[encantotom]

ok,  i went through this when i built my shop.  because of strange building codes, i had to raise the floor of my shop up significantly higher than ground level. 

i am an engineer, my son is an engineer, my son in law is an engineer....you get the picture.

so, trig came into play and pivot points etc.  in doing so we came up with pretty much different answers.
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with my shop the entry in was straight and not curved like richard said to look out for.  also, i have no street, curb or curb drain area to account for.  just straight crushed granite and concrete pad

ends up the place on mine where it is easiest to get high centered on is the middle of the coach where the exhaust for the aquahot and genny is.  it hangs low and could easily hang on where the drive meets the garage. 

when you are backing up and incline and the rear of the bus goes over the point where the drive meets the garage, the hitch really isnt an issue.  but that is because i have a very long run in front of the concrete pad so i never have my hitch hit.  btw, my hitch is only about six inches off the ground.  i have the humongo big hitch.

so, my farmer friend looked at me and the pages of calculations and laughed.  so he said get 2 dump truck loads of crushed granite and lets build the ramp and pack it and try the bus.  we did that keeping in mind how long i wanted the concrete drive to be (35 foot)

so we would build, it, try it and repeat.  the concrete guys loved it because we had a hard pack base for them to start with when they formed the drive pad.  my pad is 35 ft deep and almost 40 foot wide. 

another thing to keep in mind with a garage is the door height.  when you are backing up and incline, the back of the bus might be a little higher.

i did 15 foot high doors so i would never have any issues.


so in summary, like richard said there are way too many variables to give a generic answer.

tom