I'll just throw this out there for you also, lumberjack. I find a very important figure is: how far the rear (tag) axle comes off the ground, when unloaded (air up). I quite often pull my lower pin on my rear tag, so the axle can fully ride up, for example when coming off a road up a steep driveway. If that tag axle hits the ground in that situation (without enough clearance), you can pick your drives off the ground and be spun out, point loaded between your front (steer), and the rear tag axle. The further the tag is from the drives, the higher it has to come off the ground.
Smaller tires on the tag would help. Making it a pin on behind the crane would be more helpful, but remove the possibility of a trailer (even if it doesn't unpin like mine, you would have more room for the tires to come up when raised without the crane above it).
Maybe you could extend the frame behind the crane enough for the tag tires to come up behind the crane, and have the frame extension there also for the trailer hitch, also gaining you length for bridge. Maybe not moving the drives quite so far ahead then, and leaving room for the pusher?
You only want to move those drives once, and then only if you have to, so those paper calculations are way easier to do than moving axles around. I was just a little concerned when looking at the drawing, at how much rise you would get from a tag placed under the crane, vs behind the crane. The crane above really limits how high the tag can raise up.
Without my bottom pin being removed on my tag, as far back as my rear tag's sit on both my larger cranes, I know I could get in trouble in a hurry. I can hear in the cab when my rear tag hits the ground, in the up position and rides up with the pin pulled, and its quite often on rough terrain.
I do like the idea of moving the drives ahead, I think the nicest part of that will be improved turning radius.
Can they run a calculation for you on where you would be with just a pusher ahead of the tandems, but leaving the tandems where they are? and see what that does to your front axle loads. I also think pusher first and then tag will give you the most gain on your steer weight issue.
I did own a crane like that once- single steer, pusher, tandems,(no tag) and with just adjusting air, pull weight on and off the steer.
I don't think I ever saw what rear suspension you have on the truck, if it is a camelback spring or spring over walking beam, the air axles, as tag and pusher will make a huge difference in how it rides, taking a lot of bounce out of it. I can really notice on my truck cranes if I don't have them aired up. (both cranes are simple walking beams rear- no springs).
. I don't want to offend anyone- if this bothers someone please delete, but I try to laugh at life's little foibles and troubles. My grandpa said getting old isn't for sissies.
