> Education can be a dangerous thing. Next quarter at the VoTech
> school, I'm taking suspensions and front ends. Reading ahead I came
> across a paragraph that discussed tire speed dynamics> It said that
> at 55 mph, the portion of the tire directly fore and aft of the axle
> was travelling at 55mph, the portion of the tire at the very top was
> travelling 110mph and the portion of the tire at the very bottom was
> travelling 0mph.
>
> We start classes next week so I have not had a chance to ask my
> instructor but I know with the brains and experience of this exalted
> list. someone ca explain it to this old mind...or what's left of it!
Like Einstein said, it's all about frame of reference. That paragraph is
talking about the speed of the surface of the tire relative to the road.
If you look at it from the road's point of view, hopefully it will become
clear. The bottom of the tire is not sliding, it is not moving relative to
the road. It's speed relative to the road is zero. The top of the tire is
moving forward at 55 mph relative to the axle, which is moving at 55 mph
relative to the road, so the top of the tire is moving at 110 mph relative
to the road.
I'm not sure what the *** it has to do with anything, but that's what they
are talking about.
Note that they are only considering motion in a horizontal direction. The
portion of the tire directly in front of the axle has two components of
velocity relative to the road ... it is both moving forward at 55 mph and
also moving downwards at 55 mph.
Randall
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