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Following on from the braided hose question. I noticed on Hope's website they say
about the new tech X2 caliper.an increased piston diameter, generating more usable braking force on the rotor.
Now, bearing in mind my maths if pretty(ok very) iffy at the best of times, the way I understand it a larger piston will exert less force for a given pressure, 'cos the pressure is being spread over a larger area - is that right 😐
I'm guessing that the increase in usable braking force at the disc might be due to smaller than previous pad area (plus different pivot point on new Tech lever)?
p.s. some of this ruminating is because I'm trying to work out whether it'd be worth changing my existing Hope 'original Mini' caliper for a Tech X2 or M4 caliper, to increase braking power. Running a Tech M4 caliper with original Mini lever on the front and it's very good, but think I could get away with something a little less powerful (and heavy) on the back.
p.p.s anyone know the diameter of the Tech X2 pistons?
pressure = force / area.
force = pressure * area.
the pressure within the system is created at the lever: (pressure = force / area). using a smaller piston at the lever will create more pressure*.
a bigger piston at the calliper means more force*, cos force = pressure * area.
(*in both these cases, you'll get less piston movement at the calliper - which is something you need to keep to a minimum to stop the pads 'dragging')
It's just leverage - if the master cyclinder (at the brake lever end) is made smaller relative to the caliper pistons then it's like shifting to an easier gear - you move the pads less distance for a given lever throw but more force is being applied to them.
Hmm...if that's the case, it sounds like I really need to find out the diameter of the Tech X2 piston, so I can compare and (don't laugh!) calculate the % of additional power I'd get.bigger piston = more force.
but without knowing what pressure is behind it, for a given input force at the lever, you won't be able to ... oh never mind, knock yourself out, go nuts.
X
Yeah, I getting the idea now 😀 I've got some Elixirs on another bike, which from the lever design, I'm guessing have v.small pistons compared to some. (very good power on Elixirs BTW, but the 'original mini' lever M4 combination has much better modulation/power balance).
er...yeah, maybe some massive assumptions to be made 😆 Now, where's the back of that fag packet 😉but without knowing what pressure is behind it, for a given input force at the lever, you won't be able to ...
If you can find out the piston diameters of the caliper and the lever pistons, you can then compare the ratio between different brakes. the size of one set of pistons only tells you nothing (unless you're say comparing hopes and they've only changed the caliper piston size).
Yes, I'd just be changing the caliper, so no change at lever. Tho, I don't know the diameter of the piston in the lever - mind you, got half a shed full of Hope spares, so shouldn't take too long to find & dismantle a disused lever of the same type.the size of one set of pistons only tells you nothing (unless you're say comparing hopes and they've only changed the caliper piston size)
In that case, you just need to compare the areas of the pistons old:new - if it doubles for example with the new piston, you'd get double the power (though pad clearance would be an issue!)
