Can I put a 110/90 tire on a 1.85 rim? Website tire rim chart says I shouldn't...

Sep 26, 2005
Main questions for those who don't want to read the background information:
(1) Is it possible and safe to put a 90/90-21 size tire on a 1.60 (inch) rim?
(2) Is it possible and safe to put a 110/90-18 or a 110/80-18 size tire on a 1.85 (inch) rim?
According to the chart at I shouldn't do this.

Background to questions above:
I live in Thailand and have a Honda Degree dirt bike (I think that's the XL250). When I bought the bike from a local dealer, it had the Vee Rubber 2.75-21 tire on the front and a Vee Rubber 4.10-18 on the back. I don't know if these are the original size (stock size) tires or not, since this kind of bike is shipped to Thailand from Japan in parts and assembled here in Thailand, and the tires are obviously added on here, since Vee Rubber is a Thai-owned company. I lost traction on a rain-slick road a couple of months ago while testing my brakes (not a smart move, since it had only been raining for about 5-10 minutes, and the accumulated oil & grease on the road had apparently not washed away yet!). I went down at about 45 mph and the bike & I slid along the road for quite a while, throwing sparks the whole way. Fortunately, this happened on a straight stretch and late at night when there was little traffic, and I was wearing my trusty Fieldsheer Mach 3 jacket (recently lost/stolen) and a Taiwanese helmet (not great but adequate for that spill; I now have an HJC Symax - much better), so I wasn't hurt. That accident, along with comments I've heard about Vee Rubber tires being copies of Dunlop tires, and not as good, have motivated me to want to buy a better set of tires for my bike.

Since I do 99% of my riding on pavement, I'm looking for a tire that's made for pavement, but could work on dirt in a pinch. My first choice is the Pirelli MT60, especially after reading a review at Pirelli has just starting selling here in Thailand. The smallest size available here for the MT60 is a 90/90-21 front tire and a 110/80-18 back tire. My second choice would be the Dunlop Trailmax (also due to the review at, with the smallest sizes (I think) being a 90/90-21 front and a 110/80 rear. After that, I'm considering the Dunlop K560, with an 80/100-21 for the front and a 110/90-18 for the rear. (The Pirelli MT40s would fit my bike for sure, but it doesn't look like they'd give as good of road performance as the MT60s.)

Thanks to anyone who can help.
- Paul