Since you started..?
Generally it takes a good year to develop a problem.
Thats probably not good dude.
I had a sore back riding 17s, so i gradually moved my bars up 1 inch at a time til i was at 20, so i still had my tricks, but was riding 3 inches higher
im like 5'3 and i ride 18's...in the begining my back was screwed up for like 3 weeks. ive gotten used to it now though...my back is fine, and im getting 19 buffs in the mail like really soon so i will have to adjust
I'm 6'1 and my bars are 20 high I think... My back only hurts if I ride for long distances or times. I would raise them but I cut my t-tube, it's kinda only just in the steertube already.