Anyone running Tom's new Ultimate 9" brake booster and 1.25" master cylinder combo? This looks like the strongest set up for vacuum assist.

[79INA69]

My current set up is the WH booster and bracket. Had the HD master on there and am currently installing a 1.25" bore master that doesn't quite fit under the hood, had to modify the booster rod, oval the mounting holes along with brake lines to get it to bolt up. haven't bled the rear lines yet. I have the big Ford dual piston calipers up front and Chevy JB6 calipers on the rear. Not sure if my brake pedal ratio is still at the manual height or not. Had too much travel and no stopping power. I want to run the vacuum assist set up for now and just came across this in my desperate search for a 1.25" master that would clear under a bronco hood.

 

[Yeller]

I use a master cylinder for an 85 chevy K30 with hydro boost, several of us here are running that with big calipers successfully, its the shortest master that I could find with a 1-1/4 bore, for hood clearance. Since you already have the angle bracket and linkage look at a brake booster for a 1980 C3 Corrvette, my guess from what I could see, it is the unit that Tom's is providing. Last I checked Rockauto was carrying new AC Delco master cylinders, so no need to deal with crappy reman units. They also had the booster for $70, had to replace my JY one last summer. Only other real option is to go hydro boost with a stock 1-3/8 or 1-1/2" bore MC, they usually clear the hood since it puts it more in line with the motor and gets into the hump in the hood.

 

[79INA69]

I use a master cylinder for an 85 chevy K30 with hydro boost, several of us here are running that with big calipers successfully, its the shortest master that I could find with a 1-1/4 bore, for hood clearance. Since you already have the angle bracket and linkage look at a brake booster for a 1980 C3 Corrvette, my guess from what I could see, it is the unit that Tom's is providing. Last I checked Rockauto was carrying new AC Delco master cylinders, so no need to deal with crappy reman units. They also had the booster for $70, had to replace my JY one last summer. Only other real option is to go hydro boost with a stock 1-3/8 or 1-1/2" bore MC, they usually clear the hood since it puts it more in line with the motor and gets into the hump in the hood.

Good info. I think the master I have is a delco unit from rock auto from a 1977 K20. I have a really old fiberglass hood that had wood runners. I chopped out a 6" section just to get the 7" booster to clear... I could relocate or shim the angle bracket too. Once I feel the brakes this weekend, I will know if Im going the right direction. The master cylinder that Toms sells is very compact looking 1.25" and only $90.

 

[Yeller]

I wonder who is making that cylinder for Tom's, the largest I have been able to find in that style is 1-1/8. Now that I know it is available it will be the go to simply for the machined cover that won't leak. As we all know the old school cast iron masters with the tin top are terrible about leaking brake fluid.

FYI K20 and K10 usually use the same master cylinder for the same year, they use the same calipers or close enough to the same depending on year and GVW. K30 is always different, They used the largest calipers offered by GM. Another just for that GeeWiz file. OEM hydroboost systems usually use a 1-3/8" - 1-1/2" since they generate higher boost a larger master is used to reduce pedal travel and make it more firm. Due to the higher boost available it does not need the master cylinder bore to caliper diameter balance to have good brakes.

Edit:
I just stumbled on this option too: AC Delco P/N 19175960
summit 1-1/4 bore master, corvette style

 

[79INA69]

I wonder who is making that cylinder for Tom's, the largest I have been able to find in that style is 1-1/8. Now that I know it is available it will be the go to simply for the machined cover that won't leak. As we all know the old school cast iron masters with the tin top are terrible about leaking brake fluid.

FYI K20 and K10 usually use the same master cylinder for the same year, they use the same calipers or close enough to the same depending on year and GVW. K30 is always different, They used the largest calipers offered by GM. Another just for that GeeWiz file. OEM hydroboost systems usually use a 1-3/8" - 1-1/2" since they generate higher boost a larger master is used to reduce pedal travel and make it more firm. Due to the higher boost available it does not need the master cylinder bore to caliper diameter balance to have good brakes.

Edit:
I just stumbled on this option too: AC Delco P/N 19175960
summit 1-1/4 bore master, corvette style

Yeah that master looks promising. Are you running the super duty HB unit? I know Mustangs, Astrovans and most of the new big trucks. I have a saginaw pump, single return reservoir.

 

[toddz69]

I wonder who is making that cylinder for Tom's, the largest I have been able to find in that style is 1-1/8. Now that I know it is available it will be the go to simply for the machined cover that won't leak.

I'm guessing it's the latest off-shore knockoff that's available -following in the footsteps of Wilwood's masters of the same style. Typical cycle - good parts manufacturers come up with something and then in a matter of months/years, China knocks off the part and offers it for a lot less.

Todd Z.

 

[nvrstuk]

Well I'm following this thread closely!

Been waiting for someone to find that elusive 1.25" or larger bore in alum with a reservoir that fits under a ProFlow hood (unlike the SD's.)

Like Steve I'm running the 1.338" mc from mid 80's Chev truck. Works great, short travel due to the huge bore and leaks like a sieve w/o the redneck 2 radiator hose clamps around the dang thing. No leaks any more tho!

