Topic: Nice chart for master cylinder sizes

[MRieck]

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

[slikwilli420]

I've heard a lot of good feedback about this chart and plan to use the methodology whenever I am selecting brakes. Chose the 12mm to go on my race bike with single Grimeca caliper.

[bwaller]

This is the bible of charts re brake ratios.

[MRieck]

This is the bible of charts re brake ratios.

....and that is coming from the "Pope". 

[SOHC4 Cafe Racer Fan]

Good info.

[grcamna2]

subscribed 

[bwaller]

This is the bible of charts re brake ratios.

....and that is coming from the "Pope". 

More like the choir boy. 

[kmb69]

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

Good stuff, Bro. Tx 

[PeWe]

So an MC with 14mm piston need more than 2 original calipers with 38mm pistons for a nicer feeling?
like this: https://www.davidsilverspares.co.uk/CB750K6-FOUR-1976/part_123916/

[seanbarney41]

yeah, I don't understand.  If cb750 stock brake piston is 37mm, there is no master cylinder in existence to get the ratio into the sweet spot?  Is that why these brakes suck so bad?

[PeWe]

More information for fully understanding would be fine. If my and seanbarney41's thoughts are correct.
Here a pdf where the text is easier to read.

The ss lines gave harder brake feeling despite dual brakes. It was long time ago I used the CB750 rubber lines, but they felt better with a softer feeling. I had in mind to switch to rubber again to test, but the upper line I have is too long, 38cm when I need 31cm.

[turboguzzi]

manufacturers have to account to riders with widely different hand strengths, from pretty ladies to hulks with an iron fist, so will tend to go for bigger diameter M/Cs than recomended to make sure the later dont lock wheels at every stop. Then there are the pads, the disc material, etc. It's a trial and error thing, just keep a good collection of M/C in different sizes to try on. I always grab another one for my stash at swapmeets.

[PeWe]

OK, hording MC's in the hunt for the perfect feelling! The clutch can be softer though.... The chart to have numbers when comparing

[01Thomas]

IMHO this chart should be used as a guide only. There's more to the brake system than just comparing diameters of the M/C with the Slave(s). The diameter ratios determine the ease with which it is displaced. And of course the length ratios of the brake lever also affects the ease of the application.

The travel of the M/C piston plays a very important role. It is after all the volume of fluid that is displaced which is important and which is often neglected.

[RAFster122s]

He talks about the ratio also being a function of the disc diameter versus the wheel diameter but he does not explain how to factor this into the equation.  There should be a ratio for a multiplication factor to the ratio of the diameter of the disc diameter to wheel diameter to normalize these readings somewhat...

David

[frodef2]

Could you use lever calculations to calculate the effect of the disc size? I mean if you have a 11 5/8" disc on a 19" wheel. With the tire, the diameter is about 26" so the disc to tire lever ratio is about 0,45. If you clamped the brake disc to hold 1 kg at the disc, it would be 55% less at the tyre contact patch. I think the size of the rotor has a lesser impact on the brakes than the master to caliper ratio, and the grip of the pads.


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[NobleHops]

Fantastic. Swiped. Or is that "swope". Got it, either way :-)

[bwaller]

Maybe the issue can be overthunk? Most of us along the way mounted a second stock caliper and bought a master from a newer bike, usually 15mm or 5/8". Then we proclaimed to the world how much better our brakes were. Rock hard levers and little to no feel isn't what makes for good braking.

Sure there are other factors but #$%* guys, follow Micheal's chart, he gives suggestions on a suitable master cylinder option and I for one have seen the light.   

[turboguzzi]

the table sure helps but lets not forget that if you stick to OEM japanese Nissin M/C, there are essentially just 3 sizes to play with 1/2" (12.7mm), 14mm and 5/8" (16mm). Brembo might have some other metric sizes but i never liked how their M/Cs work & feel. 
the 5/8" are meant for modern bikes with twin 4 pistons calipers (i.e. lot of piston area) so at the end of the day  for our bikes you have only the 1/2" vs. the 14mm to choose from. easy.

AP Lockheed might have some other sizes M/Cs but they are out of my price range

[RAFster122s]

Ok, so, if you double a stock single piston caliper, for the 550 this is a 38mm piston, then his recommendation is to use a 14:1 to 12:1 ratio for single piston calipers like we have.  So, for a stock single single-piston caliper to get to that ballpark you need a 10 or 11mm caliper and for twin stock single-piston calipers you need it in the 14, 5/8, or 16mm range.

So, what does a twin 30mm single caliper need, non opposed design like the Honda calipers used in 80s on lots of bikes need?

Yes Brent, you are very much correct in stating this helps a great deal get you into brakes that work much better.  I am just trying to understand some of the other things that can affect this to get things in a better ball park.

With a single modern 4 pot (twin opposed) caliper you would use the 27:1 to 22:1 ratios suggested.

Do the radial designed MC have any different affect than the older design MCs?

Thanks!

I guess if you can afford to get rid of the stainless disc for a cast iron disc you would have far more effective brakes as well.  Too bad there are not any inexpensive sources for a bolt up disc for the 550s and early 750 bikes.

[bwaller]

TG, I use a Brembo master & love the thing, great feel.

[turboguzzi]

good to know, the brembo M/C i tried might have been a bit of a lemon... they do indeed have smaller sizes than 1/2" like 11mm and 12mm

[bwaller]

Mine's a 12mm and new was $100. That's with twin F05's.