hondarocks61
Active Member
*patiently awaits cr46's rebuttal attempt*
Upgraded the IRS Cobra suspension with Poly and more
- Thread starter cobraracer46
- Start date
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OP
cobraracer46
Active Member
the significant increase in NVH as you put it is a quite common occurrence with your Cobra IRS parts, bruise. As a review, here testimonials from "satisfied customers" who followed who followed some bad advice on the Mustang internet forms and installed the full tilt IRS bushings and are now unhappy with the "significant increase in NVH." Keep in mind that the NVH complaints all come from from mustang owners running full tilit IRS parts in street cobras with the factory insulation, not gutted street cars.
"Much louder. REALLY LOUD above 75mph. Would not want to take this car on road trip."
I love the response the poor guy above got when he asked for help in solving the horrible gear noise caused by installing the full tilt IRS diff mounts:
"These aren't luxury cars, if you want a quiet ride go buy a Caddy!"
I have a better Idea, How about thinking with your head instead of your ass and put in some more compliant material like poly instead of solid aluminum mounts so you wont have to buy a Caddy?
Why should other enthusiasts enjoy world class handling and nice street manners like this Lexus ISF performance sedan while us mustangs guys endure painful NVH in our rides? Makes no sense to me.
More unhappy full tilt IRS bushing manufacturs:
"After I had the rubber differential bushings replaced with aluminum, I started getting a howl that starts at about 70mph and gets louder."
"Mine is horrible. REALLY LOUD after solid bushings. Unacceptable. Sucks."
"... My only complaint is the freaking noise on acceleration and deceleration, and cursing [sic] on the fwy (gear noise), other than that I couldn't be happier."
"Yup. Did the same mods as you. Still have the hop and now lots of gear noise too."
"Clunk is GONE!... well, almost
My cobra had a bad case of the clunk, 'down there'. I replaced the following:
14mm front IRS bolts
Full tilt front diff bushing
Full tilt rear diff bushing
Full tilt IRS subframe bushing
and the clunk, for the most part, is gone.
still has some wheel hop under certain conditions with 275 Nitto 555s. Rear end gear noise is significantly higher....."
"did all of the above and my clunk rapidly turned from a clunk to a slam. Its so bad now it bounces when I let off the gas, I can feel it slamming back and forth with all the slack in there. I'm about to have a new set of gears installed because I'm afraid its going to break soon with the way it is now."
"I hear so many noises now I'm scared my rear end is going to fall apart. There is even some clunking noises! I know the rear end would be noisy, but the whirring noise is loud as shit and I have frpp 3.73 gears!"
Bruise, Denial is not just a river in Egypt. The Full full tilt parts have a problem with causing elevated and painful levels of NVH on street driven mustangs with full interiors and factory insulation. The common exuse or lie from you is that the gear noise is the result of aftermarket gears and that is simply not true. My Cobra has 4:30 gears and a True Trac diff and with the poly diff mounts, my car is quiet. No gear noise at all. Why torture yourself on long trips with aluminum diff mounts when you can put in a more compliant material like poly and have a car that is nice to drive on the street? Poly is not hard core enough and only Aluminum will do? If thats the case why stop with aluminum bushings? why not run a spool diff on the street of you are such a tough guy.
The whole point of this thread I started was to inform Mustang Cobra enthusiasts that Poly is a very nice bushing material to use in the Cobra IRS and that poly is a good bang for the Buck as well. I also wanted to prevent Mustang Cobra enthusiests from making the stupid desision of running delrin and aluminum parts on their mostly street driven cobra's and turning them into rolling torture chambers. If you decide to go all out in the bushings on your street driven cobra , you may not like it. Consider yourself warned.
I've been at this Mustang game since the 5.0 scene in the early 90's and I remember the days of street driving a stripped out 5.0 with Delrin and aluminum bushings and realizing how brutal that car felt when the streets were less than smooth. I've grown up since then, and I am no longer willing to make painful NVH sacrifices on the only car I own that mainly sees time on the street. My 2001 Cobra will never see Delrin and Aluminum. Since Poly in the IRS does not come with a brutal NVH penalty and since stiffness of poly close to delrin, why torture yourself with a shitty ride on less than smooth streets and horrible clunck, slam and wirrling noises?
