Eli5: Why do offroad bicycles have fatter tires while offroad motorcycles have skinnier tires?
In: 17
When it comes to tyres – on any vehicle – width is a balance between speed and stability.
Wide tyres are more stable, but slower. Thin tyres are faster, but less stable.
On top of that: How heavy and powerful your vehicle is determines the minimum width the tyres need to be in order to support the vehicle. You couldn’t put motorbike tyres on, say, a truck, for obvious reasons – it isn’t going to hold.
Putting these two facts together gives us our answer:
Bicycle wheels/tyres come in broadly three categories: [thin, slick road tyres](https://contents.mediadecathlon.com/p2035470/k$51774e160b325ec55c6d57ee5147ab34/sq/26×12-folding-bead-slick-mountain-bike-tyre.jpg?format=auto&f=800×0) for stable, smooth road surfaces, [mountain bike tyres](https://encrypted-tbn2.gstatic.com/shopping?q=tbn:ANd9GcSSt_tVLGmlW9NIPzf1kI-GNusnMWyjiJLLj-obSnfqz84PRCteC7gM7Mj8Iqmexk4vWJLHbeqW1o6Ov7fC4mpNeQ7GzGSP_gT1p8WSItUSWrLiBtmxNkh4Kw&usqp=CAE) for somewhat unstable dirt and gravel, and [sand tyres](https://www.tradeinn.com/f/13894/138948534/michelin-starcross–5-sand-62m-nhs-motocross-tire.jpg) for – you guessed it – beaches and other sandy areas. Bike nerds – I know it’s more nuanced than this, but we’re five years old.
If you look at the [tyres used by offroad motorbikes](https://www.maxxis.com/uk/wp-content/uploads/sites/4/2021/02/tyre-image-MaxxEnduro-1024×1024.png), they look like a heavier version of a mountain bike tyre. A motorbike is heavier than a bicycle and generates more torque, so the tyres need to be appropriately heavier.
And there you have it.
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