I think the word you're looking for is tires. tiers are a different thing entirely, and won't do you much good ;).

Sorry, I could not resist.

by 23mm or 17mm i assume you're talking about the hex size ? So you need the rims as well ?

I like proline dish rims, 1/2" offset, and 17mm hex. For tires, I like HPI's aggressors, or HPI dirt bonz. Not quite as tall as the stockers, but they wear nice and provide good grip.

J.