My Cobra handles really well thanks to all of the poly bushings and more importantly, since I was sensible with the bushing choice and realizing that 90% of the time, the car is on the street, the car is still nice to drive on long trips as the ride is still nice and the rear end is quiet.
I sincerely hope that a 6' tall, 290# ex-hockey or rugby player with a 700 RWHP Cobra, that lives in Northern California, actually takes your advice and puts those shitty poly bushings into his IRS. Then comes to hunt you down two weeks later to beat your ass for for giving out that lousy advice. My only hope is that the beatdown shows up on youtube. :laughing5:
Waffles > Pancakes
Ketchup > Mustard
Red Sox > Yankees
LSU > Alabama
Handling/Precision > Wine & Cheese
I'm letting this thread continue because there's nothing to watch on TV and I am amused.
Please continue...
Ketchup > Mustard
Red Sox > Yankees
LSU > Alabama
Handling/Precision > Wine & Cheese
I'm letting this thread continue because there's nothing to watch on TV and I am amused.
Please continue...
I am purely speaking from my personal experience here with my choices of IRS bushings. I bought my cobra and realized that I needed to get rid of the stock IRS bushings that were on the cobra. I think we all can agree the stock rubber ford bushings are junk.
My next choice was do i go poly or do i go Delrin? After talking to my friend who had installed MM poly bushings in his cobra 4 years ago and only had 6,000 miles on the bushings, the choice to me was evident. I chose Delrin. Why did i make that choice? I made that choice because the poly bushings my friend put in 4 years ago that had only 6,000 miles on them were complete junk...my cobra with stock IRS bushings that were almost 10 years old drove better than my friends cobra that had poly bushings that were 4 years old. His rear end was all over the place and he had bad wheel hop 2 years after the installation. That is why i chose to go with the FTBR kit for IRS bushings.
I am going to address the NVH that i had (or in this case DIDN'T have!) yes, after the installation of the FTBR IRS bushing kit, I had ZERO increase in NVH ...let me repeat....ZERO NVH increase! not only did i not have any increase in NVH, my cobra now handles so much better around corners, and i have zero wheel hop in my 2003 cobra which puts down 491 RWHP.
I am glad that i went the FTBR route for my IRS and suspension needs. Bruce is a stand up human being who stands behind his product and always takes the time to answer questions you have. In my years of owning mustangs, (i have owned 3 of them dating back to my first 1985 GT) I have never met any mustang enthusiast like bruce - he has more hours of track time using his own product, refining that product and making sure that product does what he says it does than probably 99.9% of us mustang owners out there. That is another reason why i chose FTBR.
At the end of the day the choice is yours to make.. poly or Delrin... all i know, is that for the 3 or so unsatisfied FTBR customers, there are thousands of happy customers! And i am one of those happy customers. Also, when i was researching poly or delrin, i found this post that i saved....its a good one!
http://www.pro-touring.com/showthread.php?7709-Delrin-Del-a-Lum-vs-Polyurethane-and-Rubber
I recommend bushing material in this order:
Del-a-lum
Rubber
Sand
Polyurathane
You may notice that 'sand' is a better choice than poly for bushing material.
Look up a thread called '69 Camaro-blank slate wanna help?', or something to that effect. It had a good cut-n-paste of a very budget minded street suspension setup that Chicane came up with a few years back. It will do wonders for your handling, and leave some padding in your wallet.
Tyler
My next choice was do i go poly or do i go Delrin? After talking to my friend who had installed MM poly bushings in his cobra 4 years ago and only had 6,000 miles on the bushings, the choice to me was evident. I chose Delrin. Why did i make that choice? I made that choice because the poly bushings my friend put in 4 years ago that had only 6,000 miles on them were complete junk...my cobra with stock IRS bushings that were almost 10 years old drove better than my friends cobra that had poly bushings that were 4 years old. His rear end was all over the place and he had bad wheel hop 2 years after the installation. That is why i chose to go with the FTBR kit for IRS bushings.
