Just yesterday I noticed that my tyres soon need to be changed but my tyre size is 27.5 x 2.8 But the closest sizes I can find are 2.35, 2.4, 2.1. Those were the closest sizes I could find in store (because I don't buy stuff overseas). What should I do or which size will fit?

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    Possible duplicate of How are tire sizes measured?
    – ojs
    Commented Nov 20, 2017 at 9:49
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    Your tires are plus-sized, I'd advise to ask other local bike shops if they've got some or would order a set for you. Smaller sizes are most likely to fit OK, but you should factor inner rim distance into the equation, but 2.4" should be totally fine IMHO. Commented Nov 20, 2017 at 11:09
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    Note that you should probably ignore the inch metrics and use the ISO size to find a match. Commented Nov 20, 2017 at 19:18

2 Answers 2


'27.5' refers to the rim diameter, It is the same diameter as '650b' or ISO 584. The inch measurement tends to be used for MTB wheels, '650b' for road wheels. You obviously have to fit tires for the correct rim diameter.

'2.8' is the approximate tire width when mounted on a suitable width rim.

The inner width of your rims (distance between flanges) determines what range of tire width you can use. There are a few tables available on the internet that give general tire width ranges for different inner rim widths, but none I found cover the plus size range.

You can probably use tires that are narrower than 2.8". To make sure, measure the inner width of your rims in millimeters (a ruler is accurate enough), You should be able to find the rim width range that any model of tire is compatible with on the manufacturer's website.

An approximate rule for minimum tire width is no narrower than the outer width of the rim, preferably a little wider.


So you your tires appear to be 27.5+ sized, which are generally less common to find in bike shops and may require a fair amount of searching around for. I have faced these problems myself when trying to look for new plus bike tires but keep at it :)

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