Hi SH forums,

TL;DR: 954rr calipers+F4i master is not working as expected; that combo feels very similar to stock. Anybody have some wisdom they can share?

I tried upgrading my brakes recently by going with a 954rr system. However when it arrived, the master was in worse condition than I thought, so I picked up an F4i master cylinder because those are so cheap. When I put it all together, I bled the system relentlessly but the lever still goes back almost all the way to the bar, just like stock. I made sure there was no more air coming out of either caliper and used both vacuum and simple lever bleeding, concluding with the latter to make sure the vacuum wasnt sucking more air into the system. I rode around the block a few times and it seems to work, but I cant get full braking force with only 2 fingers because my ring finger and pinky get in the way (stock-style levers). The braking feels almost exactly like stock!

Anybody know if I should have expected this? Do I need to run a bigger master cylinder to get the feel I desire? Should this system perform better than what Im experiencing now?

Thanks,
Nathan

 

It sounds like you still have air in the system or the lines are expanding.

If your using quality Stainless steel braided lines then it would point to air trapped in the system.

You also did not say if the used master cylinder and calipers were serviced or not before installed?
If not, then its all just a guessing game.. your problem could be anything, leaking master cylinder seal, pitted master bore, compressible contamination in the calipers which is commonly not "bled out" they need to come apart to be cleaned, and that means new seals.

 

Yeah that's not what stock feels like. I mean my personal biggest gripe with these bikes when they first came out were the weak brakes when you're riding hard, but your lever shouldn't be pulling all the way back to the bar unless you're on a Harley.

 

I'm thinking what Erik mentioned. Old rubber brake lines and cause this feeling. I'd also want fresh seals in the master cylinder and why not caliper rebuilds too. These parts are starting to age so some upkeep is in order.in

 

Fortunately part of it turned out to be a short circuit between the headset. I adjusted the lever and now I get a nice firm lever pull not all the way back to the bar. Guess the F4i lever position is slightly different than the SH, though they use the same lever. Also I have a set of stainless lines lying around so if this proves to work I'll throw those on.

I'll try a longer test ride and see what happens so that way I can get the brakes nice and hot. So far around the block I get a slightly firmer lever than stock but the power overall feels lower, which I guess makes sense (maybe the pads on there are garbage, or maybe the brakes were just too cold). Also yep I'll have to check out the quality of the pistons. The 'assemble now, check later' feature of my work is what distinguishes me from somebody who has experience and patience. Maybe eventually people like me will learn to do it right.

Thanks for the input. Will keep this updated as to whether or not this combo is worth anything.