# How does C width translate to inch width in tires?



## aBicycle (Jun 13, 2012)

What inch width would a 42 c tire be?


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## sbchisholm (Apr 10, 2011)

The 'c' can be interpreted as millimetres.


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## ryguy135 (Sep 24, 2010)

And so, take 42mm divided by the 25.4 mm to an inch and you get 1.65"


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## Wishful Tomcat (Mar 6, 2009)

I always thought the 'C' was the abbreviation for the speed of light.


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## Gasp4Air (Jun 5, 2009)

Trail6 said:


> I always thought the 'C' was the abbreviation for the speed of light.


Depends on the rider. In my case, it stands for the speed of molasses on a cold day.


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## cockroach (Jun 12, 2009)

Just to confuse you even more, 26 x 1.5 and 26 x 1 1/2 aren't the same!


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## PretendGentleman (May 24, 2011)

cockroach said:


> Just to confuse you even more, 26 x 1.5 and 26 x 1 1/2 aren't the same!


the important difference in this context is the required rim diameter. Width won't be much different.

The c number, as in 42c is a marketing number, so it tells you what the manufacturer thinks you want to hear, which is probably going to be fairly accurate when interpreted as millimeters. Tires also have ISO numbers, and sometimes a tire will even list two widths, i.e. for the casing and the tread. these numbers begin with 559 or 622 for 26" and 29" rims, respectively. so 700x42c might have an iso of 622x42 or 622x42x41.

Width depends on your rim's width, I'm sure ISO numbers are based on a specific rim width, though I don't know it or how it varies with the tire width, perhaps someone else can provide these details.


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## cockroach (Jun 12, 2009)

In this case there's a big difference, 26x1.5 will fit your standard 559 ISO 26" MTB rim.
26 x 1 1/2 is for an obsolete French rim size, 584 ISO.
Interesting reading on Sheldon Brown's site.


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