I used to ride a 52cm bike (which fit very well). It was stolen about 9 months ago though, and now I think I I'm ready to get a new bike for the summer. I found a really good deal for a 53cm bike and was wondering how much of a difference that really is.

Depends on the geometry.

The two bikes I'm trying to compare are 52cm Trek 1200 and a 53cm Specialized Allez 2011. Hope that info helps.

Usually, no, but you'll need to check the geometries to be sure. Most bikes with a one frame size difference can be setup near identically by adjusting saddle fore/aft and stem length/angle.

The difference is very minor. Measured in cm, which is a fraction of an inch. I think people make way too much about having a perfectly sized bike. Ride the bikes. If it is comfortable, then you are fine. Even if it's not "perfect", you can adjust the seat in three vectors, change the stem for $20, and adjust the bars to compensate for the different size frames. You probably would not fit on a 60cm, but if you used to ride a 52, then I don't think a 53, 54...maybe even a 56 would be out of the question, especially when one brand's 54 is the same as another's 56. Don't get all wrapped up in a number. I don't think you will notice any difference between a 52 and a 53.

Yea, I figured. I tried riding a friend's 56cm once. I was able to reach the pedals and get moving, but I was wayy stretched out. haha. Thanks for the input guys!

TBH, it depends on the geometry. You just cant rely on the measurement from BB to Seat collar because a 52cm here isnt the same as the 52cm over there. Top Tube length is an important factor as well. Just try out the bikes. Because even within a millimeter of an adjustment can drastically change how the bike feels.

couple of cm.

well keep in mind that his bike was set up for him (or her), if your friend is taller than you then yeah, you'll be stretched out. i actually found that i like riding a bike that's sized 2-3 cm smaller than what's recommended for someone my size. i rode a 56 cm for a while and when i got a new bike this past weekend decided to test ride some 53/54 cm frames and i ended up going with a 54. the top tube is a bit shorter, as is the seat tube, but when the shop fitted me everything came out feeling just perfect with a slightly longer stem, which they swapped out for free from their parts bin.

just test ride various sizes and see what feels best, and PLEASE don't let them adjust your reach to the handlebars with a saddle fore/aft adjustment. the shop where i got fitted on my first bike did this, and being the ignorant newb i was, didn't realize it compromised my leg positioning and i've been battling a case of patellar tendonitis ever since. adjust the seat height and fore/aft to get the proper fit for your lower body, and then a new stem (if necessary) for your upper body. you can pick up decent stems for $20-$30.

This.

Went from a 54cm Trek 2100 to a 52cm CAAD10.....huge difference. 54cm had me stretch out to the point where I was holding onto the top curve of the bars as opposed to the hoods for 90% of my riding on the Trek. Geometry on the CAAD10 is racy, with a longer top tube than a comparable Trek. 52cm was perfect on the CAAD.

If the trek is not compact and the allez is compact it's a big difference. I ride a 56 trek 1500 (not compact). It's a touch on the big side, but fits fine. If I picked up a tarmac or allez today a 54 would fit perfectly. A 56 would be way too big.

My Felt was a 54. I'm only 5'7", but it always felt a bit small. My Giant is a M/L and it says right on the sticker 5'10"-6'. It feels much more comfortable than the Felt and a lot more stable at higher speeds. I am however going to switch to a shorter stem. It has a 100 on there now, trying out an 80 today (that's one of those things that sounds like a lot, but it's only a 3/4in difference). The moral is to not get overly concerned about numbers. If it's comfortable, it fits.