F4i Front Master Cylinder Upgrade Suggestions

I am looking to upgrade my front master cylinder on the 2001 F4i. I would like one that has the round plastic style resevoir, because it's alot easier when bleeding the system. I also need to upgrade, because I think mine has an air leak.

What do I need to know about when looking for replacements? How do I know an upgrade will work with my bike? I've never done anything with master cylinders before, except use them

Thanks for any suggestions or things that I need to look for.

 

http://www.yoyodyneti.com/detail.aspx?ID=4569

You'll never need another master cylinder. Simply the best. Well worth every penny. The stopping power is amazing. So on and so forth. I got one and I love it!

 

I have a brembo 19x18 on the RC51 and am getting the same for an f4i,This braided lines and HRC pads, The thing will stop on a dime.

 

You will probably want the 19x18 it has better feel. I have the 19x20 on my street bike but it has 6 piston calipers. 16mm sits on my track bike with stock calipers and is plenty, it is a 2004 R1 which is a radial brembo. You can probably pick on up on ebay cheap.

 

Don't just count the pistons.

If you want to figure out the hydraulic leverage ratio, you need to know not only the number of pistons in the calipers, but the diameter of the pistons.

I happen to have recently done a bit of work with a Nissin F4i caliper, fitting it to a GS500E, and the piston diameters of the Nissin are 32mm leading and 34mm trailing. That gives a piston area on one side of the rotor of 1712mm^2. I also ran across a Tokico 6 piston caliper from a GSXR750, and the pistons were all 27mm. That gives a piston area on one side of the rotor of 1717mm^2. The effective piston is practically identical.

Now, an R1/R6 caliper, that's a different ball game. Those have pistons of 27mm leading and 30mm trialing, for a piston area on one side of the rotor of 1279mm^2. That would require a different master cylinder than the F4i or GSXR calipers.

If you want to play around with this stuff, here is a spreadsheet I wrote before actually selecting which caliper to use on the GS. Juggle the piston diameter sizes and see how it works. I have it set up for a old school master cylinder with the bore running parallel to the handlebar, but the math will work with a radial master cylinder if you just measure the lever arms on the brake lever and input them accordingly.


OpenOffice spreadsheet

Excel spreadsheet

Here's the Nissin caliper going onto the GS

Of course, all that is useless to the guy who wants a new master cylinder, because you probably just want an ANSWER. For that person, what are you looking to accomplish? If you want the bike to stop harder for a given lever travel, you'll need a greater hydraulic leverage ratio. Your stock master cylinder is 5/8", which is 15.88mm. You can buy a $300 adjustable radial master cylinder, or you can swap to a 14mm master cylinder. 2000 GSXR750s have 14mm Nissin master cylinders with remote reservoirs, I believe. I'm sure there are others. Going from a 5/8" bore to a 14mm bore will give you a 13% higher hydraulic leverage ratio, which translates to 13% more stopping power for the same lever effort. You will, of course, also have 13% more lever travel, so if you're borderline on lever throw now (lever coming back to trap the fingers still wrapped around the throttle), you'd definitely want some braided lines to go with the new master cylinder.

If you're having a problem with the lever coming back to the bar in longer races, and want a harder lever, then you'd have to go up to a larger master cylinder. I don't know of any commonly available (like, you'll find it on a crashed production bike) master cylinders larger than 5/8", but I also do not know the effective leverage ratio of the new breed of production radial pump master cylinders. I define effective as the bore size worked in with the distance from your fingers to the lever pivot, and the lever pivot to the master cylinder piston contact point. So maybe one of those is the answer. Or, you could throw $300 at Yoyodyne...

 

New Master, now what fluid?

I just installed a Brembo master (19X18) and need to know what type of fluid I should run. Do I have to run somthing special? DOT3? DOT4? Thanks

 

Re: New Master, now what fluid?

You just want a good DOT3 or DOT4 fluid.

We switched to "Super Blue" racing brake fluid a few years ago, and the stuff is simply awesome. It's what you'll find a lot of car guys running. It comes in a 1 liter can and should run you about $15 - $16 (we get it from the local car speed shop).

- Roach

 

Got one for sale...

http://forums.13x.com/showthread.php?s=&threadid=102633

 

Thanks Roach - Any idea where I can get crush washers without spending $5-$10 for shipping? Maybe I can get the washers and the fluid from ya...

 

Most auto parts stores should carry some copper washers. Just find out the diameter of the banjo bolts.

 

The problem is, UPS doesn't take a box anywhere for much less than that

Like someone said, you should be able to get washers at an auto parts store (or a motorcycle dealership). If you wanted brake fluid I'd be more than happy to send both, but the big brown truck needs to be paid.

- Roach

 

Re: New Master, now what fluid?

I assume that you already had stainless brake lines installed, any issues with fitment (room between the clipon & upper fairing) or needing slightly longer lines to get everything setup?

I'm also curious if you have any feedback (good/bad) on how the new master cylinder is working? Was it worth the expense?
thanks for the info.

 

Yes - I had the steel lines already. Can't tell how well they work yet. It's a track bike only and it's still cold here in the Chicago area.