The only way to know for sure is to measure them mounted on the same width rim and inflated to the same pressure.
Even tires with the same numbers on the sidewall will measure differently. Same manufacturer but different model tire; different measure, never mind different manufacturer.
The 120/80 should measure 120mm wide and 80% of that as the sidewall height.

 

If you're thinking of buying a 270, use the 4.50 rear. I think I read that that 4.50 was actually wider than a 4.60. I used the 4.50 and it was perfect.

 

I'm thinking bout the Mechlin t63 for a 60/40 tire now better tread than the 270

 

I went with the Sedona's again, same as the michlin HP4's.

 

I'm on my 3rd MT43. Love that tire. It hooks up in all conditions including mud. The knock on it is the deep sticky mud and although I've not had any issues in the mud, I can see where it could be a slight issue in the really deep stuff. I've not had any problems breaking loose the rear end when needing to. Maximus, we ride a lot of the same trails here in the Northeast...all I can tell you is I'm a huge fan and have it paired with an Pirelli XCMS up front. I'm averaging 2500-3000 miles on the MT43 with lots of those miles being on pavement.

 

Thanks bcliff, I just realized I got one with my KTM, I'm going to toss it on and try it out.

 

4.60 is a low profile 4" wide tire supposedly around a 60% profile, 4.10 is the same deal, a 4" wide tire with a slightly lower profile. Then, keeping in character with the bizarre inch measurement methods, there is the 4.50, which is actually about 4.5" wide. Go figure... stay metric, it makes sense.

120 is about 120mm wide (4.75" wide) with an 80% profile.

 

Tires seem to be a lot wider off the wheel, so you really have to go by the sizing listed on the tire. Although sometimes it is not completely accurate. My new 110/90 is considerably narrower than the 120/80 it replaces. Comparing the 110 off a rim to the 120 on the rim, they had about the same width, but not once mounted.

 

Have you run the 110 yet? What do you think?

Like I said, I went small due to past experience and what the competition bikes run, going to a 4.00 (slightly narrower than the 110). My sand experience (discounting the tipping over and breaking my ankle) told me I went the right way. I could pretty much rev it a bit, let out the clutch and churn my way out with the tire instead of having to slip the clutch more, which would likely be the case with a wider tire... unless I had one of those from a TW200 - then it would stay on top of the sand!

 

What kind of tire do you guys like to use for desert conditions?

If the trail isn't a rock garden, it's a sand pit. Can't choose TOO soft a tire or the rocks chew the *****, but too hard a tire would SUCK in the sand. No specific brands, but rather hardness and tread design. Would it be best to find a "non" dot tire for conditions like this? I'm noob when it comes to dirt bike tires.