Originally Posted by spunkyruss
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It's a bad idea to use a tire that is skinnier than your rim.
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More accurately, it's a bad idea to use a tire whose stated diameter is less than 1.5 times the width of the rim channel. On a 19 mm rim channel on an ISO 406 rim, you should run at least a 1.5 x 19 mm = 28 mm diameter tire (406 x ~1.125" is not the same as a 406 x 1-1/8"). I use 406 x 1.35"... = 406 x ~35.