(It's just marks on the tyres. not tyre). Tyre OD (outer diamter)=Tyre ID+Tyre width 2. ◈ Bicycle Accessories. ◈ Bicycle Parts. ◈ Bicycle Tools. Understand tyre sizes before order! "Fit Rim OD,Groove "--these two datas is the first & most important to make sure the solid tyre can fit onto your bike rim!
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