Brake calipers - big and little pistons

[pete376403]

Looking at front brake calipers - in the case of floating (sliding) types, some have two equal sized pistons, others have one large and one small piston. Does one type have an advantage over the other?

[AllanB]

Oooooh I have read the theory. Can't remember why! Something about either more even pad wear or heat distribution.

[pete376403]

Thanks Allan, that jogged a few brain cells. Many years ago I read something about heat in the pads but I can't recall the details (ageing is a bitch). With the rotation of the disk the small piston is the "leading" one and there is gong to be less pressure on the pad at this point than from the bigger piston. I'd like to know if this was better or just a theory of the time thats since beed disproved. Goggle hasn't been much help so far but that may be because I'm not asking the question correctly.

The calipers in question are from an early 2000's Kawasaki Concours 1000, and will be replacing the single piston items on the GS1100, along with larger disks.

[SaferRides]

Google was indeed not that helpful. The first answer here seems correct, but he doesn't explain the meaning of the diagrams very well.

https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper

One thing to note is that the "turning moment" will decrease as the pads wear, so it's not possible to accurately compensate for it by having different piston sizes. It also depends on the coefficient of friction (µ) between the disc and pads.

[Grumph]

Doesn't matter which way round you fit them - they'll be shitloads better than the OE Suzuki ones...

[pete376403]

Google was indeed not that helpful. The first answer here seems correct, but he doesn't explain the meaning of the diagrams very well.

https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper

One thing to note is that the "turning moment" will decrease as the pads wear, so it's not possible to accurately compensate for it by having different piston sizes. It also depends on the coefficient of friction (µ) between the disc and pads.

Thank you, that explains it well.

[pete376403]

Doesn't matter which way round you fit them - they'll be shitloads better than the OE Suzuki ones...

Yeah the Suzi ones were pretty crap. the bigger disks (CBR600) wont hurt either. I got the Concours master cylinder along with the calipers, and the calipers have received an All Balls rebuild kit each, plus new pads. Might get a stoppie out of it yet :eek:

[F5 Dave]

No it will just slide the front wheel.
I ran CBR600 calipers on plate with std cylinder of my 1100G. It was a wonderous improvement all the way to 'just about safe' actually more would have been silly on the tyre.
Sold it before they started getting tough on brake mods. You will need LVV to get a wof unless you can somehow convince them it is how they came.
Not sure who you'd use now . Last guy got out for health or I would have recommended him.

[pete376403]

going to try "don't ask don't tell" initially, take from there.

[F5 Dave]

Worked for my YZF with blue spots, but figured I'd just tell them the SP had them.

[pete376403]

The GSX1100 used the same calipers (as the Concours - same rebuild kit, anyway) so it's only stretching the truth a wee bit to say they are standard Suzi 1100 parts.