Brake Caliper reducer for RDB???

[CruisinTiger]

I have been following this thread daily for I am about to do a 4 wheel disk conversion. I have a 79 axle that I am swapping into my truck and I am going to use rear disk brackets with rotors and mote carlo calipers in the back. I have a link with the part numbers needed for the rear disk conv. My question is, why is everyone having different problems? Is it because everyone here has different "brands" of calipers, rotors etc. Is it because some are running a boosted master and others aren't? Is it because some are running mini truck or corvette masters? Trollhole has 4 wheel disk setup with no prop valve, the PO put in a mastercylinder/booster from a 94 TLC(I believe that is the year) and he has no problems. Could it be that everyone is tryin to adjust them on there own and it's a trial and error thing, where as if you took it to a mechanic he could adjust them in no time flat and you would be good to go? Could it be the type of brake line you are using if it expands or not(don't think this is the case)?

My feeling is it has to do with the Master cylinder whether it is boosted or non boosted. And the type of calipers you are using...monte carlo or mini truck.

Sorry for all the questions, just trying to sum up all that I have read here. Thanks for all the help in advance.

Chuck

 

[Trollhole]

Okay my take.

As said above I don't have issues with braking in emegency situations. We at least after I got my ant wrap bar. I'm SOA and I have a huge rear bumper

and large heavy shackles which could account for my better than most braking ability. I would think later 40 would be better with the mod than I due to the fact the gas tank ins in the rear. Also I'm sure weight distribution has a lot to do with it. Winch, bumper ,hard top, soft top and biggest of all is tires. All of things effet WD. I can say I have perfect braking with stock front discs and monte carlo rears with a TLC 95 brakemaster. I have never looked at the braking master much cause everything works perfectly but in the last months I've looked at it more and noticed one part I didn't see before. I do have a proportioning valve but it came stock on 76 cruisers.

#60. Now I don't know if it's adjustable but I do know spector wants 150$ for it. Maybe someone can chime in. My belief is it not adjustable. You can just see it in this pic under the master.

I don't think the booster has much to do with it other than making it a lot easier to stop fast and with little force. But I can say I can almost throw you out of your seatbelt when I put on the brakes so much that my rear Hypershackles will unload which means all the weight is on the front two tires and at this point the rears will lock. But with 33x 12.5 AT's I probably have a better contact patch than most. BUt you don't want to hit a big puddle with those cause it will hydroplane instantly.

 

[tfdcruiser]

Gangle and anyone else running a fj80 mc, You may need to switch your front and rear ports on the mc with the front and rear brake lines. In other words on some Fj80 mc the front port does not mean they go to the front brakes and vice versa. I was ready to drive my forty off a cliff in frustration until I found in a small obscure thread that this was the problem. I had several near misses until I switched the lines and now my rig stops like a race car rain or shine.

 

[Trollhole]

I'll look at front and back tonight and come back with my findings.

 

[miker]

I have been following this thread daily for I am about to do a 4 wheel disk conversion. I have a 79 axle that I am swapping into my truck and I am going to use rear disk brackets with rotors and mote carlo calipers in the back. I have a link with the part numbers needed for the rear disk conv. My question is, why is everyone having different problems? Is it because everyone here has different "brands" of calipers, rotors etc. Is it because some are running a boosted master and others aren't? Is it because some are running mini truck or corvette masters? Trollhole has 4 wheel disk setup with no prop valve, the PO put in a mastercylinder/booster from a 94 TLC(I believe that is the year) and he has no problems. Could it be that everyone is tryin to adjust them on there own and it's a trial and error thing, where as if you took it to a mechanic he could adjust them in no time flat and you would be good to go? Could it be the type of brake line you are using if it expands or not(don't think this is the case)?

My feeling is it has to do with the Master cylinder whether it is boosted or non boosted. And the type of calipers you are using...monte carlo or mini truck.

Sorry for all the questions, just trying to sum up all that I have read here. Thanks for all the help in advance.

Chuck

For reference, I'm using:

1975 TLC 1" bore drum/drum master cylinder with residual valves removed.
1979 FJ40 booster

Front Brakes:
1979 FJ40 Land Cruiser Disk
4-piston TLC Calipers (1-small and 1-large piston on each side of each caliper)
Raybestos pads and vented rotors with no slots or holes

Rear Brakes:
Mid-70s Metric GM Intermediate floating Calipers with single 2.6" piston
Calipers are mounted in upper rear position (I don't think caliper position matters but throwing it out there)
Rotors are Mid 90's GM truck - don't know brand but they cost about $25 each
Raybestos Pads

I'm using a proportioning valve on rear brake line. Its attached to master cylinder rear output within about 8" of master cylinder. I think the brand is Stainless Steel. Its basically adjusted all the way, maybe 95% of its adjustment, to limit rear brake pressure.

I'm using OEM style rubber brake flex hoses and 1/8" steel hard brake lines. I have 3 flex hoses on front axle and 3 flex hoses on rear. FT and RR Center hoses are about 20" each, FT sides are about 7" each, RR sides are about 10" each. So total flex hose length for FT is about 34" and RR is
about 40".

I'm NOT using the factory proportioning valve.

Braking:
On a hard stop, the fj40 stops nice and straight and pretty fast but I can still lock up rear tires. This setup is much better than the factory disk/drum for panic stops. The disc drum setup would always lock up one or the other rear tire on a panic stop.

I think the proportioning could be better, but I'm ok with the way it is now.

Just thinking if perhaps using different stype pads or rotors front vs. rear might help with front vs. rear tire lockup but I'm not sure I want to go to the expense or the trial and error testing at this point in time.

I believe my cruiser is pretty heavy in the rear vs. front. I carry a lot of spare parts, tools, gear, etc out back as well as a family roll cage. Up front is a SBC with alumimum heads, intake, water pump and radiator so definitely lighter than those running F or 2F . It does have a winch up front. I'm running 37" MTRs on steel wheels.

 

[dgangle]

Gangle and anyone else running a fj80 mc, You may need to switch your front and rear ports on the mc with the front and rear brake lines. In other words on some Fj80 mc the front port does not mean they go to the front brakes and vice versa. I was ready to drive my forty off a cliff in frustration until I found in a small obscure thread that this was the problem. I had several near misses until I switched the lines and now my rig stops like a race car rain or shine.

tfd,
This is very interesting. I have never heard this before and want to believe it's true. Where did you find this? Also, is this the MC you are using?
http://www.marlincrawler.com/brake.html

Trollhole, that is the factory Toyota non-adjustable proportioning valve. $OR's prices never fail to amuse me. You can buy an adjustable Summit/Wilwood for $50-ish.

Edit: I spoke to Chris @ Marlin Crawler today. He siad he never heard of such a thing and looked at two non ABS 80's in the shop and claims both showed the front port is plumbed to the front brake circuit and the same for the rear. I'm not sure who to believe.

 

[Plowboy]

This is a run through of my rdb on my 78. Stock front, 78 cad calipers w ebrake, stock 78 toyota proportion valve, and a stock 78 booster and master. The only change I made in the system was to remove the 6 lb residual valve in the rear filler cup and replace with a 2lb (Saved from a previous 78 master) which is used in the front disk filler. No problem with rears locking up with 33's

 

[snailwagon]

The reversal of front and rear ports is only for the abs unit, as the above picture shows. An abs mc is identified by the vertical front port. Non-abs has two horizontal ports. I have not tried switching lines yet on my fj80 abs mc, just run the front port for the rear brakes, opposite of every other toyota master I've used. Now how about someone takes their mc apart and see if their really is a volume difference between the front and rear circuits.