I have some XT M785 brakes on 180mm front and 160mm rear. I'm considering going up a size at both ends but am concerned a little that they will be more on/off. Am I correct in thinking modulation may get better?
Thanks
Define modulation!
A bigger disk doesn't alter the ratio of lever throw/piston pressure, but it does alter the friction at the pad for any given speed of wheel rotation. A bigger disk will give you more stopping power, but that's more likely to be more bite at any point on the lever rather than a progressively increasing ratio of lever force to piston friction.
You can learn to be more gentle....
I though the theory was that as you went up a size the modulation got worse but the power got better?
Can't say I've noticed since going from a 160 front on the old bike to a 180 on the new one.
It will make you more gnar. And highly virile. I once got a girl pregnant when I rode past her using a 203mm rotor.
If current power is difficult to control adding more will make matters worse.
I noticed before that my SLX brakes were a bit grabby on 26in wheels, but when I put the same set-up on 29in they felt better modulated.
This is the equivalent to going down in rotor size, so maybe try 160mm on the front?
Try softer pads...
years ago i read a article on car brakes which basically said the larger the disc the less likely it was to lock due to clamping force being less for same effect.
It's nonsimple imo. There is more power but it's also delivered differently. The key part of the process is you and everything else is pretty much about feedback loops and reaction. Some folks find powerful brakes harder to modulate, others find that because there's lots of power easily on tap they can be more subtle about how they access it.
I don't find them too grabby at the moment but I know they have a reputation for it. i think Northwind and sq###### have it, learn to adjust to the power. Might give it a go but will bear in mind the warning from no eyed deer.