losing my turbo coupe rear and going back to drum...a few questions...

carbed87 · Jul 8, 2007

so with the turbo coupe rearend i now have under the car, it's givin me more problems then solutions, mainly just dictating the width of my tires due to the wider track it has. anyways, when the TC rear was installed, a lincoln mark VII master cylinder was put in along with it due to having rear disc. so heres where im asking the questions...

a friend of mine is selling a drum equipped 8.8 that has been equipped with five lug axles for cheap (about $250 for the rear, wheels and tires) plus, the rear only has about 5k on it. my question is that if i put this rear in my car and lose the TC one, am i going to have to change back to a stock style master cylinder, or can i just leave the mark VII one in there.

lol i now it sounds stupid going this route, and i do know what it'll take to convert my Turbo coupe rear end to five lug, but i just dont like it. i cant even run a 26/10.50/15 slick without rolling my fender lip and that's not something i really want to do due to the fact that i might want to put it back to original one day. anyways, all help is appreciated as usual...thanks guys

vristang · Jul 9, 2007

Is the axle length correct?
It sounds like the tires are located too far outboard...

Whether the rear is 5 lug or 4 lug won't make a difference to the brakes.

If you are planning to install drum brakes, then you will have issues...
With drums in the rear, you will want to put the stock brake setup back in the car...

jason

carbed87 · Jul 9, 2007

vristang said:
Is the axle length correct?
It sounds like the tires are located too far outboard...

Whether the rear is 5 lug or 4 lug won't make a difference to the brakes.

If you are planning to install drum brakes, then you will have issues...
With drums in the rear, you will want to put the stock brake setup back in the car...

jason

well thats what im saying dude. TC rears are a full 1.5" wider then the normal stanky rears. the only thing that was changed for the swap was the master cylinder and i was curious if it would need to be changed back... like would a mark VII master cylinder work for drum brakes.

93 LX · Jul 9, 2007

I am assuming you gutted the stock port valve then you wil have to replace thos parts. You went to the MK7 MC because the stock drum MC does not give enough pressure to the rear to operate the calipers. With drums and the MK 7 MC you will have way too much pressure to the rear. I am not sure if a adjustable porp valve will help. You could just get the north cobra caliper brakets and use stock length axles and keep the rear disks.

Anyway good luck.

maxine-70 · Jul 9, 2007

master cylinders arent pricey, so id put it back the way its supposed to be.

since i know more about musclecar dodges than i do modern era cars, the master cylinders on those were different. disc/drum combo masters had a residual pressure valve installed in the masters outlet that fed the rear drums. the point of that was to keep a minimal amount of pressure on the rear wheel cylinders to keep them in place. rear disc cars did not have that little valve.

it may work, it may not. why chance it on your safety over a $30 part?

if you changed the proportioning valve when you went with rear discs, change that back too, or it will feed too much volume to your rear brakes and lock them up first and lose control of the car. if you didnt change that part, you probably never got the full advantage of the rear discs anyway, but its easier to swap back now since you dont have to change that.

rear discs are overrated. spend your time and money on upgrades to the front discs.

Mustank · Jul 9, 2007

The rear-ends are the same size right? The only difference is the length of the axles. Just buy a couple of stock-length 5-lug axles and keep the discs.

carbed87 · Jul 9, 2007

Mustank said:
The rear-ends are the same size right? The only difference is the length of the axles. Just buy a couple of stock-length 5-lug axles and keep the discs.

yeah, but im saving an assload of cash this way...oh well...i guess the master cylinder will have to go. no big deal. thanks for the help guys

93 LX · Jul 10, 2007

hmmm 5 lig ranger axles from the bone yard are around 20 - 40 bucks and the north cobra brackets with 86 V6 MPV front rotor with 1/4" spacers and you are right at the 250 mark and you retain the rear disks. Did I read rear disks are over rated? I guess Mopar man hasint driven a new SRT8 Charger. 4 wheel disks are the bomb!

