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tr6lover
03-11-2008, 08:49 PM
hi guys, who would be interested in a rear disc brake set up for the tr6? ive got some cad drawings and i want to have a set made up for myself and anyone else who is interested. here is a link for the set up and its on the cheap, probably equivelant to a totally rebuilt disc set up cost wise. https://tr6.danielsonfamily.org/don_watson.htm let me know as i have to figure out how many sets for the machine shop to make, thanks
Randy

DNK
03-11-2008, 11:20 PM
Finally, an E brake disk conversion YEA!!!!I'm in . Probably won't install right away but just to have it.

tr6lover
03-12-2008, 01:27 PM
ok sounds good, right now im trying to find a machine shop and get prices, paul (brosky) has come up with one that will make a few sets, but im still checking on prices. thanks guys
Randy

Tinster
03-12-2008, 01:34 PM
Very nice looking Randy!

Do you have an idea what the entire conversion setup
might cost? All the components required.

thanks,

d

crj7driver
03-12-2008, 03:06 PM
Check your PM's I am interested as well.

DNK
03-12-2008, 11:17 PM
I want mine in carbon fiber :jester:

tr6lover
03-13-2008, 12:48 AM
hey dale, im thinking its going to cost about 150 a set, but thats just a guess. that link i have in the post is not my set up but thats the set up that im going to be duplicating, just dont want to take credit for it. that cost im guestimating is only for the brackets, you still need rotors and calipers which can be priced at the local parts store.
Randy

Tinster
03-13-2008, 06:28 AM
hey dale, that cost im guestimating is only for the brackets, you still need rotors and calipers which can be priced at the local parts store.
Randy

Ah yes, my <span style="font-weight: bold">local parts stores</span>! Lets see- there's Western Auto and then we also
have Western Auto plus we have Western Auto. And then there's Sears auto that
sells mostly tires and bottles of oils.

oh well, my rear drum brakes work pretty good.

Thanks,

dale

billspit
03-13-2008, 08:33 AM
I wish someone would work on a set for Spitfires. It cannot be that difficult. I've seen some for Spridgets.

tr6lover
03-14-2008, 12:02 AM
hey dale, sorry about that. i could look up prices and all for you and send the parts, but im assuming that would probably cost more than getting them locally. nothing but variety on that island huh?
Randy

RonMacPherson
03-14-2008, 02:47 AM
Used to see ads for an outfit in the land of Oz(Australia) that made kits for thses. Believe it was in the rear of Classic Motorsports or Grassroots Motorsports. Might try a search engine search and see what you pull up.

Perhaps SpitBits might know of one.

03-14-2008, 03:56 AM
Interesting concept. Consider that one is putting all that stopping power on an inherently weak aluminum housing (the trailing arm). That seems to be a lot of twist on aluminum and 5 bolts in aluminum. Any thoughts here? Drums seem to have a shorter torque angle.

03-14-2008, 09:35 AM
I've still yet to see a side by side comparison of the stopping distances between this and the Morgan cylinders upgrade, which cost $58 for two last time I checked.

Given most of the braking is done by the disks up front, I don't see that it can make ~that~ much difference.

Just so you know, if someone does a side by side test and it IS better I'll be right there in line for a set, but until that time it is just suspension bling imo.

Tinster
03-14-2008, 10:00 AM
Interesting concept. Consider that one is putting all that stopping power on an inherently weak aluminum housing (the trailing arm).

By golly, Bill !! You are correct.

That about kills any ideas I might have had concerning the
rear disks concept. Having had one rear wheel assembly fall
off of the trailing arm, while driving, is an experience
I hope to never repeat.

I'll stay with my drums and leave the T/A in peace.

d

Opa
03-14-2008, 10:44 AM
Alan I agree with you.I have played with rear brake several times as i increased tire size which in my opinion has a lot to do(if not all) with stopping power..

