progressive shifting

[mattjohnson207]

Going to professional truckdrivers school, talked about using progressive shifting on motorcycles, one participant has a KLR 650 thumper, doesn't use the clutch, he says he shifts when the torque starts to come in around 1900 rpm, says it should slip into gear like an automatic.   Instructor said, when  you start to feel torque, shift,  by floating the gears, ie, no clutch. I found this to be true, go into 2nd at, say 8mph, 3rd at 18-20 mph, 4th at 30mph.  miss the synchro point, and the bike lurches into gear, making you wish you'd used the clutch.  Have not had much success at clutchless  downshifting, but have only been trying it for two days.  Just curious, any thoughts ?

[greenie]

have tried clutchless shifting (out of neccesity) on my '95 ural as well as my '06 electra with a minimum of luck. shifts were chunky, at best. i drive over the road and can float gears with the best of 'em in a big truck. it is all about rpm-imho.up or down. :-)  paul

[matthewjohnson480@gmail.c]

Thanks for the expertise...back to the clutch, but now I know what to do when the cable breaks!
matt in Glendale

[barenekd]

Thanks for the expertise...back to the clutch, but now I know what to do when the cable breaks!

I have ridden quite a few times with a broken clutch cable. Starting from a stop is the biggest PITA about it. You need to push you bike up to a few miles an hour, astride it or otherwise, then shift it into first. It is usually fairly seamless depending on the speed you can get it to.
A little blip of the throttle as you downshift helps, too.
However, Kevin doesn't recommend clutchless shifting with the Enfield as their somewhat fragile sifting mechanism can be knocked out of whack.
Bare

[Vince]

     This is a racing technique to save time. You can shift a bike without clutching it. I too have had to ride home with a broken clutch cable. Technical terms for folks that regularly use this technique is "Job Security" or "Pedestrian". I don't recommend this as a matter of course. A racer trades the quicker shifts for a shorter transmission life. There is no reason to do this for regular street or dirt riding with ANY bike.

[Chasfield]

I smashed a Bantam gearbox while trying clutchless down-shifting (age 17) - actually knocked two teeth off one of the gears.

My subsequent Triumph twin would shift effortlessly up the box - the gear dogs would just slide in with a momentary closing of the throttle. Though I was nervous of down shifting because of the Bantam incident!

[Arizoni]

Just my opinion but the only time I would consider shifting my RE's transmission without using the clutch would be during an emergency where my clutch cable broke and even then I would be as gentle as possible.

The crankshaft in these Royal Enfields weighs about 20 pounds and it stores a LOT of energy when the engine is running.
If I did my math right, if the shift point was when the crankshaft is at 4000 rpm, the crankshaft will need to loose about 650 rpm when shifting from 2nd to 3rd.

If the shift is made without using the clutch all of the stored energy that 20 pounds of spinning steel, when it almost instantly slows down 650 rpm has to go somewhere and the massive shock from this energy must be absorbed and transferred by all of the parts from the crankshaft sprocket to the rear tire is where it ends up.

Anyone who has pounded a nail knows that a heavy mass stopping almost instantly can break/bend whatever gets in its way and although it is not a direct comparison, there is a lot of similarity when slamming into the next gear to a 20 pound hammer traveling at over 8 feet/second coming to a total stop almost instantly.

The fact that the transmission and drive chains can tolerate this is a testament to  the robust design but even strong parts can only take abuse for so long before they break.
Yes, on the RE, the 'cushion drive' absorbs some of this shock but only for so long.

[dampking]

At times..  I actually do something similar but I do use clutch. Instead of throttling down for the next shift.. I keep the throttle open and hit the clutch(with throttle wide open)/shift gear and release the clutch. So basically building the engine rpm and not letting it drop. Will this harm the clutch in anyway?

[Ice]

It is a little rough on things.

[dampking]

I will have to change my riding style then I guess

BTW ! HI ICE! Long time no see

[barenekd]

It's a hell of a bang on the primary chain, too.
Bare

[dampking]

Yea last time I had big time issues with my primary. One of the plates were out of shape.. and it was leaking real bad. So I guess I will stop doing that.. but that was a very good way to keep the rpm up.

[Lwt Big Cheese]

The idea is that you match the revs between the gears, then all that rotating crank shaft mass stuff is irrelevant.

[barenekd]

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progressive shifting
« on: October 06, 2012, 03:29:24 PM »

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Going to professional truckdrivers school, talked about using progressive shifting on motorcycles, one participant has a KLR 650 thumper, doesn't use the clutch, he says he shifts when the torque starts to come in around 1900 rpm, says it should slip into gear like an automatic.   Instructor said, when  you start to feel torque, shift,  by floating the gears, ie, no clutch. I found this to be true, go into 2nd at, say 8mph, 3rd at 18-20 mph, 4th at 30mph.

One thing you have to remember about truck driving vs motorcycles is that a truck has a neutral between each gear. You can pause in to synch the revs. You don't have that bit of slack in the motorcycle gearbox.
Bare

[LarsBloodbeard]

A friend of mine who used to race motocross taught me this, many years ago.  Since then I've tried it on all the bikes I've owned.  Some are smoother than others, which leads me to believe that it might be safer for some transmissions than others.

Aside from satisfying my curiosity, I always use the clutch.  Any moving part is gonna wear out at some point.  And I figure a bad clutch is a lot easier and cheaper to replace than a transmission.