exact diameter of tires

most of the trials unis have 19" rims but its written on tires "20 x 2.5" isnt the 20 the diameter? is the 20" tire compatible to the 19" rim? im going to buy a new tire now and I wanted to know exactly because its not me whos going to the store but a friend wholl be in germany. help me out!

Noooo!!! it wont fit.


of course it will fit…nobody makes a 19 inch tire except monty so just get a 20x2.5

This is a link to a site that lists most cycle tyre (tire, my spelling :wink: ) sizes and the compatibilities, as well as the correct size for (again) most of the weird :thinking: sizes the cycling industry has come up with. A 17 X 1 1/4 is bigger than an 18 X 1 1/8! And a 26 X 1 1/2 is bigger than a 26 X 1.5! Thankfully there is a trend to standardizing - ask your LBS to use ISO sizing and if they don’t know what it is, printout the chart and give it to them, they need it.

Sorry, a 20 X 2.5 isn’t on the chart, I guess it’s too weird.

If you check out the tire chart on unicycle.com you will see that the 20" trials tires fit on 396mm diameter rims whilst standard 20" tires fit on 406mm rims. This is why the the 20" trials rims are sometimes referred to as 19" rims because they are smaller than standard 20" rims, and trials tires are referred to as 19" tires because they fit on these rims. Using the metric sizes of the tires is often more reliable of checking what rim they will fit, but nobody but the French uses metric.