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TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Rear Disc Brake Brackets

We are comtemplating another batch of TR4A(IRS)/TR250/TR5/TR6 rear disc brake brackets. The set up is primarily aimed at racers, but can be used on street cars if you are willing to forego a parking brake or come up with your own solution in that regard. In addition to the brackets, you will need calipers, brake discs, the brake lines and should consider an in-line residual pressure valve. The particulars on sourcing the parts will be supplied to those interested. When we did a bunch of these a few years ago, you were looking at about 1000 to 1100 USD by the time you rounded everything up needed. This would be an at our cost deal on the brackets. We have these done at a machine shop that normally makes military aircraft parts. Getting the numbers up helps bring the unit price of the brackets down.

If you are interested, drop me an e-mail:

marblepea at mindspring dot com

you know what to do to convert the text to an e-mail address

Once I have new pricing and the price break points, I will get back with those that e-mailed on the brackets.
SteveP

For the parking brake you can plumb in a Jamar mechanical/hydraulic line lock.

Mike
Mike Munson

Hi Mike,

not familiar with that, can you give details?

Regards,
KJ
k jackson

I found them at JC Whitney.
They are a simple mechanical line lock. It works the same as an electric line lock but without the drain on the battery.
Mike
Mike Munson

Another solution would be to make the caliper fittings mount to an old 280zx or 300zx as they had the parking brake built in. I would be interested if they went this route.
Adam Beasley

I simply have not had time since I am trying to keep a TR6 on the race track. The 280 pads were too small as i remember but i need to look into the 300 rear pads. Maybe my friend SteveP has the time to look into it.Ya Right!
Mike
Mike Munson

How about rear disks from a mustang or other car that has the combination disk/parking? If it is done to use the calipers from a common car it would definitly keep the prices down.

Also, I heard somewhere that wilwood was coming or already has a caliper with the built in parking brake.
Adam Beasley

Adam- You completely countered yourself. You talked of keeping the price down and then you mentioned Wilwood. They cannot be used in the same sentence as low price.
dk
DON KELLY

Don,

You are correct there! It just popped in my head so I wrote it down! :)

Adam
Adam Beasley

The late series 300 rear pads are pretty small and I don't see any real advantage going that route. The 280 and early 300 series pads are somewhat larger, but there is a catch. The caliper on those is relatively large. If I am remembering correctly, they use a 2 piston, through bore, floating caliper that takes up a good bit of real estate. Since it gets rather busy back there with the damper link or the damper itself on most tube shock conversions, the frame rails and the body, a caliper that needs lots of real estate is the wrong answer.

In the way of compact calipers, I have seen a few that I thought would have a prayer of fitting, but then we get back into the pad size is small trap. I keep my eyes open whenever we go junkyarding (hey, where do you think we get all of those 4 piston Toyota calipers for the front?), but just have not seen the right one (or left for that matter) yet.

There are a number of factory rear disc applications where the caliper itself does not have any provision for a parking brake, but there is a mechanical drum brake set up that uses the inside of the hat section of the disc as a drum. Once again, it is a matter of not enough real estate in the area to support such a system on the TR6.

I have not given up on a parking brake, fixed caliper or even floating caliper rear disc brake system for the TR6. However, I have been rather busy of late with stuff at work so my car related time has been on the short side. In the mean time, we do have a set up that works, just no built in, pure mechanical parking brake.
SteveP

Hi Steve,
You are probably one of the few people that can answer this question. But anyone else is welcome too.

Why have so many new cars moved to 4 wheel disc brakes?
I have installed the Toyota calipers up front and the larger Alpine wheel cylinders in the rear of my TR6, I can easily lock up all four wheels. And with threshold
braking technique can stop the car faster than any ABS system. So why the move to disc's all around?
Do disc brakes fade less than drums?
Thanks,
Chris
Christopher T.

Steve,

Good point. I looked at my car today and there isn't much room with a tub shock back there! It would be nice though!

Adam
Adam Beasley

Chris,

Disc brakes are inherently better than drums for heat disipation, brakes primary purpose in life i.e. convert kinetic energy into heat energy, then disapate it. When they are unable to disipate the heat, we get brake fade. If it happens at one end and not the other we could get some severe and immediate changes in handling.

If we look at their basic design, a brake rotor rotates with the pad wiped area in free air that is continously moving. The heat can then be transfer directly into this moving air stream.

