Advice needed about new bike

caitlin

Hi there. A couple of days ago I purchased a Marin San Anselmo (a hybrid, "city" bike). I've been riding it to and from work (10 mins each way) and have found I get a tightening in my lower back and possibly the middle as well. I'm not sure if this is due to the type of work I do (market research, sitting in chair for 6 hrs) or the bike itself. I can't remember if I had this problem with my last bike (a mountain bike). The bike is reasonably upright, this may be the problem. The seat is raised to about 10 centimetres and I can almost stand on the ball of my feet. Is this the right height? I'm 5"2 (157cms) and the bike is a size 15.5. If I put the seat down any further, I feel like my knees are coming up too high, I'm quite conscious of the movement of my knees and legs at the moment as it is, probably because the bike is quite upright. If the bike is causing the problem, does anyone have any suggestions as to what I could do about it? Also, I've found the bike is quite slow going up hills. I've tried it on two different gears; the 6th and on another occasion, the 2th, 3rd, or 4th (can't remember which sorry!). Having it in 6th gear seems to give it a bit more grip going uphill, but it's still slower than I would like. Also, the design of the bike doesn't allow me to stand up and pedal like my previous bike did. I also need lights and am wondering which kind would be the best to get? I often ride at night, anytime between 6pm-5am, so need to be seen easily. My bum also gets a bit sore on the seat and I slide forward, I can't seem to sit back on it.
Would seat suspension make a different to either the back or seat problem? Is it any good? The bike has lock-out suspension, but I haven't turned it on as I think it would make it slower. Any help would be appreciated.