some advice re: downshifting in corner entry

Randy Grein randygrein at comcast.net
Tue May 10 14:04:45 PDT 2011


We'll have to agree to disagree Chris - although I agree that you need  
to balance ultimate braking force with control. Some corners won't  
work; if the entry chute is too short, the corner is too wide or apex  
speed too great for the bike. An SV, with slower top speeds will have  
fewer opportunities. At Pacific there are 4 hard braking corners - 2,  
3, 9 and 11. The entry for 2 is wide enough that some lines don't  
really have a long braking chute (but the fastest one does, as does  
the 2 inside lines). Most lines for 3 have VERY long braking chutes,  
even the fast inside line has an initial braking chute that qualifies.  
Later in 3 the turn and banking passes my ability to generate brakies  
and precision is more important than absolute braking effort. Turn 9  
has a decent braking chute only if you're going slow on the inside; on  
the fast line from 8 to 9 you're heeled over quite a bit - no brakies  
there. I've seen people execute brakies going into 11, but it's short  
enough that it's hard to get it right.

Keep in mind I'm not talking about getting big air, more bouncing the  
tire off the pavement. The higher the back end goes the less braking  
force you can apply. (Of course, you know that.)
Randy Grein

On May 10, 2011, at 12:59 PM, Chris Burgess wrote:

> Um...
>
> "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. "
>
> I completely disagree.  There is only one time at Pacific (for  
> example) wher
> eyou would be lifting the rear on braking and that is turn 3.   
> Otherwise you
> shouldn't be or you are introducing toooooo much chassis pitch which
> unstabilizes the bike.
>
> -Chris
>
> On Tue, May 10, 2011 at 12:50 PM, Randy Grein  
> <randygrein at comcast.net>wrote:
>
>> 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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>
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