Quote Originally Posted by violette View Post
I bought specialized pro tires size 700x23. They are narrow but I could go smaller. My LBS told me not to go any smaller 700x20 because it is dangerous. He said if you hit sand or gravel, you're toast! Does anyone here have narrower tires. I think the smaller the less rolling resistance???
Here's my experience with different size of tires, hope it helps.
I used 700x21 tubulars on a bike for about 2 years, but then when I changed from that particular bike I decided to go back to clinchers and to a size 700x23. Don't get me wrong, I did love the feel of the tubulars!!! They give you a more sharp ride, and the narrower tires definitely are a bit faster - but not enough that you would really notice the difference unless you race or do speed work.
Frankly, weighing the pros and cons, 700x23 offer more stability and higher resistance to puncture, and have a longer life compared to the 700x21.
I did try 700x25 once, but removed them right away after the first day. Those were definitely too wide for me - I noticed a lot more rolling resistance and no advantages.

All in all I think it's mostly personal preference, so my suggestion would be to try 700x23, then 700x21, and see what you like more. However, if you do not race, I would stay with clinchers either way because taking care of a flat on a tubular is really not a nice experience if you do not have a mechanic following in the car with an extra wheel...