Page 69 - Issue 49

Ditching the straight Axle: Part 2 (IRS)

PHOTOS AND WORDS BY LUKE MERRILL (TINMAN 2 KUSTOMS)

WOOFTA! That’s a scary title. Fortunately this article is not on the IRS that might
give you the goosebumps: rather, it’s based around “Independent Rear Suspension”.
IRS is a somewhat modern form of suspension which was initially developed by
European engineers in the 1950’s. The design of an IRS is very similar to the design
of an IFS (my previous article), but with some important differences; the largest
being the addition of a drive axle (in rear wheel drive applications).

(aka drifting, drag racing, etc.),
more confusing to setup & align.
Function of IRS

The primary purpose of independent
suspension is to keep the wheels in
maximum contact with the ground
at all times. The wheels essentially
act independent of each other, so
if you hit a pothole on one side, the
other side is not affected. This helps
keep one tire in maximum contact
with the road at all times, which
leads to the best ride & handling.
There is also less “unsprung”
weight. Basically, this means there
is less weight that isn’t dampened
by the suspension, which leads to a
more stable ride.
Although many of us “Rat-
Rodders” are resourceful and
ingenuous: The factory designed
IRS assemblies are tried & true.
You may be able to engineer and/

RATRODMAGAZINE.COM RAT ROD MAGAZINE 69

68x72tinman.indd 69 4/23/18 10:52 AM