Does the brake control input displacement (joystick movement) emulate brake force directly or brake lever displacement?
Thank you
I'd say input displacement dictates the pressure. Braking force then should also depend on discs temperature (iirc discs thermals have been implemented, if not, or in older betas, then input displacement dictates the braking force). Better if Pib can confirm though :)
Thanks for the thoughts, at the moment changing master cylinder size does not appear to create the expected change in controller input. It is normal to consider that for a given system just changing to a smaller master cylinder will require more lever displacement, currently the reverse appears to be true so would support the idea that the control input is simulating pressure rather than lever displacement which makes some of the options for cylinder/lever a bit confusing compared to real life expected observations.
If this is the case it would be nice to have the option to simulate lever displacement instead.
Ideally, there's no lever displacement at all (after the initial displacement to put the pads in contact with the disc), it's just pressure from that point on.
Putting a smaller mc (again, ideally) would probably require more displacement to put the pads in touch (no braking force up to that point), so the mc setting should alter that sort of deadzone (to put the pads in touch), but it's probably a tiny detail and it gets messy with the brake input deadzone setting.
I'd be in favor of not overcomplicating this and consider that as soon as you move the stick, you're applying pressure to the discs (pads already in touch), unless you have configured a deadzone on the brake input, of course. It's already a bit hard to grasp (for casual players) with the mc and levrage settings :)
Quote from: h106frp on March 07, 2018, 05:23:04 PM
Does the brake control input displacement (joystick movement) emulate brake force directly or brake lever displacement?
Thank you
Brake input is directly converted to force on the lever.
Thank you for the clarification.
So.. is the fact that a smaller MC needs to travel further to displace as much fluid as a larger cylinder accounted for? I am guessing that currently we are just simulating a proportional change in pressure with respect to the force applied by the lever so the smaller cylinder just starts to feel 'snatchy' or 'wooden' when IRL a smaller MC is used to create the reverse of this situation and give a more progressive feel at the lever.
Certainly feels counter-intuitive to me. I understand that a larger m/c will require more lever force....
...but my mind equates joystick travel with lever travel - the thing in my hand that I'm moving in both cases.
...so if the brakes are reacting too quickly and I want to introduce more travel into the joystick I'd expect to be lowering the m/c bore size.
Quote from: h106frp on March 08, 2018, 10:28:31 AM
IRL a smaller MC is used to create the reverse of this situation and give a more progressive feel at the lever.
To me it should be the opposite: smaller MC means you get more disc pressure (hence more force) for the same amount of lever pressure, so that is somehow less progressive no ?
Quote from: Grooveski on March 08, 2018, 01:07:55 PM
Certainly feels counter-intuitive to me. I understand that a larger m/c will require more lever force....
...but my mind equates joystick travel with lever travel - the thing in my hand that I'm moving in both cases.
...so if the brakes are reacting too quickly and I want to introduce more travel into the joystick I'd expect to be lowering the m/c bore size.
Ach, I agree on your 1st sentence but your last goes against it no ?
If brakes are reacting too quickly, you should increase the MC size (at lest in GPB).
Quote from: HornetMaX on March 08, 2018, 01:46:36 PM
Ach, I agree on your 1st sentence but your last goes against it no ?
If brakes are reacting too quickly, you should increase the MC size (at lest in GPB).
No, because the force and travel are related inversely. Going to a larger master cylinder will require less lever travel but more force wheras going to a smaller m/c will require more lever travel but less force.
The more important sentence is the middle one. When I pull back on my joystick I mentaly equate it to lever travel rather than force.
...so changing m/cs in GPB's pits has the opposite effect to what I'd expect to happen.
Quote from: Grooveski on March 08, 2018, 02:08:59 PM
Quote from: HornetMaX on March 08, 2018, 01:46:36 PM
Ach, I agree on your 1st sentence but your last goes against it no ?
If brakes are reacting too quickly, you should increase the MC size (at lest in GPB).
No, because the force and travel are related inversely. Going to a larger master cylinder will require less lever travel but more force wheras going to a smaller m/c will require more lever travel but less force.
