Master Cylinder/Caliper ratio chart

[dingy]

One of the interesting discussions that has been on here in the past has been the braking ability of the Ventures and the relative effects of items such as swapping caliper/rotor/master cylinders and the benefits of de-linking the first gens.

 

I came across an article on another site which is linked below discussing the ratios between the master cylinder area and the caliper area and the effects on braking.

 

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

 

I created a chart that shows some of various Yamaha bikes and these related calculations for anyone that is interested. There is a screen picture attached as well as the excel spreadsheet if you want to experiment with various combinations.

 

Bottom of chart also shows calculations for de-linking brakes on a 1st gen.

 

Explanation of the numbers shown:

 

Master Cyl dia: The I.D. of the front or rear master cylinder bore

Master Cyl. Area: The area of the I.D. of the master cyl.

Piston Dia. A: The I.D Of the 1st piston bore or only piston bore in a 2 piston setup

Piston Dia. B: The I.D Of the 2nd piston bore, only shown in a 4 piston setup

Piston area A: The area of the piston bore of piston A

Piston area B: The area of the piston bore of piston B (if used)

Total Caliper Piston area: Total area of the pistons in a caliper assembly

Rotor Dia.: O.D. of the brake rotor

 

Ratios are expressed as : Piston area/master cyl area:1 (numbers shown in graph do not have the :1 shown. Didn't know how to do that in excel 2003)

 

If you find any errors in this, let me know & I will correct.

 

Gary

 

http://i1007.photobucket.com/albums/af193/gdingy101/ratiospreadsheetpicture3.jpg

Edited June 23, 2011 by dingy
fixed error in total fron piston areas

[winston66]

Thanks dingy for posting this very interesting info.

I have one of the rare 1996 VXZ 1300Royal Star"s.

In Australia here, it is almost impossible to get any relevant information about these scoots, Hence I have found such a wealth of information from this great site and happy band of guys that one could call a brotherhood.

Even though my Clymer manual M374 covers most things from 1996 to 2003 it still leaves a lot of questions unanswered for me, and I have been able to fill a lot of gaps when following the different threads on this awsome Venture Riders Site.

I recently installed the R1 brake upgrade supplied from Skydoc, even though I did not notice any real improvment in either applied effort or stopping power over the origonal set up , with the new rotors and the new lines etc, the brakes now work as well as could be hoped for and the shuddering that was caused by the warped rotor,s is now completly eliminated.

I now can ride this scoot with confidence and I am very pleased with my investment in saftey and reliability in replacing the 15 year old (origonal) stuff with new parts, cos I believe that stopping safely is even more important than trying to (perhaps) break the sound barrier.

 

 

[GaryZ]

Excellent post! Very good information for those of us that are into swapping parts.

 

OK, the referenced web page recommends 27:1 as his favorite for master-to-cylinder volume ratio. He says that ratios below 20:1 feel "wooden". Your chart does not have this ratio listed. What ratios did you calculate at the bottom?

 

Applying this to the original linked brakes of the Gen 1 they should have a "wooden" feel on the front brake (1140.1/126.7 = 8.9). The rear brake calculates to a 13:1 volume ratio. Better than the front, not close to 20. My experience was exactly that when I first got my '85. The front brake felt like I was squeezing a plum . . . Very little effect.

 

De-linking my brakes has made my front brake "feel" good with a lot better control. The front master-to-cylinder ratio is now around 18 (2280.2/126.7).

[dingy]

Actually quite a few are below 20 if you look across lines 24 & 25.

Then the 1st gens rear brake drops down when delinked with stock calipers in line 33.

Some other factors to consider which are not accounted for in this chart are the master cylinder/lever mechanical contact point ratio and the diameter of the rotors. The rotor sizes are shown, but not used in any way in calculations.

Also the 1140.1/126.7=8.9 you show is incorrect. The 1140.1 number only takes into account 1 piston in the caliper when there are 2 pistons on an MKI. Lines 24 & 28 should reflect the single front caliper on a linked MKI system.

Gary

[GaryZ]

OK, the "total caliper piston area" is the number that you are using, divided by the master cylinder area. This is what I was not seeing . . . Thanks!

[dingy]

I just reloaded files in first post. I had made a mistake on the front caliper area total used in line 24 for the R1, FJR,R6 & VMax. I only included the total from one caliper with 4 pistons in total area. There are two calipers with 8 pistons on front brakes on these bikes.

 

The RSV has 2 calipers with 4 total pistons.

 

MKI's have 1 caliper with 2 pistons.

 

MKII's have 1 caliper with 4 pistons.

 

Whoops.

 

Gary