Originally Posted by ricohman
You need to reduce the pressure on the nerves running through your palms.
You can do this by varying hand positions frequently or trying to find the exact position that causes you grief.
You may also find that no amount of padding eliminates this.
But raising the bar level or higher than the seat can work wonders.
Thing about touring is that you're not generally putting out a high level of power so there is less body weight on the pedals and more on the butt and hands. My hands tend to go numb touring much quicker than if I'm road biking where there's generally less weight on the hands.
So, you need to figure out how you can either comfortably put less weight on your hands, or have the weight better distributed so it isn't aggavating the nerve(s). Like ricohman said, padding may help or not. The best stuff I've found is sill seal foam used under sole plates in construction. It's soft but retains its shape so it doesn't just squish out and become useless. You could probably get some scraps from a framing crew or buy a roll if you can think of something to do with the rest. Then a nice cork tape wrap over the foam.
As far as putting less weight on the hands goes, there are many strategies. Higher bars that are closer to the saddle will move weight off the hands and onto the butt, which may work for you or not. Personally, my Brooks saddle is not comfortable in an upright position, but a different saddle might be. Alternatively, you could try peddaling harder (more weight on feet) and taking more frequent rest breaks. Periodically standing out of the saddle with a very light touch on the bars or even pulling up on the bars should alleviate the numbness as well.
Other possibilities that I haven't tried: A parallelogram type suspension stem found on older mountain bikes before front shocks became ubiquitious to mitigate vibration. mustache bars or flat mtn bike bars with bar extensions pointing backwards rather than forwards.
Numb hands was my biggest issue on my first big tour. In the end, varying my riding style/power and frequent breaks was the only solution. On big decents, I just accepted that my hands would go numb, but otherwise I tried very hard not to ride with numb hands, because of potential permanent or semi-permanent nerve damage.