Does anyone know how inner tubes are sized. I have 25x13.5x10 rear tyres and need tubes but cannot see what size I need
Do the sizes relate to the average width or diameter.

 

they are sized specifically for each tire. but one tube usually does about four or five sizes of tire. but if you put tubes in the tires and get on it good you will tear the valve stems and have a flat. so you may wanna just save your pennies and get some more tires.

 

Yes I'll be changing rims and tyres once I've worn the rubber out.I'll look up an equivalent tyre in 12 inch rims or whatever fits and is more common.
The exisitng rims have some pinholes in them and the tyre shop says they are designed for tubes although tubeless tyres are fitted.
I think he ordered a 22 inch tube, I'm assuming this is less important than the rim diameter