Mates just shown me the bike he wants to SS.
It’s a Trek 7.1 hybrid (I think he wants SS mainly for winter road use) and has a 7 speed hub.
The DMR and On-One kits seem to only be for 8/9 speed hubs so I presume I can’t go down this route.
What’s the best/cheapest way round this problem other than a new rear wheel?

You could buy one of the 8/9 speed kits and file one of the spacers down or buy a kit with different sized spacers like this to fine tune the chainline.

The 7.1 uses a freewheel, not a cassette. A singlespeed freewheel will screw directly onto the hub (after removing the existing freewheel) but the chainline will be way out. You could maybe play around with axle spacing to sort it though.

Ahhhh…….. booger. Well he’s got two other bikes that may but suitable for an easy conversion, I’ll see what they are like.

I have ss kits for 7 speed cassette hubs, and also screw on freewheels. Please feel free to email or call me if you need any help on the conversion…

… one more of us – one less of them.