Empowering The Bicycle Traveler

Tire Sizes – Actual vs. Nominal

I had a question from a customer about actual widths for some models of the Schwalbe Marathon tires we carry. He is concerned about getting tires that will fit without rubbing on his fenders. I figure others probably have the same questions, so I have compiled a chart showing the actual measurements of some of the tires we carry. I will be updating and adding to the list. If there is a tire you want to know about, and it is not shown, just post it on the comments and I will try to provide actual dimensions for you.

I was going to go into some detail about tire sizing nomenclature but, as usual, the late great Sheldon Brown does a better job than anybody else could. So if you are unsure about what the size markings on your tires mean, check out Sheldon’s page.

All tires will be marked or stamped with the size. 700c and 28″ are two different nomenclatures for the same diameter.

As can be seen a 700c or 28" tire is actually neither. The numbers refer to the diameter of the tire when mounted on a rim and inflated.

The ISO/ERTRO measurement is the first pair of numbers

The ISO/ERTRO number is the most important in determining if a tire will fit on a particular rim. The second number in the pair is the diameter of the rim measured where the tire bead will seat.

This tire has a 622 ERTRO diameter and will fit on any rim with the same diameter measured to the points where the tire bead seats.

So called 29’r tires fit on rims with an ERTRO diameter of 622, but generally have a more voluminous casing so the overall diameter and widths will be greater.

So on to the Tire Width Chart. I measured the width of the inflated tire with a pair of calipers. The “height” is measured from the outer edge of the rim to the road contact surface of the inflated tire.

Measuring width

The "height" measurement

Chart shows nominal vs actual tire sizes.

Schwalbe Tire Width Chart

7 comments… add one
  • John Orme December 2, 2013, 1:45 pm

    I have an Argon 18 Arsenic cyclocross bike and I am trying to figure out if the Marathon Plus Tour 700 x 40c tire will fit between my chain stays. I measured the stay clearance and I have 43.5 mm. I assumed the ERTRO number which is 42-622, would make the width 42 mm to wide for my bike. Can you confirm the width of a Marathon Plus Tour 700 x 40c? Thanks

    Reply
    • Bike Hermit December 2, 2013, 2:30 pm

      John, one cannot go by Schwalbe’s ERTRO number for width. Schwalbe tires are, at a minimum, 1.5mm narrower than the nominal size…so 700 x 40 would measure at most 38.5mm wide. Sorry I do not have one here to measure but I guarantee it would measure less than 40mm wide.

      Reply
  • Brent Lorscheider November 9, 2015, 8:20 pm

    What is the outer diameter of a 622 rim. …im guessing around 635 or so? thx, Brent

    Reply
    • Bike Hermit™ November 11, 2015, 9:26 am

      That’s about right according to the couple of rims I just measured.

      Reply
  • Andy August 6, 2016, 12:57 am

    Thanks for taking the time to measure and post these sizes. I have some 26 x 1.6 Supremes and they measure 38mm wide. I haven’t checked the height. I also have 2″ (50mm) Big Apples and these are closer to 46mm wide. Both tyres were mounted on a Rigida/Ryde Andra 30 rim when measured.

    Some 700 x 35c Marathons I have measured 37.2mm wide on Mavic A719 rim and 35mm on Alex Adventurer. The tyre on the Alex rim is from memory a Marathon Plus but I can’t confirm because the label has worn off.

    One thing I’ve noticed in case it matters to some is that new tyres seem to expand or perhaps stretch a little once in use. The Big Apples gained a a mm or two in width after several rides.

    Have you measured the new tread pattern Supremes?

    Reply
  • Matt Benton October 15, 2016, 5:57 am

    Thanks for this guide. Shame bike manufacturers don’t standardise their sizes more.

    Looks like Schwalbe tyres come out slightly under the ‘official’ size. But they do stretch a bit. I just checked my Marathon Supremes 700 x32, been on the bike for a year and I reckon the actual width is 31mm.

    I’m looking to replace tyres on a old 531 Commuter/MTB – continental Traffic 1.9in actual width 51mm after 4 years. I don’t have great deal of spare width in the frame. But it’s nice to have the max width for comfort especially with 26 in wheels. Looking at your chart I’ll probably be ok with Marathon Green Guard 26 x 2.00 as the 26 x 1.75 comes out closer to 1.5in.

    Reply
  • mark January 2, 2017, 1:49 am

    Hi, great source of info, but any chance you could measure 700 x 35 Schwalbe Landcruisers. Thanks.

    Reply

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