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Why the 19" rear wheel on MX bikes?

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did you know theres a search feature on this board?

this has been discussed here before, they did it to sell more 19" tires to Canada.

🙂

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Just curious why they put a 19" rear wheel on the MX bikes when the others have an 18". Thanks

That's a good question and while I'm not 100% sure, I think it's designed so there is less flex of the tire's sidewall. I read the 18" and 19" rear knobbies are the same outside diameter. 18" for trail use and 19" for MX.

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Thanks for the info, Vector. I'm quite familiar withthe search feature, when you type in 19" wheel (s) nothing comes up, hence my question. I hope the Canadains are getting their tires.

Mr.Gadget, I wondered about the side wall flex when I noticed there was almost an inch less sidewall than my 18" on my X. Proably has to do with jumps and hard turns.Thanks, Pete

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did you know theres a search feature on this board?

this has been discussed here before, they did it to sell more 19" tires to Canada.

🙂

No one respects a smarta$$... You should always make sure the answer is there before you mouth off about using search... 🙂

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the differenece is side wall. Mx bikes using 19inch tires have a stiffer side wall then say a trail bike with an 18inch rim. You get less flex in the side wall on an mx bike which is how you want it. Hope that helps.

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well for a few reasons. A larger side wall will be less likely to pinch flat. Since you generally dont run a ton of pressure in the tires you want as much movement as possible without pinching the tube. I think the larger side wall also helps absorb some obstacles without greatly compromising traction. Like small roots, rocks things of that nature and helps you stay planted. In motocross you generally dont need to worry about that. You want a stiff sidewall so its more predictable and you dont have great amounts of tire deflection, especially when railing a berm.

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well for a few reasons. A larger side wall will be less likely to pinch flat. Since you generally dont run a ton of pressure in the tires you want as much movement as possible without pinching the tube. I think the larger side wall also helps absorb some obstacles without greatly compromising traction. Like small roots, rocks things of that nature and helps you stay planted. In motocross you generally dont need to worry about that. You want a stiff sidewall so its more predictable and you dont have great amounts of tire deflection, especially when railing a berm.

YOUR RIGHT I THINK

JUST LIKE THE TRIALS BIKES USE SURGICAL RUBBER TYPE TIRES WITH LIKE 5 PSI FOR TRACTION

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tyre cross section profile + 19" wheel and tyre is lighter

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Another advantage of a 19" tire is less rotating mass. This allows the wheel to spin faster with less engine effort. Also, the reduced sprung weight helps the suspension work better. One drawback is that with a shorter sidewall, mounting is slightly more difficult. I can swap a rear tire on my WR in 20 minutes with a little sweat. On the YZ it takes about 35 minutes and a lot of sweat.

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