Joe,

Actually the bus does know the difference.

It is all about air pressure. The air springs or air bags as we call them are inflated until they raise the coach up to the ride height based on the adjustment of the ride height valve. Once the ride height valve arm reaches the neutral position no more air is introduced to the air bags.

So if you have two different size air bags on the front axle, they will both have the same air pressure because they are tied together. The air bag with the larger size will lift more weight at a given pressure than the smaller one, so it will tend to lift up that side of the coach a greater amount.

If you do nothing to compensate for that your coach will lean towards the small bag side. Depending on the difference in size of the small versus the large bag the lean can be great or barely perceptible. But let's presume you decided to check your coach ride height and fine tune its adjustments. To zero out that lean you adjust the side with the lean in the rear and raise it up a little and with the exception of having higher air bag pressures on one side compared to the other you will never notice it. But your coach will go down the road with a constant extra lifting force at one rear corner. It doesn't mean diddly, but it is there.

Lew's coach has a heavy front end and where the bigger air bags help him is that without them his originals could barely lift the front end. Once the front end came up to the correct height it was probably OK, but those original air bags probably took every pound of pressure his air compressor could generate to lift the True Value Hardware store.