Can you imagine a dirt bike with 12" of suspension travel and vertical shocks? The shocks would have to be over 24" long. When you consider the reservoir, mounting eyes, etc. the shock would actually end up being nearly three feet long. Add half a wheel diameter to that and we've got a seat height of at least 4 feet....
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I basically stated this (in this thread or another similar thread) a month or two ago. Oh well.
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For the historians ....... Suzuki put a spotlight on this around 30 years ago when they introduced the 1975 RM125 with the long travel rear with canted shock absorbers.