I have no idea why, but today I started to get the ‘popping’ sound on hills that tells that the drive belt is too slack. I pushed it uphills so as not to wear the pulleys by slippage and rode it on the flat until I got back home. The SLO has been ridden about 250 miles and never a ‘pop’ until now really and when I investigated, the BB was tight and seemed well secured by the adjustment hex screw. I suppose it might be possible that some mighty torque applied by me on a hill made the BB slip around even though the securing / adjustment screw remained seemingly secure, but I don’t feel it is likely. Another possibility is that the rather warmer temperatures of today have made the belt expand (it is 10c here now, and the bike has been ridden in somewhat cooler temperatures of around -3C to about +5C). However, the belts are not supposed to react like that. Kevlar has a strange negative expansion when warmed. The belt is supposed to be kevlar reinforced, so that shouldn’t happen if it’s true.
Anyhow - I adjusted it and all seems well now, but I don’t have a lot of adjustment left if there is any more expansion. Nothing else can move as far as I can see, so either the belt has stretched or expanded, or the BB slippped around.