tire size
 

I have an 04 Bianchi axis, and I want to put road slicks on it. What is the skinniest tire I can get on the stock wheel? I went to the bike shop and they gave me a 700x25, is that the lowest I could get?

I have 700x23 on the same wheelset, you probably could even do 700x20.

Will there be a big speed difference between 25,23 and 20?

I doubt you will notice a difference in speed. Of course the smaller you go the harder they are to change & you'll probably get more flats. What are you using the bike for mainly, commuting? If so, in my oppinion, i would stick with the 25's, they'll be fine.

DP

I was planning to ride in a triathlon this weekend, so I wanted as fast as possible

As a tool your wheel set may be the most important aspect of riding fast. If you were racing on a regular bike I would recommend a light pair of 700X20C , it limits rolling resistance, which will make you faster. However, cyclocross wheel sets are not that light to begin with, which will adversely affect your rolling resistance. Since your wheel set is not that light I would probably go with a 700 X 23C, to limit your chances of getting a flat. I would probably go with some foldable Continental Grand Prix 3000 or foldable Victoria Rubino Pro’s in the 700 X 23C. Foldable tires are significantly lighter then beaded tires, but cost about $20 more. I hope your triathlon goes well.

Thanks for the advice, for now I will probably just stick with the 700x25's then since that's what I got. Later I want to get a different wheelset, so I can easily swap them out. Any good suggestions for wheelsets and tires that won't put me in the poorhouse?

That depends on your definition of poorhouse?

lets say 2-300 max

The Alex 320 wheelset is not that bad at 1630 gr.
Compare to Mavic Ksyrium Equipes at 1835gr ($350), Ksyrium Elites at 1770gr ($550), and Ksyrium SLs at 1500gr ($850) and you have a veritable bargain. Plus the Ksyriums aren't even very aero.

Keep the ALX 320s and get light 700x23 and it'll be plenty fast plus be able to handle CX racing.

what if I was going to get another wheelset anyway so I can easily swap them out? Just another set of alx 320s?

Not sure what retail is but the FSA RD-400s are very nice & lighter that Ksyriums. If you can score a pro deal on them they are around/under $200. Retail would usually be double that plus some. The RD-200s are a bit easier on the wallet as well & I think they retail for about $350ish. They are all hand built too.

DP

RD-400s for $200? Sign me up!