Originally Posted by
u235
A much bigger factor is one tire model compared to another tire model. A 2c difference is relatively minor compared to what one model tire at some pressure can offer over some other model. There may be a 30c tire (are there 30c tires?) that may feel like a frozen garden hose compared to a different model 28c.
+1 Is there much difference between a 560 pound bear and a 600 pound alligator? Note also that tires are often not exactly the claimed width. The variation off claimed can be different for different sizes of the same tire, never mind, different manufacturers.
Probably your best bet - first measure the width of your tire. Buy a tire that is 2 mm bigger than what you measure from a shop under the condition that it is advertised size and you can return it if it is not. (If they don't want to do that, ask them to mount it on one of their rims of similar width and measure it.) Do take into account that tires stretch with inflation time so an old tire will be significantly bigger than when new. (The amount of stretch is not the same for different tires.) In short, this is not an exact science.
And as said above, the tires themselves can have differences in feel by construction that are larger than differences in tire size. I promise you that Vittoria's Corsa G+ in 28c are a lot more comfortable than many 32c or even 35c tires. (Cost twice as much too.)
Ben