So here's the deal... I did a rear disc brake conversion on my 1983 Pickup. Here's the specs:
-Sky brackets
-Monte Carlo Calipers
-GM 1/2 ton rotors
-Braid stainless steel lines on the rear axle
-All new hard lines throughout
-Wilwood manual proportioning valve
-New 1" bores Aisin MC
-Stock brake booster
-Stock front brake setup with new rotors, calipers and pads
-Rolling on 15" alloy wheels wrapped in 31x10.5 tires

The brake lines of have been bleed, there are no leaks and th proportioning valve has been adjusted properly prevent rearend lock up.

Now here is my problem. My brake pedal has a really firm feel to it with about half of the travel that I feel that it should have. The brakes are also VERY touchy - if I go from driving my Tundra to my Pickup I damn near give my passenger whiplash when I first hit the brakes! The pedal also seems to not want to pump up like it should. The brakea definitely stop, but I feel like something isn't right. Any suggestions out there? Do any of you suppose that I need to upgrade to a dual diaphram booster? Do I need a residual valve even though I have a 1" MC and a proportioning valve?? Any help is appreciated - thanks guys!

 

Here are some pictures of my setup:

 

Oh, and I forgot to mention. I read somewhwre that the shaft in the stock booster is too short to fully compress the piston on the 1" bore MC. Is this true??

 

Hey dave,
I have a similar setup that I very recently put on. Mine is V6 rotors and calipers up front and the SFA disks and calipers on the rear ("economy kit" from Lowrange offroad), Landcruiser MC, and prop kit from Dave's offroad.

Did you go with the Landcruiser MC that has the residual valve for front and rear or did you get the V6 MC? I would guess the LC because you have a firm pedal.
I did my conversion in phases, starting with the MC, and it firmed up my pedal A LOT. With everything on now I have the prop valve almost completely backed off (least press to rear) and the pedal will only go about half way to the floor if I jam on it. I wouldn't say I'm locking up all 4 or giving people wiplash by "touching" the brakes but it's WAY better than the stock setup with almost non-functioning rear drums. Part of the difference might be that I'm stopping 35's and you have Monte rears. I would think an upgraded booster would just make this problem worse.

Oh, just remembered, when I put the LC MC on it was pretty grabby on the fronts but after I went to the V6 fronts it eased up quite a bit. Bigger MC pushing too much fluid for the small SFA front calipers maybe?

Sorry I don't have a direct answer, but maybe we can noodle this out.

 

Bingle, Thanks for the input so far. I have the 92-95 4Runner/Pickup master cylinder Aisin Part #BMT-081 or Toyota Part #47201-34010. I'm fairly certain that it does not have a built in residual valve and I too was thinking that upgrading to a dual diaphram booster would only magnify my issue.

It's not that I'm not getting good brakes - they are definitely there. It's just that I don't have much travel in my pedal so it is really touchy and I have to be sure to apply gentle pressure when I'm braking which isn't a big deal, but my concern is if I have to quickly slam on the brakes that I may lock up and lose control of the truck. It seems the volume within my brake system is just significantly lower than the that my 1" MC puts out. Also keep in mind that I have new brake pads all the way around so that also takes volume out of the system.

Now tell me this, I assume that the front V6 calipers have more volume? How difficult is that upgrade? Actually, I don't care about difficulty, I care about what parts are involved. Do the rotors and calipers just bolt on or do I have to completely swap hubs? I rebuilt my front axle with this resto so I'm not exactly eager to throw that work away.

 

V6 upgrade up front is a bolt on affair. I believe the taco front brake upgrade is more involved but it gets you to a width that matches the v6 rear, or that's what I've read, but that doesn't aply to the problem at hand. I had to trim the dust shield a little and I had to grind down the cooling fins (not a ton, maybe 1/8") on the outside of the V6 calipers to clear my wheels, but otherwise it was exactly the same as changing out normal disks and calipers. The SFA calipers have one large and one small piston and the V6 have two large pistons, so I would assume it takes a little more volume to move the V6's. I got some nice LCE vented/slotted rotors, I know you hate dealing with those guys, but that's what I went with.

