disc brake conversion question

[fj40fan]

I have a 71 FJ40 that I recently put a disc brake front axle from a 79+ FJ40 on but am still going to use the stock rear drum axle. My question is, can I use the stock M/C, booster, for the front axle and just remove the residual valve for the front brakes from the M/C? My booster and M/C are in good shape. I did a search and it seemed that this was all that was needed to run the discs.

The main reason Im asking this is because I saw the SOR catalog they sell a disc brake conversion for 71-75 40s and they recommend replacing the M/C with a disc brake master as well as the stock disc brake proportioning valve. So I was wondering if I needed to do this. If I could save some money that would be nice, but I dont want to skimp too much when it comes to the brakes.

 

[bikersmurf]

Need proportioning valve

You can use the stock master without the residual valve. You will need to get hold of a brake proportioning valve from a disc brake FJ 40. If you are planning to get rear discs in the future buy an after market adjustable one. Both go between the M/C and the rear brake line. Without one the rear end will be locking up all the time... trust me. Not a lot of fun unless you like doing 180s at the stoplight and sliding into the intersection backwards.

 

[3_puppies]

I have a 71 FJ40 that I recently put a disc brake front axle from a 79+ FJ40 on but am still going to use the stock rear drum axle.

just double checking you changed the diff also, so you have the same ratio, front and back???

 

[dgangle]

Your plan sounds good. Use it and see how it performs.

Other MC & prop valves solve problem you may not have. Cross that bridge when you get to it.

 

[fj40fan]

just double checking you changed the diff also, so you have the same ratio, front and back???

Ooops! Forgot to mention, I used the 3rd member from my 71.

Your plan sounds good. Use it and see how it performs.

Other MC & prop valves solve problem you may not have. Cross that bridge when you get to it.

So what you're saying is just remove the residual valve from the front brake circuit and run it? So I may not need a proportioning valve like bikersmurf stated. I don't want to take it for a test drive and have the brakes lock up or something worse.
Thanks for all the input.

 

[nuclearlemon]

Ooops! Forgot to mention, I used the 3rd member from my 71.



So what you're saying is just remove the residual valve from the front brake circuit and run it? So I may not need a proportioning valve like bikersmurf stated. I don't want to take it for a test drive and have the brakes lock up or something worse.
Thanks for all the input.

you most likely will need the prop valve, but you can always test it and see. i don't run a prop valve, but i've also got 4w discs. i just pulled both residual valves. i've had to do a panic stop from about 40mph when some penisboy in his crappy blinged h2 pulled out in front of me and all was good

 

[vk7ybi]

Your plan sounds good. Use it and see how it performs.

Other MC & prop valves solve problem you may not have. Cross that bridge when you get to it.

This is good advice.. When I did my conversion, I just pulled the residual valves and ran it.. I get some premature rear wheel lockup in poor traction situations, but when loaded with extra fuel and camp gear the biasing is pretty good.. My vehicle isnt a DD and I'm happy to run it the way it is, YMMV..

If I were to ever install a prop valve, it would be adjustable in the cabin so I can set the bias 1:1 for offroad..

 

[jtoro]

I have installed front disk brakes on my 68 FJ40 and replaced the old master with a FJ60 booster and master cylinder. Where I live it's almost impossible to get a proportioning valve and a friend suggested switching brake lines (front hooked up to rear and rear hooked to front). Now I have great performance and rear tires only lock on extreme conditions (sudden hard braking in loose gravel). Give it a try.

 

[fj40fan]

This is good advice.. When I did my conversion, I just pulled the residual valves and ran it.. I get some premature rear wheel lockup in poor traction situations, but when loaded with extra fuel and camp gear the biasing is pretty good.. My vehicle isnt a DD and I'm happy to run it the way it is, YMMV..

If I were to ever install a prop valve, it would be adjustable in the cabin so I can set the bias 1:1 for offroad..

Whats you're setup? I am running stock rear drums so from what Ive read I should just be removing the front residual valve, right?

If using a proportioning valve, which one should I use for my setup (79+ FJ40 front axle, 71 drum rear axle, stock lines and master)? Stock Toyota or aftermarket?

I plan to drive my 40 regularly so driving in L.A. traffic would be very likely.

Once again thanks for all the input.

 

[vk7ybi]

I had a wierd setup.. First I had all drums that functioned poorly with seized adjusters.. I then did a rear disc setup, with front drums still.. When I did this, I removed the rear residual valve only.. Then I did front disc, so removed the front residual valve.. It was at this stage that I discovered I had an internally leaking master cylinder, so I replaced it with a 1 1/8 inch drum brake master.. Best brakes I have on any of my cruisers, although the pedal effort is a bit high, eventually I'll change to a 7/8 master..
If I needed one, I would just go for one of those Willwood adjustable prop valves in the rear circuit rather than stock.. My 81 has factory front disc, rear drum and it has some combination valve thing mounted under the master, I believe it handles proportioning, keeps residual pressures in each circuit and provides pressure differential warning signals..
Swapping lines front to rear isnt going to achieve anything in a system thats working properly, really..
There is lots of reading on here about rear disc conversions and prop valves, but as has been mentioned you might not need one yet, do the conversion and go test on some gravel roads..

 

[fj40fan]

thanks for the info, we'll see what happens.

 

[H2o]

This is good advice.. When I did my conversion, I just pulled the residual valves and ran it.. I get some premature rear wheel lockup in poor traction situations, but when loaded with extra fuel and camp gear the biasing is pretty good.. My vehicle isnt a DD and I'm happy to run it the way it is, YMMV..



Wow, That's crazy. the REAL problem if you lock up at all in the rear would be around a turn with questionable traction (snow, rain, gravel, sand), if you had to hit the brakes. Your rear end would slide out fast. In a panic situation, it could be deadly. IMO you really need to have a perfectly balanced system.

 

[Bossman]

With your planned use on the highway I would recommend a prop valve. Just go to someone like Summit or Jegs and get their adjustable valve. Find a gravel road and do some stop/starts as you adjust till your front brakes just barely lock up first. All vehicles change with load so, again, depending on how you will be using your rig you may have to readjust if you are heading out to the trails with a heavy load.

 

[Downey]

With your planned use on the highway I would recommend a prop valve. Just go to someone like Summit or Jegs and get their adjustable valve. Find a gravel road and do some stop/starts as you adjust till your front brakes just barely lock up first. All vehicles change with load so, again, depending on how you will be using your rig you may have to readjust if you are heading out to the trails with a heavy load.

OR, another good choice is to go to a professional brake shop where they put gauges on the front and rear brake lines to properly set your 60% front to 40% rear ratio!!!!!