I appear to be compressing a nerve in my hand on the road bike. On longer rides (80km+), I can start to get what can only be described as 'electric shocks' in my right hand. It appears to be the fleshy part at the base of the thumb that is causing the issue - just in line with the outside of my wrist. Placing my hand back on to the tops can trigger it, or oddly, reaching back into a jersey pocket. It shoots up my forearm, and can make me jump and wave my hand around like I have just placed my hand on a hotplate instead of the handlebars.
I have positioned the hoods and the handlebars to a postion where I don't put pressure on that part of my hand, the bars have Fizik microfibre tape on with Gel pads (BikeRibbon firm flavour) underneath on the tops. Castelli Rosso Corsa gloves also seem to be helping. I did 130km yesterday, with it only happening a couple of times towards the end of the ride. My hand does feel a bit tender in that area today though (so does the left a bit, but I don't get the shocks in that one). Bike is a circa 2008 Cannondale Synapse, and have 25mm tyres. I do try and vary my hand position as much as I can.
I'm not sure what to do next. It's improved, but I would like to stop it all together.