Upgrading the brakes on the j10
 

Booster is going out on my truck, and the rear brakes dont work. So time to upgrade. Going to convert the rear drums to 1/2 ton chevy discs. Get a wagoneer dual diaphragm booster. When I convert the rear to discs, I am going to move the front calipers to the back and get the bigger 3/4 ton calipers for the front. Anybody running the Chevy calipers front and rear, what master cylinder are you using? Also want to put a ball valve in (paging Matt where did you get them)

the 1/2 and 3/4 ton GM D52 calipers are all the same piston size. i think 79 was the break to "metric" calipers, same thing but a 10mm bango vs 7/16". there could also be a difference between a 1" or 1.25" thick rotor on the 1/2, but 3/4 should be only 1.25" thick. i'd make the calipers/rotors/pads match f/r for convenience later.

booster - best stock one available should be fine

master - my YJ has the 69 corvette, the TJ has the ram 2500, both are good. i might like the vette master better, but i need to replace mine now for leak-down. (been a hard 15 years :lol:) here's the pirate thread with fitting info
https://www.pirate4x4.com/forum/jeep...ade-yj-tj.html

prop valve - delete anything factory, get the basic willwood adjustable (i think summit sells it as a summit brand cheaper too). make a mount right under the master for it. chances are unless you have a big load it'll just be run all the way out. the bias will still be a tad back heavy, and i tend to wear the rear pads a touch faster. good pads stay in the TJ, rotate old pads into the YJ

lines - i have earls braided -3an stainless thru the entire YJ, zero hard lines, and would do it again in a second. it's so easy and zero loss of pedal. just gota get all the inverted flare and npt to -an adapters for the prop valve and master or linking back to hard lines.

ball valves - these are a good Parker valve sold under a different name on the cardboard for cars. love them! https://www.summitracing.com/parts/aaf-all48010

Total piston area:
Stock D52 ----- 6.78
front wilwood -- 6.28
Rear wilwood -- 2.46
Cadillac ('76 -'78) Eldorado rear E-brake Calipers -- 4.55

the rear wilwood are sized for a corvette on the track, a place you NEVER want the rear to lock up, and would be paired with huge fronts brakes. tried em on the TJ, they are NOT enough for a big-tire truck. the stock d52 vs the front wilwood looks close, even backwards by a little, but all reviews say the better force distribution of the dual piston wilwood will stop better than a stock slightly larger single. also less fade on the track with the AL, but not sure the added cost is worth it for a jeep.

the one thing i have never tried, and would love to, is the caddy rears. they are 2x the stock gm, but still half the wilwood in cost. but also usually sold out and hard to find. having run the rear wilwood with the prop valve all in, and the front gm on the rear with the prop vavle all the way out ... the caddy sizing should be cherry.

another thing to help proportion better is a smaller rotor in the back. i'd have to go back and dig for info, but pretty sure i found different Dia with the same hat/thickness. might be like gm vs dodge? if doing a weld-on mount, easy to change the running Dia of the caliper to match.

again though, matching f/r cheap stock stuff is great and should be a huge upgrade for ya. but if someone pulls out on ya and you MASH the brakes ... expect the rear to lock before the front.

Pretty set on doing the jb7 front calipers and maybe rotors. Calipers are 3 5/32 and moving my fronts currently (jb6 2 15/16 pistons) to the back.

Just need to figure out master cylinder bore diameter. Looks like stock j10 is 1.125

well sh!t, i've never heard of the JBx designation ... i've never heard of a 3-5/32 caliper for the half-ton bracket. how the hell have i gone this long reading THAT many articles on gm brakes, and never seen that before??

that's a 7.82 piston area

the JB7 mounts to the same bracket with the same pads as the JB6 ... just larger piston?

found this ... posting for future finding

JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder

JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"

JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder

JB8(10000lbs)
1.312" Bore MC
Conventional Calipers 3.4" piston
Front Disc- 12.50x1.54
Read Drum- 13.00x3.50
Hydraulic Hydro Boost
1 3/16 rear wheel cylinder

it looks like the JD7 is only in "metric" ... but that's an easy swap ... i guess i never looked at anything 79 or newer before.

Yes mount to the same brackets.