BRR is not promoting harder tyres to lower CRR. What it lets you do is compare CRR across different tyres at similar pressures. Generally, wider tyres with lowe

BRR is not promoting harder tyres to lower CRR. What it lets you do is compare CRR across different tyres at similar pressures. Generally, wider tyres with lower pressure gives better CRR than narrower tyres at high pressure. Happily, this is also more comfortable.