I just traded for a 9670 and they asked me if I had a preference on the rear axle height position with 20.8 duals and 28-26L rear tires.
I figured, if anything, the difference was mainly just for looks. Anybody have any thoughts?
They recommended the rear higher on the walker machines to help with grain separation, which seems to have carried over to the STS machines but isn't as much of a necessity as it once was. It's now more personal preference, but myself I would rather it be leaned a little forward if possible (meaning in the upper position on the rearend).
With 38" rim most people put it in the lower position, for 42" they would put it in the higher position to keep the combine level. I don't think most dealers consider how it would affect the cleaning rather just how it looks.
I always look at the rear axle and how the combine sets because it can cause problems running platforms. It should set level to a little up in the back and this will make setting platform easier and help wear and feeding, also adjust fh tilt so it doesn't run on its nose. it also helps shoe
its better to have the rear end up high. well on our combines it seems to be if you are going down a hill it will barely throw anything over but if you are going up a hill we have to slow way down because the monitor is pegging out
I agree with Don, keep it level. In high volume crops you tend to get a little grain in the fan when tipped forward. We leave ours level to down a little in the rear to get the grain a little further back on the sieve.
Also, you probably know that 28L's should be set wide to avoid "interference" with side shields at full axle tilt.