But unless GPB somehow simulates the "flexibility" of the hydraulic circuit (or the lever), there's no travel to speak of.
There's only force on the lever.
Quote from: Grooveski on March 08, 2018, 02:08:59 PM
The more important sentence is the middle one. When I pull back on my joystick I mentaly equate it to lever travel rather than force.
...so changing m/cs in GPB's pits has the opposite effect to what I'd expect to happen.
But as Pib said, this is not what GPB does: brake input = force on the lever (so pressure in the circuit), not lever travel.
So the change in MC size behaves correctly: smaller MC => less joystick travel for the same braking force.
Quote from: HornetMaX on March 08, 2018, 02:20:25 PM
But as Pib said, this is not what GPB does: brake input = force on the lever (so pressure in the circuit), not lever travel.
So the change in MC size behaves correctly: smaller MC => less joystick travel for the same braking force.
Yeah - funky - I know that now. ;)
But the question is "Should it?"
...or should joystick travel equate to lever travel?
....which to me would seem like the more intuitive way round.
Quote from: HornetMaX on March 08, 2018, 02:20:25 PM
But unless GPB somehow simulates the "flexibility" of the hydraulic circuit (or the lever), there's no travel to speak of.
There's only force on the lever.
Yeah I understand that too - but I'd argue that that flexibility is exactly what you're swapping master cylinders to fine tune in the first place - so perhaps it should be getting simulated.
...and that "no travel to speak of" is an oversimplification. I prefer pretty soft levers(in real life) - not spongy but on the spongy side of normal.
...and there is most defiantly lever travel between on and full-on.
By the way - I have no problems with the brakes on GPB or the operation of them - I don't really think lever flex, hose expansion, caliper porosity, etc need simulated.
This whole thing is simply about swapping m/cs in the pits and how a smaller m/c makes for what I'd consider a more wooden feel on the brakes - it just feels the wrong way round.
Quote from: Grooveski on March 08, 2018, 05:31:35 PM
Quote from: HornetMaX on March 08, 2018, 02:20:25 PM
But unless GPB somehow simulates the "flexibility" of the hydraulic circuit (or the lever), there's no travel to speak of.
There's only force on the lever.
Yeah I understand that too - but I'd argue that that flexibility is exactly what you're swapping master cylinders to fine tune in the first place - so perhaps it should be getting simulated.
...and that "no travel to speak of" is an oversimplification. I prefer pretty soft levers(in real life) - not spongy but on the spongy side of normal.
...and there is most defiantly lever travel between on and full-on.
Yeah there is, but aren't better hoses (stainless, braided) just trying to avoid/minimize that ?
Also, I'm pretty sure your brain doesn't actually "reason" in terms of lever displacement: could you imagine a brake lever with a very light spring behind it (and no "hydraulic" feedback) work fine ? It would be tremendously hard to use. On a real lever, what you modulate is probably more the force you apply. The displacement is just a side effect. Zero displacement is probably a simplification and it may turn out to be a bit weird to use, but keep in ind that car-simmers do like load cells for brake pedals ...
Quote from: Grooveski on March 08, 2018, 05:37:39 PM
This whole thing is simply about swapping m/cs in the pits and how a smaller m/c makes for what I'd consider a more wooden feel on the brakes - it just feels the wrong way round.
I never swapped a MC in real life. What do you expect to happen in real file when you lower the MC diameter ?
Would you need to apply more or less force on the lever to get the same braking force as with the bigger MC ?
I'd expect less, hence the "wooden" feeling (or less progressive as h was saying before).
Quote from: HornetMaX on March 08, 2018, 05:46:31 PM
I never swapped a MC in real life. What do you expect to happen in real file when you lower the MC diameter ?
Would you need to apply more or less force on the lever to get the same braking force as with the bigger MC ?
I'd expect less, hence the "wooden" feeling (or less progressive as h was saying before).
As I said earlier:
Quote from: Grooveski on March 08, 2018, 02:08:59 PM
Going to a larger master cylinder will require less lever travel but more force wheras going to a smaller m/c will require more lever travel but less force.