When I first built my car back in 89 it had 185x15 dunlops and the brakes were adequit, then i went to a 195x15 and noticed a slight loss of brakes in the back so I took out the .70 stock wheel cyl. and put in .75 cyl.used in tr3 with 10"drums (direct replacement) if i remember right.Then I went to a 205 70r x15 and again noticed a loss of brake power.I did put on a set of 240z aluminum drums which really did,nt change anything,looked cool tho.

This winter I did the Morgan wheel cyl. upgrade with brand new alum. drums from TRF which I bought in Laughlin @Triumphest. Once the weather gets a little better i'll give them the works and see if it improved any.Be advised that the wheel cyl's. i got are not a direct replacements, some work required to fit properly, even tho many i talked claim it is direct fitting.

I do notice more freeplay in the pedal by probably
3/4 of inch or so. Will check master cyl. pushrod for clearence as discussed about a month ago,Hondo's thread i think it was.

Dale iknow what your talkin about,had similar experience with a daily driver i had for a while.
puts a lotta pressure the on sphincter muscle momentarily :crazyeyes:phew
no long studs in there for this guy

swift6
03-14-2008, 05:45 PM
I've still yet to see a side by side comparison of the stopping distances between this and the Morgan cylinders upgrade, which cost $58 for two last time I checked.

Given most of the braking is done by the disks up front, I don't see that it can make ~that~ much difference.

Just so you know, if someone does a side by side test and it IS better I'll be right there in line for a set, but until that time it is just suspension bling imo.



:iagree:

DNK
03-14-2008, 06:52 PM
There is a test done somewhere. Saw it a few years ago. For all out braking a disk has to stop better more often or they never would have gone that direction.

swift6
03-14-2008, 07:49 PM
The only tests that I have seen are on Lee Jansen's page and the VTR page. The two are actually based on the same testing but the conclusions differ slightly between them. Oh, and these tests involve the differences between standard front brakes and Toyota Four pot calipers, with and without larger (Morgan) rear wheel cylinders. They do not encompass rear disc conversions.

There were other reasons for switching to discs as well but all those reasons still doesn't change what Alan, Casey and myself are all getting at. The rear brakes on the TR6 don't do very much of the braking, only about 10%. Enough to help with stability and provide a good parking brake but not much else. Just slapping on a disc conversion will not yield better braking.

The only way that a rear disc conversion would be effective is to redistribute the braking proportions as well. So if your willing to also change your master cylinder set up as well, you could possibly greatly enhance your rear braking. Though you could do the same thing with better shoes and Alfin drums as well and also see improved braking.

Adding a disc conversion could also add extra weight and complication.

Casey brings up an excellent point though. Your tires actually stop your car. The brakes convert kinetic energy into heat. Tires really are not places to skimp on money if you like to drive in a spirited manner. Tires that have higher speed and traction ratings will also reduce your braking distances. High mileage and cheap, low speed and traction rated tires will not. As Casey also pointed out, wider tires don't always help with braking (or cornering).

Its always a balancing act!

DNK
03-14-2008, 08:33 PM
Shawn- i totally agree with you on the proportioning matter. I think it is a given.
If you do this set up you must run a proportioning valve!

TR3driver
03-14-2008, 08:38 PM
For all out braking a disk has to stop better more often or they never would have gone that direction. Not 'better', just 'more often'. The advantage of disc brakes is that they cool better, so less likely to overheat under extreme conditions. But my experience is that the front discs will overheat first even with drums out back, so any upgrades should start in the front, IMO.

amcboy
03-14-2008, 08:39 PM
This could be an alarmingly long post, but I'll be briefer than usual.

Depending on how you use your brakes, most of the stopping power comes from the front.

Most fixed bias systems are 70/30 to the front.

We ran adjustable bias on a (granted, heavier) road-race car and ran closer to 90/10 front bias. And places like Mid-Ohio where there is giant transitional braking areas even more was dialed into the front.


