Question: what size mountain bike tyres do i need?
Answer: Trail and all-mountain bikes will have tires in the 2.25" to 2.4" width range. Downhill bikes, which are meant to withstand the abuse of drops and rock gardens, are typically equipped with tires up to 2.5" wide. Fat bikes, which can be used for all-season trail riding, have tire widths of 3.7" to 5" or more.