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EX250 Wheels
General Information SOMETHING ABOUT TIRES, WHEELS AND ROTATING MASS GOES HERE Stock Wheels The stock rims are 16" in diameter. The front rim is 2.15" wide and the rear is 2.50" wide. Unfortunately there isn't too many tire choices for the Ninja's little rims but, the Dunlop GT501's are generally regarded as being the best. A 110/90 front tire requires raising the front fender about one inch. This is done by removing the metal bracket and drilling new holes in the fender about an inch below the old ones. For more details check out Jim Race's tutorial at ninja250.info. A handful of people feel that the Ninja's skinny front forks suffer without the extra rigidity provided by the metal bracket and get a Fork Brace to compensate. The GT501 rear tire's belts split after a couple of race weekends for me and I found that this affected my lap times so, I replaces 'em - other racers don't. Almost everyone uses a 130/90 rear tire but, if I was to go back to the 16" rims I'd try mounting a front 120/90 in back because I might prefer the more aggressive profile.
There's also the Bridgestones but, nobody uses 'em:
GET WHEEL WEIGHTS FRONT AND BACK - Shipping weight approx 55 lbs w/ GT5401's but no sprocket carrier. Kosman Wheels The Kosman weld-up wheels start off as standard EX250 wheels that have the diameter increased by one inch to seventeen inches and are typically widened some. Many people choose a 3"x17" front and an ~3.75" x 17" rear (mines 3.8"). You'll have to sacrifice a set of stock rims and about $1000 for this mod. The advantage is that with 17" rims you can run quality radial tires - Traditionally a 110 up front and a 120 in back (front tire). Jay Kinberger had some 3.25"/4.00" ones made up for 2003 and runs a 120 and a 150 tire on his Ninja and this size has become very popular since he won the 250p championship in 2005.
Originally I ran SC1's front and rear until Pirelli talked me into running an SC2 in back for the stiffer carcass (that's another story) toward the end of the 2003 season. Now I get about two race weekends out of an SC1 front and four out of an SC2 rear. If I'm forced to run an SC1 rear, due to availability, I might get one race out of it. You need to run slightly taller gearing with this mod even though the rims are larger because the tire's sidewall height is so much smaller. You're also giving up a little bit of ground clearance for the same reason and may have to adjust your fork height to compensate for the new, less aggressive, steering geometry.
GET WHEEL WEIGHTS FRONT AND BACK Alternatives If you've got lots of money to play with, Performance Machines will sell you some lightweight rims for about two grand. In addition to the massive bling factor, they're lighter than the weld ups and easier to mount tires onto. I've also heard that a 17" front EX500 wheel might be a straight swap but, that the EX500 rear wheel takes alot fo work to get the spacers and rotors to match up (for AFM production rules). I'd love for somebody to make captured wheel spacers for the EX250 similar to those made by Zip-Ty for dirt bikes. Allen Price does make a "speedo eliminator" wheel spacer for the front wheel which looks pretty nice but, Allen hasn't respond to any of my emails so, I don't know anything about it. Rim Widths Tire Size Conversions courtesy of the Dennis Kirk Catalog:
Helpfull Links
Tire Track - Sidewall Markings
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