So, where does all this ‘modulation’ come from with hydro brakes.

Just seems like a lever squeezing fluid through a tube and forcing pistons together with no special ‘modulation’ valves to speak of.

Couldn’t be just bullsh by any chance could it?

Often wondered this myself. I think that ‘modulation’ is just squidginess in the system.

Just try some different makes, some have a horrible, wooden feel, some have a nice progressive feel.

Just seems like a lever squeezing fluid through a tube and forcing pistons together with no special ‘modulation’ valves to speak of.

But it’s still subject tot he laws of pyhsics so initially the fluid compresses more until it reaches a point where I can not compress further, this would create the feeling of modulation. Also there’s bound to be some effect of the pads hitting the discs and the energy transfer.

I’m not a physics buff but modulation seems to be a fairly likly outcome of the forces in a braking system.

Modulation is very important.

Without it, people would say all kinds of offensive stuff on the forums, so modulators are needed to make sure everyone behaves.

What got me asking was reading that someones hayes brakes were on-off no modulation.

Given that we were all on superstar pads with similar quality brake hoses with the same brake fluid, is the modulation then in the caliper or the lever.

Presumably the rubber bits I suppose that fit under the lever cover……

If so you could maybe change that to get a different feel for little cost

Well, technically it’s not modulation, but it does describe things rather nicely…

forget compression of the fluid, it’s negligible. I’m told some brakes are grabby, though I’ve never experienced this myself, and never had any trouble getting exactly the amount of braking I wanted by adjusting how hard I squeeze. One can imagine that it might be possible for the brake to be constructed in such a way as for the pads to be pulled into the disk by its movement to provide a servo effect – but that would be a bad thing 🙁

initially the fluid compresses more

now shoot me down in flames but i thought you couldnt compress a fluid anymore than it is already. i.e. because it is a liquid you cannot get it to take up less volume. am i very wrong?

modulation, my interpretation of this is:

essentially you are squeezing fluid from one end to the other, its how the pistons force the fluid down the tube (piston), the internal shape of the ‘tube’ (reservoir), viscosity of the fluid, expansion of the hoses and the resistance of the moving parts.

how wrong am I then?

And the award for dullest thread of the day so far goes to…. 😉

not sure what causes it but it definately exists, I was told its to do with piston size, so brakes with big slave pistons (V2, HFX9, mono trials) have less modulation than brakes with smaller pistons (mono mini, shimano). The ideal comprimise being brakes like the M6 which use lots of small pistons the get the same power as one big one, but the modulation of small ones.

Theres some new brakes coming out next year with extra pistons within the slave piston, which are adjustable to alter when they kick in and thus the modulation.

try these three brakes;

hope mono mini
shimano xt (pre servo weave)
hayes HFX9

the first has naff all power (comparitively), but the lever moves a long long way, which some people like asi it give modulation in the sense that the further you pull th elever the more stoping power you get.

the second has less lever movement once the pads and disk contact, but the more yousqueeze the lever the more braking you get.

the third, has one power and one power only, and its fairly brutal. But unless your a nancy boy who drags the brake its all you need 99% of the time.

My experience of “modulation” differences was when I went from standard to sintered pads on Shimano brakes. Suddenly there was very little lever movement/effort for my braking. I don’t mean taking up the slack I am talking about after pad/disc contact. Quite grabby but it did wear off.
So I recon that the pad friction properties must have a large effect on the modulation. If a pad needed a fair bit of pressure on the disc to get some heat and start stopping then these would give good modulation. If the pads gripped at cold then they would be grabby. Someone on here was describing these two types of friction related to – you guessed it – pad bedding in.
So, does pad bedding in affect modulation?

…well I’m excited!

modulation is how the power is fed to the caliper. Think of it like this, if you have a hose and turn on the water it squirts out of the end you then stick your finger over the end and you get more pressure, it the same theory for brakes, it is how the fluid is controlled when the lever is pulled thus pushing the pistons/pads onto the rota. Pads can have some effect on how a brake feels but generally its all about the internals of the brake itself.

captain pugwash, thats boy cow poo

the hose pipe is a hydrodynamics problem

the brake is a hydro static problem

your finger slows the water down, thus the pressure drop in the pipe decreaces, as the overall pressure drop is the same (from the water mains to the atmosphere) the rest of the pressure drop is past your finger (nominaly) so the water speeds up.

OK thisisnotaspoon please explain why say the old Magura Julie which was low pressure had a huge piston where as the new one is high pressure and the piston is small…..