The shoe wiped area of a drum has the air trapped within the drum area (drum plus backing plate) and with little air movement. It can also disapate heat through the drum itself (e.g. see finned brake drums) to the air around the drum but it is not nearly as affective as a brake rotor.

There is also the issue of brake modulation between disc brakes and drums. The pads are pushed off the rotors after the pressue is released and the pads return to their rest postion (with a little help from rotor run-out).

Brake shoes typically pivot at one end and are actuated by the brake cyclinder at the other end. The result is one shoe that is being pushed away by the rotating drum, while the other might otherwise bind were it not for the springs to make the shoes return to the rest position.

Now why do many new cars have 4 wheel disc brakes? It may be that for ABS, disc brakes are preferable to modulate them. I strongly suspect that it is might also be a marketing ploy.

With the weight distribution of FWD (front wheel drive), relatively high centre of gravity (particularly when compared to a TR6) and the resulting weight transfer under braking, I would expect that a modern FWD cross-overs / sport-cutes / cars would require about 70%+ of their braking effort under severe conditions on their front brakes. So why 4 wheel discs?

I can see it for our friends at the track where they are braking hard and frequently, with little time to disipate the heat before getting back on the brakes again, but on the rear of a FWD sport cute?

Hope that helps,

Len
Leonard G Middleton

Chris T.
The upgrades you have done to your car will do for most people and the majority of tire choices.
Keep in mind that the limit of any braking system is the amount of grip the tires have.
The Wilwood rear disc brakes were designed for TR6 race cars that have extremely wide 23" gumball tires.
(We run vented Jag. 3 piston up front).
When my tires are fresh and hot I can't lock them up.

On a street car the issue is fade. Our local Triumph club has a lot of mountain driving events. Most all drivers at some time or another have experienced brake fade. My crew cheif has a 72 with EBC pads and drilled and slotted rotors and just recently experienced it in 40 degree weather. My 73 with Toyota/Wilwood combination & 245 tires has never experienced fade even when I drive "Stupid Fast".

The reason most all newer cars have gone to discs all around is cost and performance. A disc system has fewer parts to manufacture and takes less time to assemble. Discs do fade less. Look at the available cooling; more air and fluid available at the friction surfaces.

Mike
Mike Munson

Mike,

What are you running on the back of your 73?

Thanks,

Adam
Adam Beasley

Len and Mike,
thanks! It all makes sense now.
Chris
Christopher T.o

Mike,

While a typical disc brake (i.e. front) would have fewer parts and assembly requirements than a comparable drum, when you add the parking brake requirement, the situation is reversed.

The parking brake on a drum design is typically just a cable pulling on a lever to move one of the shoes into contact with the drum (e.g. TR6 rear).

For disc brakes, either one needs a system to drive the pad into contact with the rotor (cable turning a screw on older Saabs and Fiat 124 Spyders)), or use the inside of the rotor "hat" section as a drum and install small parking brake shoes there (e.g. Toyota Matrix XRS).

Certainly your comments on performance are correct. If we look at higher performance versions of the same vehicle, the higher performance unit will have 4 wheel discs while the lower performance (and lower cost) may have rear drums. That would indicate to me that the drums are the lower cost option.

My thoughts,

Len
Leonard G Middleton

Adam,
I am running the Wilwood 4 piston disc brake conversion on the rear of my 73 with the Toyota 4 piston on the front.

Mike
Mike Munson

Len,

My comments about newer cars and disc brakes being cheaper were generated by a conversation I had with a brake engineer at GM where I work. He said that Starting from scratch a disc system is definitely cheaper than a drum system on the rear of a car when the parking brake is integrated with the caliper. This confirms your first sentence. I asked him why any company would still make cars with drum brakes and he said they probably have a large "parts bin" to draw from.

Mike
Mike Munson

Mike,

Thank you for the insights. I have been out of the auto industry for a few years now and can appreciate how qucikly one can get out of date.

I can understand the part of the conversation where starting from scratch they can build a disc system cheaper than a drum system, given the potential changes in technolgies and resulting change in economics.

And I certainly respect the auto industries' ability to drive costs down.

I am puzzled however by his explaination of a large "parts bin" to draw from, given the efforts in the industry to reduce inventory levels. Could you shed some further light on that?

Thanks,

Len
Leonard G Middleton

It is a combination of inventory and already having the tooling in place to manufacture the drum brakes.

