How Much Slack Should A Bike Chain Have. Maybe if you go to a bike shop. The chain slack that you can move by hand length SS see Figure 74 should be about 4 percent of the span length A-B unless one or more of the following conditions apply.
1216 inches 3040 mm is typical for streetbikes while dirt bikes may need 1420 inches 3550 mm of slack. The above assumes the bike has no derailleur. And if there is too much slack then you need to tighten that chain.
When the bike is in the smallest rear sprocket and smallest front chainring a chain that is too long will sag between the derailleur and the chainrings.
They should have a just discernible amount of slack. Chain will gradually stretch over time so keep an eye on it and adjust tension as required. Rotate the crank clockwise to take up the slack on the left side. What happens if bike chain is tight.
