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Discussion Starter · #1 ·
has anyone tried the tsm rear disc conversion kit. mine is for 83 cj7 with model 20 and moser one-piece alloy axles. seemed to go together fine, but now have a lower pedal and the fronts seem to be the only brakes that are stopping the vehicle. bled the living @#$%$ out of the system with no improvement. am considering an upgraded m/c - booster combo from a vehicle that came with factory 4-wheel discs. any ideas on how to get these rears to work right??? thanks steve-0

 

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Official Curmudgeon
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First, if the brackets are the same as the ones TSM supplied when I did mine they hold the calipers at a
45 deg angle. If you used the rear brakes from a Riviera, Eldorado, etc. they need to be straight up and
down to bleed. If you try bleeding them in the brackets, you will leave an air bubble at the top. Take
them off of the brackets and either use a caliper clamp to hold the puck when you bleed them or gravity
bleed them. Which ever way you do it the bleeder screw needs to be held horizontal and at the top.

Next, once you are sure you have all the air out, set and release the parking brake a few time to adjust
up the pads.

 
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Discussion Starter · #3 ·
I am very interested in your success with this upgrade as I hope to do the same shortly to my 84 CJ-7 w/amc20 and 1 piece axles. I have heard that the problem you are having may be caused by the stock brake master cylinder being too small for 4-wheel disks as the piston moving in the rear calibers require more fluid movement inorder to do the job, thereby requireing a larger master cylinder. Please keep us posted with your results cause I want this deal to work for both of us! Jeep on!

 
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Discussion Starter · #4 ·
Did the kit come with a proportioning valve? If not, that could be part of your brake problem. If it came with one try adjusting it to put more preasure on the rear brakes. As far as the other gentlemens comment about the brake calipers, I have a toronado with rear discs and they are on an angle, they are not straight up and down, so you shouldn't be having any problems with bleeding them. Steve

Mopar360yj
87yj+20,74CHR.030360,SOA,35BFGATs,46RH,241DHD,
D60-44-4.10
 

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Official Curmudgeon
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Just to clarify, when I did my CJ, TSM recommended small (5-1/2" between mounting screws) rear
calipers from a 79-85 El-Dorado, Riviera, Toronado or 80-85 Seville (that's their spelling of Eldorado from
the manual which I have in front of me). These mount straight up and down at the rear of the rotor. This
is a problem that TSM told me they were working on at the time. Mine have worked fine for more than 4
years but they are a b----- to bleed.

For Red Dogg and any others that might be doing this conversion, I noticed a late model Cutlass in the
parking lot at the office and I could see through the spoke wheels that the rear calipers were at the 45
deg. angle. If these fit the TSM, I would by all means use them. It will save you a lot of trouble.

As to the master cylinder issue:

If the master cylinder has a residual valve, it must be removed. This valve keeps a small amount of
pressure on drum brakes which is normal. If the residual valve is in the combination valve it should be
removed there too. Failure to remove this will cause disc brakes to drag with the small pressure
remaining on them. This will not cause the rear brakes not to apply though.

If the master cylinder cannot supply enough volume to the rear brakes, you have used a caliper with too
large a piston. The rear calipers you install should not have a larger diameter piston than is used on the
front. Going to a larger master cylinder will result in less stopping force at the brakes for the same
pressure applied to the pedal.

Master cylinders for use with disc brakes have no residual valve and the reservoir are about the same
size. Drum brakes have a mechanical adjuster so they don't require more fluid from the time they are
installed until the time they are worn out. Discs, on the otherhand, move the puck out further and further
as they wear requiring more and more fluid from the master cylinder reservoir. Most dual master
cylinders for combination disc/drum brakes have a small reservoir for the drums that is insufficient to
supply fluid for the life of the pads on disc brakes.

Lastly, disc brakes are not as effective as drum brakes. The shoes on drum brakes have their pivot point
such that the shoes are pulled into the rotating drums to assist braking (ever notice drum brakes don't
work as well in reverse?). The advantages of discs are that they shed water better, they don't fade from
heat with continued hard use, and for us jeepers, they work equally well going in either direction.



 
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Discussion Starter · #6 ·
i have a 66 wagoneer with a rear d44 and the TSM disc kit. i used a 6lug rotor supplied at my request, from TSM in replacement of the 5lug rotor that is supplied with the normal 72-75 cj rear kit. my axle tube ends r the same as thoses years cj...

u shood removed the disc/drum combo valve and replaced it with a unit from a Eldorado, or other disc/disc car. u may want to obtain a unit from a vehicle that is in the same weight class as ur jeep type.

also, the discs need much more pedal effort than drum systems. either use hydro boost or dual diaphram vacum boosters. i use the later.

my rear 85 eldo calipers r mounted at an angle and i cannot bleed them on the brackets. i remove them and place the appropiate sized deep socket between the pads and use wire to suspend them while i bleed.

u shood note that the disc system will not give greater stopping power than ur previous system. only more consistent braking with less lockup of a tire on steep downhill use.

check out me attachment...


 

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Discussion Starter · #7 ·
I must have a strange 84 toronado, because my calipers are on about a 45 degree angle. Steve

Mopar360yj
87yj+20,74CHR.030360,SOA,35BFGATs,46RH,241DHD,
D60-44-4.10
 

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Official Curmudgeon
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4,707 Posts
Steve, does your '84 Toronado have the rear calipers at a 45 deg. angle or just the front ones?

 
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Discussion Starter · #9 ·
CJ7Taz,

On your earlier post on removing residual valve is that the same as the check
valves coming out of the MC? Is so do you remove just the valve for the rear
(smaller) resevior or both?
I got the tsm kit on the rear of CJ and haven't really had problems but could
use more stopping power in the back.

Lee

[email protected]
 

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Official Curmudgeon
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No, I don't believe what you are describing is the residual valve especially if there is one front and back.
I think for your 84 CJ it would be in the combination valve, but I'm not sure Again, the residual valve keeps
pressure on drum brakes and will cause discs to drag when the brakes are not applied. The residual
valve does not restrict fluid to the brakes, only coming back. If your discs are not constantly dragging,
you shouldn't have a residual valve.

For more stopping power at the rear, you need a proper proportioning valve. You can do this by getting
a combination valve for a vehicle that had 4-wheel discs or do what I did and buy an adjustable
proportioning valve. I removed the tubes for the rear brakes from the combination valve and connected
them to the proportioning valve. If you do this you need to know how to adjust the valve. Right or wrong,
what I did was opened the valve until the rear wheels locked up before the front. I then closed it back
down until the rear brakes no longer locked up. I have a fiberglass body so there's not much weight back
there and I had to close the valve quite a bit.


 

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Get yourself a '79 Firebird 4-wheel disc master cylinder and perform the Tri-County mod to your bellcrank assembly. The Tri-County mod will give you 'normal' power brakes and the Firebird master cylinder will take care of activating those rear calipers.

 
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