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Triumph TR6 - Rear Disc Brake conversion - DONE

A while ago there was some interest shown in a rear disc brake conversion - well it's been done, and the info / pics is at http://triumph.hottr6.com/rear_disks.html
(at least the parts source etc).

Check out the rest of his site - some interesting stuff

R
Roger H

oh .... forgot to mention that there appears to be no handbrake so modification is for track use only - (damn!)
Roger H

There is a street TR6 around here with that same conversion. I have all the bits to do that one also, but have not done anything with it yet as it will probably go on the TR250 project (in waiting) car. In the meantime, I have collected some other bits for playing around with a rear parking brake caliper set up. A bit trickier as you have to allow room for the park brake mechanism and cable and there is not alot of room to play with.

So far it looks like the fixed caliper set ups just do not fit. A floating caliper set up (likely single piston) with internal brake mechanism will be the way that must be taken. Some time back, there was a post out of the UK that had done a rear conversion and i seem to recall that they used Ford Sierra rear calipers and Nissan rear discs. I pulled a set of rear calipers off a small Ford sedan and at some point will go play with a bracket design and cable linkage for them. Right now, I enough on my plate that it is such a low priority that it doesn't even show up on the screen.

Perhaps, this will be seen and some useful information, like a bracket drawing, on the Sierra caliper set up will make its way to the board.
SteveP

What's a hand brake?
Don K.
DON KELLY

The 'handbrake' Don, is the only thing that can get you out of the sheet when you realise, all too late, that you have no pedal pressure!! Proved useful when my first car, a 1957 VW beetle (with optional passenger side sun-visor) snapped something serious. That was also before I read Ralph Nader's "Unsafe at any speed" and I saw the light regarding Beetles.
I must have no long term memory though as I'm not sure that the TR is proportionaly safer! - goes a lot faster and has about the same amount of tin. (P.S. 'handbrake' <noun> - from the mother country aka 'parkbrake' in the northern hemisphere colonies ;)

Roger H

I had to smile after reading Roger's tale - here we simply refer to that lever as the "EMERGENCY" brake.
R.C. Blair

Roger,
Great site! I'm not very quick when it comes to the
internet so bear with me. How can I email this fella and chat with him? I'm sure his address is staring me
the face but darned if I can see it.Some wonderful
modifications.
Thanks,
Chris
Christopher Trace

Chris
Without posting it here..just keep hitting the back button and you will see it below the funky tr6 with the qu-te beside it. If still not find e-mail me and will send back to you. It is not obvious as he is hiding it slightly..you will see what I mean.
Rick C
Rick Crawford

I had e-mailed back and forth with Shane concerning the park brake issue and had wondered why you wouldn't/couldn't use a line lock like the drag racers use or even some of the heavy trucks. It simply goes in the line feeding the rear brakes and can be mounted under the dash out of sight. Could also work as a theft deterent if placed out of sight. If used while driving, as a emergency brake, would result in tire lock up until released.
Gene Holtzclaw

Line locks had crossed our minds, but the problem is that you have a solenoid holding the pressure on the system. This would be an electrical drain on the system and I can't help but think that it would not be all good for the solenoid either to remain energized at full tilt for long periods of time. Even the OD solenoids drop back in pull to keep from being burned up.

Mike Munson sent me to a picture one time that appeared to have a small master cylinder that was actuated by the parking brake lever. I liked that better than the line lock one, but still have a concern with bleed down over time with a hydraulic system. I keep coming back to pure, simple, dumb cable actuated mechanical systems as the way to go.

To me, this means that you either need a caliper with a built in actuating system or you need separate mechanical spot calipers, such as that used on the in-board brake IRS Jaguars. I have periodically dug around for small mechanical calipers, but have yet to find one that:

a) Would work with the disc width,
b) had sufficient strength to hold the car and
c) that I thought would fit. (and that didn't weigh or cost too much either)

This took me back the a caiper with an integral actuating mechanism that used the pads pressing against the rotor. The only fixed, two piston caliper I could think of that might have a prayer was that from a 914. Nope, sorry, the cailper was just too wide. There are any number of single piston floating calipers out there that have integral actuating mechanisms for pressing the pads against the rotor. The trick will be getting one and developing the mount for it that matches up with the disc width, that is narrow enough that it will not foul any of the suspension or body work when mounted and that can be plumbed up and cabled up without any of that fouling anything either. Several Ford, GM, Nissan, VW calipers all look like potential candidates just from going around junkyards and observing/nose poking. The brackets would not be that different from those used on the set up referenced in this link.

