The XT headset on the Catalyst had developed a stop slightly off-center a good while ago, meaning it seemingly worked smoothly but centered itself off-center.
It had been over-tightened.
This week I finally came round to inspecting the headset.
I found quite clear marks in the upper cup and...
First ride proved that the Roox Roller-Coaster is not a chain tensioner. It's a chain guide.
I'd need it to move more than the spring could handle. It bent as soon as there was enough tension on the chain for it to not jump over the cog.
And this while the chain was not even long enough in...