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Motor Trend "History of the Ford Mustang IRS" Writeup

S550guy

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http://www.motortrend.com/features/...pendent_rear_suspension/mustang_platform.html

Despite the resurgence in Mustang sales following the introduction of the low-cost 5.0 LX, a new version based on the MN-12 was deemed, you guessed it - too expensive and too heavy. Instead, Ford went back to the drawing board and opted for a major refresh of the already decade old Fox body, resulting in the 1994 SN-95. While the SN-95 restored a lot of classic Mustang design cues that had been missing since the demise of Mustang II, it stuck with a live axle at first. Fortunately by this time, the Special Vehicle Team (SVT) had replaced the defunct SVO and was having some sales success with the SVT Cobra. As a result, the primary Mustang team went to work on a mid-cycle styling refresh that would arrive in 1999, but SVT went further.

Realizing that an all-new platform was still well off into the future, SVT engineers decided to see what they could do within the confines of the SN-95 (aka Fox-4) platform. They devised a short-long-arm rear suspension system that could bolt directly in place of the four-link live axle setup that had been used on Mustangs since 1979. A tubular steel subframe was designed that would bolt up to the same points as the pairs of leading and trailing links that located the live axle. Space constraints meant that the geometry was less than optimal and suspension travel was somewhat restricted, but it was still an improvement over the solid setup. The result was the best-handling Mustang to that point.

Mustang finally gets a new platform

While all of this work was going on with SN-95, Ford had also created another new rear-drive platform for Lincoln and Jaguar known as DEW98. As planning for the fifth-generation Mustang was getting underway around 2000, the decision was made to use DEW98 as the starting point. As usual, that platform was also too heavy and expensive so the Mustang engineers worked on changes to bring it within their budget limits. By the time they were done, the short-long-arm suspension at each end had been replaced with front MacPherson struts and a three-link live rear axle and the only piece of the original platform that was retained was a central portion of the floorpan. However, while the S197 Mustang was being developed, there were two offshoots in progress. In addition to the obvious SVT model, code-named Condor, there were plans for a more premium version to be badged as a new Mercury Cougar. In addition to more upscale interiors, the Cougar and Condor were also expected to retain an IRS system based on the DEW98 layout. In fact the first Condor prototypes were actually built with IRS. Unfortunately, the Cougar was killed before it was ever announced. As we wrote years ago, product development executive Phil Martens reportedly managed to convince Bill Ford Jr. the automaker could save $100 per car if the Mustang switched to a live rear axle. The S197 platform was then reworked to accommodate the old-tech suspension. Read more about the S197 Mustang's development in a 2009 blog from Angus MacKenzie here.
Great read! Here is a thorough write-up on the history of the Ford Mustang, and gives you an idea of just how many times an IRS was considered, but failed to make it into the Mustang. Until now, that is!

Enjoy!
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Horse

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Glad that IRS made it to the 6th generation. This time it shall stay.
 

S550Boss

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What a terrible article.... it's the thinnest rehash of a very small part of the total story. There wasn't any research, no interviews, about 1/100th of the total story. Apparently enough to fit on a sidebar, but nothing new.
 
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S550guy

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What a terrible article.... it's the thinnest rehash of a very small part of the total story. There wasn't any research, no interviews, about 1/100th of the total story. Apparently enough to fit on a sidebar, but nothing new.
Maybe not to you, but someone learned something new. Being a Ford employee, I also knew all of this. Just was entertaining to read again. Feel free to fill in the other 99/100ths if you so choose :)
 

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S550Boss

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Here's the complete story, in two parts, all verified by the actual Ford insiders who worked on the IRS for SN95 and S197 at that time.
http://www.drivingenthusiast.net/sec-blog/?p=12501
http://www.drivingenthusiast.net/sec-blog/?p=11329
As they say, all's well that ends well, and we finally have an IRS in the car standard, 10 years late and 16 after one was first an option (which I had, twice). What the old Ford Motor Company set out to do several times before, and failed to set in stone for 2005, has finally come to pass in 2015. And it's a good job, too.
 
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S550guy

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Here's the complete story, in two parts, all verified by the actual Ford insiders who worked on the IRS for SN95 and S197 at that time.
http://www.drivingenthusiast.net/sec-blog/?p=12501
http://www.drivingenthusiast.net/sec-blog/?p=11329
As they say, all's well that ends well, and we finally have an IRS in the car standard, 10 years late and 16 after one was first an option (which I had, twice). What the old Ford Motor Company set out to do several times before, and failed to set in stone for 2005, has finally come to pass in 2015. And it's a good job, too.
Now, if only this could be merged with MT's story.

MT's story is more of a summary on all previous Mustang IRS attempts, while this really dives into the cold, hard facts of the SN95 experiments, and the S197 IRS that almost was.

In any case, the IRS is here to stay for 15MY and beyond!
 

S550Boss

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The big question now is if, like so much Mustang engineering before, the S550 will start to noticeably age around 10k miles as all prior Mustangs do. Aged bushings, squeaky body, tired aircon, worn (fake) leather, worn transmission, etc. This is the difference between a cheap car and a well engineered car and the reason people move on.
Problems like the transmission (noisy), diff (grinding) and shocks (loose) in my 9k mile '13 Boss, the blown engine in my '03 Cobra (casting sand in the engine block!, and a factory tune that took Ford a year to get right - fortunately I didn't have an early one with the T56 problems or the bad head casting), the worn out bushings in my '99 Cobra (something it took until 2003 to get right, and then there was the engine's intake and exhaust issues), the lost synchros in my '96 Cobra (if they were ever there in the first place, the first-year T-45 was very poorly engineered - and then there was the terrible cooling system which couldn't deal with hot rush hour traffic much less track use), the broken seat frame in my '94 Cobra (SVT engineered a distinct magnesium frame, which broke), or many more examples. The worst of this can be blamed on SVT's lousy engineering, and their only doing delta testing instead of the entire set, but even then the base car has had numerous and fundamental cheap design, engineering, and testing issues.
I trust that the "new" Ford has done a much better job engineering the new car.... but I'll let it sort out for a year first. While the new GT is an ->|incremental|<- step up from my Boss (fixing much of what's inherently wrong with it), it isn't enough of a step up given what's coming. And it's also nice to see that Ford is for the first time ever testing the Mustang on the Nurburgring (the cruise around it in the GT500 was purely for marketing, no engineering was done). The question remains if anything was changed from that testing or if it's just a signoff.
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