Vintage 27" tire width?
 

I'm still confused about tire and wheel widths.

The 1984 Trek 620 came equipped with 27" wheels and 1 1/4" wide tires. 1.25 inches converts to 31.75 mm.

So if you set that vintage wheel next to a modern 700c road wheel with a 32mm tire mounted, would they be pretty close to the same width?

Thanks!

Yes.

Thanks!

Yes, some tire sizes are indicated using fractions of inches, some with decimal fractions of inches, and some in millimeters.

Note that not all tires run true to their label or callout sizes. Continentals I have owned run small (700Cx28 being closer to 25 or 26mm), whereas Specialized have run full or even a bit larger (same 700Cx28, more like 29 or even 30mm wide). Mounted tire width is also affected by rim width, but, yes, 700Cx25 should be about as wide as 27 x 1", 700Cx28 should correspond to 27 x 1-1/8", and 700Cx32 should come in around as wide as 27x1-1/4".

Roughly.

And 27 x 1 3/4 is *about* 35mm.

Close enough for government work.

John E. brings up an important point, as you also may want to investigate as to which tire brands run more true to size and which do not(--run smaller width--)

Michelin Protek (32 x 630) 27" x 1 1/4 tire is probably among the wider ones, as most cheat.....
(This is a great tire, however it's weight in grams is among the heavier tires in that size..................)

I have some Kenda knobby 27x1 3/8" that are barely 32 mm wide, even on a wide rim. Nashbar branded tires (from the pre-bankruptcy company), always were smaller than the stated size. 27x1 1/4 was 28 mm. 700x 35 mm was 32 mm. All the Pasela tires I have bought in 27 inch sizes were true to size.

And tyres, like waistlines, tend to grow as they get older. Basically, the cords in the casing relax a bit and stretch.

No, you're thinking of 1-3/8

Yup! Sorry!

Numbers and me don't get along to goodly.