dirt bike wheel size?

[killerniceguy]

I know this is a Ducati Monster forum but you are all so smart!

I just picked up a 2005 KTM 300EXC.  What is the rational between a 19" and 18" rear wheels on DB? 

As a side note, I was able to register it as a street bike, although it will spend the majority of the time on the dirt as it was intended.  That being said I am going to pick up a DC loss light kit from sicass racing and some new wheels to mount street tires on.  For the time being I will stick with the OEM tire size and run some street orientated dual sport tires (Avon Gripsters) as I don't want to mess with the braking system on the bike.  Any recommendations on where to find a used set of wheels?

KNG

[Speeddog]

I haven't ridden a serious dirt bike since long before they had the 19" rears, so YMMV.

From what I've seen, there was something that the Supercross guys liked about the shorter sidewall.
For true off-road use, as opposed to closed circuit stuff, I consider a 19" a liability.
I haven't really followed dirtbikes for a long time, so perhaps the 19" tires aren't lower profile any more.

[Punx Clever]

Google says....

http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=EEA104E204554903B02ED1745A68004F

Also, for anything dirt bike related, thumpertalk is a good source,
http://www.thumpertalk.com/forum/archive/index.php/t-101490.html

General consensus is that for trail riding it provides a better cushion against roots and rocks to prevent flats, plus there is apparently a meatier dirt tire available in 18" rims (140/80)

[jwoconnor]

Larger diameter wheels may flex more for big jumps?

[JustDucky]

Try KTMtalk.com for great info and classifieds.  For the street look for a cushdrive rear wheel off an LC4.  It will help your clutch and tranny last on the street.  You'll need the cushies and sprocket carrier too.