Correlation between QR Skewers and Cassette Rear Wheels
 

I'm trying to help a friend in TX pick out a decent used bike.

I can spot a cassette rear wheel from across the room based on the lock nut. But he doesn't know what to look for.

Could I safely tell him that if it has a quick release lever on the rear wheel, it's almost definitely a cassette/freehub style wheel? In my experience, bolt-on rear wheels are always freewheels, and QR rear wheels are always freehub wheels.

Is this a pretty reasonable assumption?

Not at all, a lot of new bikes with freewheels have QR's. Hell, 20 years ago all bikes had freewheels with QR's.

No, you cannot say that. It would be better to tell him to count the cogs in the back, but that isn't entirely accurate in some cases also. I would tell him to make sure there are at least 8 cogs in the back for it to be freehub (which isn't always the case), but its a pretty good indicator and the easiest thing to do.

Again, I sell a lot of new bikes with QR's and 7 or 8spd freewheels so not a good way to judge. Best way to judge is the age/quality of the bike, if you can't recognize a freewheel/cassette just by looking at it for the prescense of a lockring.

Most popular bike at the shop is freewheel/quick release. Tell him to see the bike in person, then tell him what to look for.
http://www.lifecycles.co.uk/bikes/images/trek_3700_.jpg

You might want to refer him to my page about this:

http://sheldonbrown.com/free-k7

Sheldon "Kah Sept" Brown