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Rear disc brakes
Posted: Tue Feb 21, 2023 8:07 pm
by RichardHyde
Hi guys, I keep coming back to rear disc brakes… this thread gives lots of useful info…
https://forum.triumphdolomite.co.uk/vie ... c&start=30
Is wiggybum still around ?
He used Orion discs that are quite high meaning that the disc / calliper are away from the Sprint alloy.
Appreciate brake balance with be out. Does anybody know the rear braking force ? Think they measure that for the MOT ? Could fit an adjustable brake valve and match the standard brakes ? Got TJs up front btw.
There’s also a drawing of the brackets. What material should they be made of ?
Thanks, Richard
Re: Rear disc brakes
Posted: Tue Feb 21, 2023 8:37 pm
by new to this
Richard
I made my bracket from Aluminum
Dave
Re: Rear disc brakes
Posted: Wed Feb 22, 2023 8:04 am
by SprintV8
Wiggly Last active: Sat Jun 04, 2022 5:40 pm
Maestro discs where mention by dolly racer.
Brackets Steel or Aircraft hi Spec Alloy Would be my preference.
There’s quite a bit of soft alloy around
at the moment so why I’ll chose Aircraft Hi spec Alloy.
But then I Al Ready have a rear disc conversion ready to go on.
Re: Rear disc brakes
Posted: Wed Feb 22, 2023 9:20 am
by xvivalve
When I bought the late Chris Cox’s racer project, it came with the above components he’d had cut which I’m presuming are for a rear disc conversion; quite why he didn’t have the bolt holes accurately cut at the same time is a question that will never be definitively answered now!
I have no intention of adding rear discs to the car, so they’re surplus to my requirements. Open to offers if they’ll save someone some effort…
There are actually 4 brackets, but two appear to have been stuck together.
Re: Rear disc brakes
Posted: Wed Feb 22, 2023 9:51 am
by djw113uk
Not cheap, and I am unsure what other parts you need to make it fit, nor if you end up with a handbrake but these appear to be made to order if required?
https://shop.retro-engineering.co.uk/re ... -193-p.asp
Long time no chat Richard!
Re: Rear disc brakes
Posted: Wed Feb 22, 2023 10:20 am
by bazyerma
Hi
For a few years now I have rear disc fitted to my 1500TC (different rear axel from the sprint) and they have worked a treat using parts from MG TF and my bracket made out of mild steel plate(Drawing in the link).
It was a fun project, only differents is the brake pedal travel is a bit longer, but the car stops great!
https://forum.triumphdolomite.co.uk/vie ... =4&t=36321
Regards
Barry
Re: Rear disc brakes
Posted: Wed Feb 22, 2023 1:26 pm
by xvivalve
SprintV8 wrote: ↑Wed Feb 22, 2023 8:04 am
This is time taken at the Sprint not necessary time worked.
That sounds like Mrs Reader is keeping the tally!
Re: Rear disc brakes
Posted: Thu Feb 23, 2023 7:31 pm
by cleverusername
Rear disk brakes are completely pointless, frankly they are only fitted to modern cars because naive customers assume disks equals better.
The majority of braking is done by the front wheels, so you don't need better brakes at the back. It is also a pain to get handbrakes to work with rear disks. Drums are simply a better solution.
Re: Rear disc brakes
Posted: Thu Feb 23, 2023 8:26 pm
by Carledo
The other day I both saw something i'd never expected to see and learned something new too.
I was watching a Youtube video from "Uncle Tony's Garage" where he was retrofitting FRONT drum brakes to a disc converted 60s Chrysler drag racing car (which I never thought i'd see anyone do, why would you?) BECAUSE the drums are several pounds lighter per corner than the equivalent discs!
I'm not suggesting ANYONE go back to front drums, this was a particular niche adaptation, Drag racing cars don't really NEED brakes. But putting rear discs on a Dolomite, when the stock Sprint rear drums are ALREADY too powerful for the car, seems to be an excercise in expensive futility. You fit the rear discs and then have to strangle out 50% of their braking effort to avoid destroying an already delicate brake balance. The weight advantage with the rear drums, I consider inconsequential compared to the weight of the live rear axle, but it IS still an advantage.
The final nail in the coffin for rear discs, as far as I am concerned, is that by the time you have bigger piston TJs on the front and MUCH bigger piston calipers on the back, you are into bigger bore master cylinder territory or you'll have a pedal that is uncomfortably low. And you'll need some sort of pressure limiter/LSV/brake balance control, to rein in the rear discs. More expense and time for zero effective gain.
WHY? Because you CAN? Just because you can, doesn't mean you SHOULD!
Keep It Simple, Stupid!
Steve
Re: Rear disc brakes
Posted: Fri Feb 24, 2023 4:55 pm
by cleverusername
Carledo wrote: ↑Thu Feb 23, 2023 8:26 pm
The other day I both saw something i'd never expected to see and learned something new too.
I was watching a Youtube video from "Uncle Tony's Garage" where he was retrofitting FRONT drum brakes to a disc converted 60s Chrysler drag racing car (which I never thought i'd see anyone do, why would you?) BECAUSE the drums are several pounds lighter per corner than the equivalent discs!