I am going to address the NVH that i had (or in this case DIDN'T have!) yes, after the installation of the FTBR IRS bushing kit, I had ZERO increase in NVH ...let me repeat....ZERO NVH increase! not only did i not have any increase in NVH, my cobra now handles so much better around corners, and i have zero wheel hop in my 2003 cobra which puts down 491 RWHP.
I am glad that i went the FTBR route for my IRS and suspension needs. Bruce is a stand up human being who stands behind his product and always takes the time to answer questions you have. In my years of owning mustangs, (i have owned 3 of them dating back to my first 1985 GT) I have never met any mustang enthusiast like bruce - he has more hours of track time using his own product, refining that product and making sure that product does what he says it does than probably 99.9% of us mustang owners out there. That is another reason why i chose FTBR.
At the end of the day the choice is yours to make.. poly or Delrin... all i know, is that for the 3 or so unsatisfied FTBR customers, there are thousands of happy customers! And i am one of those happy customers. Also, when i was researching poly or delrin, i found this post that i saved....its a good one!
http://www.pro-touring.com/showthread.php?7709-Delrin-Del-a-Lum-vs-Polyurethane-and-Rubber
I recommend bushing material in this order:
Del-a-lum
Rubber
Sand
Polyurathane
You may notice that 'sand' is a better choice than poly for bushing material.
Look up a thread called '69 Camaro-blank slate wanna help?', or something to that effect. It had a good cut-n-paste of a very budget minded street suspension setup that Chicane came up with a few years back. It will do wonders for your handling, and leave some padding in your wallet.
Tyler
I can say that I wholeheartedly agree with this guy that says "SAND" is actually a better bushing material than poly!! :headbang:
Particularly when you are talking about a Cobra IRS. :thumbsup:
OP
OP
cobraracer46
Active Member
I disagree that the stock IRS rubber bushings are junk. For the cobra owner that never goes to the track and wants the smoothest possible ride with least amount of NVH, the factory rubber IRS bushings are the best option; As bushing stiffness increases, the ride quality will suffer and NVH will go up and only a retard would disagree.
For performance, the 99-01 IRS bushings are quite soft, but the 2003-2004 Terminator factory rubber IRS rubber bushings are 400% stiffer than the 99-01 versions, so they are not to bad for performance.
A 2003 Car and Driver Terminator road test proving that the factory IRS is pretty good right out of the box with the stock IRS bushings. Remember that Car and driver guys road test a ton of cars and they gave the terminator very high marks in the handling dept. The 2003-2004 IRS bushings certinely are not junk.
http://www.caranddriver.com/reviews/2003-ford-svt-mustang-cobra-road-test-review
Car and Driver article
"Of course. But it wouldn't have been as much fun if Ford's Special Vehicle Team engineers hadn't nailed the new '03 Mustang Cobra's chassis calibrations right in the sweet spot."
Since the supercharger installation adds about 160 pounds to the front end once you add in the Eaton blower, the cast-iron block, and the intercooler installation, one might expect the resultant weight redistribution (56.6/43.4) to produce a nose-heavy car with snappy rear-end breakaway characteristics.But somehow that's not translated to the road, even with that phenomenal low-end-torque potential waiting for an injudicious stab of throttle. Somehow, SVT has made the chassis tolerate the nose-heavy weight distribution and big rear-drive muscle. Tolerate it? Hey, this thing loves the track.
The obvious point here is the engine, and blender whine aside, it's a gem. But the chassis was what really blew me away. Considering the age of this Fox platform, the SVT bunch did an incredible job. Every Mustang I've ever driven plows like a John Deere, but this one feels more inclined to do a four-wheel drift. I usually do four test laps on the skidpad. In this car I did 12; I couldn't help it. It'll turn tail-out, tail-in, or anything in between. You ever watch those lurid car slides in the movie Ronin? Here's your car to practice in. And don't be afraid it'll beat you up on the highway—it won't. If Ford ever gives these guys a modern platform, watch out.
