipers suitably spaced to accommodate the width, so same sized pads, swept area etc.
Could be interesting, if I got fade ever. With no servo, I would have to look at how much cooler they would run in normal use - I'm not going to argue with SWMBO (there's always the risk I might win). But I didn't like the type 12s that much - but then they were over 50 years old.

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).


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PostPosted: Sun Feb 14, 2021 7:40 pm 
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I believe the ST vented discs still used the type 14 callipers suitably spaced to accommodate the width, so same sized pads, swept area etc.
Also, haven't we been through the proof that relative pad area don't matter to brake effect, just wear rate - Amontons' Law (and one of Gauss' Laws?) as I remember. It's relative piston area and distance from the hub centre that matter in an upgrade (pad material aside).

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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).


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PostPosted: Sun Feb 14, 2021 8:09 pm 
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Quote:
I believe the ST vented discs still used the type 14 callipers suitably spaced to accommodate the width, so same sized pads, swept area etc.
I know some Tr6 owners,fit spacers between the calipers so they can fit vented disc,ive done the same thing on the Stag

Dave


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PostPosted: Sun Feb 14, 2021 8:21 pm 
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Quote:
Quote:
I believe the ST vented discs still used the type 14 callipers suitably spaced to accommodate the width, so same sized pads, swept area etc.
Also, haven't we been through the proof that relative pad area don't matter to brake effect, just wear rate - Amontons' Law (and one of Gauss' Laws?) as I remember. It's relative piston area and distance from the hub centre that matter in an upgrade (pad material aside).
The point I was making is the 'upgrade' was the introduction of vented discs in isolation in response to the earlier post.


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 Post subject: Re: Hmm.....
PostPosted: Sun Feb 14, 2021 8:28 pm 
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Quote:
Quote:

If it was not possible to upgrade the brakes on one, I wouldn't own a Dolomite.
Triumph did upgrade Sprints to vented discs......

Ian
I take it then that you'd not like the Herald/Spitfire cross we have, which has type 14 front calipers (upgraded by me from type 12s) and no servo. But even the wife said they are good enough. Though it may help that it's hard to get more than 90 from it on the flat - and that with a fortnight's run-up - and I'd just said they could be better.

Was the vented disk conversion from Triumph an ST option? Possibly Jeroen can say what the Group 1B (Group 1-1/2) race cars had fitted.

Graham
I ran my GT6 (the one I tried a servo on) on type 14 calipers and messed about with it considerably before I got bored and moved it on. The servo I fitted wasn't the optional tiny Girling Powerstop that was offered by the factory, but a Lockheed remote jobbie from a Hillman Hunter (IIRC) So yes, I probably DID overdo things on that front! It was just too easy to lock it up so I ditched the servo and went back to stock. I actually circuit raced that car back in the 80s and had very little trouble with fade, nothing that fat new discs, some mintex race pads and race fluid couldn't fix. But again, the car was VERY light and fade is a function of weight, grip and brake power in an exotic ballet, the calculation of which isn't really in my wheelhouse. I just know it makes a difference if the car is lighter or heavier for the same stopping power.

The vented discs offered by Triumph/BLST seemed to cover the BSCC championship cars and pretty much anything else if you wanted them. Ken Clarke (I think it's Ken) still offers exact replicas of the ST originals and bits to convert the calipers. The price is eyewatering, but they are available if you need accuracy for your homologated Goodwood Revival racer! Even using these, there are, on Youtube, several period films featuring the Sprint racecars with Gerry Marshall and others being less than complimentary about the Sprint's ability to stop on a regular basis!

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

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
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 Post subject: Well
PostPosted: Sun Feb 14, 2021 9:21 pm 
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Quote:
I admit, I've never seen an upgrade that just swapped solid for vented disks.

Graham
That is exactly what was done for race prepared Sprints




Ian

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 Post subject: Re: Hmm.....
PostPosted: Sun Feb 14, 2021 9:48 pm 
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the calculation of which isn't really in my wheelhouse. I just know it makes a difference if the car is lighter or heavier for the same stopping power.

Steve
Force = mass x velocity!


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