Front tyres have single tyres, the other tyres are dual rims. The rims are fairly similar – a dual tyre has two of them back-to back, but the front wheels only have one of these rims. It is mounted ‘backwards’, much like an ordinary car tyre is, so that the wheel and its load is closer to the pivots and bearings, reducing the leverage you’d get by mounting the wheel the other way, holding the wheel away from the hub.
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