So why replace the IRS bushings? for the 99-01 Cobra guys like myself who want an IRS that is at least as stiff as a Terminator, but wont cause nasty NVH increases, poly is a good compromise. The obvious point here is the engine, and blender whine aside, it's a gem. But the chassis was what really blew me away. Considering the age of this Fox platform, the SVT bunch did an incredible job. Every Mustang I've ever driven plows like a John Deere, but this one feels more inclined to do a four-wheel drift. I usually do four test laps on the skidpad. In this car I did 12; I couldn't help it. It'll turn tail-out, tail-in, or anything in between. You ever watch those lurid car slides in the movie Ronin? Here's your car to practice in. And don't be afraid it'll beat you up on the highway—it won't. If Ford ever gives these guys a modern platform, watch out.
[*=center]
Some Cobra owners experence an extreme rear end sway under hard acceleration and the cause of this problem is worn out IRS Tie rod ends. Therefore eliminating the cobra rear end sway can be fixed by replacing the IRS tie rod ends. No need to touch the bushings.
Some Cobra owners experence wheel hop and think that replacing the IRS bushings will eliminated. Wrong. Remember this guy?
"Yup. Did the same mods as you. Still have the hop and now lots of gear noise too."
When you understand what really causes the Cobra IRS to wheel hop, you can see why the above situation happened. GM engineers discoverd that that IRS axel shafts are the root cause of wheel hop and fixed it with different dyamater axel shafts.
To quote GM:
"
Traction LimitedEven with the gigantic meats bolted to the backside, the ZR1 will be what is euphemistically called "traction limited." In other words, all that power just goes up into expensive smoke when you try to lay the power down.
And since launching a car with so much horsepower can become a violent, axle-hopping mess, Chevrolet has come up with two novel countermeasures.
First are the rear shocks. When you're stopped and the clutch pedal is depressed and you pile on some revs, the car assumes you want to launch it hard. It automatically softens the compression damping of the rear shocks, and this allows the rear end to squat and effectively shift more weight to the rear of the car for added traction. At the same time, the rebound damping of the rear shocks goes up to 99 percent of full stiffness. This means that the rear cannot spring back up under power in the up-and-down monkey motion of axle hop.
All this is perhaps the cleverest use of adjustable shocks that we've ever heard of. Also, according to Juechter, the standard magnetic shocks allow the ZR1 chassis team to use softer springs than the Z06 for a more compliant ride. To further mitigate power hop, Chevy has also fitted the ZR1 with axle half-shafts of different diameters (33mm on the right and 40mm on the left).
We'll see how all of this works next year when we finally get to drive the thing. We might just try a hard launch or, you know, several.
"6. Asymmetric shaft diameters (33mm left /40mm right) keep half-shafts from establishing a resonance in wind-up, thereby reducing propensity for axle hop.
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
7. MR shocks allow spring rates to be softened slightly
8. Anti-roll bars stiffened"
The different size axel shafts and stiffened shocks makes sense. In my 2001 Cobra, I eliminated the wheel hop by installing 315/35/17 Goodyear eagle GSD 3 tires, Eibach pro kit springs and Bilstien HD aftermarket shocks that are stiffer than the 03-04 cobra units. None of the IRS bushings were replaced, not one! Hard to say witch mod cured the wheel hop since the springs, shocks and tires were done at the same time.
I doubt the Above statment is true. My Cobra has had a Set of Steeda Offset poly front control arm bushing since 2007 and even today, they are still fine and perfectly quiet. I expect no less from the Prothane and Maximum Motorsports IRS poly IRS bushings I installed in January 2013.
If your buddy Bruce is such a stand up guy, why did he respond in this thread with threats of violence against me with these words?