I understand what you mean about pannic stops, if I was running smaller tires I believe I might be having similar issues to you, with 35's it just stops more like a normal vehicle should.

I am wondering about the residual valve issue, do your brakes firm up more if you pump them a little? I feel like I might want to add another 2lb residual to the rear because the rears do back off a bit, even with the LC MC. Maybe the Monte calipers have a residual built in? It cirtainly doesn't sound like you need a residual because that would just firm the pedal up more. My issue might also be partially because I have so little pressure going to the rears, I'm about 1 turn in from backed all the way out on the prop valve.

Just have to say, this is the first time I've heard of a guy complaining that his first gen truck's brakes work too well!

 

i have the V6 Calipers up front with the FJ rotors, big difference over stock, those with my stock rear brakes seem to stop my 35's pretty good.

The Taco front brake from Front Range is a great kit, better brakes and you don't have to take the entire thing apart to service the front bearings etc.
http://frontrangeoffroadfab.com/taco...-mounting-kit/

Dave you have pretty much the same brakes I will have on eventually- the rear monte carlos etc, have had the stuff on the shelf for 5+ years
The only difference I will have is a dual diaprahm brake booster from a Turbo truck.

Have you messed with proportioning valve to try multiple settings?

 

I adjusted the proportioning valve enough to keep rear from locking up but I haven't really played with it much. I probably should because I noticed a little more brake steering earlier this week when I was braking hard so I may need a little more pressure to the rear end to keep it from rearing up as bad under hard braking. I removed the stock torque rod so obviously it is a little more apt to brake steer with the stock push/pull steering. It's really not bad once you get used to it.

I really think that my problem is volume which I don't think that I can solve without any changes to the calipers. I also haven't driven the truck in a couple years so I don't really remember what the brakes used to feel like in order to compare. I do know that you don't want to be in my truck after I drive my Tundra if you have neck or back issues.... My Tundra brakes are really soft so the first couple of stop signs in my 83 can be a little hazardous until I become more conscious of what I am driving. Who knows, this may just simply be the difference between and modern and classic brake system. Anybody want to slide by and take it for a test drive to see what you think? LOL

 

If I wasn't on the other side of the country you better believe I'd be over checking your truck out. It turned out beautiful. Yoours is what I wish mine was, but I've gone too far down the off roader/ beater work truck to come back to pretty stock-ish head turner.
I drove mine to work today and there is less brake pedal travel on mine than any of my modern rigs, and way less than the spongy stock system trying to stop 35's, downshifting and engine braking were necessary, now it's just habbit.
Borrow someones 35's and see if that "fixes" your brake problem.

Probably like everything else with these old trucks (like brake steer) you just get used to the way it handles and becomes a non issue for you, just don't hand anyone else the keys cuz they'd end up putting it in a ditch.

 

I have v6 front calipers, buick rear calipers on sfa discs (very similar to monte-carlo calipers), 1'' v6 MC, stock booster, wilwood proportioning valve, residual valves. I have a very firm pedal, but I also have to apply a quite a lot of of pressure to lock my wheels (31''), and I have brand new discs with ceramic brake pads all around, so our only differences seem to be the front calipers and proportioning valves. My brakes are definately not neck braking and I feel like I would need a dual master to take full advantage of them.

 

yeah, like I said, my only fear would be a quick hard braking situation, but they do work. I could be over thinking it too since my Tundra is has pretty softer than normal brakes and my pickup has stiffer than normal brakes. Could just be that the scenario makes me notice it more, but you can never be too safe with brakes. My son loves riding in my truck so I don't want to have an unsafe situation with him in there.

 

Who wouldn't want to go for a ride in your truck?!
Again, great job on your resto-mod truck.
These old girls have personality/quirks when driving them, it's part of the charm in my opinion.
Safe travels.

 

When I drove my friends 2000 tundra I was amazed at how soft the brake pedal was, I was sure there was a problem, but he works at toyota and assures me that's the way they are, I really don't like it!

 

yeah, going from my '83 to my Tundra can be a little hairy at the first stop sign! My Tundra brakes are good, but the pedal definitely has to be mashed to get it to stop.

I'm going to roll with my brakes for now to see if anything improves. I think they are getting better, or maybe I'm just getting more used to the feel.