Consider the weight transfer when you brake.

All that mass landing mostly on the front end...


Considering we are talking about shear values and not tensile values on the TA hub bolts from braking, calculations could be made to see what the average loading is per bolt/stud. I'd expect this value to be pretty low (really).

Now, moving the hub further from the TA will add tensile differential to the fasteners and the TA.


IMHO the hub should be where designed and any bracketry should be outboard of the hub.


I'd also install a manually adjustable proportioning valve and set the differential for the intended use.

Tinster
03-14-2008, 09:02 PM
Shear values on the T/A studs yes but there is also an "overturning"
moment of the steel studs in the aluminum.

Think of the steel stud as a telephone pole anchored in soil.
As you increase the height of the pole you must then increase
the depth of the pole buried in the soil. The exposed portion
of pole is in shear; the entire pole has an "overturning" moment
as well. I am thinking it is approx 4:1

Extending the length of the six T/A steel studs should require
a proportional increase in the depth they are anchored into the
aluminum trailing arm. I know for three studs, this is
impossible.

But then, I ain't a wrench, as everyone knows.

dale :shocked:

amcboy
03-14-2008, 09:14 PM
Good point.

You could do a "body fit" on the portion that goes through the hub to load the hub flange a little with those forces.

Not so convenient though.

And hard to assemble...


Hmmmm, must ponder....

BobbyD
03-14-2008, 09:47 PM
Darn.............I forgot completely that I added his conversion to my site. Glad to see that it's helping ya'all out! And noooo.....I haven't done the conversion. I'm keeping the drums with a beefier wheel cylinder.

tr6lover
03-15-2008, 12:01 AM
hi guys, didnt mean to start such a controversy by posting that. i want a cheaper alternative with less maintainence. disk brakes work very well, better than drums for their ability to self clean and cool reducing brake fade. due to more surface area you could get more stopping force with a disc than a drum but you are correct about having a portioning valve to increase the force. honestly for even stock drums and all stock parts in the back it adds up quick then you also have to adjust all the time. in addition once you decide to go aluminum drums, kevlar brake shoes and morgan wheel cylinders it adds up. by going with discs you can easily and cheaply replace parts. as far as braking force applied to the trailing arm i believe thats rubbish, the mounting points are all the same and all taking the same load, although the clamping force is applied differently to the wheel it still applies the force to the trailing arm the same way through the same points, yes if you extend the studs out farther it will change the load some, but not significantly and this has been done successfully before. there are many benefits to rotor/caliper set ups which originated on aircraft and this is why jaguar decided to use them on cars back in the 50's and this drastically reduced stopping distances, just a thought for everyone saying this could not possibly reduce stopping distance....
Randy

swift6
03-15-2008, 10:26 AM
The advantage of disc brakes is that they cool better, so less likely to overheat under extreme conditions. But my experience is that the front discs will overheat first even with drums out back, so any upgrades should start in the front, IMO.


:iagree: You'd overheat more often too if you did 85-90% of the work. The rear drums on a TR just don't work very hard. So with a stock M/C set up your money and effort would yield much better results by improving the front brakes over the rear.

swift6
03-15-2008, 10:51 AM
hi guys, didnt mean to start such a controversy by posting that. i want a cheaper alternative with less maintainence. disk brakes work very well, better than drums for their ability to self clean and cool reducing brake fade.

Don't see it as controversy, just good discussion. :smile: Just because we don't agree with you doesn't mean its controversial. :wink:

Less maintenance? A set of shoes on a TR should last through a few sets of front pads. Seems pretty low maintenance. Unless you don't like adjusting them occasionally. How often do you imagine changing pads on a rear disc conversion. With a conversion that would make use of the extra ability, you would be changing pads on the rear probably twice as much as you would shoes. Equalling more expense and more maintenance.