Mike
Mike Munson

Mike,

Yes, I am well aware of the tooling issue having previously worked as a program amanager for a Tier One heavy metal stamping supplier. Worked on a pick up box assembly that invovled some new large dies for the box sides, and they were extremely expensive.

Thanks for your response,

Len
Leonard G Middleton

Mike,

What did you do for rear parking brakes with the wilwoods?

Adam
Adam Beasley

There are three things that I keep considering on the addition of a parking brake feature to the basic set up. First, it has to fit the car. Second, The price has to be at least within the fringes of sanity. Third, it has to work well enough to justify the effort and cost. Then again, three is probably nothing more than an outgrowth of two.

My initially prefered approach mentioned above is the use of a combined hydraulic/mechanical caliper that serves to supply both the braking and the parking brake function. This one would involve a redesign of the existing bracket to accommodate the different caliper and the use of a different disc. Given all of the considerations of the existing set up, I think there is a high likelihood that a two piece hub hat/disc section would be requiredhere is also that nasty problem of reality rearing its ugly head and saying that I haven't really come across one that I think will really do the braking job as well as the current set up. The closest I have come to date was off a European Ford product, but even it was somewhat iffy and added at least another $400 to the cost of the set up. Due to the lack of ready caliper availability, the cost factor and the whole "iffiness" of that potential set up, I decided that it was a set up that was not worth further effort. I haven't given up on this completely, but the more time I spend on it, the more it looks like a dry hole.

I have also come up with a preliminary system that relies on a seperate mechanical caliper. It uses the same bracket with some modification, the use of a secondary bracket, and two different thoughts on an actuation system. The down side is that it too requires bringing more money to the table. On the other hand, it doesn't compromise a known braking set up. The price would be comprable to the Euro Ford set up mentioned above and looks to be pretty much in line with what other suppliers are charging for rear conversion set ups where you have seperate hydraulic brake and mechanical parking brake mechanisms.

Despite the perception, the Wilwood calipers are actually rather reasonably priced in the big scheme of things. In the seperate system described above, the small mechanical calipers cost more than than the Wilwood hydraulic units. It is when you start adding in the all the stuff that you need to get the calipers to actually do something that you start parting with money. That is going to be true regardless of whose system you decide to use. The reason the regular Toyota conversion is so inexpensive is that you don't have to change out anything but the calipers and the hard line that runs between the calipers and the flex line. As far as the caliper price itself, if you were to go and purchase the rebuilt Toyota calipers outright at a parts store, they would probably run fairly close to the price of a set of Wilwood calipers of similar piston count and size.
SteveP

Adam,
I don't park much. LOL
Actually the performance advantage far outweighs the disadvantage of not having a parking brake.
I suppose one could use a couple of blocks of wood connected by a rope under the LR tire.
Sorry, it is 71 deg. here today and I have spring fever.

Mike
Mike Munson

Mike,

I wish I didn't have to park much! I would much rather be driving my car around instead of it being in pieces in my garage. I did the toyota conversion on my front and am considering the 280z conversion on the rear since it'll be some time before I'll be able to get on the road.

I think the wood blocks would look nice!

Have you tried the Jamar mechanical line lock for your parking brake? I'd be interested to see how that would work.

Adam
Adam Beasley

I hesitate to enter into this discussion due to the somewhat overwhelming level of knowledge and experience, but I can't resist...

A couple of months ago I acquired a 1978 Fiat 124 Spyder - my first foray outside of the land of Triumph. Most of you probably know that it has disc brakes all around, and as I have been reading through your posts the rear design seems to come very close to what Steve is describing as his preferred setup. It is a simple combination hydraulic/mechanical caliper with a standard fluid-driven piston setup for pedal braking. The piston can also be driven mechanically via the handbrake cable which pulls an armature that turns a cam that moves the same piston. I have a stock brake setup on my 6, and find the Fiat system to be superior in terms of response and consistency. I would have to assume that other European designs are similar. It would really be a matter of looking at the most logical mounting method.

Just something to consider.

Jim
Jim Vandenberg

Thanks Jim,
We will look into it.
You never know if your contribution to a discussion will help someone or not so don't hesitate to chime in.

Mike
Mike Munson

Along that same line, I had a 1995 Acura Integra that had rear disc brakes with an integrated parking brake. The parking brake worked by twisting the piston into the pad... I believe alot of the integrated systems work that way.

Adam
Adam Beasley

This thread was discussed between 17/01/2006 and 06/02/2006

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