Another Zwift Cog compatibility question

My buddy is looking at getting the Zwift Hub One. He’s concerned by this line in the Cog description:

Zwift Cog works with almost any 8-12-speed bikes

He’s got a Diamondback Lakeside hybrid bike from 1997. The cassette is a 7 speed with 11-28 teeth. The chain is listed as 1/2 X 3/32.

My thought is that he might need a spacer to get the Cog into position, but I defer to the experts here. Can this 7 speed work with the Hub One? Many thanks!

In reality all you need is for the rear mech to be aligned with the cog in a straight line so it doesn’t really matter how many gears etc…No spacer needed.

The issue you have is that the distance between rear dropouts on 7 speed is narrower than the mounting points on the Zwift Hub.
It will work but you’ll have to bend the frame a touch for it to fit. After that it’ll be fine. Just put it into a gear that’s aligned with the cog.

I am in a similar situation with 135mm dropouts and a 7spd mountain bike. I don’t have a Zwift Hub One, I have a Zwift Hub (original). Not sure if I will be able to get the Zwift cog to work. I’ve got a few questions. Can it even work with the original Zwift Hub? When you mention bending the frame, how do you even do that?

You don’t need to touch the frame. A frame with 135mm axle spacing will work fine. You are not obliged to use the Cog - you also have the option of putting a 7 speed cassette on the trainer.

If you do use the Cog you may need to put an 8 speed chain on the bike if it rubs on the plastic guards. (And if the chain is old, you should definitely replace it.)

I would like to use the cog, wondering if it can work with my 7spd bike.

Yes it should work fine. Zwift recommends it for bikes with 8 speed drivetrains (or more) but there is nothing stopping you from putting an 8 speed chain on your 7 speed bike if you have a 7 speed chain that’s too wide for the Cog. Many chains sold these days are marketed as 6/7/8 speed compatible. For example:

Great, thanks I might give it a go. I’m a total noob at any work on bikes. Would the be cutting the chain at the same length as my current 7spd, assuming my 7spd chain doesn’t work, or would it depend and I might need to make it shorter/longer?

My 2019 Stumpjumper (148mm boost) did not work with the cog, the inside of the chainstay fouled the outer plastic bulb thingy.
When I refit the wheel to the bike I can see the clearance to the cassette is pretty darned tight at that point and as the cog outer portion is so bulbous it’s never going to work.

Thankfully my wife’s whyte hardtail works fine, (135mm QR)

Check the clearance you have with the cassette.