The old 16", later 17" and current 18" front tyres are all very close in overall diameter, so their fit in the bike is similar. Really is down to which size you prefer.

 

Do you mean that I could fit any size wheel(front & back) on my '06 Ultra?

 

Whoa! That is a leap too far!

This thread is about wheels for a 2010 bike. Sizes of wheels changed, along with the entire frame, in 2009. For your bike look out for threads relating to earlier bikes. We shouldn't hijack this one!