has this/can this be done? Any drawbacks?

been toying with the idea of getting 17" supermoto rims laced on my dual sport hubs - but wondering could I just do an 18" on front and continue with the 18 in the back. Might actually look more balanced than 17s given the copious fork height and ground clearance

Would the rim negatively limit the width of tire I could run?

I'm running Shinko 705 right now...

 

It sure can be done, there are a number of guys over at supermoto junkie who have done this for a cheap sumo conversion.

The only real draw backs that I can think of is finding a narrower 18 rim for the front so you don't get stuck with a overly wide front tire and i'm not sure anyone makes a sportbike type tire for 18" rims. So you may be stuck with less than optimal tires for the street if that is something you care about.

 

There is a decent variety of street tires, just not sport tires. Nothing wrong with doing any wheel size. Just realize what happens. The 18 may steer a bit quicker due to smaller diameter wheel that turns in easy and the front end having less rake and trail unless you make changes to keep it the same. Doesn't really hurt anything, you just need to start in relatively easy to start to see how the handling has changed. It will be totally rideable.

The matching wheel size may give it more of the American Flat Track Singles look, sort of a street-tracker. They lower the suspension though.



They're using a bigger tire than would be best on the 250.