Allen

maxine-70 · Jul 10, 2007

for a street car under normal driving to even mild performance usage, disc brakes on the rear are overrated. yes, they perform better. no, they dont perform significantly better to justify the work and expense to put them on. rear brakes only account for up to 30% of stopping capacity and dont experience the heat fade that the front brakes do when trying to slow down a speeding beast from 70mph. rear disc brakes are more for aesthetics than performance on passenger cars.

i got into the rear disc hype years ago. i built a 525hp 440 4 speed duster and started with an 8.25 rear with huge 11x2.50 rear drums and 11" rotors in the front. it stopped fantastically. i thought i could get it better, so i dropped in a 9" versailles rear with rear discs. brake performance fell off. i had a 9" from a big body lincoln rear disc car narrowed and put that in and it still fell off from the drums. i even used an imperial rear-disc master cylinder and both an adjustable proportioning valve and the lincoln versailles valve. the drums were better, and the reason is contact area and the fact that rear drums do not eperience the heat front brakes do. at brake contact with 11x2.50 shoes, the shoe to drum contact is CONSIDERABLY larger than the tiny pad to disc contact. now if this were on the front of the car, or if you were doing serious racing where the brakes are in constant on and off usage, rear discs would take the advantage, but for the street cars we are building here, they just dont warrant it. so again, i argue to put the money into upgrading the front discs to the largest diameter rotor you can get with the largest pad surface area you can get with the most number of pistons you can get in the caliper, and leaving the drums out back. they dont look as cool, but youre wasting your money on a street car. if youre wanting more out of your rear drums, use aerostar backing plates and drums.

talk to an automotive engineer and ask why cars originally went to rear disc on performance cars and they will likely tell you it was because their competition did it and they didnt want to look behind their competition.

millhouse · Jul 10, 2007

maxine-70 said:
for a street car under normal driving to even mild performance usage, disc brakes on the rear are overrated. yes, they perform better. no, they dont perform significantly better to justify the work and expense to put them on. rear brakes only account for up to 30% of stopping capacity and dont experience the heat fade that the front brakes do when trying to slow down a speeding beast from 70mph. rear disc brakes are more for aesthetics than performance on passenger cars.

i got into the rear disc hype years ago. i built a 525hp 440 4 speed duster and started with an 8.25 rear with huge 11x2.50 rear drums and 11" rotors in the front. it stopped fantastically. i thought i could get it better, so i dropped in a 9" versailles rear with rear discs. brake performance fell off. i had a 9" from a big body lincoln rear disc car narrowed and put that in and it still fell off from the drums. i even used an imperial rear-disc master cylinder and both an adjustable proportioning valve and the lincoln versailles valve. the drums were better, and the reason is contact area and the fact that rear drums do not eperience the heat front brakes do. at brake contact with 11x2.50 shoes, the shoe to drum contact is CONSIDERABLY larger than the tiny pad to disc contact. now if this were on the front of the car, or if you were doing serious racing where the brakes are in constant on and off usage, rear discs would take the advantage, but for the street cars we are building here, they just dont warrant it. so again, i argue to put the money into upgrading the front discs to the largest diameter rotor you can get with the largest pad surface area you can get with the most number of pistons you can get in the caliper, and leaving the drums out back. they dont look as cool, but youre wasting your money on a street car. if youre wanting more out of your rear drums, use aerostar backing plates and drums.

talk to an automotive engineer and ask why cars originally went to rear disc on performance cars and they will likely tell you it was because their competition did it and they didnt want to look behind their competition.

While you seem to be correct on most of your points…there is one glaring point that you left out. Today's drum brakes are far superior to those of yesterday. While a great majority of us would notice no significant difference on modern vehicles in regards to brake fade…the same cannot be said of the vehicles of yester year. For those of us that have a commute that consists of an average of > 10 high speed stop's per day….disc brakes can really shine. In the past I had commuted with the stang under those conditions and brake fade was ridiculous. All it took was one good 80 to 0 stop and the brakes were Jell-O for the rest of the commute. Stopping at the dragstrip was the same way. Brake fade was HORRIBLE!!! Heaven forbid you try to hot lap. My current brake setup (out of a 99 v6 stang) is worlds better than the original brakes. When I commute with it I notice virtually no fade…and stopping from high speeds is extremely stable and easy.

