18" rear wheel on a 04 YZ450F

I do mostly woods riding here in New England (very tight single trail.. low gear stuff, rocks and roots) and I've read that some people use an 18" rear wheel for the trails. What will I gain from going to an 18" rear. How is the handling affected and will I need to regear because of the diameter difference?

18" wheels are used offroad mostly for more compliance (smoother ride) & better resistance to flats when riding over trail junk like rocks, roots.

The overall diameter doesn't change much, since the 18" tire has a taller sidewall than a 19", it makes up for the smaller wheel.

So it looks like it's all about compliance, a smoother ride and less resistance to a flat. I didn't know the sidewall height was smaller on my 19" rim than an 18" rim.

I run the stock size of 110/90 - 19. If I get an 18" wheel, what tire size should I run?

If I get an 18" wheel, what tire size should I run?

110/100-18

I use an 18" wheel on my '06 and my son's '02 426. The extra sidewall is nice for rim/flat protection. You can get away with lower air pressure with the 18" wheel for better traction in the gnarly stuff too.

There are several sizes available for the 18" wheel. 110/100, 120/90 and the big burly 120/100. The other nice thing about having an 18" rear wheel is that you can run a trials tire if you want.

What tire size do you guys recommend for very tight single track stuff? I did a hare scramble recently and never got out of 2nd gear. I'm new to hare scrambles but I did finish 15th out of 22 in the seniors class, woowee that did kick my ass.

Try a 120/90/19 rather than a 100/90/19 and see if that gives you more traction. Only 10mm wider but it is a little noticable. I just put one on mine.

I have a heavier flywheel on my YZ, I'm tryin to get the power down on the trail here and I've been playing with gearing. I think you may be right, a 120 may reduce the power somewhat and give me more traction.

I have a heavier flywheel on my YZ, I'm tryin to get the power down on the trail here and I've been playing with gearing. I think you may be right, a 120 may reduce the power somewhat and give me more traction.

I also have the Dr. D. 6oz flywheel weight in addition to the 120 tire and it does help.

I use the smallest 18" rear tire I can for the mountains and single track. The smaller tires just handle better. Be cafeful not to go to big if you are wanting to slow tire spin. I ran a huge Tera Flex once and really hated it. It robbed the power everywhere, was heavy everywhere and handled like crap. Some guys like a bigger footprint on their rear tires, I am not one of them. I like the feel and control of a small rear tire. See what works for you.

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