It probably looks really stupid to post this after a dozen warnings to the contrary, but I have put a cracked disc in the drive with no problems.
A friend’s kids got into his DVD collection with predictable results and I helped him backup the worst victims. One had a badly cracked hub where the two edges were no longer on the same, flat plane. Ripped in my Lite-On 167T (which fortunately was a relatively poor reader, so the speeds didn’t get much above 8x). Sounded a bit sketchy as the drive was spinning up, but as I said, I wasn’t too fond of the thing anyway.
Just like a recovering crack addict though, I would advise someone to do as I say and not as I do.