correct master cylinder for de-linked front CalVin brakes?

[lazlokovacs]

Planning to operate both calipers

PS16?

NB Cali vintage has P30/34 calipers....

======PS=========
(this isn't intended to be a thread to discuss the pros and cons of linked brakes )

thanks as ever

[rodekyll]

Assuming by banning the discussion of linked brakes you're NOT also banning the question of one caliper or two up front:

If two calipers, An 11/16 radial will do that nicely with a lot of "touch".  A 3/4 will do it too, but with less sensitivity.  If one caliper, a 5/8 radial will give an acceptable feel.

[lazlokovacs]

Thanks RK,

have edited original post to clarify

[lazlokovacs]

okayyy, some imperial to metric calculations....

11/16 equates roughly to 17.5mm
and 3/4 to 19mm
and 5/8 is 15.6mm

So.... the PS16 (16mm) would be pretty good for single caliper use if I'm getting this right?

which seems odd... as Guzzi fits a 13mm master cylinder (PS13) for use with the same caliper on the single disc CALIFORNIA STONE

Now I'm confused for sure!

maybe I'm getting this all wrong,

further advice gratefully accepted!!

[rodekyll]

You're comparing radial to axial m/c's.  The effective surface ratios are different.

[lazlokovacs]

thank you

[lazlokovacs]

So, may I prevail further upon your knowledge and ask

a 19mm radial m/c would be roughly equivalent to which size in axial?

(google really not bringing me much info on this one!)

much obliged

[Antietam Classic Cycle]

The V11 Sport, etc. series uses the same calipers, non-linked, operated by a PS16 master cylinder.

[lazlokovacs]

^^yup charlie, that's what I thought^^

hence my 1st guess....


Radials must have greater mechanical advantage then?

all interesting stuff

[rodekyll]

I answered the way I did because I didn't know what your oem bore was. 

Yes, there's not a lot of information about the conversion from axial to radial.  My experience is consistent with the little information that I've read, which say go +1.5mm to +2mm when you move from an axial to a radial.  So if you use a 16mm axial OEM, the ballpark radial would be 19mm.  I've used both a 19mm and a 17mm radial with those calipers to good effect.  The 19mm (3/4) radial is probably the more common choice generically, although those fancy GSXR front ends in that other current topic use a 17mm (11/16) with (I believe) 34/30 caliper pucks.  So either would be an acceptable choice depending on personal feel.

The advantages to a radial are that they come on a lot of modern UJM bikes as well as EU stuff, so they're getting commoner and cheaper.  You can generally get one with a lever for $75, USD here in the states.  They have adjustable lever points to fit your grip and lots of aftermarket lever designs.  They're generally (except some Brembo) rebuildable.  They take up less handlebar space and clear fat bars that some axials can't.  They have remote fluid cups and mirror lugs in the handlebar clamp. 

I don't understand the physics and hydraulics enough to tell you about the advantage or disadvantage that way.  I know that the distance from the pivot point to the m/c piston is different between the two, making for different mechanical leverage.  Some fancy radials, such as the Brembo RCS line, have adjustable pivot points, allowing for a range of mechanical advantage.

[Caffeineo]

Lots of info here; http://www.vintagebrake.com/mastercylinder.htm There is a chart that shows what size the master cylinder piston should be to get the correct ratio when you have a single or dual disk and the number of active pucks on the slave cylinder.....plus a lot of technical info above my level of understanding.
I just got a bike that had a dual disk swapped for a singel disk with the original master cylinder. The brake felt like the pads were a block of wood. The lever moved easily to a solid end point and had to be squeezed very hard to move very little and still not give enough front brake. Put a different master cylinder and now it is much more powerful and progressive. 

[Steph]

If your CalVin has fat bars like my Stone you’ll need a remote reservoir for the master cylinder.
I just got a used one from a Ducati S2R 1000. It clears the thick bar and has a mirror thread built-in
Progressive two finger pull.
With Four finger, in panic situation will lock it up, don’t ask me how I know..