Originally Posted by
ckindt
It sounds like you need to work on your core strength.
I had the same problem last year when I started my fitness comeback. I felt fine on 10-20 mile rides, but any longer or not enough rest in between and my hands got numb and back got sore. I stepped up my core training and it made a big difference in just a few weeks to a month.
I am 6'4" and don't quite have a traditional cyclists build so I put a fair amount of weight on my hands even in good form.
I swapped between a 60, 80, 90, and 100. The 90 seems best. I wanted to try a 100 so I bought a used stem off Ebay for 9.99. I am not out anything if I go back to the 90.