I usually use both brakes, unless doing slow manouvers, then rear only.
As for proportion on each, on a non-ABS bike in particular, the proportion for each depends on the conditions.
1) Before braking, you can apply the rear brake fairly hard, but not the front until weight transfer has loaded the front tyre.
2) If the road surface is perfect, as you approach doing a stoppie, the rear brake will make the rear wheel lose traction (no weight on it).
3) If the road surface is slippery, the proportion of front brake gets less, but neither brake can be used as hard (it's all to do with the proportion of weight over each tyre).
4) In a corner, the dynamics get very complicated. Minor speed correction can use either, but I tend to find the front keeps things more stable. But, if riding aggressively, the rear can aid stability (I said it was complicated). But the harder you are cornering the less braking you can do (and vicar versa).
[censored]5) If you ride an HD, your brakes aren't very good anyway. [/censored]
Whatever the proportions used, you want neither brake to lock a wheel, so for hardest braking you have to modulate each for best result. Specifically, hit the rear brake first, followed fractionally by squeezing the front lever (in practice, start your squeeze as you push down on the brake pedal). As the bike starts to slow, continue to squeeze the front harder, with full squeeze within a second of starting to brake, meanwhile release the pressure on the rear brake as the weight transfers. This is especially important if the bike isn't absolutely upright (as I once found out to my cost).
In an emergency, there's a consensus of opinion that says don't bother with the rear brake, concentrate on keeping the front brake on the verge of skidding (I could do this after a lot of practice on my non-ABS Trophy under most conditions). Since the rear brake is doing little to slow you, any benefit you would get from it would be lost from your not concentrating wholly on the front. Things are a little different on a slippery surface where a higher proportion of what braking is available is from the rear ('cos you don't get as much weight transfer because you can't decelerate as quickly).
And, if you do lock the rear wheel while braking hard, consensus suggests riding it to a standstill without releasing the rear brake, or risk a high-side (unless your name is Rossi).
As a final thought, how do you tell you are applying 80/20 (or whatever) front/rear? I think we get confused with being told that that is what each brake can achieve as a proportion of available deceleration, as opposed to how hard we squeeze the lever or push down on the pedal.
Anyway, I'm now very happy with my ABS. It's probably saved my bacon more than once. I'd still like to know what happens if you brake hard in a corner, or conversely steer while braking. I'm too chicken to experiment :sadsmiley02: .
