[simonbarker87]

Not sure how valid this really is for mountain bike tyres as the terrain is so varied.

For example if you run an MTB tyre hard it will bounce around on a rocky surface and roll less efficiently than if you run it at lower pressure that allows the tyre to deform and bounce around less.

Interesting site nonetheless and a useful data point to compare tyres in a systematic way.

[bluecalm]

It turns out the test is remarkably useful: fast tires on BRR are fast tires on various terrains. It turns out that fast tires are fast on everything and slow tires are slow on everything. It's true you can't say that about pressure (high pressure is slightly faster on perfect road but much slower on not so perfect one) but when it comes to tire choice it's a very good resource.

[bradfa]

It isn't valid for mountain bike tires, except for when you're riding your mountain bike on a smooth road.

The only tests which BRR does which are likely applicable to mountain bike tires mounted to mountain bikes ridden on trails are the puncture tests, as you're likely to find sharp objects even on trails. Maybe the wet grip tests matter, if you often encounter wet large rock that you ride on.