Rear master brake cylinder

I have a 1985 FXST with drum brakes on the rear. What size bore do I need on the master cylinder?

Hi Bob, :welcome: to Trike Talk and your first post

This can be a question that has many variables

3/4 bore seems to work for many, kind of a happy medium if you will

Do plenty of research specific to your trike kit ( be it drum or disc) and how much pedal leverage you will need to stop

Here is a standard rule to follow,

[FONT=Verdana]A smaller bore master cylinder will increase line pressure and therefore braking power, but it also may not move enough fluid to completely activate the piston(s) in your caliper(s). The feel of the brake system is greatly affected by bore size. A too small master cylinder will give a stiff feel; too large a bore, a mushy feel.[/FONT]

[FONT=Verdana]

Keeping in mind, there are still variables to think about, ( swept area of drums or rotors, actual size of wheel cylinders and or calipers including the number of pistons, also how much travel of the pedal to stop )[/FONT]

welcome

Hello and :welcome: to Trike Talk, glad to have U with Us. :clapping:

Welcome to Trike Talk Bob!

:wave4:WELCOME ABOARD FROM MONTANA:wave4::clapping::clapping: