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This weeks interview is with Craig Morrison and Matt Jones of Art Morrison Enterprises (AME). I’d heard through the grapevine that AME had just released a new Independent Rear Suspension (IRS) package and wanted to find out all about it. It had been generating a lot of buzz, and the Queen of Autocross herself (Mary Pozzi) was singing it’s praises.
Craig Morrison is the Vice President and Operations Manager at AME. Craig has been on The Muscle Car Place and Cars for a Living podcasts previously and I am always glad to have him on the show. As we learned during the interview, AME has had a number of customers come forward looking for AME frames with IRS and started to see the need to produce an IRS system with a real performance advantage over a live axle rear end. He admits that while AME is not the first to bring an IRS to the market, they are the first to develop such a high end system with the features it offers.
I then talked to Matt Jones, Lead Engineer at AME to get the technical side of this discussion. Matt grew up watching his grandpa drag race and remembers being in the garage with the cars and it got into his blood. He’s been with AME for nine years and has worked on designing this IRS package for the last three of those years. He is so invested in the project that he even offered up his very own 1969 Camaro as a test bed to work out bugs under real time driving and racing. Mary Pozzi even test drove his car at the Super Chevy Suspension Test Challenge.
As an engineer myself I was most interested to understand the initial design criteria of the AME Multilink IRS system. Essentially, Matt’s goal was to create a system that would allow independent adjustment of multiple critical parameters that are usually affect each other inadvertently (i.e. camber, caster, toe, and roll center).
To achieve these criteria the lower arms of the system are “disconnected”, meaning they are not a traditional “A-arm” style design that connect to the spindle at a point, but two arms that connect to either side of it. Following, there are eccentric adjusters designed into the lower control arms. The adjusters have marks that are a 1/4 degree of change each and these little lines show you where to aim and make adjustment easier to determine. This package also has the ability to pick the toe curve you want and maintains that through out the whole process.
In regards to how Roll Center affects drive-ability, Matt described it as an axis that is drawn front to rear on the car and is the point at around which the car rotates (roll) laterally at any given time. It is important to have that roll center axis very stable so it does not float left to right. A floating roll point axis can be described as driving like an overloaded pickup truck. AME designed this IRS to have a very stable roll center axis.
Some of the major components of the Art Morrison IRS system are a Strange cast aluminum rear end housing, featuring Dana 60 components, 9.9 inch ring gear, and 35 spline inner stubs. The housing offers roller bearings and a choice of clutch type or locker style differential. Matt said the Strange differential provided is a direct drop in replacement for a Gen 5 Camaro. The rear axles are from the Driveshaft Shop and are rated at 1400+ horsepower.
For braking there is a choice of stock type 12.5 inch GM rotors and calipers or a customer could upgrade to a Wilwood 14.25″ brake package. An integrated sway bar is also provided as part of this IRS system.
As far as packaging goes, this system is available in several different widths (55.5″, 57.5″. 59.5″, 61.5″ wheel mounting surface to surface width, specifically) for integration into nearly any vehicle that a customer would like to use it on. The whole package will only add 20 pounds over a standard 9 inch rear end, but reduces the unsprung weight by 100 pounds. Reducing unsprung weight is important as it allows the rear suspension to work easier and more accurately, reduces road noise, and improves ride quality.
Thanks for the great interviews Craig and Matt!
This interview sponsored by our pals at National Parts Depot – your premier source for muscle car restoration parts!