I am very surprised with how the Trakmaster feels. It does make the bike wobble at high speeds on the super slab but nothing that sitting on the passenger's seat won't fix. I was riding 80 mph + yesterday. I am very pleased with the cornering on pavement. It is not squirmy at all and I can lean it way over. Of course the off-road performance is improved over the stock 603s. I also like the fact that I can virtually flat-foot bothfeett simultaneously, and I'mpretty short.
Here is the only downside that I can see. And it's a pretty big one. The braking on the pavement seems like it's going to be drastically degraded. Also I notice the tire breaking loose quite often on downshifts and during braking. Is this normal? Does it go away with the tire being broken in? I still have the stock 603s on the front by the way.

 

I believe its just the way the knobbies do that. I've just recently installed Kenda K270's, and noticed the rear tire does seem to lose some of its braking and locks a little more easy. But compared to the Dunlop 603, which is bald, its easy to understand that the new tires, with bigger knobbies flex and give more.

Answer to the oringal question. 4.60 would be a indcation of how wide the tire is. It does differ from the real world, but not much. I'm glad that when I ordered the K270's that I went up one size for the rear, wanted to get a 4.00x18 but decided to go to the 4.50x18. It was bigger than the stock, but no where near the 27" dia asadvertised. It measured 26-1/4", and probably once woren out, close to 25-1/2". Also the front tire did the same thing. Instead of 27.7", I got 27.25".