i would like to use an f450 (1-5/16" bore) master cylinder on my 89 f350 (stock 1-1/8")...if it fits what affect will it have? will the booster have to be upgraded?

 

Anytime you increase the bore of the master cylinder, you increase the amount of pressure you will need to exert to stop the vehicle. That is a big jump, and I would bet that you will be very disappointed if you go through with it. If you use the booster that might overcome the increase force required, but then why do you want to do this?


Kenny

 

so i am going to have to press harder...i thought it would be the other way around and would help stop my 14k# truck better...the booster for both trucks might actually be the same

 

Yes, you have to press harder. Think about it this way....if you need 100 psi in the lines and you have a 1 1/8 cylinder (which is about .99 square inches), you have to press the pedal with 100 lbs of force.

Now you need the same pressure (100), but now you have a 1 5/16 cylinder (about 1.35 square inches), you will need to press the pedal 135 lbs to get the the same 100 psi.

Increasing bore is usually due to the size of the pistons on the system is actuating (they caliper bores or brake cylinders are huge and take a huge amount of fluid).

Remember, I am talking theorhetical psi in the system, brakes work at a much higher pressure, and the design of the pedal amplifies your foot pressue.

If you want to improve your braking distance, work with the pads. If you still need more, you might be able to find 6 pot calipers for more squeezing force (and a longer pad).

Kenny

 

so there would be no advantage in using a bigger bore mc...it just seems like something is missing in the equation

as far as the pads-i am going to use pfc zrated and brand new dorman calipers (nobody makes aftermarket calipers)...inline tube can make me ss brake hoses ($110)but dont think they r worth the little gain (over-hyped)

 

what r your opinions on ss brake lines?

 

SS brake lines don't expand like the reinforced rubber ones do, so they are a nice upgrade, but under 90% of your braking situations, I don't think they do a thing.

As for your pads...sounds like you have a high performance pad (high metalic content). These are great once they get hot but are horrible everyday driving pads. The higher metalic content in the pad, the more pedal force it will take to stop your vehicle. Stock pads are a decent compromise between fade resistance and lighter pedal effort. If you constantly tow huge loads, then the higher metalic pads make some sense, if you don't haul loads, tow big trailers or run it around the racetrack, then high performance/high metalic pads just cause increased pedal effort with no street improvement.

My opinion...from first hand experience.

Kenny

 

what is the 10% of driving that applies to ss brake lines?...this truck is mainly driven in the city and carries a 14k# load 247

 

Anthing that requires full pedal stops...emergency stops, braking going into corners on the race track, high speed stops, stopping heavy loads constantly. The SS lines will firm up the pedal when you are giving it all she's got. All lines swell a little near their pressure limit, but the SS limit is much higher than the reinforced rubber lines, thus you probably won't approach that limit, thus a firmer pedal.

With your rig, and that much load, you really are in a different league than most poeple who operate pickups. You actually use yours!!!!

That is quite the load you carry, I can see why you want more brakes! Are the trailer brakes up to snuff? Do all 4/6 trailer wheels have brakes on them (I am assuming 14,000 pounds is a loaded 4 or even 6 wheel trailer).

You might want to check out some RV magazines/companies to see what they suggest for your load/vehicle.

Kenny

 

this is an 89 f350 cc lb drw severly overloaded (gvw is only 10k)...no trailer!...normal load is somewhere in the 13k# range and has probably had a lot more from time to time