# Thread: ?n for Brake gurus

1. ## ?n for Brake gurus

Going from 2 pot to 3 pot caliper with the same lever/reservoir/line (from 2pot) = loss of power? They look identical, but is there a difference?

Thanks!

2. Well, basic physics of hydraulics will tell you it's not the number of cylinders, it's displacement.

But, the basic math goes something like this: If x amount of fluid will move 2 calipers of similar diameter distance y, then if you have 3 calipers, each one will move 2/3 as far. But maybe the pots on yours are a different diameter, which would throw off the whole formula.

But then again, on most of the 2 pot calipers I've seen, one is smaller, so it will move faster, since the same volume of fluid in a cylinder that has a smaller diameter must have a longer length to compensate... as a result, the smaller one hits the rotor first. But I have no idea of knowing on your particular model how big each pot is, so I have no idea if they'll move faster or slower.

Maybe they're all bigger, so they move slower, but with more force. Or maybe they're smaller, and faster, and 3 fast ones will grab as well as 2 slow ones.

At some point in this little lecture, you probably wanted to ask me how you could tell what measurements you had on your 3. Or how you know how much faster this one will move, or how much slower, etc. Most likely you wanted a no BS answer about whether or not your specific component will work with this new specific componenet, because you really wanted to know how fast you could stop, not how hydraulics actually work.

The answer is simple: Call the manufacturer. They know their own product, they'll be able to tell you if it'll work. If you'r emixing brands, I'm sure one company will be able to give you the numbers for hte amount of fluid moved by the lever, and you can call the other company and find out if it's compatible. Because, without knowing anything more than that you now have 3 pots, instead of 2, it's almost impossible to say, without knowing the specs, how the new one will behave. Maybe it'll lose power. Maybe it'll grab faster. Maybe you needed a different caliper because your levers weren't displacing enough for the old brakes to begin with. I doubt it, but since you really haven't provided any substantial information about what you have, it's hard to say.

And even if you had specified model numbers and such, really, the best people to ask would still be the manufacturer. You want a guru, find the one that made your brakes in the first place. He knows them best.

3. ## Putting physics aside...

...the Hope Mono Mini (2-pot), Mono M4 (4 pot) and Mono 6Ti (6 pot) all run the same hose, reservoir and lever - the "Mini" lever.

So, everything else being equal - braking power increases due to # of pots. Each pair of opposing pots engage at a slightly different point to provide better modulation and more bite overall under a fistful of brake lever.

Further note is rotor sizing:

Mini - Fr (185 or 165) Rr (165 or 145)
M4 - Fr (185 or 205) Rr (165, 185 or 205)
M6 - 205 only Fr and Rr

I can't imagine but only the heaviest, fastest riders "needing" the 6 pots but they sure are freaking cool.

Sean

Hey, thanks a lot for your detailed answers. This is just what I was looking for. VueltaUSA (Grimeca dealer) doesn't know a f*** about what they sell! It's Grimeca System 17 caliper that I want to mate with System 12 or 8 lever/reservoir.

System 8: 13.5 and 15.5 mm
System 12: 15.5 and 18 mm
System 17: 3x15.5 mm

5. ## I Might be dumb...

but look at the levers and their website... I saw somewhere in grimeca's site a compatiblity chart for sifferent Grimeca systems. I don't remember if the info you want was there but it's very worthy of a try.

Page is www.grimeca.it there's the italian and english version.

6. Originally Posted by Lucky13
Hey, thanks a lot for your detailed answers. This is just what I was looking for. VueltaUSA (Grimeca dealer) doesn't know a f*** about what they sell! It's Grimeca System 17 caliper that I want to mate with System 12 or 8 lever/reservoir.

System 8: 13.5 and 15.5 mm
System 12: 15.5 and 18 mm
System 17: 3x15.5 mm
According to Grimeca Site:

For System 17 M/C = 10 mm diameter. To the handlebar sloping of 45° with oversized round transparent reservoir. Ergonomic lever. Light special aluminium alloy. Weight 108 grams.

For System 12 M/C = 10 mm diameter on the handlebar sloping of 45° with transparent, round and oversize reservoir. Ergonomic lever. Light special aluminium alloy. Weight 108 grams

For System 8 M/C = 9 or 10 mm diameter - on the handlebar - sloping of 45° with "rounded" reservoir and ergonomic lever. Light special aluminium alloy. Weight 98 grams

I guess your ticket is the System 12 lever.

I hope it helps....

7. ## yep

Been there, seen that, thanks! That's what I wanted to do: sys12 lever + sys17 caliper. The question is whether there will be a noticable power gain.

Thanks!

8. Originally Posted by Lucky13
Been there, seen that, thanks! That's what I wanted to do: sys12 lever + sys17 caliper. The question is whether there will be a noticable power gain.

Thanks!

http://www.h-e-l.co.uk/HEL_Performan...ton_Travel.htm

After reading it, you might be better off by using the Sys 12 lever (10mm diam M/C)

The sys 12 lever moves a 2*18 mm dia pistons while the sys 17 moves 3*15.5. Area for sys 12 is 443mm2 vs 563mm2 of sys 17. Each mm you move the piston (10mm dia) will move the pistons 0.18mm on the Sys 12 and 0.138mm on the Sys 17.

Given that your pads reach the rotor, your Sys 17 will have a bit about 27% force than the Sys 12 at the rotor. You'll have a bit more power but you'll have more modulation and much less fade.

9. ## wow

Thanks man, sick site! And thanks for your time explaining all that stuff.

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