As far as your last comment goes…it's simply not true. There are so many benefits of using 4 wheel disc for performance applications…to think that they switched over to them simply because "their competition did it" is asinine (no pun intended).

25thmustang · Jul 10, 2007

For anyone who has done the rear disc swap, it is much, much better. I would be scared in a fast Mustang on stock drums.

As far as the rear ends and MC goes, they are cheap enough to just change, but then again for a little more you could have the narrow disc set up out back. I grabbed the rear brake parts for $150 and the axles for $90. Sell your TC rear, buy some rear disc stuff off a 94+ car, and then the NRC brackets and you should be all set to run any tire and rim you want. I would get some extended studs as well, I am learning that now.

maxine-70 · Jul 10, 2007

millhouse said:
While you seem to be correct on most of your points…there is one glaring point that you left out. Today's drum brakes are far superior to those of yesterday.

you just reinforced my idea. the 35 year old rear drums on the back of a brutal 440 duster were better at stopping the car than the discs were. and you just argued that modern drums are better than older ones. id like to know the logic on that too, as drums havent changed their technology between 1972 and 1992.

besides, i DID agree discs were the better setup. my point was that on a street car they dont offer enough of an advantage to warrant the time, labor, and cost of putting them on....unless youve got the rear apart anyway and just happen to have a setup laying in your garage. i wont waste the money on a swap.

25thmustang · Jul 10, 2007

With all the 11 second and faster cars driving around, and driving fast, I would feel much better if they had 4 wheel discs. Some people consider 800 whp cars, street cars, and if you saw an 800 rwhp fox, on stock drum brakes covered in dirt and surface rust, your telling me you wouldnt be worried jamming on the brakes in front of him? I think once your trap speed crests 110 you should really be thinking about discs, because that is a faster than average car, and should have better than average brakes.

I dont even think my discs are all that great, I really want some Cobra ones, but don;t have the money at the moment.

millhouse · Jul 10, 2007

maxine-70 said:
you just reinforced my idea. the 35 year old rear drums on the back of a brutal 440 duster were better at stopping the car than the discs were. and you just argued that modern drums are better than older ones. id like to know the logic on that too, as drums havent changed their technology between 1972 and 1992.

besides, i DID agree discs were the better setup. my point was that on a street car they dont offer enough of an advantage to warrant the time, labor, and cost of putting them on....unless youve got the rear apart anyway and just happen to have a setup laying in your garage. i wont waste the money on a swap.

Reinforced what idea? All I did was agree with you on some points. A modern, properly sized disc brake setup (including matching master cylinder, brake booster, prop valve etc) would blow your old drum setup out of the water in both stopping power and fade. Your conversion did not work the way you expected….but that does not change the fact the disc brakes are superior.

As far as technology changes go…there are far more than you would believe. Although from the outside the drums may look the same, materials used in construction as well as the overall mechanical design (including piston, mc etc.) has had a great impact on stopping ability. Hell, I'd venture to say that most modern drum brakes offer far more stopping power and less brake fade than most disc setups (be them front or rear) from the 70's.

If you had a commute like mine which involves many high speed stops on a regular basis you would change your mind on the advantage. Just because your commute does not necessarily require it does not mean the rest of us would not notice the advantage.

Boss 351 · Jul 10, 2007

I converted my ZX2 (back in the day) to rear disc using 93 Escort GT parts. I got to tell ya, the disc brakes made a difference in stopping and mostly made the car more stable esp. on rainy or roads covered in snow. And yeah disc brakes DO look better

I'd put the stock master cylinder back if you go to the drums.

carbed87 · Jul 10, 2007

just for the record...i love the discs, i just hate the wider track, i cant run wider then a 245 tire without murdering the sidewall. rear discs are awsome though

losing my turbo coupe rear and going back to drum...a few questions...

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