18” or 19” Rear wheel?

Ede

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Mar 31, 2000
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#1
I have a KDX 200 SR with a 19” rear wheel.

It is very difficult (at least in Thailand) to get tires for this size. So I think about changing the rear wheel to 18”. I know that the bike is smaller after this modification what I don’t really like :( . Are there any other advantages or disadvantages between 18” and 19”?
 

Canadian Dave

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#2
The total diameter should be the same whether you are using an 18 or 19” tire. The sidewall will be wider on the 18” tire to make up the difference so you shouldn’t be concerned about lowering the seat height etc. Most enduro bikes use the 18” rear tires because the sidewall is wider. The wider sidewall better protects the rim from impact damage, which is a plus especially in rocky areas. 18” tires are typically heavier that a 19” tire making them a little harder to get spinning, a good thing when conditions are slippery, a bad thing when you are in the sand etc. I’m surprised that you are having troubles finding a 19” tire, that’s what most MX bikes are using. I’m guessing there aren’t a whole pile of MX bikes kicking around the Thialand country side though. Around here its 18” tires that are hard to find on the shelf.

David
 

Ede

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#3
Hello Dave,
thanks for the fast and interesting answer. Only for Info: It is not difficult to get Moto Cross tires in 19" here but nearly impossible to get 19" Enduro Tires.
 

jaguar

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#4
yeah I have the same problem. I import tires but couldn't find an internet business that offered a good dual purpose 19" tire. And the other day I bent my rear rim on a rock so now I've got two reasons to change to an 18". Jeff at MXSouth is extremely helpful and he suggested a new 18" Excel rim (#56-123 $109) and spoke set for '91 KDXs (#56-712X $58 and includes nipples although he said I may have to drill out the holes in the hub a little bit). Jeff can be reached at mx@pipeline.com
good luck
 
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#6
I also bent my rear rim last week and was wondering if changing rim width will make any difference. If so, what changes in performance or strength should i expect when going from a 2.15x18" to a 1.85x18" rim?
 
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Ede

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#7
Now I changed my rim from 19” to 18” but it is not 100% perfect. So here are two questions:

1. I have now the original Hub and a new Rim 18” x 2.5”. The spokes and the nipples are not perfect aligned but the “wheel specialist” told me this is always the case when you change from 19” to 18”. He said the alignment is no problem and if I have a problem he will repair it for free.
Jaguar wrote about that “although he said I may have to drill out the holes in the hub a little bit”. Any ideas about that?

2. I have now a rim 18” x 2.5” with a Dunlop D605 4.60 18” tire. It looks for me that this rim is wide compared to the original. What difference does the with of the rim make?