I've been to a LBS and was fitted on a 54cm Bianchi'07 Bianchi
Via Nirone 7 (Tiagra).

I've recently found an 08' Bianchi (http://www.jensonusa.com/store/product/BI297C02-Bianchi+C2c+Nirone+Carb+Wfree+Ult+07.aspx) for a much better price but its a 55cm...

I'm a noobie and was wondering what they better deal was. I'm very concerned with fit and would like to know if the 55 would be too big for me..

Thanks in advance :)

What are your specs? Height etc.

I'm pretty sure that bianchi does not make a 54. They make either a 53 or a 55

That being said go with LBS if they treat you well. Remember you get free service on the bike for at least a year. And they usually give you a discount on clothing or other accessories

Yup, I picked up a 59cm from JensonUSA recently. Seems like they go by odd numbers on the Via Nirone. The next size up for me was 61cm.

im 5'8" 175

Do a search for those online bike fit calculators. They got me pretty much spot on. I'm 6'1 with a 33 3/4 inseam on the 59cm frame

Don't confuse inches (") with centimeters (CM).

1"=2.54CM

1CM=0.39"

I suspect those 2 Bianchis you are looking at are 54CM & 55CM (not 54" and 55" (unless you are 7' or taller)) so the difference is only 0.39" between the seat tube lengths. Check the top tube lengths of the 2 models and if it too is only 1CM different than that just isn't worth worrying about.

A quick seat post adjustment and perhaps a small stem change and if one fits you well than the other will too.

I'm 5'9" and the 55 and I have to use a 9mm stem. So you would probably be a 53. Of course this is just based on your height.

im 5'8" 175
52 or 53cm'd be my guess.

Keep in mind too that these bikes already have short head tubes. While the reach might be longer on a 55, you can make up for it with a shorter stem. If you can't get the bars up at a height comfortable for you you'll have bought the wrong bike.