Ideal Gearshifter Geometry

[j3gq_imp]

@LP
No apology needed ever, forum/s are fun and it's hard to not "cross-read" and focus on one post. I'd rather have you read my post and get it (slightly) wrong, than not read my silly posts at all

[Charlie Bravo_imp]

I like to understand how everything works on my motorcycle. The control that is designed with the most adjustability is the gear shifter. Having this set up right makes riding easier and reduces a potential source of distraction. Besides, it's a cool little mechanism and easy to adjust to fit your unique situation.

A few years ago I had reconstructive surgery on my left foot. Several joints were immobilized and my range of motion is smaller than normal, so I have had to adjust the shifter to suit. I understood the idea behind displacing the shifter pivot away from the transmission spindle but until I did the following drawings I didn't really appreciate the beauty of this mechanism.

Displacing the shifter pivot allows the designers to position it in the right place without regard to where the spindle is, and also use differing arm lengths to control the amount of force needed to execute a shift.



Above is the normal geometry of the shifter. I would assume this is how it comes from the factory, but since I adjusted mine before taking a close look and measuring it, I'm not sure of that.



Above shows upshifting and downshifting behind the normal, at rest position.



When linkage length is about 3.86” (98mm) and the spindle dots are aligned, right angles are formed at both linkage connections; to the lever and to the arm.

Gear changes require a 10° rotation of the transmission spindle, which takes about 1.04” (26.5mm) of gearshift foot peg travel.

The spindle is splined with a 12° pitch which raises or lowers the gearshift foot peg about 1.25” (31.75mm) if the gearshift arm is moved one spline.

For finer adjustments than 1.25” you have to change the linkage length. Facing the bike, the left end is reverse threads. Both 10mm nuts must be loosened so the rod can be turned.

This mechanism is designed to be adjustable to suit individual preferences but it works best with ideal geometry.

I felt the need to disclaim this post. I hope it doesn't spoil it for you.

All the graphics are 404 errors for me.

[Gone in 60]

Funny that this thread came back up. Was riding the Bonneville to work this morning. I adjusted the shift lever years ago and have been happy with it, but for some reason, was just thinking that it's sitting too high, and that maybe I should lower it by a notch.

[PowerDubs_imp]

My Aprilia has an adjustable toe piece on the shifter and brake pedal for fine tuning in a circle..I thought that was kind of neat.

...and there are aftermarket pieces to replace the piece to allow greater travel in any direction.

It wouldn't be impossible to cut / weld something like that onto the CB... pretty is a different story.

[GoldOxide_imp]

Funny that this thread came back up. Was riding the Bonneville to work this morning. I adjusted the shift lever years ago and have been happy with it, but for some reason, was just thinking that it's sitting too high, and that maybe I should lower it by a notch.

You losing weight Gone?