My 10 year old montain mountain bike has quite an upright seating position and front tyre, which is what I think makes it very comfortable to ride for long periods of times.
Having recently bought a new mountain bike, with modern geometry and ridden several of my friends new mountain bikes with modern geometry as well, I noticed they all feel the same. Wide handle bars, where you lean more forward when riding and it feels like there is slightly too much weight on your arms, which over time makes it them much more uncomfortable to ride than my old mountain bike.
I'm not sure what it is about these new MTB's but I am trying to figure out what I need to adjust to make my new MTB more comfortable.
How do I reduce the effect of too much weight on my arms? Seat up / down? Back / forward? etc.
EDIT: My new bike is size Medium and this is the geomtry table:
I normally try to keep the saddle as high as possible and I'm 5ft 10 tall. My old bike has 26 inch tyres and this new one has 29's.