The vast array of tire widths available can be confusing. Here are some general guidelines:
21mm
– Ideal for triathlons and time-trials
23mm
– General road racing
23mm – 32mm
– Training and general daily riding
If you have the luxury of changing tires based on weather conditions a thinner tire at regular pressure is best for dry roads. If it’s wet out go with a wider tire at a slightly lower pressure.
The same guideline applies for smooth roads vs rough roads. Smooth roads = thinner tire and higher pressure. Rough roads = wider tire and lower pressure.