OneDragons wrote:This is (hopefully) a short question. If you lock the rear wheel up on a bike does it make any difference to your stopping distance?
I am assuming your front wheel is not locking up and you remain in control i.e. the front wheel remains in control of your direction and the rear wheel doesnt travel very far sideways.
The "yes but not much in the dry" answer is essentially as correct as you need to care about, but I think it's worth pointing out that there are lots of variables that make the real answer a definite "it depends" (oh what a surprise!)
The primary factors are the geometry of the bike and the grip provided by the tyres. Traction is obviously affected by the tyre compound, tread, oil / water / gravel / whatever on the road, uneven road surface, tyre pressure, the effectiveness of your suspension and probably 101 other things I've not thought of. Be aware of how changing conditions affect your traction.
Depending on this balance, some bikes will lift the rear wheel under heavy braking, some will lose grip on the front wheel first. In the first category the rear wheel's contribution to braking is almost irrelevant, though keeping it on the ground and turning (probably not using the rear brake at all) helps in terms of control, and if you're not using 100% of the braking potential of the front wheel, this leaves you with some you can get out of the rear wheel, so I don't recommend neglecting the rear brake as a matter of course.
Bikes whose geometry/grip characteristics (in the prevailing conditions) favour losing grip on the front tyre before lifting the back tyre will, however, some potential for braking power even when the front wheel is at its maximum. In those circumstances, treating the rear brake in such a way as to maximise that (not locking the wheel, for a start) will reduce your braking distance.
How much difference it makes is again a function of traction and geometry and such, a harley fatboy will behave very differently from an aprillia 125.
It's worth noting that in wet weather, there's enough grip loss on the front wheel to make a significant difference to the balance between the two wheels' braking potential.
All in all, though, as the honourable gentleman said, for most bikes the front tyre is doing almost all the braking anyway unless it's wet
Cheers & God bless
Sam "SammyTheSnake" Penny
Posted: Mon Aug 21, 2006 10:27 pm