Why does my back hurt after riding?

So you had no soreness until you changed your saddle? That is quite possibly the source of your problem. If you kept the old saddle, put it back on and go for a ride, see if your back gets sore.

Have you tried swapping the old seat back for a few rides to see if it helps?

EDIT - Hey I was typing this while you were typing your answer. Too bad I'm so slow.

No i have not tried to put back the old saddle cause it would make my BUM sore lol. I upgraded to this one just for that reason but now i feel it in my back. I guess i can try that and see how it goes. Do you have any other suggestions?

I would have your LBS check your fit if you could. It seems likely the seat is the source of the pain, but it may not be an issue with the seat, but an issue with its positioning.

Changins saddles could change where you pressure points are and basically shift your hips/seatbones to a new position. Your back is probably not used to the different pressures.

I noticed it when I changed saddles. No matter how close you put the new saddle position, it is a different saddle.

I agree it is most likely a fit problem with the new saddle.

Try adjusting the tilt of the saddle. The new one supports you differently than the old one and may need the nose higher or lower.

It could be many things. If you have weak core muscles, you will probably have pain during or after you ride. It could be the fit, it could be the saddle. It could be bad form in your cadence.

Soooo.. you should have a bike shop check your fit and your saddle, but make sure it is a shop that knows how to fit a person to a bike. Many bike shop employees know nothing about that stuff. But first, how is the mid section looking? How would you rate your core muscle strength? I find that many people who have back pain, have weak cores and need to strengthen them.

Well now that you mention cadence I did just receive my first pair of clipless shimano shoes and shimano clipless pedals. I forgot to mention that in my first post. I did switch over from toe clips.

Also, as for my physical condition I would consider myself in between average and above average condition. 170lbs, 5' 11" and workout 4 times a week and bike 2 more days a week.

Sorry for not mentioning the clipless pedal upgrade guys.

Thanks

Sounds like its time to get a fit from someone whom knows what they are doing .