# Will the 26" tyre fit my 25" rim bike?

I have this 2002 Esperia which, and I need to change the tires cause I am getting back to it. The tire dimensions appear to be 25 x 1.90, 50-559. I read a bit about these new and old dimensions specifications, but I cannot find 25" (or col, I am not sure whether it's inch or col) in the online stores, but I can find 24" and 26".

Any advice? Will all (or none?) 26" fit my rim or what?

Additional question - I plan to ride on roads. Do I get slick tires?

• I'm pretty sure that 25" does not exist. Have you actually measured the diameter of the wheel? 6 can look like 5 sometimes :) Aug 30, 2015 at 19:37
• Yep, you nailed it, 13 years made 6 look like 5 :P Aug 30, 2015 at 19:41
• 25' tires? you must be a giant. ' is for feet, " is for inches Aug 30, 2015 at 19:43
• Sounds kind of ordinary sized to me :-)
– dlu
Aug 30, 2015 at 19:58

The significant numbers are the "50-559" which translate to 26" x 1.90" – my best guess is that what you're seeing is a molding problem that causes the '6' to look like a '5'. The 50-559 is the ISO size of the tire. The first number is the width (50 mm) and the second is the "bead seat diameter" (559 mm).

Beware of 26" tires – there are two sizes that are called 26" and they are not compatible. The easiest ways to tell them apart are by the width where you will see either a decimal width, say 1.50", or a fractional width, say 1 1/2". The other method is to compare the ISO size which would be something like 37-559 for a 26 x 1.5 inch tire or 37-590 for a 26 x 1 1/2.

For riding on roads slick tires are nice, they give you the largest contact area for a given tire size. You need to balance that against durability and availability. Tires like the Schwalbe Marathon are built for durability, but aren't really slicks (at least not in the sense of a tire like the Kojak). Do look for a tire with a "slick" strip down the middle which is where you'll be riding most of the time.

• One more question, if you can help me - Can I put 26 x 1.40 tyres on my bike? I'm browsing in the online store for the slick ones, and they seem to have smaller second number. Currently my tyres are 26 x 1.90 (they aren't slick, for what I can visually tell). Looking at this one, specifically: bike.hr/vanjska-guma-byte-tures-26-x-1-40.html (it's in Croatian, sorry) Aug 30, 2015 at 19:59
• Probably, that would be going from a roughly 50 mm wide tire to a 37 mm wide tire. You wouldn't have clearance issues since you're going smaller, but depending on the inside width of the rim, you might be pushing the limit of how narrow a tire will fit well. This table of rim to tire widths from Schwalbe will help you decide if it is a good fit.
– dlu
Aug 30, 2015 at 20:04
• Update: I found the rim size, it says "Sanremo 20 x 559" Aug 30, 2015 at 22:23
• In the second photo I see what looks like a label with 20x559 written on it. If I'm seeing that right, I would guess that it's the rim size and 37 (ish) mm tire should be fine on that. Good job, I see you beat me to that…
– dlu
Aug 30, 2015 at 22:29