These sound promising!

 

[richg]

I just installed this setup last weekend. https://tomsoffroad.com/parts/66-77-ford-bronco-complete-9-inch-power-brake-kit

Have front Chevy disc conversion and an old rear disc conversion using caddy calipers. Very pleased with brake feel and stopping so far. I had some sketchy braking before adding this setup (partly due to no-assist, partly due to rear disc with standard H-distribution block). I have 33x12.5’s.

The hard lines are a bit tight to the steering column so needed a bit of tweaking, and since the master sits at a bit of a downward angle, have to be careful when filling.

Anything else in particular you’d want to know?

Rich

 

[nvrstuk]

How far is the pedal throw b4 engagement (essentially slop & travel el) and then how far is the actual pedal l travel after?

 

[richg]

How far is the pedal throw b4 engagement (essentially slop & travel el) and then how far is the actual pedal l travel after?

Feels like a 2000’s vintage Tahoe . An inch or less at the top before you notice some braking action (likely engages before then, but not enough for you to notice) and then good modulation throughout the full travel.

Basically it was such that this was the only time I have ever driven the truck and was not hyper aware of stopping distance. It is just much more normal and uneventful when I hit the brakes.

 

[79INA69]

Feels like a 2000’s vintage Tahoe . An inch or less at the top before you notice some braking action (likely engages before then, but not enough for you to notice) and then good modulation throughout the full travel.

Basically it was such that this was the only time I have ever driven the truck and was not hyper aware of stopping distance. It is just much more normal and uneventful when I hit the brakes.

Im curious to hear from someone who has been running the WH 7" dual booster set up and stepped up to this. I just my Bronco around the block with the 1.25" bore master and the pedal is high and firm, but the pressure went down. I feel like this 7" booster is not enough.

 

[.94 OR]

I installed a 9" booster about 30 years ago on mine with 4 wheel drums. Just now thinking of installing discs on the front. Watching to see what pops up for a preferred MC.

 

[ngsd]

I had it on there but did not have enough vacuum. Changed to WH Moab Hydra boost, night and day difference.

 

[nvrstuk]

Sounding good!

 

[Yeller]

Im curious to hear from someone who has been running the WH 7" dual booster set up and stepped up to this. I just my Bronco around the block with the 1.25" bore master and the pedal is high and firm, but the pressure went down. I feel like this 7" booster is not enough.

I did not go to this exact booster from Tom's but did go to a 9" booster from a 1980 C3 Corvette, replacing a 7", was a significant improvement in braking power and made my set up acceptable. With my even larger 1.33 bore the 7" was not sufficient, but the 9" is adequate. Hydroboost I feel would be even better but its about packaging.

 

[nvrstuk]

Well, if your boost was improved just going to the 9" that's a huge step. Thinking of staying with this combo then till I try the 1.25" and report back??

 

[79INA69]

I did not go to this exact booster from Tom's but did go to a 9" booster from a 1980 C3 Corvette, replacing a 7", was a significant improvement in braking power and made my set up acceptable. With my even larger 1.33 bore the 7" was not sufficient, but the 9" is adequate. Hydroboost I feel would be even better but its about packaging.

I found the booster your talking about on RAuto. I'm going to purchase today for $100. This is a 9" dual booster for a 1980 vette. Hoping the bracket is set up for the 3 3/8" square pattern. It will be very tight fit with the 400m, but I have stock valve covers on there, fingers crossed.

 

[79INA69]

I found the booster your talking about on RAuto. I'm going to purchase today for $100. This is a 9" dual booster for a 1980 vette. Hoping the bracket is set up for the 3 3/8" square pattern. It will be very tight fit with the 400m, but I have stock valve covers on there, fingers crossed.

I measured vacuum at idle and had 15-16" available. Seems a little low for a mostly stock 400. I know that the dual boosters are better for lower than stock vacuum.

 

[79INA69]

I did not go to this exact booster from Tom's but did go to a 9" booster from a 1980 C3 Corvette, replacing a 7", was a significant improvement in braking power and made my set up acceptable. With my even larger 1.33 bore the 7" was not sufficient, but the 9" is adequate. Hydroboost I feel would be even better but its about packaging.

Got the new 1980 C3 9" booster installed this weekend. Clears the 400 valve cover by .5", clears the hood with 1/8" of washers on the top booster bracket. The bolt pattern was the same. All I had to do was shorted the pedal rod .5" and shorten the 3/8" rod end .5". The pedal feels much better. Did not finish my exhaust, so no fast stops yet, but the initial bite exists now. So big thanks Yeller! This booster was a good call. Bonus: The ac delco master bolts right up, so all the work modifying the 7" booster and master bolt pattern to fit was completely unnecessary with this booster. Had I only chimed in earlier I could have learned the easy way...

 

[richg]

Just wanted to add some more about Toms setup. Now that I’ve had some more time and miles on the setup, I am really happy with the braking action. I can stop with ease. Plenty of power to lock up 33’s, but real easy to modulate.

I re-bled them and the little bit of slop/free play that I had before has reduced as well, pedal feels very tight and firm.

I’m very happy with it.

Rich