The perceived stretch could be belt slackness because of wear on the sprockets and belt teeth. Nitpicking? Maybe. Also, I could be wrong.
None of them are made from just rubber, though. The elasticity of that material is not a factor.
I’m not a touring guy but I hear belt drives are still popular in those things. They say it affects the feel because backlash is reduced and hitting the ends of the backlash is softer compared to shaft drive. They don’t do bumps and jumps so the rigid chassis required by the belt is not an...
A belt drive is less efficient when there’s no load or a low load. Anyone can see this by giving the wheels a spin when the car is on a pit stand.
Things change when you apply load and many critics of belt drives forget this. A belt drive under load is quite a bit more efficient than a shaft...