Articulation Ramps are nice to be able to see if anything is
getting close to hitting. I have seen rigs with tremendous articulation
get so crossed up that they can't move on the trail, while the mildly setup rigs
drives through the same spot. These were shot on the clubs 20 degree
ramp. I will have to get a picture of a stock Rubi since I don't have one
from the first time. I feel that a score between 800 - 1000 will do just
fine on most of the trails.
Here is a quick comparrison between by 2003 TJ and the new 2007 JK in stock form. There wasn't much difference between them on the ramp, but I would have to say that the 2003 actually flexed better than the 2007. Here is the reason's why the 2003 ramped better. The 2007 only went 2" further, but was able to do this because wheel base was 2" longer and the axle width and tire size was wider.
Stock Disconnected 82"
Stock Disconnected 84"
Stock Suspension
Stock Suspension Disconnected
Distance
Wheelbase
Score
Est. Tire Height
Distance
Wheelbase
Score
Est. Tire Height
56
95.4
587
84
95.4
880
My
Ramp Opinion: I use ramps mainly to check clearance and rub issues.
It's nice to be able to flex it and see what rubs and what doesn't.
Here is the basic problems with a ramp.
1) The people measuring, unless it is the same person for every measurement,
doing it exactly the same way the measurements will change.
2) Tire pressure, try this experiment one time. Run the ramp at street
pressure, then run the ramp at trail pressure. You will get a better score
at trail pressure.
3) Tire placement. The tire needs to be run on the ramp near, but not
over the edge of the ramp. I've seen them run up the edge of the ramp
with half the tire off the side of the ramp (i.e. hanging below = larger
score)
4) The Ramp construction. Take a look at the mesh on the ramp and see
if is pushed down or is pushing down with the weight of the tire. If it
is, you can actually get a higher score.
5) Take identical rigs, but with different tires and run the ramp. You
will get different scores. Now run identical rigs, but have one with a
wider axle. The wider axle will get a better score because we do not calculate
for axle width. example would be a rig that could rotate its front axle
completely vertical. With a 36" axle it would only be able to get
up the ramp about 34" vertical height (compensate for tire on ramp
and other tire hitting ramp) now, put a 48" axle on this rig, guess
what, you could now go up about 46". Who has greater flex? In reality
neither.
6) The number of times you run it up the ramp before you measure. I never
thought about this until I saw an actual ramp competition and one of the
guys mentioned it. Limbering up the springs is the way it was described.
I tried it and got a better ramp score, not much, but better.
7) Reality wheelbase measurement. Actually measuring from hub center to
hub center, then comparing the ground measurement to the ramp measurement
of wheelbase.
8) Ground slope the ramp has to be perfectly level in all aspects. Not
very likely. Also the surrounding area has to be perfectly level so that
all the tires of the ramping vehicle have to be on the same plane as the
ramp.
In my opinion the best way to run a ramp score (at least until I figure
out the axle width computation, and build a 3d laser holographic terrain
mapping and vehicle ramping system) is to measure from the ground to the
lowest part of the tire on the ramp squared off of the ramp (takes away
possible ramp ground slope). This will give you height to ground. Put
it in to the calculation below and it will give you a ramp score. Any
monkey with a level can do this height.
Examples: (I used my scores with my known measurements.)
(33.5/ sin (20))/ 93.4 * 1000 = 1048.68 ramp score
(33.5/ sin (23))/ 93.4 * 1000 = 917.95 ramp score
(33.5/ sin (30))/ 93.4 * 1000 = 717.34 ramp score
