M or XL frame?
 

My current bike is a Medium Size frame with a sticker on the frame stating that if your height is between 5'8'' and 6' the bike should fit you. I ride it a lot (55 kms RT daily commute to work) I don't feel that the fit is perfect but it's ok. I've bought a bike for parts and the frame size is XL (58cm) I wonder if it would be a better fit for me. By the way I'm 5'11''.

Thanks

ODP is right.

Type of bike matters. On a straight top tube road bike 58cm would probably pushing the large edge of the sizing envelope for sure. Is it assembled so you can at least ride it?

It's not a straight top tube, it's a Specialized allez 2005 frame. There's a few parts missing so I would have to switch parts from my regular commuter to this bike before I can test ride it, that's why I asked for advice before touching anything.

Thanks

If standover is a concern, you could always bring a pair of wheels, attach them, and stand over the frame when you check it out.

Not knowing the specific geometry, in general I'd advice that most folks your height would not take a 58cm bike but some absolutely would. Those with shorter legs and a long torso that would prefer to have a more upright position would do well on some 58cm bikes. Going from Med that only maybe seems to be off to an XL is quite a jump. I think it's worth a look, particularly if you have a long torso. If you know you have long legs for your height then I wouldn't bother.

I was looking at the Allez (great bike, but I got a killer deal on a CAAD10), and I think the 58 has about 1-1.25" more reach to the bars over the 56. I'm 6'1", 175lbs, and fairly normal proportions. I found the 56 Allez to be slightly cramped, and the 58 was a noticeable improvement. I preferred the 58, and found it very comfortable. I'm 2" taller than you, but if you have a long reach and inseam for your height then the 58 may fit be okay. Instinctually I would imagine the 58 might be a little on the large size though. Do you ride with a club, or know anyone with an Allez that you could possibly try out for fit?