"I sincerely hope that a 6' tall, 290# ex-hockey or rugby player with a 700 RWHP Cobra, that lives in Northern California, actually takes your advice and puts those shitty poly bushings into his IRS. Then comes to hunt you down two weeks later to beat your ass for for giving out that lousy advice. My only hope is that the beatdown shows up on youtube.:laughing5:"
[/QUOTE]
OP
OP
cobraracer46
Active Member
I disagree that the stock IRS rubber bushings are junk. For the cobra owner that never goes to the track and wants the smoothest possible ride with least amount of NVH, the factory rubber IRS bushings are the best option; As bushing stiffness increases, the ride quality will suffer and NVH will go up and only a retard would disagree.
For performance, the 99-01 IRS bushings are quite soft, but the 2003-2004 Terminator factory rubber IRS rubber bushings are 400% stiffer than the 99-01 versions, so they are not to bad for performance.
A 2003 Car and Driver Terminator road test proving that the factory IRS is pretty good right out of the box with the stock IRS bushings. Remember that Car and driver guys road test a ton of cars and they gave the terminator very high marks in the handling dept. The 2003-2004 IRS bushings certinely are not junk.
http://www.caranddriver.com/reviews/2003-ford-svt-mustang-cobra-road-test-review
Car and Driver article
"Of course. But it wouldn't have been as much fun if Ford's Special Vehicle Team engineers hadn't nailed the new '03 Mustang Cobra's chassis calibrations right in the sweet spot."
Since the supercharger installation adds about 160 pounds to the front end once you add in the Eaton blower, the cast-iron block, and the intercooler installation, one might expect the resultant weight redistribution (56.6/43.4) to produce a nose-heavy car with snappy rear-end breakaway characteristics.But somehow that's not translated to the road, even with that phenomenal low-end-torque potential waiting for an injudicious stab of throttle. Somehow, SVT has made the chassis tolerate the nose-heavy weight distribution and big rear-drive muscle. Tolerate it? Hey, this thing loves the track.
The obvious point here is the engine, and blender whine aside, it's a gem. But the chassis was what really blew me away. Considering the age of this Fox platform, the SVT bunch did an incredible job. Every Mustang I've ever driven plows like a John Deere, but this one feels more inclined to do a four-wheel drift. I usually do four test laps on the skidpad. In this car I did 12; I couldn't help it. It'll turn tail-out, tail-in, or anything in between. You ever watch those lurid car slides in the movie Ronin? Here's your car to practice in. And don't be afraid it'll beat you up on the highway—it won't. If Ford ever gives these guys a modern platform, watch out.
So why replace the IRS bushings? for the 99-01 Cobra guys like myself who want an IRS that is at least as stiff as a Terminator, but wont cause nasty NVH increases, poly is a good compromise. The obvious point here is the engine, and blender whine aside, it's a gem. But the chassis was what really blew me away. Considering the age of this Fox platform, the SVT bunch did an incredible job. Every Mustang I've ever driven plows like a John Deere, but this one feels more inclined to do a four-wheel drift. I usually do four test laps on the skidpad. In this car I did 12; I couldn't help it. It'll turn tail-out, tail-in, or anything in between. You ever watch those lurid car slides in the movie Ronin? Here's your car to practice in. And don't be afraid it'll beat you up on the highway—it won't. If Ford ever gives these guys a modern platform, watch out.
[*=center]
Some Cobra owners experence an extreme rear end sway under hard acceleration and the cause of this problem is worn out IRS Tie rod ends. Therefore eliminating the cobra rear end sway can be fixed by replacing the IRS tie rod ends. No need to touch the bushings.
Some Cobra owners experence wheel hop and think that replacing the IRS bushings will eliminated. Wrong. Remember this guy?
"Yup. Did the same mods as you. Still have the hop and now lots of gear noise too."
When you understand what really causes the Cobra IRS to wheel hop, you can see why the above situation happened. GM engineers discoverd that that IRS axel shafts are the root cause of wheel hop and fixed it with different dyamater axel shafts.
To quote GM:
"
Traction LimitedEven with the gigantic meats bolted to the backside, the ZR1 will be what is euphemistically called "traction limited." In other words, all that power just goes up into expensive smoke when you try to lay the power down.
And since launching a car with so much horsepower can become a violent, axle-hopping mess, Chevrolet has come up with two novel countermeasures.
