some advice re: downshifting in corner entry

Randy Grein randygrein at comcast.net
Tue May 10 12:50:02 PDT 2011


I think we're a little far out for a physical meet but I'll give you  
what I have online; generally I'm pretty good at corner entry - it's  
getting my carcass out of the hole that's the problem. (grin)

MOST people who have corner entry problems with downshifting never  
raced a 2 stroke and end up trying for more engine braking. Bang a  
couple of downshifts, dump the clutch and wonder why the rear is  
hopping all over. Compensate for that and you end up either braking  
early, miss your turn-in point or just go slow. The important thing to  
remember is unless it's raining you can and should lift the rear wheel  
under braking. Keep that in mind; the ideal corner entry has no weight  
on the rear wheel until you tip in, and you can't brake on air. Add to  
that the uncontrollable nature of engine braking. Under most braking  
conditions you'll want to ease in (quickly) to a maximum rate, hold  
that level for a period of time and then taper off smoothly. In  
contrast when you let out the clutch rear wheel braking is greatest  
(by 2-4 times) as the engine spins up, drops as engine RPM stops  
accelerating and drops rapidly as the bike continues to slow. The  
slipper clutch allows a set amount of engine braking and no more,  
matching ideal racing requirements which is why they are so popular.

If you want to experience maximum deceleration with high accuracy pull  
in the clutch. Do this first during practice, in a race you'll end up  
on your head. As you have time while braking bang the correct number  
of downshifts with the clutch still in, then blip the throttle to get  
the engine near redline and EASE out the clutch. When in doubt use one  
less downshift than you think you'll need, power needs at maximum lean  
are pretty minor and it will keep the rear wheel from spinning. In  
fact, you can usually begin acceleration MUCH sooner and carry a  
higher corner speed.

This technique works best on wide and decreasing radius corners;  
you're in the entry zone for a long time and even a small increase in  
speed can net big gains. Ideally you'll want to get used to using a  
little rear brake as well. Without having excessive engine braking to  
contend with the rear brake becomes very useful when near the edge -  
not when straight up, but as you tip in and all the way to your apex.  
1st gen bikes have a bigger rotor and too much rear brake for racing,  
using a smaller GSXR or 2nd gen rotor reduces braking leverage and it  
becomes quite controllable. The important part is to limit rear brake  
to a small fraction of front braking. Feet are not nearly as sensitive  
as fingers and you don't want to spend a lot of attention on that  
brake pedal that could instead be used for feeling grip.

History, and why this works: I mentioned 2 strokes earlier; they have  
next to no engine braking and were THE purpose-built racebike motor  
for over 30 years. The common engine lube was premix, and shutting off  
at the end of a straight cuts off cooling fuel AND lube making  
seizures common. The solution was, and is to pull the clutch at the  
end of the straight and (usually) blip the throttle during braking.  
Modern water cooled 2 strokes generally had good enough carbs to make  
blipping unnecessary so it's just a matter of banging shifts, letting  
out the clutch at the right time and tossing it in. With one less  
thing to worry about a good 2 stroke rider has a higher entry speed, a  
more precise apex and a higher apex speed. This is especially true  
with decreasing radius corners which throw in yet another variable.  
Rain does too. Slam a downshift under braking and the rear tire breaks  
loose and slides. You lose all braking effect and most of your  
steering until it hooks back up; if you're leaned over at the time you  
fall before that happens. Use a bit of CONTROLLABLE rear brake instead  
and you can outbrake the field, both straight up and leaned over. Just  
keep in mind what I said earlier - you are applying a SMALL amount of  
rear brake over a very long distance to scrub off speed.

HTH,
Randy Grein

On May 10, 2011, at 11:20 AM, Jo Rhett wrote:

> Anyone on this list willing to spend a few minutes talking to me  
> about downshifting?  Not street, just race corner entry  
> downshifting.  I'm really struggling with this on my z-built  
> superbike.  Obviously a slipper clutch is probably a good answer,  
> but I'd like to learn how to do this better without the technology  
> assist.
>
> Beer or favorite poison of choice for time to talk about it?  Dinner  
> on my tab?
>
> -- 
> Jo Rhett /  velociRaptor Racing
> #553 WERA / AFM
>



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