| Numb Fingers Solution
Numb fingers when riding a motorcycle is a common problem. The fact of the matter is that when you apply engine vibration to the nerves in your hand, the nerves go tingly and fall asleep. The amount of vibration and frequency is different for different motorcycles and at different speeds.
Keep in mind that the position of your body on the bike affects the overall weight distribution. Sportbikes are designed specifically to have a more forward riding position to place the center of your body weight lower and further forward, to better balance the bike and improve handling. But certainly for street riding it isn't the most comfortable position and the heads-down orientation isn’t the safest.
The weight of your upper body transmitted through your hands to the grips causes compression of the palmer cutaneous branch of the median nerve. This nerve compression temporarily impedes peripheral nerve conduction, causing numbness. Further, the more weight you put on the grips the better the transfer of the vibration to your hands.
I installed Helibars on a 916 mainly to provide a more comfortable upright sitting position and to take some of the weight off my hands that helped solve a problem with numb fingers.
However, after making this change I have mixed feelings about the new riding position. I prefer the factory handlebar position for more aggressive riding, but I like the more comfortable neck position and posture with the Helibars. Further, during certain riding conditions the angle of the bars just don’t feel right to me.
If I was to do it again, I’d buy bar risers with some range of adjustment. The Helibars can be slid down the forks and rotated front-to-back but they always keep their less-extreme tip-down bar angle. I’d recommend instead a riser bar similar to that sold by Cycle Cat that are quite a bit more adjustable (but quite a bit more expensive.)
Also, they allow you to switch back to a better position for track days.
For street riding and touring, bar risers won’t change the handling enough to be concerned about. Most of us would rather have a bike that handles slightly different than stock, but tailored to allow you to ride longer and sharper without physical fatigue (fatigue being a HUGE enemy of handling), rather than a bike that folds you into a full-race position meant for the track.
There's a couple of more things you can do.
Try foam grips ($5 grips from a bicycle shop work very well). You can lessen vibration by isolating yourself and/or the bars from the vibration source by positioning a cushion (low frequency spring) along the path of vibration (foam between your hands and the bars) and/or use something to isolate the bars (i.e. rubber mounts) from the rest of the bike at high frequencies. You can also try riding gloves with thicker leather or gel padding on the palms.
Add weight to the handlebars - at the ends - LOTS of it (sorry, Alex.) The handlebar is actually responding to the engine's vibrations and will vibrate in harmony (resonate) at certain engine RPM. You can change the resonant frequency of the handlebars so that the bars do not respond to the engine vibration at say cruising speeds (shorter stiffer bars will tend to cause the high amplitude vibration to shift to higher speeds, longer or weighted bars will tend to cause high amplitude vibration to shift to lower speeds). Some manufacturers include weighted bar-ends as part of the design.
Weighted bar-ends are added mass that will lower the resonant frequency of the bar so it vibrates less strongly but does not eliminate all vibration. In many cases, that's enough. You simply change the resonance to a frequency that the bike rarely generates or to a RPM that has less effect on the nerves in your hand. Shifting the resonant frequency is intended to reduce the strength (amplitude) of the vibration at your normal cruising RPM.
I went to a dive shop and paid $3.00 for a 3 lb. lead belt weight (wheel balance weights and lead fishing weights mixed with epoxy would work too), cut it up, hammered it into shape and shoved/wedged it in the handlebar. It’s got to be in there tight to work, closer to the free-end works best. The lead piece in each of my handle bars is about 5 in X 1/2 in.
After adding foam grips, handlebar lead and Helibars, the numbness stopped for me altogether. Before these changes, my throttle hand would go to sleep to the point I was afraid that I wouldn't be able to use my front brake in an emergency.
So, start with the foam grips and then the lead weights. In the meantime, while riding, get rid of the numbness more quickly by momentarily tapping your fingertips hard against your thigh to get the feeling back.  |