First are the rear shocks. When you're stopped and the clutch pedal is depressed and you pile on some revs, the car assumes you want to launch it hard. It automatically softens the compression damping of the rear shocks, and this allows the rear end to squat and effectively shift more weight to the rear of the car for added traction. At the same time, the rebound damping of the rear shocks goes up to 99 percent of full stiffness. This means that the rear cannot spring back up under power in the up-and-down monkey motion of axle hop.
All this is perhaps the cleverest use of adjustable shocks that we've ever heard of. Also, according to Juechter, the standard magnetic shocks allow the ZR1 chassis team to use softer springs than the Z06 for a more compliant ride. To further mitigate power hop, Chevy has also fitted the ZR1 with axle half-shafts of different diameters (33mm on the right and 40mm on the left).
We'll see how all of this works next year when we finally get to drive the thing. We might just try a hard launch or, you know, several.
"6. Asymmetric shaft diameters (33mm left /40mm right) keep half-shafts from establishing a resonance in wind-up, thereby reducing propensity for axle hop.
6. Magneto-rheological shocks redesigned to cope with extreme track duty and provide base coupe ride quality. When drag-strip launch detected, shocks provide zero jounce and 100-percent rebound stiffness to encourage squat and minimize wheel hop
7. MR shocks allow spring rates to be softened slightly
8. Anti-roll bars stiffened"
The different size axel shafts and stiffened shocks makes sense. In my 2001 Cobra, I eliminated the wheel hop by installing 315/35/17 Goodyear eagle GSD 3 tires, Eibach pro kit springs and Bilstien HD aftermarket shocks that are stiffer than the 03-04 cobra units. None of the IRS bushings were replaced, not one! Hard to say witch mod cured the wheel hop since the springs, shocks and tires were done at the same time.
I doubt the Above statment is true. My Cobra has had a Set of Steeda Offset poly front control arm bushing since 2007 and even today, they are still fine and perfectly quiet. I expect no less from the Prothane and Maximum Motorsports IRS poly IRS bushings I installed in January 2013.
If your buddy Bruce is such a stand up guy, why did he respond in this thread with threats of violence against me with these words?
"I sincerely hope that a 6' tall, 290# ex-hockey or rugby player with a 700 RWHP Cobra, that lives in Northern California, actually takes your advice and puts those shitty poly bushings into his IRS. Then comes to hunt you down two weeks later to beat your ass for for giving out that lousy advice. My only hope is that the beatdown shows up on youtube.:laughing5:"
[/QUOTE]
OP
OP
cobraracer46
Active Member
A good read on how the IRS was developed and built:
The inside scoop: The engineers at Ford that were responsible for designing the IRS suspension and the supplier that built it for Ford.
Mustang Finally Gets An IRS
Automotive Industries, March, 1999 by Norman Martin
12Next
After 35 years, Ford's pony car adds a modular independent rear suspension with help from supplier Benteler.
Why has the Ford Mustang gone without an independent rear suspension (IRS) for so long? It's a question Mustang enthusiasts have been asking for years. Good handling has always been part of the pony car formula, but mainly for cost reasons Ford kept its sporty horse saddled with a solid rear axle. But finally, after 35 years, comes a big change for '99 -- a modular IRS, available only (for now) on the limited-edition SVT Cobra model.
Developed by Ford's Special Vehicles Team, the Cobra IRS program began three years ago, as rough sketches in Eric Zinkosky's Dearborn, Mich., office. The Mustang suspension systems engineer says he didn't even show it to Vehicle Engineering Manager Paul Giltinan "until I was sure it would fit."
Giltinan knew it would be cost prohibitive to re-engineer the rear of the Mustang's old "Fox" platform for a new suspension setup. Whatever they did for the Cobra needed to fit within the confines of the existing axle space. The resulting concept is a suspension module that bolts right into the current Mustang to create the $27,995 Cobra, and still allows the company to produce its high-volume Mustang models. More than 60% of the 144,000 Mustangs sold last year were value-oriented V-6s. These and the GT versions will retain the solid rear-end at least for '99.
