I'm about halfway through reading Lee Parks' Total Control book, and he makes a statement about clutchless upshifting that I just don't understand how it could be possible. Here's the quote:

"In fact, it's actually harder on the transmission to use the clutch in this type of situation [full-throttle upshifting] than to just let the loading forces do their job." :eek:

I can't wrap my brain around this being easier on the transmission. I'm certainly no mechanic -- can anybody offer some insight?

you should try both methods and find out ;)

Just to clarify, I understand how clutchless upshifting leads to smooth, quick shifts. My issue is that I don't understand how the engine loads could make it easier on the transmission.

"In fact, it's actually harder on the transmission to use the clutch in this type of situation [full-throttle upshifting] than to just let the loading forces do their job." :eek:



it depends on what he means by "full throttle upshifting".

Here's the sentence immediately before the one I quoted -- "For regular shifts at less than full throttle, a simultaneous, light stab on the clutch will help ease this process."

So I think he means exactly what he says -- attempting maximum acceleration by shifting at full throttle and upshifting at the proper point in the powerband.:idunno:
The only thing I can think is that maybe by letting the engine pull a bit on the transmission, it might easier for the teeth on the input/output gears to mesh.

Edit: Er, I think I meant dogs when I said teeth.

Maybe he thinks that when a person uses the clutch under a WOT application, people tend to "pop" the clutch more than they should due to the speed of the shift. Doing that causes an increased load on the transmission, while a clutchless shift tends to be smoother, when it is done correctly that is.

Even in WOT applications, I BARELY pull in the clutch. My reasoning is that just in case the shift isn't precise, or I have the bike leaned over, a little extra smoothness never hurt. I don't fully disengage the clutch, I just barely pull in the lever to assist the shift. The action causes the clutch to slip, and smooths out power delivery, keeping my suspension in check.

He has his opinion, but it may not work for others in some situations. You won't find me with a knee on the ground and doing a clutchless upshift. Forget that. :D

Here's a decent thread (http://www.ninjette.org/forums/showthread.php?t=25516&) that talks a bit about clutchless upshifting. Check out the link within that thread to Sport Rider's artiicle on it as well.

In clutchless shifting, you must back off the throttle, make the shift and then reapply the throttle. In the "using the clutch" scenario, perhaps he's making reference to keeping the throttle pinned, pull the clutch lever and making the shift w/o ever letting up on the throttle? In that case, I'd agree clutchless shifting has less shock to the transmission.

However, if you use the clutch in conjunction w/ letting off the throttle during a shift, I'd say that's better for the transmission than clutchless shifting.

this is, of course, for street riding. all bets are off when racing and you don't care what it takes to win. besides, it's someone else's job to fix the hosed up/worn tranny. :D

My understanding about anytype of clutchless shifting is that it comes down to matching the engine RPM to the transmission RPM. A perfect example is a case I have with my pick-up truck. When I'm driving off-road in a particular bumpy road in 2nd gear going a certain speed, I've had the transmission jump into neutral because I just happened to be at the right (or wrong) engine vs. transmission RPM. I further experimented with this and I've found that in my truck I can get into neutral from any gear without using the clutch, but I have to match the engine RPM with the tranny RPM. I've actually made a smooth clutchless shift in my truck, but I'm too scared to hurt anything so basically all I will do is pull it form 2nd, 3rd, or 4th into neutral as I coast to a stop. Now remember this is with cross cut gears and synchromesh transmissions.

Motorcycles on the other hand feature straight cut gears (just like the reverse gear in your car), if I am not mistaken. They're stronger than cross cut gears, albeit louder. (i.e. that whinney sound you get when you back up in reverse). For those that don't know what a "crash box" transmission is, it's a car transmission featuring strictly straight cut gears, and is basically made for clutchless shifting in a drag racing situation. Doesn't have the greatest lifespan of a transmission, but you won't find a quicker way to shift a manual transmission.

So back to motorcycles, My understanding is that the gears are stronger, and can handle clutchless upshifts with relatively little pain. I personally enjoy using a clutch, particularly when I nail a perfect upshift. I, like an earlier poster, do not pull the clutch lever all the way in. I've found that partial clutch pulls tend to yeld much smoother gear shifts.

Don't be afraid to experiement with clutchless up-shifting. These transmissions are stronger than most people think.