...and honestly, now that I know it's the force that's the being simulated it'll never be a problem again - but I'll always be thinking of it as the wrong way round in the pits when I go to change it.
Since we're chatting - here's another copy/paste from when h and I were blethering last night. :)
QuoteThe wee zxr is on it's fourth m/c. :)
The original was crap(right size(12.5mm)) - just a poor OEM unit that had no feel.
Fitted the Brembo off a Guzzi Daytona for a while. 12mm conventional design but a larger pivot length and longer barrel so a pretty good match. About the same lever travel but much more feel - just a better manufactured piece of kit.
Was only a loan though so replaced that with an OEM Brembo Radial from an R1. 16mm but radials are measured different - the barrels are shorter so the bores have to be larger. Felt much the same as the Daytona m/c.
...then changed my calipers to a set with bigger pads and pistons and to match them splashed out on a Brembo RCS19. 19mm radial with adjustable pivot length. Far better quality than any of the previous units and you can feel it.
Having upped the pad size there was also less force required for the same bite. Now it's 1 or 2 fingered loveliness. ;D
...so while I've done a few m/c swaps, they've been more about improving the quality of the unit rather than adjusting the travel/lever force. The earlier ones were all about the same size, had about the same travel and took about the same force. It wasn't until the calipers were changed that there was less force required at the same travel.
Quote from: Grooveski on March 08, 2018, 06:12:41 PM
...so while I've done a few m/c swaps, they've been more about improving the quality of the unit rather than adjusting the travel/lever force. The earlier ones were all about the same size, had about the same travel and took about the same force. It wasn't until the calipers were changed that there was less force required at the same travel.
Yeah, hard to compare if the quality is changing. But when you say "bigger pad/pistons ==> less force required" the you're also saying "smaller MC ==> less force required".
BTW, what would justify the quality difference between the different MC in your opinion ? I have my idea ... :)
And you're still factoring in travel in the overall feeling: probably makes sense in real life, but not in GPB.
In GPB it seems to be a simple "input displacement vs braking force" relationship: smaller MC = steeper line.
(I say seems as I thought disc thermals where somehow simulated, no longer sure since PiBoSo last comment).
I think where we are coming unstuck is that we do not model the caliper piston numbers and diameters so we can go to a theoretically small MC without any unwanted side effects that would occur in real life as we struggled to shift enough volume to drive the pistons or too large in MC and end up with on/off braking and no modulatiion range.
Quote from: HornetMaX on March 08, 2018, 07:03:19 PM
Yeah, hard to compare if the quality is changing. But when you say "bigger pad/pistons ==> less force required" the you're also saying "smaller MC ==> less force required".
BTW, what would justify the quality difference between the different MC in your opinion ? I have my idea ... :)
Bigger pads increase the overall efficiency of the system - you need less pressure on the lever to achieve the same braking force becuse there's more friction at the end.
Assuming the m/c matches the calipers of course. When I changed calipers I didn't even try the new ones with the old m/c because it'd have been too soft at the lever - so I increased the m/c size at the same time to give the same amount of travel.
As for quality - that's more about feedback/feel. The R1 Radial m/c didn't affect how hard I could brake compared to the one that came with the bike but totaly affected the feel.
The lighter return spring and more direct plunger direction of a radial m/c probably played the biggest parts but I'm sure if there was a Brembo employee here he'd be telling us about the bore surface treament/o-ring materal/alloy perosity..... ;D
Was £60 well spent in my view and done me fine for a few years.
...but I was riding other bikes too in that time, and they pretty much all had better brakes that the wee zxr - so I decided on the caliper upgrade.
Even before I started faffing around I'd replaced the hoses with braided affairs and the pads for hh sintered. Now the only component that's original is the little splitter that branches the hoses mid-line. ::)
Quote from: h106frp on March 08, 2018, 07:18:59 PM
I think where we are coming unstuck is that we do not model the caliper piston numbers and diameters so we can go to a theoretically small MC without any unwanted side effects that would occur in real life as we struggled to shift enough volume to drive the pistons or too large in MC and end up with on/off braking and no modulatiion range.
