97 f350 duel 2WD.
I want to upgrade rear brake cylinder to a larger size. currently it is 1 1/4" and being in Australia I need to find someone who knows can supply the correct bit from USA

 

welcome to fte.

what benefit do you think you will get?

i do not think any.

not real sure why you want to do this.

 

The object is to increase the pressure on the rear brake shoes to give more braking on the rear duels.

 

duh!!!

if it was already a dually then it has the correct size already.

 

If you are wanting more pressure to the rear axle brakes, you can route the brake line around the RABS cylinder on the frame. Also, are you using the correct brake pads on the rear axle? More pressure isnt going to stop any better, just increase the probably of throwing yourself into a skid by locking the back brakes up.

 

thanks for your suggestions, I know what i want and and now have the information on people in USA who supply f350 upgrades for heavy load applications.
Engineers certificates on mods are law over here. Insurance also becomes null and void unless up to RTA requirements.

 

Your original post was talking about an F350 not an F250.

 

explain exactly what the goal is and what you are doing.

you are not being clear in what you have already.

 

I am changing my original f250 on singles to f350 dual wheel specs (for stability), to carry a set specified load and tow a set weight trailer. f350 rear brakes needed improvement.
eg:-3"wide rear shoes now, upgrading to 3 1/2". larger wheel cylinders. 1" up to 1 1/8th.

 

a 250 with dual rear wheels still has 250 suspension doesnt increase your payload any

 

that has been sorted with air bags.