Long time bike commuter here. Recently got a new job which is quite a ways from my house, 20.8 miles to be exact (by bike). I don't have a car, and no interest in ever getting one again. I did a dry run of the planned commute, and frankly it sucks. The roads I'm taking are narrow, 10 foot single lane highways with no shoulder, and 35-55 MPH speed limit. There is no way around it unless I want to add about 8 more miles to the trip.
Luckily, there are sidewalks most of the way. Some parts the sidewalks are uninterrupted for almost a mile, which makes this a functional bike lane. However, the sidewalks are concrete with lots of mismatched expansion joints and terrible transitions where it meets the road. This persists for the majority of the commute. There is another portion over a mile long that is on choppy brick roads :-\ The problem is that I was beat up by this, and I'm feeling it today. Not good. I have extended work weeks, 7 days on, multiple days off. My main concern right now is that I won't be able to do this 7 days in a row because I will get injured eventually, or just really damn sore.
I'm riding a 60 cm Salsa Vaya, 700x38 Schwalbe Marathon GG, 6'4" 230lbs. I'm seriously considering splurging on a 650b wheelset so I can squeeze some fat rubber in there. Looks like 650 x 50 Big Ben's will easily clear. Is this enough 'suspension' to smooth out the ride? Should I buy an MTB and put slicks on it? Any one else have this dilemma?