Is this a bad idea?
Got the puffer next week doing it on my 29er s/s but don’t want to shell out £120 on spikes that I might not use or maybe not for long. Have access to a set of 27,5 spikes and have spare 27,5 wheels that will fit. Opinions please

It’ll just drop the bb height a wee bit won’t it? Shouldn’t be too much of an issue I don’t imagine, though changing a bike set up just before a long event like the puffer would bother me a little on general priciple!

It’ll drop the BB a fair bit – there’s 38mm in the difference (assuming tyres are equal, they’re probably not so a few mm one way or the other there)

So it would drop your BB 19mm give or take – that’s three quarters of an inch. Really depends on your bike and the terrain as to whether that becomes a horrendous pedal striking nightmare or not.

Think of the mud clearance!