Thread: wheelbase

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Whats the best way to measure for wheel base set up. My wheelbase is 112".
I need to hang/weld my spring perch's. My springs/rear alignment pin are centered in the spring, so is that ok to measure too for wheelbase set up ? I don't see another way. Thanks for any inputs.

1940 Ford P/U
Mustang II front end
9" ford rear

A few things to think about; make sure the frame is square to start with. On a Ford like this, in stock config, the spring center holes on the cross members would be the best reference for wheelbase, but that no longer works on yours other than as a general reference against original measurements from a drawing such as Wescott posts online: http://www.wescottsauto.com/WebCatal...ram1935-40.pdf Keep in mind, as the new semi elliptic springs in the rear are loaded they will flatten out extending the wheelbase slightly (how much depends on arch, spring rate, how much load).

If your MII front end wasn't a hack piece to start with, and if it was installed correctly, the front axle center-line should be in line with the upper shock mount holes (once the rails are square to each other that can be checked for square in relation to them). Then you can calculate/measure to the rear axle center-line. This is where it gets a little busier. 112" is the nominal value, but then there's reality. The good news is you can always change the location of the locating pin hole in the axle spring pads for fine tuning. The ideal would be to have the full body mounted, wheel/tire combo representative of the final selection, and chassis with a typical load on it. When that's done you may find that the alignment of the wheel/tire looks better moved slightly one way or the other.

Thanks for the input Bob. I see this is going to be a bit more of a pain as the truck is in pieces , so loading it down will require some more work.

You don't need to load it----------just measure the spring curve from the front eye to the center bolt and then measure in a straight line from the eye to the center bolt-----ajust for the extra length of the curve----------

Originally Posted by jerry clayton

You don't need to load it----------just measure the spring curve from the front eye to the center bolt and then measure in a straight line from the eye to the center bolt-----ajust for the extra length of the curve----------

Seems like that's a good idea, and it would indeed give you the maximum shift to the rear if the truck were loaded to the max, totally flattening the spring, but is that what you want? Seems to me the dilemma is to know just how much that spring is going to flatten under static load - the time when you want the placement of the wheel to be "right" for the wheel well opening, sitting still with everyone looking. A pickup's pretty light in the back end, so I wouldn't think you'd want to use that spring arc measurement to set your wheelbase. You could get an idea from another truck, but only if you're using the same springs, etc, right? A dilemma for sure.

Roger---------it will also give you the shortest----pick somewhere inbetween for where you want it--------issue is to get an equal/square wheelbase/track for the chassis----

Originally Posted by jerry clayton

Roger---------it will also give you the shortest----pick somewhere inbetween for where you want it--------issue is to get an equal/square wheelbase/track for the chassis----

Oh I understand that you have the shortest and the longest with your method, but as Uncle Bob pointed out it's often that little "tweak" that makes the world right for the "look" on wheel position. My point is that arbitrarily choosing that mid-point is pretty much a crap shoot. You don't want the longest, especially considering the light loading on a truck, but you also don't want the shortest, and what spot in between is going to be right? Like Uncle Bob said, you can relocate the pin hole in the axle spring pad to fine tune. Sure, getting it square & tracking is #1 (first line from Uncle Bob), but once that's done you're chasing the "right look".

I seem to be missing something here------I'm trying to give an example of how to get a square to the world axle mounting at the wheelbase you want----
And it seems that you want the fender well to look right????????? That comes down to the idea that you should have your tire/wheel combo fiqured out, on hand for mockup into the fender to determine where you want the wheel to be--------and then mount the springs so the axle center line swing will be there.

Of course this assumes that you have the placement of the body on the frame fiqured out--on an original frame/body that is pretty much a given, altho on a repro body, fabricated frame you do need to (and lotsa guys don't) mount things where they compliMATE instead of compliCATE matters----

As far as moving the spring center bolt hole in the axle bracket, do so equally as it will effect the spring rate at the axle-----

Wow guys thats the kind of inputs I like, different points of view that I can mix together and come up with just the right fix. Right or wrong it will be done and than maybe redone but lets hope not.! Thanks again