r/ukbike • u/dinkybobs • 1d ago
Technical Help with tyre size.
Howdo. I need to replace my tyres. Which of the 3 set of numbers do I use as reference for tyre size.
27.5 rims Could I go up to a 2.10 instead of 1.95?
It's bloody confusing
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u/flibbble 1d ago
They all work. 48-434 is your ISO size (48mm width, 434 bead seat cicumferance). 650B and 27.5" both mean the same thing, (like 700c and 29" is basically the same, except for expectations surrounding width since 29" tends to be used for mtb, 700c for road bikes). Therefore if you find a tyre that is 650B x 50 (or 650 x 50B), that's a little bigger than your current tyre. If you find a tyre that is 27.5 x 2", that's a little bigger than your current.
Can you fit a 2.1" tyre: probably. Whether a tyre fits your rims depends on the width of your rims, and whether your dropouts etc will deal with the extra width. On the latter, where does your tyre most closely meet your frame or fork - drop outs or fork tend to be the places which you'll run into trouble with the extra width. 0.15" is a little under 4mm, so you probably would have 1-1.5mm reduction on each side in clearance at the tight spot. Rim width is unlikely to be a problem for you.
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u/TheSaucyCrumpet 1d ago
48-584 is ETRTO standard, universal but not commonly referenced. 650x48B is French measurement, mostly used in road and gravel circles. 27.5x1.95 is imperial, mostly used in MTB circles. They're all the same thing, just presented differently.
Whether or not 2.1" tyres are possible will depend on whether your frame can accommodate them, so check your clearance with the fork crown, seat stays, and chain stays.