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OK, but just remember, you started it...lolOriginally posted by RandyO
ALL Other things being equal. yes I WILL START
You are basing you statement on the equation F=MA ( force = mass x acceleration for the non mechanical types) and that is true, but the disscusion is about resultant damage in a motorcycle crash, not a steel ball impacting a concrete wall. Damage to a motorcycle is more dependant on the size, thickness, and choice of material, not just the total mass of the motorcycle. Lets look a typical crash where a bike hits stopped car in the passenger door at 20-30 mph.
Suzuki's SV 650 weighs about 435-440 wet and ready to ride. It comes with an aluminum frame and a 41 mm convetional fork. The frame is bolted to the engine in 6 locations. When these bike crash as stated above, they regularly bend or even break off the fork tubes at the lower clamp. The frames rarely bend, and the swing arms usually only twist a little and can esily be fixed.
Now take the same crash and substitute the GSXR for the SV. These bikes have 43 mm inverted forks (heavier than the SV's), and the motor bolts on in only 4 locations. The bike also weighs about 40-50 lbs less that the SV. In these same types of crashes the forks are less likely to bend, the triple clamps will be twisted beyond repair, and the frame will be bent in ( a steeper rake angle we call a "tuck under") and to the side. Also the lower steering head bearing race will be pushed up in the head stock casting and will lose it's press fit. Many times the plastics are still intact.
We used to cart wheel the old steel frame Honda CBR F2/F3 down the hill into the bowl at NHIS and just replace the handle bar and go. They weigh about 435 ready to race.
In these cases the lighter, stiffer chassis has sustained more damage than the heavier, more flexible chassis. This based on my observations over 12 years of chassis and suspension work on road, roadracing and dirt bikes, using a very sophisticated and accurite chassis measuring machine.
So back to your original statement, less mass=less inertia= less damage, is incorrect. Less mass = less inertia = less force, but not aways less damage.