Hiya. My hybrid bike has 26 x 1.75 tires which I feel are quite thick for my work commute (12km road). I ordered 26 x 1 3/8 tires and when I tried to put them on I noticed they are way too big. When I compared them to the 26 x 1.75 that I currently have on the bike, the outer circumference seems the same but the inner seems way bigger. (Ie there is less tire).
Am I missing something?
Any help would be appreciated greatly!
by Toprocker3
3 Comments
26″ tyre sizing is confusing, there are five completely different tyre sizes that are all marked 26″. The 26 x 1 3/8 tyres you bought are for a 597mm BSD rim, whereas you most likely have a 559mm rim. Look for some 26″ tyres where the width is expressed as a decimal (i.e. 26 x 1.75) not a fraction.
This page is useful for getting your head around the madness of tyre sizing: [https://www.sheldonbrown.com/tire-sizing.html](https://www.sheldonbrown.com/tire-sizing.html)
Look for a number like 590 or 597 or 559.
This is the bead diameter, this number needs to match your old tire / tube.
26 fractional was an older size that was common on some Schwinn, or 3 speed type bikes.
I think your tube is for this style and may not work with your set up.
> Am I missing something?
Yes. 26 is a series of wheel sizes in a trench coat.
Decimal 26 (for instance 26×1.75) has a rim diameter of 559mm (iso diameter). This is the mountain bike 26 that is still used.
Road 26 or 3 speed 26 is larger and is measured as a fraction (for instance 26x 1 3/8). The iso diameter of these is 590mm. This is an older standard that isn’t common anymore (been replaced with 650c, 700c and 650b these days, sometimes decimal 26).
There is also Schwinn S6, iso 597, but is is an antiquated size only widely used on chicago schwinns.
Lastly there is 650c, iso 571. It is sometimes called road 26, and was only ever found on childs road bikes (sometimes size xs or s normal road bikes as well). This has also completely been replaced with 650b and 700c on these bikes now.
What you need is a iso 559, or a decimal 26.