| Re: [GMCnet] Why is the front higher than the rear on a GMC? [message #87910] |
Thu, 10 June 2010 05:00 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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I agree with Larry - the story might be crazy enough to be true. But:
Changing the front height won't make a significant difference to the rear (won't change the "formula", whatever that is).
The aerodynamic drag of a vehicle will almost always get significantly better with positive rake (front lower than back). One reason is that the air velocity underneath will be lower. The underside is not very smooth, it is is best to increase the velocity over the top and reduce it underneath. Cooling will be improved with positive rake since the pressure underneath will be lower.
I suspect it was all about ground clearance. Here's what I'll bet happened: The initial prototypes had overheating problems so the radiator was upsized. Going wider was impossible without moving the frame rails, and it couldn't be made higher, so the depth was increased. Ground clearance is always a compromise, but to keep it to some standard the coach had to be raised in front. So in the end (the front end, that is :-) the most fragile component is also the lowest. Anyone for a skid plate? I've seen various screens used, but that doesn't protect against hitting a curb.
Gary
Does anyone know the reason why GM spec'd the front raised higher than the back? There must be a reason for it.
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I was told......
Back when the coach was engineered, the reason the coach has the controls up front was so you can raise the coach when you are pulling into "rough" campgrounds or bad roads. Raising the back end improves the stiffness to take on such lumps in the roadway.
If the Front end is lowered, it changes the formula for the back end, like lowering the kids teeter totter from 18" to 3", all the forces change.
Lowering the front end also takes away clearance.
The back end on the road makes the vehicle more aerodynamic and forces air circulation when in highway mode.
The engineers designed the coach to be used in this manner but when the lawyers heard about the OWNERS moving the coach up and down on their own, they had a tissy and told GM not to publish this fact. Fact or Fiction, its for us to decide.
LarC ( Thinking the story is just crazy enough to be true. )
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Gatsbys' CRUISER :d
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