Sore back

Hey there
I'm a 'newbie' to the cycle game (only been doing it the best part of 1 1/2 years). I spin more than I ride on the road, but I do go out, a minimum of once a week with a club to do 60kms on a Saterday.
When I bought my bike i took care in getting the correct size and having it fitted to me. The shop even asked me to bring my shoes in to make sure the cleats were set correctly for the pedals.
Ok, so here's my question
On Saterday we did a 94km road race. It was a brisk pace (we finnished in under 3hours ) and the wind seemed to blow from the front constatly.
At 80kms my lower back tightened up and from there to the end I had this stiff, sore back. I kept trying to stand up and "arch" to stretch it out which helped for a min or two, but the wind made that difficult.
It seemed fine after I got off (at the end). I did take time to stretch, etc.
Now my question is, like the whole 'saddle sore" issue is this something that will get better with time, in other words as I get stronger/tougher,..... OR does this sound like a bad fitting bike ??
(dont want to cart my bike back to the shop and they fall on the floor laughing at me )
Neil

2 things: If you usually ride 60km once a week and now you increased it to 80-100, that's a big increase, so it may take time to adjust. Secondly, if you usually spin and that bike is set-up differently than your road bike, this may also impact fit and contribute to this issue.

Hi thanks for the responce.
You may be right I'll look into the spinning issue. I do think I've got the fit simmilar, but you never know. As for the distance ??, yup, maybe you're right. It's just that I did a slower 100kms the week before (broken up by two 5/10 min stops) and i didnt suffer as much. ???
regards
Neil

On each day you'll feel a little different and your body will respond differently, so maybe the sore back is an isolated incedent because of stress, bad sleep, or something unrelated to cycling.

Good luck.

Tight legs will also pull on your back. So try streching your hamstrings before and after the ride and whenever you get a chance.