How can I check the wheel I'm buying is in good state?

[KevinvdV]

Assuming I can only test it for a few minutes. Are there things I should look out for? 

There's an offer for a V8 for around €475 which is very tempting 

[RockyTop]

Listen for the “clunk” when switching directions.  Some of the units have a weak weld that brakes between the axle and armature. Click Here to see a thread on V8 axle repair. 

 

[tudordewolf]

In my opinion, you can't be sure unless it's new. (and even new wheels occasionally have defects) My reasoning is that these things lead such a rough life. Any time you fall, or even just have to "bail" and land on your feet, they tumble and bounce and it's kind of incredible how durable they are given how much abuse they can take and keep on rolling.

Even a wheel with no visible case damage might have loosened / rusted out axle shims, or be only a few hard starts and stops away from burning through the motor wire insulation. 

Though i've had some solid experiences on this forum, (thanks houseofjob!) buying and selling used wheels is awkward just because I think they lose resale value so quickly that they're probably still worth more to the original owner - unless they're selling it for 50% or more off the original price, the peace of mind / warranty support on a brand new wheel is worth more than a 10-20% savings in cost.