Which is the wider tire?

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Which is the wider tire?

4.50x18 or 110/100x 18 ?

How are tires meaured? I know the last # is the rim size but what of the other two? Height and width? In what units?

And if 110 is metric, why on earth are they mixing units because the rim is still 18 inches?

I'm looking at a Pirelli MT16 for a rear tire for rocky mountain riding. What's the widest I put on a cfr450r? (I have a 18 wheel)

Any other tire suggestions?

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110/100 is an aspect ratio. The way to decode this is in this particular example is here:

110 = tire width in millimeters.

100 = % of height that the tire is from bead to top of tread in relation to it's width.

In other words a 110/100 tire is 110 mm wide and 110 mm high because it's aspect ratio is 100% of it's width.

I am running a 110/90 tire right now and it's 110 mm wide and approximately 99mm tall because 90% of 110 = 99.

Make sense?

As for which one's wider? I would say maybe the 110 tire. 4" = about 102 mm.

Edit: oops, didn't see 4.5" in your post. That's about 114 mm. So i guess you could say the 4.5 " is wider than the 110/100. But I've always heard people say they're the same pretty much.

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It really depends on the tire manufacture and where they decide to measure the width from. (It's not always at the widest point and I know... doesn't make sense to me either)

In the terms of 110/100 x 18, the 110 is the width in mm. The 100 is the height in percentage of the width, and the 18 is intended rim diameter in inches. The 4.50 x 18 is all in inches. When you do the conversion the 4.50 should be wider but in reality it is not. Again it depends on where the manufacture wants to measure from. I think some of the widest tires I can remember were the Tera-flex at 530 x 18. I think they also made a 520 x 18. The 520 would be similar to the 120/90x18 (if they even make such a tire in an 18" today) of today and the 510 would be similar to the 110. I may be off but this is how I remember it so far.

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If dirtbike tires use the same numbering scheme as car tires, a 4.5x18 is wider. a 110/100x18 is a 110mm (4.33 inches) with 100% of its height in its sidewall. So its 4.33 inches wide and is also 4.33 inches tall. It fits on an 18 inch rim. I don't know why they mix metric and standard, but all tires do. If you got a tire that was a 110/50-18 it would be 110mm wide, have a 55mm tall sidewall (110*.50) and would fit an 18 inch rim.