Try more air. 70 seems low for someone of your size. Not sure what the max pressure for your tires are but my 700X32 tires are rated at like 90 or some such thing and I normally put them to 105. I'm down to 205 now but was 230 when I got this bike and the extra air pressure does make a difference. Also check them often as most bike tires loose air fairly fast, at least at high pressure. I top mine off every couple of days and the rear is normally the one that needs the most. I'd say go up by 10 psi until you find what feels right.