Tire Size?

Hi guys, i have on my 08 450 a 120/80-19 rear tire. I wore this thing out and purchased online a 120/90-19. I have done this before on my RM 2stroke, but when i brought the tire to the shop to be changed, he made it sound like i was going to screw the bike up. He said with that "big" of a tire i'll burn the clutch out??? Is this something i should be concerned about? I race occasionally but im not the greatest and im not quite there as far as tuning exact measurements so does anyone know what effect this will have for my bike?



Nope you wont burn the clutch out. The guys a dummy. I have typically always run the biggest tire I can find that works good. My dad runs a 140/18 on his ktm 200xc. Works great. If you are riding strictly motocross or track racing there might be some consideration for a smaller tire. For all around riding go bigger.

Wait a minute. You are riding a 450 ! The guys a super dummy.

The 450 motor is not going to care how big the tire is that is on it. The tire might effect overall handling feel of the bike but it should have nothing to effect the clutches performance.

From my experience about the only way to fry a 450 clutch is to ride it like a 125 in really tight single track. If you are going slow and constantly fanning the clutch you might get it overly hot but the tire wont be an issue at all.

I dont like a 120/90/19, although the bike will run it fine, it doesnt handle like the stock size. I found it to have to much drive.

The 90 measurement is the the tires height which would be 10mm more than you had. I don't think you will notice it much. Your bike will sit a little higher in back.

Alright great, little relief for me! You guys are awesome thanks for the responses!!


The '08 was built with the 120, so it IS the stock tire size. Any 450 can easily pull one. Some don't care for the feel of the heavier tires, and then again, tire sizes, like shoe sizes tend to be somewhat inexact, so the real size of the tire can vary quite a bit between brands, or even models within a brand.

Tire sizes explained:


they talk about this in May's MXA saying theYZ and KX's are not benefited by120's and should stay with 110's because of their "cornering problems"

you know i heard that when i thought about putting a 120 on my 250 2-stroke so i didn't and put a 110. guess it was alright on your RM? i would have liked the extra traction of a 120.....

On my 04' Yz450f, I ran the stock 110 width.......I switched to a 120, and the grip is definitely better. You will feel the bike slightly harder to "roll over", when cornering, but you will gain traction. I think guy's/gals' that demand the best cornering, are probably better with the 110. If you don't mind giving up a tiny amount of "roll-over" feel, than you'll appreciate the better grip of the 120. I think the 120 is more benificial for those who primarily ride off-road.

similar kind of question...

I'm looking at the dunlop D952's...will a 120/90x19 fit on my bike (03 YZ450f), and will it be beneficial for me to have the thicker rubber because I only do off road?

Read your link you posted.. Good topic. So you think that the 120/90 should be fine for me compared to the stock 120/80? Maybe just sits a bit higher. I also have a 50 tooth sprocket on that thing so i really think the bike should pull fine right?


The 120/90 is taller than the 120/80. In theory, it should be 108mm from bead the the base of the tread, as opposed to 96mm for the /80. The 120/80 is roughly the same height as a 110/90 (99mm), but slightly wider.

I personally don't like the 120/90's that I've tried that much, although I haven't used a 952 in that size, even though I run 952's in 110 all the time. The 120/90 feels heavier at speed and in the air, and I don't see a big difference in traction, really. I'd say it was a better tire for off road and desert than for MX on a YZF.

But, as I said, the 120/80 is different, and tires vary a lot, so the best thing is to try things and see what you like. A rear tire won't be on the bike that long in any case, so its' not as if you can't change it.

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