anyone know the difference between the two. Is the 90/90 wider?

 

Yes. The 90/90 is 3.65"wide were as the MH90-21 is 3.25"wide

http://www.dunlopmotorcycle.com/tire..._tire.asp?id=5

http://www.dunlopmotorcycle.com/tire..._tire.asp?id=6

 

And allow me to say....I's a world of difference on the road ! So much better with the 90/90 !

 

The Metzeler 880 90/90 mounted on my bike is exactly 3.5" wide

 

cool... 90/90 for the next tire then

 

Would ya'll be referring to these tires being installed on a 21x2.15" wheel?

 

will a mh90-21 tire fit on a 2.15/21 rim??

 

yes, and so will the metz 90/90-21

 

Try Avon. Their AM41 Venom is 3.7 in wide. 90/90x21.
I put an Avon RoadRider AM26 90/90x21 on my '10WG. This tire is 3.9 in wide.
Check Avon's web site.

 

MH90-21 is same as 80/90-21, so it's 10mm narrower than the 90/90-21 and the sidewall is slightly shorter (90% of 80mm vs. 90% of 90mm). Night Trains and Wide Glides come stock with the MH90-21, and a 90/90-21 fits np… I have one on a 2.15" x 21" smoothie in my sig pic.