Taking SCARY out of used bikes, one bike at a time.

Do Rims Wear Out?
There are a couple ways bicycle rims wear out. One is the braking surface where the brake pad contacts the rim. These should be flat without a curve. The depth of the wear can lead to cracking of the rim. This is unsafe to ride on because the brake has been comprised and can lead to a crash.
To check these you can use your finger or a straight edge like a ruler. Here you can clearly see the gap.
Yes, this rim is toast and you have the choice of replacing the wheel. Or if the hub is of higher quality and in good shape, you can have a new rim laced up.
If you do reuse the hub I would suggest new spokes and nipples when having it done. Spokes can wear out too and I’ll go over that at a later date.
Other things to check on rims and wheels are. Cracks around the spoke nipples on the rim. Rounded or damaged nipples. Flat spots (hops) on the rim as well as sharp bends. Plus the tricky one is cracks under the rim tape, rare but not uncommon.