I'm not suggesting ANYONE go back to front drums, this was a particular niche adaptation, Drag racing cars don't really NEED brakes. But putting rear discs on a Dolomite, when the stock Sprint rear drums are ALREADY too powerful for the car, seems to be an excercise in expensive futility. You fit the rear discs and then have to strangle out 50% of their braking effort to avoid destroying an already delicate brake balance. The weight advantage with the rear drums, I consider inconsequential compared to the weight of the live rear axle, but it IS still an advantage.
The final nail in the coffin for rear discs, as far as I am concerned, is that by the time you have bigger piston TJs on the front and MUCH bigger piston calipers on the back, you are into bigger bore master cylinder territory or you'll have a pedal that is uncomfortably low. And you'll need some sort of pressure limiter/LSV/brake balance control, to rein in the rear discs. More expense and time for zero effective gain.
WHY? Because you CAN? Just because you can, doesn't mean you SHOULD!
Keep It Simple, Stupid!
Steve
That is my opinion, I can understand expensive and complex mods when they improve the car. For example fitting fuel injection isn't simple but if done properly will improve the performance, fuel economy and starting.
Rear disk brakes don't achieve anything, at best you will get the car back to place you started. After spending a great deal of time and money on the project.
Re: Rear disc brakes
Posted: Mon Feb 27, 2023 1:32 pm
by bazyerma
Hi
I now have rear disc conversion and TJ brakes on my 1500Tc and the brake pedal is longer that before but still perfectly drivable.
The joy of any project, is the fun of creating and problem solving. It was fun, so expense and time weren't really an issue, can you put a price on 7 hours of pottering in the garage?
Let people have there fun I say!
Regards
Barry
Re: Rear disc brakes
Posted: Sun Apr 02, 2023 10:46 am
by wiggybum
I am still around Richard.
What would you like to know?
Re: Rear disc brakes
Posted: Wed Apr 19, 2023 3:15 pm
by TrustNo1
whats the beneift in fitting rear discs apart from the lkleyhood of the rears locking up easer which personally I don't see as a benefit, if your brakes are not good enough this is down to one of two things, you're too used to a modern car with better brake balance etc OR there is actaully something wrong with your brakes such as old pads, weak fluid, sticky caliper or poor adjustment all of which can by sorted in a few hours
Re: Rear disc brakes
Posted: Thu Apr 20, 2023 10:30 am
by SprintV8
TrustNo1 wrote: ↑Wed Apr 19, 2023 3:15 pm
whats the beneift in fitting rear discs apart from the lkleyhood of the rears locking up easer which personally I don't see as a benefit, if your brakes are not good enough this is down to one of two things, you're too used to a modern car with better brake balance etc OR there is actaully something wrong with your brakes such as old pads, weak fluid, sticky caliper or poor adjustment all of which can by sorted in a few hours
On a standard Sprint or Dolomite I can’t see any advantage at all.
But on a Sprint or Dolomite that potentially could double the the original power I can see an advantage.
Why have some of the race Sprints been converted to rear disc’s ?.
My swap has 100Bhp more than a standard Sprint and that’s without the supercharger.
I’m going for it.
Set up correctly you shouldn’t be locking the rear wheels.
They should be on the verge of locking but not completely.
It’s down to personal preference.
Re: Rear disc brakes
Posted: Thu Apr 20, 2023 3:41 pm
by Carledo
SprintV8 wrote: ↑Thu Apr 20, 2023 10:30 am
TrustNo1 wrote: ↑Wed Apr 19, 2023 3:15 pm
whats the beneift in fitting rear discs apart from the lkleyhood of the rears locking up easer which personally I don't see as a benefit, if your brakes are not good enough this is down to one of two things, you're too used to a modern car with better brake balance etc OR there is actaully something wrong with your brakes such as old pads, weak fluid, sticky caliper or poor adjustment all of which can by sorted in a few hours
On a standard Sprint or Dolomite I can’t see any advantage at all.
But on a Sprint or Dolomite that potentially could double the the original power I can see an advantage.
Why have some of the race Sprints been converted to rear disc’s ?.
My swap has 100Bhp more than a standard Sprint and that’s without the supercharger.
I’m going for it.
Set up correctly you shouldn’t be locking the rear wheels.
They should be on the verge of locking but not completely.
It’s down to personal preference.
Power has no bearing on braking effort. You have a Dolomite weighing around 1 tonne, give or take 100kg and you have a finite set of 4 tyre contact patches which limit just how hard you can brake. It doesn't matter if you have 100bhp or 500bhp, the same car on the same tyres can only brake so hard without losing traction.
You can alter the equation in your favour slightly with nice sticky tyres and a bigger contact patch, but even this has finite limits, too big a contact patch and there isn't enough weight in the car to compensate and braking ability is reduced again.
The ONLY advantage of discs over drums in this situation, is that discs are less likely to suffer from fade due to overheating, from experience (my own and that of the works teams) you only need rear discs for something like the Spa 12 hour race where fade could enter the equation. Shorter races like those of the BTCC (rarely more than 25 miles) and the works cars made do with drums, albeit with sintered linings. On a mostly roadgoing car, it's a complete waste. Even if you DO have far more horsepower than you could ever need or use.
Steve