Chain tightens and slackens while spinning crank
The chain on my my Wabi Classic started to "tighten and slacken" while spinning the crank. No adjusting of the rear wheel or moving the chain around to a different place seems to fix it. It didn't used to do this. I only noticed it when I had to change a tire a while back. When I mean tighten and slacken I mean the chain gets really tight then loosens. The crank and chain-ring don't "appear" to be bent nor does the rear cog. The chain doesn't have any tight spots/links either. Any idea what's causing this?