Quote:
Originally Posted by mans
these numbers are from way back when tires didn't have 3 numbers like we do today.
125/15 means 125(width)/R15 there is no number for the section height, just width and rim diameter
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When a tire doesn't have the middle number it's assumed to be 85 or the height is 85% of the width, more or less a round cross section of a balloon tire.
Reproduction tires for classic cars tend to be hit and miss as far as quality because they are designed for classic cars that have a top speed of 55mph and spend most of their life going to car shows.
Rubber compound has as much to do with low rolling resistance as anything else does, narrower tires are lighter weight and have less air drag, that is about it, low rolling resistance has more to do with tire deflection then how narrow the tire is, for low rolling resistance you want a tire that creates a foot print that is not as long, the flat spot caused by deflection is not as great so it is not climbing as large of a hill as it rolls.
That is why if you put me on a bicycle with narrow tires I have to pedal harder then if I'm on a bicycle with wider tires, of course the trend is that wide tires are soft and sticky, narrow tires are stiffer rubber, but how do you tell what is what? you look for the Low Rolling Resistance tires as they are often made with silica rubber, a stiff but grippy rubber so you get good traction with less resistance.