If your experiencing rear brake fade now, you've got other issues.



due to more surface area you could get more stopping force with a disc than a drum but you are correct about having a portioning valve to increase the force.

If you measure shoes vs pads, I' think you'll find that the shoes have more surface area. Its the hydraulic pressure to that surface area that provides the actual force. Which is why changing the rear wheel cylinder has the effect that it does. Even adding an adjustable proportioning valve in to increase the pressure will yield better results with the drums without making them overheat. Racers have to do this all the time.


honestly for even stock drums and all stock parts in the back it adds up quick then you also have to adjust all the time. in addition once you decide to go aluminum drums, kevlar brake shoes and morgan wheel cylinders it adds up. by going with discs you can easily and cheaply replace parts.[/qoute]

Don't forget weight as an additional cost. The disc conversion will likely weigh more right at the wheel. Especially when you add in the parts to allow a functioning handbrake. Now if you could put the discs inboard (like Jaguar did) then you could negate that weight cost. Otherwise, the more weight out at the wheels will affect handling.

[quote=tr6lover]there are many benefits to rotor/caliper set ups which originated on aircraft and this is why jaguar decided to use them on cars back in the 50's and this drastically reduced stopping distances, just a thought for everyone saying this could not possibly reduce stopping distance....

Jaguar used them on their race cars first while Triumph used them on their production cars first (then took their production cars racing :wink: ). They also designed their brake systems for 4-wheel disc brakes. As I said earlier, if you re-configure your entire braking system, disc brakes will improve/decrease your stopping distance. If you just install them without altering the master cylinder proportioning then they will not. I think we have all agreed on that part though.

One more thing to keep in mind. Insurance liability. Fundamentally altering the braking system on your car could have dire consequences if you should ever be found at fault in an accident and they know you 'altered' your braking system. Just something to keep in mind.

TR3driver
03-15-2008, 04:57 PM
i want a cheaper alternative with less maintainence.Well, opinions vary, obviously. Mine is that the stock drum brakes require virtually no maintenance, and parts are cheap. I don't think there is any kind of cost justification for a conversion unless you are planning on doing several hundred thousand miles.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]due to more surface area you could get more stopping force with a disc[/QUOTE]Even if that were true, you couldn't use more stopping force ! A locked wheel provides significanly less stopping power than one that is almost, but not quite, locked. Thus the goal should be to have both ends lock at the same time (then hold them just under that point for maximum braking). The original TR3 rear drums actually worked too well, leading to several reductions over the years to reduce premature rear lock up.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] but you are correct about having a portioning valve to increase the force.[/QUOTE]No, the proportioning valve only reduces the force, in order to keep one end from locking up first. It does NOT increase the force.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] then you also have to adjust all the time.[/QUOTE]If you are having to touch the adjustment more than once every 20-30,000 miles then there is something wrong, IMO. I check mine every 10-12,000 (when I do the rest of the chassis lube/service) but only go another click on the adjuster maybe every third time I check them. <div class="ubbcode-block"><div class="ubbcode-header">Quote:]as far as braking force applied to the trailing arm i believe thats rubbish,[/QUOTE]Well, make up your mind. Are you going to increase braking force or not ?<div class="ubbcode-block"><div class="ubbcode-header">Quote:]just a thought for everyone saying this could not possibly reduce stopping distance....[/QUOTE]I won't say it couldn't possibly ... but IMO if there is any improvement at all, it will be from subtle factors like improving front/rear balance for the tires and suspension mods you use; or improving brake modulation near the limit. Which of course doesn't mean you shouldn't do it, just be realistic about what to expect.