Why you say that with a large MC you have no (or less) modulation range ?! You're still reasoning in terms of lever displacement I guess.
In terms of lever pressure, with a large MC you've more modulation (lesser slope in the curve between lever pressure and braking force).
But what you said may also be a reason why the input is lever force instead of lever travel: travel would need some additional params about the pistons sizes and number (even if to me, the real justification is that even on a real bike, you work more in terms of force than in terms of travel).
Anyway, all this becomes mostly academical given that you can tune the input deadzone, linearity and gain, indepenently on whichever physics settings of MC, levarage etc. :)
Quote from: Grooveski on March 08, 2018, 07:54:18 PM
Bigger pads increase the overall efficiency of the system - you need less pressure on the lever to achieve the same braking force becuse there's more friction at the end.
In principle (and at a simplified level), this is wrong: kinetic friction force depends on the normal force (and friction coeff), not on surface.
The normal force is the circuit pressure times the total pistons area, so that doesn't change when you change the pads.
Bigger pads may have other advantages of course (like thermals or wear).
Quote from: Grooveski on March 08, 2018, 07:54:18 PM
As for quality - that's more about feedback/feel. The R1 Radial m/c didn't affect how hard I could brake compared to the one that came with the bike but totaly affected the feel.
The lighter return spring and more direct plunger direction of a radial m/c probably played the biggest parts but I'm sure if there was a Brembo employee here he'd be telling us about the bore surface treament/o-ring materal/alloy perosity..... ;D
And I'd tend to believe him (well, up to a point): it may well be that the perceived quality is mostly driven by how "rigid" all the components are (MC, hoses, calipers etc) than anything else.
Quote from: HornetMaX on March 08, 2018, 08:46:18 PM
In principle (and at a simplified level), this is wrong: kinetic friction force depends on the normal force (and friction coeff), not on surface.
The normal force is the circuit pressure times the total pistons area, so that doesn't change when you change the pads.
The calipers with the bigger pads had bigger pistons.
Kinda thought that went without saying - Otherwise I wouldn't have had to change the m/c to match.
Quote from: Grooveski on March 08, 2018, 09:24:07 PM
Quote from: HornetMaX on March 08, 2018, 08:46:18 PM
In principle (and at a simplified level), this is wrong: kinetic friction force depends on the normal force (and friction coeff), not on surface.
The normal force is the circuit pressure times the total pistons area, so that doesn't change when you change the pads.
The calipers with the bigger pads had bigger pistons.
Kinda thought that went without saying - Otherwise I wouldn't have had to change the m/c to match.
OK, makes more sense. But then it's not so straightforward that the modified system will give higher efficiency (lower force on the lever for the same braking force), as for the same lever force, the bigger MC will generate a smaller pressure: yes, this could be compensated by the bigger pistons, but the overall result will depends on the exact numbers (it could go either way).
Quote from: HornetMaX on March 08, 2018, 09:33:50 PM(it could go either way).
Yeah - My dad found that with his second Blackbird(or maybe it was the second 'Busa :-\ - he's had two of each) - Huge great 6 pot calipers with acres of pad but he felt the old 4 pots had better bite.
In the zxr's case it was just underbraked to begin with. When Kawasaki changed from the H to the L model they upped the disks from 300 to 310...
...but for some reason changed the calipers from 4x30 & 4x28 to a set with 8x27mm pistons (and pads only about 3/4 of the area of the earlier model).
The newer calipers were smaller so a fair bit lighter(probably the main factor in their decision) but I've noticed no ill effects since bolting on the heavier ones.
If they'd stuck with the same calipers (and the matching 14mm m/c) from the earlier model I'd have likely never even thought about upgrading anything.
Of course then I wouldn't have a lovely RCS19 at my fingertips - which I must admit puts a smile on my face with it's looks as well. ;D
Not £200's worth of smile though. ;) Thankfully it works as good as it looks.