[cerial]

Raising the floor on this 94 s10 and coming to the realization I will be better off going with floor pedals. So after a bit of searching I found this gem

https://www.ebay.com/i/220446717697?chn ... HPEALw_wcB

Is the item in the above link good enough to stop the truck? The truck should weigh 1800-2000lbs finished with around a 55F/45R ratio which could change depending on where I put the fuel tank, etc. This is just a fun summer beater. That 90hp 2.5 is not going to be getting me into to much trouble. I tend to not use my brakes much with manuals. But If I need it to stop I want it to stop kind of deal. Looking to run 1" to the front stock s10 calipers and 3/4 to the rear drums with a mechanical brake switch activated by the pedal.

 

[johnsongrass1]

You'll want a 3/4 bore for the front calipers and you'll have to dial in a lot of rear brake using that style.

 

[cerial]

You'll want a 3/4 bore for the front calipers and you'll have to dial in a lot of rear brake using that style.

Dial in?

 

[cerial]

I can order it with both 3/4" masters would that be better?

 

[cerial]

So after searching over the last 3 hours
I came across this site;

https://www.manualbrakes.com/faqs.html

They recommend a 3/4 bore with a Wilwood "big bore" Low friction 2.75 caliper pn 120-8926
Another site recommended the 7/8 bore wheel cylinders for the rear drums instead of the 3/4 that come with the power. So I will install 7/8 wheel cylinders in the rear.

So dual 3/4 bore masters. Right?

But, then I go over this again and they recommend step bore or more cylinder volume so 1" for the front?

Yes. A stock "metric" caliper with a single 2.5" diameter piston has, almost, the same piston area as a 1998-2002 Camaro/Firebird's 1.77" diameter twin piston caliper. A 2.5" diameter single piston caliper has 4.906 square inches of surface area. Dual 1.77" diameter pistons has 4.919 square inches of surface area. These calipers with these piston sizes work well with 7/8" bore master cylinders.

If you increase the caliper single piston size to 2.75", you will have to increase the bore size of the master cylinder. Most 7/8" bore master cylinders do not have the fluid volume to fill a brake caliper with a 2.75" piston. Though a caliper with more square inches of surface will have more clamping force, a larger master cylinder reduces brake line pressure and, in the end, you will loose braking performance when running manual brakes.

The bottom line for good performing manual brakes is a caliper with the largest piston area along with a master cylinder with the smallest bore. Calipers with larger piston area have greater clamping force than a caliper with a smaller piston area. A smaller bore master cylinder creates more fluid pressure than a larger bore master cylinder. In the end, the master cylinder will need to be matched to the caliper to create the most effective manual braking system.

But then I think because I am mounting the cab over the rear wheels that means I have additional volume within the lines and dual 3/4" will work because of the additional volume within the longer lines?

 

[cerial]

Looking at this yet again I read it wrong.

So, the dual system with 2 different masters and a balance bar pushed by a single pedal with masters sized as listed below;

7/8 Front with 2.5 calipers
7/8 rear with 7/8 wheel cylinders

Correct?
As you can tell I am new to the whole dual master thing. But the packaging is perfect for what I want. The master cylinder sizes just has me second guessing before hitting buy. I can easily ask for 7/8 and 7/8 I just need to do it at the time of sale or I will need to buy a 7/8 later and be left with a 1" I do not need.

 

[johnsongrass1]

The balance bar is here. It's a fulcrum point. Screw the fulcrum to the right add brake pressure to the right side MC and Left adds Brake pressure to the Left side.
You can do it with different MC bores as well. Pick a MC that gives you what pressures you want, fine tune it with the balance bar. In your case, with a 3000 truck, I'd go 3/4 on both but 7/8 would work as well. The 3/4 will have marginally more pedal travel for the same caliper pressure but a tad bit more feel.

 

[cerial]

Thank you.
I will order it tonight with dual 7/8 option.

 

[PHWOARchild]

7/8" is a good compromise. We used those in a few street stocks, were either Neal or Quartermaster IIRC. Just make it gets mounted as solid as a rock, any flex will impact braking in a bad direction.

 

[cerial]

Ok update on this and a new related question.


Back in january I found a cheap 78 f150. I really bought it for the plow and the granny 4/205.

But it has a 9 and I am going to just run a 5.3 mated to a sm465 to turn the 9.

So I want to throw disc on the 9" with gm calipers(no need for a parking brake). Can I use the big bore calipers on the rear?