The drag-race tendency to lengthen the swingarm by drastically lengthening the wheelbase has all sorts of bad side effects in terms of handling. Obviously, a longer swingarm achieved by moving the swingarm pivot forward (and leaving the wheelbase the same!) is something that is only possible to achieve when the chassis layout is still in the design stage on a computer screen. Having the swingarm longer opens up a bit more flexibility in this regard by making the anti-squat change less with suspension travel. This is also why on superbike applications, the swingarm pivot height and swingarm angle and ride height setting and sag setting (all of which are inter-related!) are so critical. if the rear of the bike is sitting a little too low you get less anti-squat which means it squats under acceleration and becomes a lot too low. With motorcycle suspensions the amount of anti-squat actually changes in the wrong direction with rear suspension compression. Having a longer swingarm means the angle of the swingarm changes less with suspension movement, and this means the amount of anti-squat in the geometry changes less with suspension movement. This is why the engines mostly have stacked transmission shafts nowadays - it allows the swingarm pivot to be pulled forward. Click to expand.There has been a trend from the manufacturers towards (slightly) longer swingarms, achieved by shortening the engine and moving the swingarm pivot forward in the chassis.
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