If you are interested in getting one of the set ups like that pictured, contact Mike Munson. We had some of the brackets machined up. As far as I know he still has a set or two. If so, he could fix you up with the brackets, modified Nissan discs, hardware and such. You would need to supply the calipers (Wilwood or JRZ)and pads plus make up the hard line. E-mail me off the board and I can provide contact information to you. If there is enough interest and there no/not enough brackets on hand, another batch could always be made.


SteveP

There is also a purely mechanical line lock made. I became familiar with these while working on fire trucks. They did not use a electric style, only pressure. It was a one way valve that when you actuated the valve, then applied the brake, it would not allow the release of the brakes. Well, not untill the lever was released anyway.
Gene Holtzclaw

Gene, any sourcing information to share to save searching time? The only line locks tht I am familiar with are all solenoid driven systems, I would be interested in looking at a non-electric line lock.
SteveP

The ones that I saw were on mid 60's to mid 70's large GM and Ford trucks. i.e. 700 series Fords, commercial chassis GM. It is a very simple device and I never saw one fail. I'll see if I can research a little on it.
Gene Holtzclaw

Steve, check this out-http://www.autocraft.com.au/hillholder.html
This is not off of a commecial truck but I know it is the same principle. It just took quirky (suburu) engineeers to apply it idiot proof. I am sure a remote attachment on one of our cars could be done and sourced from a salvage yard very cheaply.
Gene Holtzclaw

Hi guys,

I haven't been on for a while due to work and a sick child.

The mechanical line lock is made by Jamar and sold by JC Witney. It is a pretty simple device about the size of a brake prop valve. I don't run one or a proportion valve on my car because the system I have is already well balanced. I do run the Toyota's on the front with the stock rotor. I run carbotech panther plus pads on the front and Hawk HPS pads on the rear. The car stops like some of my coworkers (GM) new Corvettes. Of course they run wider more expensive rubber than I do. Now if I could just get more HP and gear...

Mike
Mike Munson

I forgot to add that I use the stock master cylinder and it seems that I actually have less pedal travel than with the stock setup.
Steve, I will try to come by your shop Thursday and let you drive it if it is not raining.

Mike
Mike Munson

Mike,
Sounds good, look forward to seeing you.
SteveP

I installed rear disks (rotors) to my tr6 a couple a years ago,check out archives.I used Nissan primera disks,i fabricated my own mounting brackets and used rear calipers with a hand brake from a ford sierra saphire,Both cars were sold in England in the mid eighties to the mid nineties.I used the ford handbrake cable but i had to modify it at the tr6 hanbrake end ,the handbrake now is adjusted at the hanbrake lever end.

Simon.
Simon

HI,

I always think simpler is better. I will made that conversion this summer and an easyway is to buy 2 front dics (MGB or TR6) and the only tricky part is the rear bracket that need some effort. I will retain calipers from a Camaro(or 280Z or Supra) rear set-up and will have a functionning rear handbrake, wich is mandatory.

Cheers, JGC
Jean G. Catford

Jean, unless you plan on modifying the rear hub flange you will not be able to use the TR6 front discs as the bolt circle for the disc is much smaller than the bolt circle for the wheel. On the MGB, I seem to recall that is is also different on those too, I just don't remember by how much. On both of these cars the disc bolts to the front hub from the inboard side as opposed to fitting over the outboard side of the hub and the wheel studs.

For the rear disc, a Nissan disc is the way to go as far as I am concerned. I have looked at dimensional information on more discs than I care to think about and the Nissan stuff is the best that I saw for this application regardless of whether it comes from a 280ZX or a Sentra/Altima (different diameter and hat section heights available so pick what looks to work best with the bracket/caliper choice). It doesn't matter which of the Nissan discs are used, there is some machining to be done. First, chuck it up on a lathe using the inside of the hat section and open up the bore in the disc to fit the TR rear hub center. Then you flip it around and chuck up on the outside of the hat section and counterbore the inside of the hat section near the hub face to fit the TR hub flange. I want to say that about 1/4" to 3/8" from the hub face surface has to be opened up to fit the TR hub flange. I did not bother to take measurements when I did this, I just removed a little at a time and keep a hub flange close by and checked against it. When it fit, the job was done for that disc.
SteveP

Simon, I have a number of questions about the Sierra and the Sierra calipers, plus your brackets. How closely is the Sierra related to the German Grenada or Scorpio models?

On the calipers, is this a single piston floating type with cast in eye for the cable guide and hooked end at brake actuating lever? If a floating caliper, for the fixed carrier that bolts to the mounting ears, were they threaded, or were they smooth bored and fixed to threaded mounting ears? Was there a standoff at the caliper or was it a flat surface to flat surface?

Are your brackets the same left and right? Any feel for how much offset there is between the bracket/trailing arm interface and the bracket/caliper interface? Would I be correct in assuming that the offset is inboard if present?
SteveP

This thread was discussed between 17/03/2004 and 23/03/2004

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