irrotational Posted September 30, 2011 Share Posted September 30, 2011 😳 I have bought some steelies, which I think are 14", however when I measure across the face they are just over 15"? BUT my 13" caterham wheels measure just over 14" across the face. Is there some other part of the wheel you're meant to measure? If so, I assume the difference in size will be about the same on most wheels so my 15"ers will in fact be 14" fr tyre buying purposes? Link to comment Share on other sites More sharing options...
Lotus Boy Posted September 30, 2011 Share Posted September 30, 2011 Interesting one. I've never measured a diameter to discover that. I'm no tyre/wheel expert but I wonder if the diameter is reflecting the 'bead' diameter of the tyre that would fit it. That is to say, if you measure the width of a wheel it is the distance between the sections where the tyre bead would sit on the wheel, NOT outer lip to lip - so I wonder if it the same for the diameter value. Not that that would be as easy to measure with a ruler! be interested to hear from someone more knowledgeable. cheers David Link to comment Share on other sites More sharing options...
6speedmanual Posted September 30, 2011 Share Posted September 30, 2011 You need to measure where the tyre beading sits. Not the full diameter of the wheel rim. The sizes are almost always marked (cast in or stamped in on steelies) somewhere on the wheel. The flange probably is about 1/2" on most wheels hence your reading being +1". Peter Link to comment Share on other sites More sharing options...
tbird Posted September 30, 2011 Share Posted September 30, 2011 more info on wheel sizes than you can shake a stick at Tim Link to comment Share on other sites More sharing options...
irrotational Posted September 30, 2011 Author Share Posted September 30, 2011 Quoting Lotus Boy: That is to say, if you measure the width of a wheel it is the distance between the sections where the tyre bead would sit on the wheel, NOT outer lip to lip - so I wonder if it the same for the diameter value. That was my pure guess but i wanted to check - thanks to others for confirming and the diagram in the link is useful! I will order some 14" rubber to slip over my rim... Link to comment Share on other sites More sharing options...
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