Caulfield Man <bicyc...@twowheeler.com>

Folks

I have a 15 year old Giant Yukon MTB and a Trek Road flat bar racer. I
like the stance of a MTB and I am principally a commuter so when the MTB
seemed too old (and there was coin in my pocket) the flat bar racer
seemed a sensible move. Trek bike is 2 years old. They have a similar
frame size and are both in excellent condition. (I think...)

Question is this.

I can ride the MTB endlessly and feel fine when I get off it. These days
  when I ride the Trek I end up with almost crippling back pain.

Do I consult my friendly bike shop guy? See a medico? I'm not sure
whether the skinny wheels and structure of the flat bar racer mean more
road vibration ends up in my back whereas,  the MTB has reasonably fat
tyres which seem to soak more of the vibrations up. (The MTB has no
suspension)

Any thoughts?

Cheers