I have been wanting to do this for quite sometime as chassis lengths are important to how your motorcycle reacts on the track. Sometimes we just go about our day, slap a different size sprocket on or cut our new chain a different length without hesitation. However, when you do that it can/does affect how your bike rides on the track. Usually race teams are locked in on a specific chassis length setting but in the real world we ride our bikes a lot longer before changing chains/sprockets/fork heights/etc. so I worked on getting you all a variance to be within. These specs below keep the most stability without sacrificing cornering that each bike gives in stock form. All of these numbers are with stock offset and stock gearing with Yamaha and Kawasaki getting a couple options (recommended fork height with these measurements are also next to each bike) If there was a gearing change that I felt like may benefit on a certain brand, those lengths are next to the sprocket size.
You can measure the swingarm length from the middle of the swingarm pivot bolt to center of rear axle.
You can measure the wheelbase from center of front axle to center of rear axle.
Option #1 2026 Kawasaki KX450: 13/50 Gearing (fork height 2mm)
Wheelbase: 1482-1489mm
Swingarm Length: 583-590mm
Option #2 2026 Kawasaki KX450: 13/51 Gearing (fork height 2mm)
Wheelbase: 1480-1485mm
Swingarm Length: 581-587mm
2026 Honda CRF450R: 13/50 Gearing (fork height flush-2mm)
Wheelbase: 1491-1495mm
Swingarm Length: 588-592mm
Option #1 2026 Yamaha YZ450F: 13/51 Gearing (fork height flush)
Wheelbase: 1482-1490mm
Swingarm Length: 580-588mm
Option #2 2026 Yamaha YZ450F: 13/50 Gearing (fork height flush)
Wheelbase: 1482-14mm
Swingarm Length: 582-584mm
2026 KTM 450 SX-F: 13/51 Gearing (fork height 3mm)
Wheelbase: 1490-1493mm
Swingarm Length: 595-598mm
2026 Suzuki RM-Z450: 13/50 Gearing (fork height 3mm)
Wheelbase: 1485-1489mm
Swingarm Length: 583-586mm
2026 Triumph T450-X: 13/49 Gearing (fork height 3mm)
Wheelbase: 1499-1501mm
Swingarm Length: 590-595mm