Just please <span style="font-weight: bold">don't</span> follow me &amp; my drum brakes too close <<GRAEMLIN_URL>>/grin.gif

Oh yeah, don't forget you also need to change the MC to one with a larger reservoir for the rear brakes.

milemarker60
03-19-2008, 11:14 AM
I guess I'll chime in on what I found experimenting with rear discs on my TR6/M3. Keep in mind I ran my tests with the Modified BMW S50 M3 Engine (325hp), R200 Diff (3:54), CV-Joint Axles, M3 Tranny (.85 OD in 5th), 225/45/17 Falken Azenis RT-615 Tires, TR6 Master Cylinder, DOT-5 Fluid, Toyota Vented Front Disc Conversion and no body panels at all (light...).

For my baseline I used the Aluminum Drums, Morgan Wheel Cylinders and Carbotech Bobcat compound pads and shoes. Then I installed my rear disc brake conversion from a well know racing enthusiast that has used it for over a decade on the track with no mechanical issues or degradations. It incorporates a set of Willwood Billet Calipers and I also installed Carbotech Bobcats on these. At this point I also installed a Willwood lever-style proportioning valve on both the front and rear systems poking thru the front of the foot well where I could adjust the f/r bias inside the car with ease.

Stopping distances are irrelevant since the car was about a ton lighter without the body panels. I did run the tests with up to 500lbs of weight distributed throughout the chassis on some of the runs. Overall, I had a 5%-10% reduction in stopping distances with the discs on the rear depending on whether they were heated up or cool. Most importantly, the initial grab was significant leading me to believe in an emergency situation, I may just have an even greater advantage. In addition, I noted no significant fading issues with the discs as I purposely heated up both set-ups and ran them hard thru some aggressive twisties.

I figured with the stock MC I might need to play with the front/rear bias and messed around with it extensively. Interestingly enough, I found that leaving both the front and rear "open" netted the best results both in cool and heated conditions. Bear in mind that this was not a track scenario but I did run the car thru the paces. Even a slight reduction in front bias would cause the rears to grab too hard in a corner increasing understeer too much and reducing the rear bias I could never get them to adequately bite in straight or twisty driving.

My conclusions to this point on my car are to leave the system "open" with no bias adjustment and indeed, there was a significant increase in braking performance. I did drill out the mounting holes on the trailing arm and put in steel inserts and where possible, ran longer bolts in (can't remember how many of them allowed for a longer bite). My system does not allow for a true emergency brake so I have installed a "park-lock" valve in-line to the rears so the button sticks up thru my floor board where I can easily engage it. This info probably wonít translate to a stock TR6 mostly due to my tire/wheel set-up as this is the most obvious difference on my car that would affect the braking performance.

I am anxious to get all the heavy panels mounted so I can see if the bias needs to be tweaked with the proper weight hanging off the tub. Iím not going back to the drums so no further comparisons will be attempted as I am very satisfied with the change I made at this point. If I start breaking rear trailing arms as some have proposed, well, Iíll revert. But as I said earlier, I didnít invent the system and it has many years of proven reliability in a much more demanding environment than I plan to run in. Are they necessary, no. Do I feel that they will enhance my safety with my modified TR6, yes.

Dave

Andrew Mace
03-19-2008, 11:33 AM
...Jaguar used them on their race cars first while Triumph used them on their production cars first (then took their production cars racing :wink: )....Actually, Triumph first experimented with disc brakes in (IIRC) 1955 at the ill-fated 24 hours of Le Mans, where they tried Girling, Lockheed and Dunlop discs on different team cars. So technically, Triumph also tried them first on their race cars.

tr6lover
03-20-2008, 05:42 PM
hey dave, that sounds interesting. the whole purpose behind what i want to do is for simplicity and any possble gains in braking performance. i keep my rear drums adjusted and it just seems to me they are not up to the task. granted i have not changed my rear hoses yet and it could be possible that over time they have swollen inside and restricted flow but overall i would be happier with discs in the back. i have by the way modified my front brakes, toyota calipers and slotted rotors. i am confident in the fact that i wont just lose my brakes or hubs, i mean really, if the hubs just break under normal breaking they have no place on any road car, drums or disks. i believe that if it had not been for cost triumph would have used discs to begin with.