The new IRS module features a traditional wishbone-type, short-and-long-arm suspension design. The aluminum knuckles are permanent-mold castings. Unlike sand castings, they give a smooth, consistent surface. The process also allowed Ford to reduce the overall wall thickness, which aided in reducing weight. While the '99 Cobra is about 40 pounds heavier than its predecessor, new features include the IRS, a new, wider body and an all-speed traction control system. The only components on the new IRS that aren't unique to the Cobra are the aluminum differential case -- borrowed from the Lincoln Mark VIII -- and the Mark's wheel bearings.
"Literally, no changes were made to the car, the body, the fuel system or anything else to put this IRS in," Zinkosky says.
"It's a case of smart design," observes auto industry analyst Jim Hall, a vice president at AutoPacific Group in Southfield, Mich. "Of all the ways they could have done it, they found a relatively inexpensive way to do it." Hall reckons the IRS's incremental piece cost to be around $250.
Benteler Automotive Inc. in Galesburg, Mich., builds the module. "We selected Benteler because they're experts in bending tube," Zinkosky says. "And if you look at the IRS design the major structure of the subframe is, in fact, 2 3/4 -inch diameter tubes that are bent to shape."
The IRS module itself weighs 80 pounds more than the solid-beam rear axle. SVT engineers were able to cut about 50 pounds from other areas of the Cobra -- 30 pounds from the front and 20 from the middle -- to almost make up for the module. Shifting weight to the rear creates a better front/rear balance, changing the ratio from 57% on the front axle of the regular Mustang to 55% front-end weight in the Cobra. That translates to about 80 pounds shifted to the rear of the car, which improves traction, especially on wet surfaces. It also improves brake bias performance and makes handling more neutral.
A number of suppliers provide system components directly to Benteler. It then assembles the module, prealigns it, and ships it to Ford's Dearborn assembly plant There are no special arrangements made for the SVT IRS on the line. The very same place where the solid axle is lifted into the car is the same place where they load the new IRS module. In fact, the same lifting device is used on both set-ups.
Benteler Engineering Project Manager John Calow says the module design is very flexible. He claims that if Ford decides at some point that it would like to change the alignment settings, the design is readily adaptable.
"We took it (the IRS) beyond the normal supply chain," adds Thomas Palumbo, a Benteler marketing vice president in Livonia, Mich. "We had to bring it ORS) all the way up to the delivery point line side." Benteler also supplies modules to Ford in Europe, as well as to General Motors and Volkswagen.
In terms of vehicle dynamics, the new IRS generally improves the Mustang's ride quality and base handling. Zinkosky adds that there are some unique geometry details that Ford "is not going to tell the rest of the world." Competitors will have to buy an SVT Cobra, drive it for themselves, then tear it down for analysis. In the meantime, Mustang Sally will sure be lovin' this new pony car.
COPYRIGHT 1999 Cahners Publishing Company
The inside scoop: The engineers at Ford that were responsible for designing the IRS suspension and the supplier that built it for Ford.
Mustang Finally Gets An IRS
Automotive Industries, March, 1999 by Norman Martin
12Next
After 35 years, Ford's pony car adds a modular independent rear suspension with help from supplier Benteler.
Why has the Ford Mustang gone without an independent rear suspension (IRS) for so long? It's a question Mustang enthusiasts have been asking for years. Good handling has always been part of the pony car formula, but mainly for cost reasons Ford kept its sporty horse saddled with a solid rear axle. But finally, after 35 years, comes a big change for '99 -- a modular IRS, available only (for now) on the limited-edition SVT Cobra model.
Developed by Ford's Special Vehicles Team, the Cobra IRS program began three years ago, as rough sketches in Eric Zinkosky's Dearborn, Mich., office. The Mustang suspension systems engineer says he didn't even show it to Vehicle Engineering Manager Paul Giltinan "until I was sure it would fit."
