Page 70 - Issue 49
P. 70
styles of IRS suspension which >> “Store-bought” Options:
each vary slightly in appearance Heidt’s,team321, roadster
as well: wishbone, single trailing shop, etc.
arm, multiple-link trailing arm,
etc. Selection here is really just a IMPORTANT NOTE: Many of us rat-
matter of what will fi t best in your rodders prefer the 15” wheel,
application. because of cost reasons.
I’m not sure about ya’ll, but Unfortunately, with some modern
I’m not a fan of vehicles that have IRS setups (2000 & up), wheel
absolutely zero backseat space or selection will be affected by brake
a pickup truck that has an unusable caliper/rotor sizing. Most modern
box (due to a raised box fl oor). axles also have a wider factory
That being said, another important stance, so it requires a higher
aspect, related to the “appearance” offset wheel in most cases (or
of an IRS, is that you will not have narrowing of axle for conventional
to “tub” or raise as much of your offset wheel).
fl oor because the suspension travel My Application: Because of the
is not present in the “pumpkin” larger OEM brakes on the ’17 mustang
of the axle, but rather in the IRS, I will be running a set of high
control arms. So in most cases, offset Detroit Steel wheels; staggered
notching of the frame rails is all 20” rear, 18” front (It’s also a good
that is necessary for suspension excuse to run a set of their bad-a$$
articulation, rather than cutting out wheels). However, if you must use a
excessive amounts of fl oor for the smaller wheel, you will (most likely)
pumpkin/axle to slip up inside of. want to start with an older IRS
assembly with smaller brakes.
The most important factors to consider
when purchasing an IRS are: Installation & Technical Tips
>> Width (wheel fl ange to wheel While the installation steps of an
fl ange) IRS assembly are very similar to
>> Design of arms (Upper arm in the procedures discussed in the
particular, for fi tment reasons IFS swap (previous issue #48),
with your full frame vehicle) there are some very important
>> Gear ratio, brakes, miles/ differences to consider. Rather
condition, other factors of than basically copying & pasting
that model/year the previously discussed 10 steps, I
or part together your own, but >> Availability of replacement have just added the aforementioned
that’s a hell of a lot of work and risk, parts important differences below.
(It’s also when a used setup can generally be >> Cost: anywhere from $100- Reference that article for more of
a good excuse purchased pretty cheap. $10,000 the “basics” of a subframe swap.
to run a set of Appearance Popular IRS Options: Driveshaft angle & pinion angle:
>> 2000’s Crown Vic
The camber is the look I am going
Driveshaft & pinion angle are always
their bad-a$$ for with my particular build. >> 70’s Jaguar important angles to consider when
wheels) Otherwise IRS looks essentially >> 80’s corvette building a rod. While important with
the same from the outside of the
any axle, it is much easier to set with
>> 70’s Datsun/Nissan
vehicle, depending on the vehicle >> 2003-2004 & 2015-2017 an IRS because the axle housing is
of course. There are a few different Mustang (Which I am using) mounted stationary in the vehicle (in
70 RAT ROD MAGAZINE ISSUE FORTY-NINE
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