Tighting, Cleaning and Lubing a Chain I get measurements under side. But I did it from the top as well. I think we measured a dozen times. After we take off the Chain guard. My dad's chain was out by 10 cm. It needed to be tighten. I think it has to be in between 30mm and 50mm. Basically by the foot peg on the outside of the chain push them together then pull them apart and those measurements should be between 30mm-50mm. Our chain was 19 1/2 cm and 9 1/2cm. So basically 100 mm or 💯 mm off. In told it was all my use😀 I've had lots of fun with it, but the chain kept falling off and I would have to put it back on. Lucky it never broke but buy another one if it did. I've been saying the chain needs tighting for awhile and since the chain falling off just stored it in my garage til it was my dad week to drive it. Then we got together ☺️ to do maintenance on it. We tighten it up to 35mm difference from loose to tight. A bit on the tight side, but one not...