radial master cylinder for left hand rear brake

[Theo]

For supermoto conversions of the Varg, I've never heard of anybody using a radial master cylinder for the rear hand brake.
I've found these on the internet:
from Accossato
from Discacciati + the bracket
and there are also radial MCs for clutches that may work.
For the front brake, I've always had supermoto trackdays with an axial master cylinder but many people swear by radial ones.
I guess that it would make sense to have an improved feeling for the rear one, too.
I've noticed that the SM they have showed in the recent video about future models looks like it has a radial MC only for the front brake, but they also have to keep the cost low and probably it's hard to find a supplier at a decent price for something like that.
Any opinion about this?

 

[Theo]

I've just noticed that Adrien Goguet, a professional, probably used this radial Beringer: look at the pictures here.

 

[Beagle]

That was 2 years ago, I haven't seen much news of him racing the Varg since then?

 

[Karinshi]

i talk with accossato and they told me that that radial master cylinder is for 2 piston calippers... it will be compatible with the sotck single piston brembo caliper on the stark varg but performance could be bad, so much pressure

 

[Theo]

i talk with accossato and they told me that that radial master cylinder is for 2 piston calippers... it will be compatible with the sotck single piston brembo caliper on the stark varg but performance could be bad, so much pressure

Well, as far as I know, the multiplication of the force of the rider's hand is affected by:

• the ratio between the lever arm of the pulling finger and the one of the cylinder: higher means more power but more stroke
• the ratio between the area of the master cylinder and the overall area of the slave cylinders: smaller means more power but more stroke
• the coefficient of friction between pads and rotor
• the ratio between the diameter of the wheel and the diameter of the rotor: higher means more power
• the stiffness of the components, since every component delay the transmission of the force through deformation, weakening the braking action before the final lever position is reached and everything is settled

So it makes sense to me that a master cylinder designed to move two slave cylinders will have a larger area than one designed for a single slave cylinder and therefore will generate too little pressure for a single slave cylinder, unless one or more of the other parameters is changed to compensate for this. So I would expect that Accossato MC to generate too little force and to have a too little stroke.

 

[Karinshi]

Well, as far as I know, the multiplication of the force of the rider's hand is affected by:

• the ratio between the lever arm of the pulling finger and the one of the cylinder: higher means more power but more stroke
• the ratio between the area of the master cylinder and the overall area of the slave cylinders: smaller means more power but more stroke
• the coefficient of friction between pads and rotor
• the ratio between the diameter of the wheel and the diameter of the rotor: higher means more power
• the stiffness of the components, since every component delay the transmission of the force through deformation, weakening the braking action before the final lever position is reached and everything is settled

So it makes sense to me that a master cylinder designed to move two slave cylinders will have a larger area than one designed for a single slave cylinder and therefore will generate too little pressure for a single slave cylinder, unless one or more of the other parameters is changed to compensate for this. So I would expect that Accossato MC to generate too little force and to have a too little stroke.

nice explanation, i want to buy another left hand rear brake, the stock one is good for offroad but not for supermotard... i just cant decide wich one... some people say that the accosatto master cylinder that we are talking about works well with the front stock brembo caliper, just need the dual caliper adapter for the rear and a longer hose

im studying that

 

[Theo]

That Accossato MC I linked is a 16 X 16 size: Ø16 mm piston and 16 mm lever arm. Those dimensions are typical of supermoto front brake systems with 4 Ø32 mm slave pistons and, altough I don't know the dimensions of our single rear brake slave piston, I think that its area must be much smaller.
This one from Beringer has a really big piston, probably way too big, and it's very expensive.

Honestly, I'm not really sure that radial master cylinders are so great; I don't really know what to tink about them. Here they explain that they were actually invented because the axial ones took too much room on the handlebars and then they noticed that it felt more linear. They point out how the force is transmitted aligned with the direction of motion of the master piston without losses to other directions like with the axial ones, but what I see is still a piston that moves straight moved by a lever that swings around a pivot point, so I don't understand how this should change anything. To me, it essentially seems the same assembly rotated by 90°.
Yet, so many people are convinced that they feel better. I have personally tried a supermoto equipped with one and since it wasn't my bike I didn't push hard, but it didn't feel special to me.

 

[Karinshi]

That Accossato MC I linked is a 16 X 16 size: Ø16 mm piston and 16 mm lever arm. Those dimensions are typical of supermoto front brake systems with 4 Ø32 mm slave pistons and, altough I don't know the dimensions of our single rear brake slave piston, I think that its area must be much smaller.
This one from Beringer has a really big piston, probably way too big, and it's very expensive.

Honestly, I'm not really sure that radial master cylinders are so great; I don't really know what to tink about them. Here they explain that they were actually invented because the axial ones took too much room on the handlebars and then they noticed that it felt more linear. They point out how the force is transmitted aligned with the direction of motion of the master piston without losses to other directions like with the axial ones, but what I see is still a piston that moves straight moved by a lever that swings around a pivot point, so I don't understand how this should change anything. To me, it essentially seems the same assembly rotated by 90°.
Yet, so many people are convinced that they feel better. I have personally tried a supermoto equipped with one and since it wasn't my bike I didn't push hard, but it didn't feel special to me.

thanks for the explanation

what are your personal recommendation for a better rear brake feel? i mean, thinking on wheelies, i want a more aggresive bite on the caliper than the stock one... it doesnt bite the disc with enough force with one finger. Supposedly those accossato 16x masters have a stronger bite on the front brembo caliper from Stark, using this adapter: Stark Varg Dual Caliper Bracket Hand Brake