There are several reasons why you can get numb fingers. Vibration is one. In my case it is pressure in the wrist that traps the nerves to my fingers. I have had the same problem mountain biking for years. I can even get the problem driving a car if I am not careful how I hold the wheel. Adjusting the handlebar position and angle to minimise the pressure point is probably the best solution. Some gloves make the problem worse. With my mountain bike, the gel padded ones seem worse - I think the gel bunches up and puts more pressure where you don't want it. Thinner gloves therefore tend to be better. I haven't had specific problems with any of my motorbike gloves though (none of which had gel). Cruise control helps, when I get the chance to use it.