front brake master cylinder all the same?

[sgrudier]

So I have a question about an alternate project I have going at the same time as the xs400.

I am doing some serious modifications to an old SR250 and putting some parts from a 95 yz125 on it. My general question is... I have the front caliper but not the handlebar master cylinder. Are master cylinders sized / calibrated for the caliper or are they somewhat uniform?

 

[foul]

There are two types of cylinders, for single caliper and for dual caliper.
Other than that they should be universal.

 

[sgrudier]

That makes sense and is very helpful.

 

[drewpy]

or one for triple caliper! linked brakes I belive

 

[CadXS]

What size m/c you use depends on the cross-sectional area of the caliper pistons hitting the disc. As Drew said there are different types of caliper with different sized pistons.

Too big an m/c and it may feel like you are going to thrown over the front or too small an m/c and the brakes feel mushy.

Try this site...

http://www.vintagebrake.com/mastercylinder.htm

Some good info on working out m/c size depending on what size pistons in your caliper.

 

[corytburkhart]

i have a beautiful new dual .. can i use it on one caliper??

 

[drewpy]

depends on what caliper.

single piston
dual piston
4 pot
6 pot

I have a dual BMW working a 4 pot blue spot caliper and works well.

 

[corytburkhart]

Thanks drewp..the stock Single piston I think??, I'm gonna try it I think it'll work fine

 

[16VGTIDave]

With hydraulic braking systems, the size of the master and slave (caliper in this case) are directly related. Since you have the caliper, you know it's piston size. Calculate it's surface area - remember geometry in math class? I'd suggest using the metric system as it is easier! Then you can calculate the volume of brake fluid required to move the caliper piston approx 2mm.

Your master cylinder has to move this much brake fluid to engage the brakes. The smaller the bore (lower surface area) on the master, more lever travel is required, but the lower the force. Increase the size of the master and you will have less lever travel, but will require more effort for the same clamping force at the caliper. To add to this, one has to consider the mechanical action of the lever acting on the master cylinder. Caliper flex and line flex will increase the required volume of brake fluid required to exert a given pressure on the pads.

This isn't 'rocket science', but it is science! I don't suggest experimenting with brakes without some consideration to the outcome, and safety of course!

Dave