Drum vs. Disk booster what's the difference?

[roma042987]

I put a disk brake axle under my 1975 fj40 this weekend and in preparation purchased a city racer disk brake booster and master cylinder to install. However, this 40 already has some sort of later style (single reservoir) master cylinder. It doesn't have a place to remove residual valves etc. I decided to bleed the brake and test them out without touching the booster and master. Seems to brake well so now I'm wondering what the booster differences really are? I have two other 40s needing new master/boosters so the purchased one will certainly be utilized my thought is though whether it better serve one of my other 40s.

Yes I hauled the new axle in my rental

 

[B y r o n]

"It doesn't have a place to remove residual valves etc." It's in there, you just need to disassemble it to find it.

You need to determine if it is a disc/drum master or a drum/drum master. If it is the later, failure to remove the residual valve will keep to much pressure on the disc cylinders and the pads will be dragging on the disc. This will lead to premature wear and poor gas mileage because it will be like driving around with your foot on the brakes.

 

[roma042987]

"It doesn't have a place to remove residual valves etc." It's in there, you just need to disassemble it to find it.

You need to determine if it is a disc/drum master or a drum/drum master. If it is the later, failure to remove the residual valve will keep to much pressure on the disc cylinders and the pads will be dragging on the disc. This will lead to premature wear and poor gas mileage because it will be like driving around with your foot on the brakes.

Negative, this an aluminum housing master cylinder as stated. No residual valves to remove. Also as stated booster is original 75 model, these had drums front and rear. Not my first rodeo with residual valves, I know what they do there is no residual pressure as suspected and confirmed. My question is pertaining to DIFFERENCE between boosters. I've heard there is one but WHAT is it?

 

[3_puppies]

I didn't think the actual booster is different
there was some years that had a dual diaphram setup which was rather large versus the single diaphram style

 

[EWheeler]

Negative, this an aluminum housing master cylinder as stated. No residual valves to remove. Also as stated booster is original 75 model, these had drums front and rear. Not my first rodeo with residual valves, I know what they do there is no residual pressure as suspected and confirmed. My question is pertaining to DIFFERENCE between boosters. I've heard there is one but WHAT is it?

I don't know of an aluminum bodied master cylinder that is designed to work with drums/drums, except for the Non-US market trucks that were built through the 80's and into the 90's with drums front & rear. I'm thinking you may have had a disc/drum master cylinder to start out with?

Sorry, I don't know the physical internal differences between boosters, all I know is I hate the size of the large mid to late 70's boosters and have swapped in early 90's 4-runner single diaphram boosters on two 40's and enjoy the space freed up by the shorter booster.

 

[roma042987]

I didn't think the actual booster is different
there was some years that had a dual diaphram setup which was rather large versus the single diaphram style

That would be what I'm trying to nail down. My OCT. 77 has that larger booster but I'm confident most 76s (disc brakes) and early 77s had the smaller boosters. I know that for instance the boosters that @Racer65 has on the website appear to be very similar dimensionally but are specific drum vs. disc. IF the difference between Disc and Drum boosters is dual diaphragm vs single. Is one required or simply preferred over the other?

 

[roma042987]

I don't know of an aluminum bodied master cylinder that is designed to work with drums/drums, except for the Non-US market trucks that were built through the 80's and into the 90's with drums front & rear. I'm thinking you may have had a disc/drum master cylinder to start out with?

Sorry, I don't know the physical internal differences between boosters, all I know is I hate the size of the large mid to late 70's boosters and have swapped in early 90's 4-runner single diaphram boosters on two 40's and enjoy the space freed up by the shorter booster.

Yes that's what I was stating incase I wasn't clear. It has a later model aluminum housing single reservoir master that indeed would not have been intended for front drum brakes.

 

[Living in the Past]

That would be what I'm trying to nail down. My OCT. 77 has that larger booster but I'm confident most 76s (disc brakes) and early 77s had the smaller boosters. I know that for instance the boosters that @Racer65 has on the website appear to be very similar dimensionally but are specific drum vs. disc. IF the difference between Disc and Drum boosters is dual diaphragm vs single. Is one required or simply preferred over the other?

I have a 10/75 76 model and almost positive it has the dual diaphragm. Would have to see if I have a picture on a hard drive. I show the same booster 9/75-7/80.

 

[roma042987]

I have a 10/75 76 model and almost positive it has the dual diaphragm. Would have to see if I have a picture on a hard drive. I show the same booster 9/75-7/80.

John, looking at some photos it does appear the 76s had the longer booster. My memory fails me at times. So I suppose it would be safe to assume the only difference between drum and disc boosters is that the latter is dual diaphragm. I wonder if the dual diaphragm provides more NOTICEABLE assist in an apples to apples comparison. I can't really seem to tell the difference between this 75 and my 77 back home.

 

[Living in the Past]

John, looking at some photos it does appear the 76s had the longer booster. My memory fails me at times. So I suppose it would be safe to assume the only difference between drum and disc boosters is that the latter is dual diaphragm. I wonder if the dual diaphragm provides more NOTICEABLE assist in an apples to apples comparison. I can't really seem to tell the difference between this 75 and my 77 back home.

Australia used the same booster in the FJ40 from 1/75-7/80. I know they didn't get a disc brake up front until 10/82 which is the start of the 83 model. 8/80 the rear axle axle only had one wheel cylinder on each rear wheel. The booster changed the same date. I do see a two diaphragm 8/80 on cruisers with drum brakes. Wonder if this was to improve stopping power because the wide drums with cooling fins ended 7/80. When bought the axles from an 84 HJ47RV I pulled all the brake lines, master cylinder and booster figuring Toyota did all the engineering.