Originally Posted by Thanas
Is it possible to run with "faster" bikes on 21/18 wheels, Yes. Certainly with road tires on the 21/18. But why have 21/18 wheels and put road tires on? You could go with 17/17 and put roadtires on, and have a Supermoto. But then off-roading through mud and sand etc. would be very difficult. Gravel and hard surfaces, it really doesn't mather what wheels or tires you have.
With the 19/17 wide rims, you can mount aggresive tires, which work well off-road, but because they are wider, also stick well on-road. And why care if the tires wear, that's what they are made for.
The point is. If you ride all types of roads in all types of conditions, and can have only 1 set of wheels, i think the 19/17 wheels are awesome.
As said before. Next bike I will definately have 2 sets of wheels. the 21/18 with knobbies for enduro/ off-road riding and a set of 19/17 with TKC80's for everything else.
That said, YMMV?
My point is I can ride aggressive enough on a KLX650 to drag my foot with a 21/17 and Duro 60/40 dual sport tires. It has a tread that can do all off road short of a full on knobby, yet hang very close with radial running SMs. No 2" drop in diameter or 1/2" increase in tire width is needed. It doesn't wash out the front and corners like on rails. That is on the strongest dual sport 650 single from Japan in spite of being out of the line up in the US for 16 years and outside the US for 10.
If you had some tank of a twin the extra grip might be needed for dual sporting, but it seems even the big twins came with 21s when they were set up for some dual sporting. Seems the 19 came in when it became obvious the trend was more street and less dirt. A 375 lb or less single just doesn't benefit in any great way, especially when you bring in the TKC80s, which are essentially DOT knobbies for adventure bikes stuck with the 19/17 wheels.
As I said, it is more about looks than reality. Same with the 17s on dual sports for handling. The standard 21/17 (or 18) can do the job very well on the street. Maybe not racing, but on the street. My only reason for doing 17s isn't due to handling and function, it's due to tire wear. I figure I'd rather wear out the dual sport tires in dual sport riding and have a set of purpose built road wheels to wear out street tires when riding the plain flatstraight highways and streets of central Ohio. That's why it's taken 14 years and 45,000 miles before doing the spare wheels. I never really needed them until about 5 years ago. I just hate to ruin good dual sport tires on street riding when I know I'm not going to get into any sort of dirt/gravel to speak of. Heck they could just as easily be a regular 21/17 combination with road tires and serve the exact same purpose, but that wouldn't look as cool.
If you like the adventure bike look of 19/17 great. It just doesn't really offer any advantage, except maybe psychologically. That is what I learned about 17s when riding with the supermoto riders, they don't give any real street advantage over the wheel/tire combination I have. And I know the bike/tires can be pushed further yet. I just won't take the added risk on the public roads.