I'm getting ready to update some completed vehicles with some individual track link sets. In doing my research, I've discovered that a number of the vehicles I'm planning to do have a difference in the number of track links on the left vs the right side. The M107/M110/M578 family as well as the M113 family have one extra link on the right side. (The M108/M109 family however appear to have the same count on each side.)

I'm not sure why the vehicles are designed this way but regardless, I'm sure on the prototype, that the total number of links required would be affected by things like minor changes in suspension/idler arm position and perhaps track tension. And I'm guessing that putting an extra link on the left side (or leaving one out on the right) would cause some problems.

So the question is, given that a plastic scale model is HIGHLY unlikely to have that slightly different dimension side to side (after all, the "rubber band" tracks supplied with the kit are not "handed" parts, and are the same length) how do you handle this?

From a "rivet counting/accuracy" perspective, I'm not overly concerned that anyone would notice that the count is off, but from a practical perspective, (given that not every after market supplier is going to have PRECISELY the same and "correct" dimension on their parts), what are your thoughts on setting the track length when the manufacturer of the kit did NOT provide a count for their product on each of the vehicles in question?

Should I make the length of both the same, check the fit and adjust if required?

You said it. Basically it takes as many links as it takes to complete them. You will usually find the number is not the same as the real vehicle. Just build as many as you need and you will be good.

Thanks Gino. This will take my mind off my OTHER problem!

leaves your own goal wide open as it were....
not going to bite though...

the reason they are different lengths is because the suspension arm torsion bars are mostly side-by-side, & therefore one of each pair will be in front of the other.

Differences left vs right side.
If you turn the kit (or real vehicle) over (a lot easier
with the kit though ...) you will notice that on some
vehicles the road wheels are not directly opposite each
other. This is caused by the type of suspension for that
particular vehicle. If it uses torsion bars that go
straight across from side to side then the wheels can't
be exactly opposite each other and the first road wheel
on one side will be further forward than on the other side.
Since the top run of the tracks go from idler to drive
wheel and those are exactly opposite each other the top
runs will be of equal length so any difference in length
of track caused by the offset road wheels needs to be
compensated for by adding one track link. If the angle or
slope uppwards from the first and last roadwheels,
left rear to right front and front left to right rear,
match perfectly then there will not be any difference in
length but usually the rear slope is steeper (check an
Abrams for instance) and that will cause a length
difference caused by the larger differences in the front
slopes compared to the rear slopes. This can be seen in
some photos/drawings when the vehicle is seen from the
side. Check the painting diagrams in the kit instructions,
sometimes they show that the front part of the tracks have
different angles to the ground.
/ Robin

Thanks for the explanation. Makes sense given that with the torsion bars going across the hull the wheels can't be exactly opposite from one side to the other.

And as far as a doing an aftermarket replacement, I guess I'll start with the "book" answer and see if it works and if not adjust.

As you get close, start test fitting them. That can be easier than going all the way to (example) 80 links, and having to pull a few off, as that can sometimes not be easy without damaging them.

That's very good advice. I'm using Space Ace Metal tracks which are astonishingly easy to put together, but I can imagine that trying to punch out the wire to shorten the run after they've been put together might be tough.

My trick for that is to leave the wire a little long on several of the last few track links untill I have test fitted the complete run. This allows me to remove them if needed without causing any unneeded damage. I did a Sturmtiger with Fruil and left the wire long on about 8 of the links. Once I was statified with the fit, I trimed the wire accordingly.
Good luck
Joe Bevans
AMPS 2nd VP West Region
AMPS So Cal

On most kits, you should be able to adjust the idler, causing a shift in the tension of the tracks. I do not count the number of links, but follow the "build them the same length and adjust" method.

Different types of model tracks require different methods.
If they are really workable (not the "can move but if you
move them once too much they will disintegrate" type) then it is matter of making a long enough track and then shorten
as needed, leave a few pins long enough to be possible to
remove.
All other types, either will-break-if-not-glued or designed
to be glued: Make separate sections or runs (first to last road wheel, a few links onto the idler wheel to a few teeth onto the drive wheel, short sections to connect the long runs). The short runs are used to take up some slack, on a
parked vehicle most of the slack will be in these short bits, check references for a moving vehicles.
Mount the top run, adjust the short bits (bend outward
before the glue has set) to meet the bottom run.
In some cases it may be necessary to move the idler (adjust "track tension")
/ Robin

Good tips! The Spade Ace are fully workable and should be easy to simply not secure the track pin wire (i.e leave it long and bent over at the ends rather than secure it with CA at the end), on the last few links and adjust to fit and then remove the unneeded links. That will also allow me to paint the entire track at one time so it's somewhat uniform.

Thanks for the tips!