Giltinan knew it would be cost prohibitive to re-engineer the rear of the Mustang's old "Fox" platform for a new suspension setup. Whatever they did for the Cobra needed to fit within the confines of the existing axle space. The resulting concept is a suspension module that bolts right into the current Mustang to create the $27,995 Cobra, and still allows the company to produce its high-volume Mustang models. More than 60% of the 144,000 Mustangs sold last year were value-oriented V-6s. These and the GT versions will retain the solid rear-end at least for '99.
The new IRS module features a traditional wishbone-type, short-and-long-arm suspension design. The aluminum knuckles are permanent-mold castings. Unlike sand castings, they give a smooth, consistent surface. The process also allowed Ford to reduce the overall wall thickness, which aided in reducing weight. While the '99 Cobra is about 40 pounds heavier than its predecessor, new features include the IRS, a new, wider body and an all-speed traction control system. The only components on the new IRS that aren't unique to the Cobra are the aluminum differential case -- borrowed from the Lincoln Mark VIII -- and the Mark's wheel bearings.
"Literally, no changes were made to the car, the body, the fuel system or anything else to put this IRS in," Zinkosky says.
"It's a case of smart design," observes auto industry analyst Jim Hall, a vice president at AutoPacific Group in Southfield, Mich. "Of all the ways they could have done it, they found a relatively inexpensive way to do it." Hall reckons the IRS's incremental piece cost to be around $250.
Benteler Automotive Inc. in Galesburg, Mich., builds the module. "We selected Benteler because they're experts in bending tube," Zinkosky says. "And if you look at the IRS design the major structure of the subframe is, in fact, 2 3/4 -inch diameter tubes that are bent to shape."
The IRS module itself weighs 80 pounds more than the solid-beam rear axle. SVT engineers were able to cut about 50 pounds from other areas of the Cobra -- 30 pounds from the front and 20 from the middle -- to almost make up for the module. Shifting weight to the rear creates a better front/rear balance, changing the ratio from 57% on the front axle of the regular Mustang to 55% front-end weight in the Cobra. That translates to about 80 pounds shifted to the rear of the car, which improves traction, especially on wet surfaces. It also improves brake bias performance and makes handling more neutral.
A number of suppliers provide system components directly to Benteler. It then assembles the module, prealigns it, and ships it to Ford's Dearborn assembly plant There are no special arrangements made for the SVT IRS on the line. The very same place where the solid axle is lifted into the car is the same place where they load the new IRS module. In fact, the same lifting device is used on both set-ups.
Benteler Engineering Project Manager John Calow says the module design is very flexible. He claims that if Ford decides at some point that it would like to change the alignment settings, the design is readily adaptable.
"We took it (the IRS) beyond the normal supply chain," adds Thomas Palumbo, a Benteler marketing vice president in Livonia, Mich. "We had to bring it ORS) all the way up to the delivery point line side." Benteler also supplies modules to Ford in Europe, as well as to General Motors and Volkswagen.
In terms of vehicle dynamics, the new IRS generally improves the Mustang's ride quality and base handling. Zinkosky adds that there are some unique geometry details that Ford "is not going to tell the rest of the world." Competitors will have to buy an SVT Cobra, drive it for themselves, then tear it down for analysis. In the meantime, Mustang Sally will sure be lovin' this new pony car.
COPYRIGHT 1999 Cahners Publishing Company
i like the part where the new guys gang up on the other new guys and then the new guys totally pwned the new guys. it was great.
I slapped my knee
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cobraracer46
Active Member
Here is another reason to run Polyurethane instead of Delrin in the Cobra IRS. Delrin will swell when exposed to water and will cause the suspension to lock up.
http://www.practicalmachinist.com/vb/general/delrin-swelling-259575/
"Delrin absorbs water[hydroscopic?] and grows. Can be enough to put you out of tolerance. I had a project where I made small gear pump/housings and when they would test run water throught the pump, the gears would swell and jam. We had to open up the tolerances to accomodate. Delrin is a very nice material but it doesnt do so well with exposure to weather and UV. JinNJ"
Swollen Delrin bushing that caused a control arm to lock up and break apart.
http://www.practicalmachinist.com/vb/general/delrin-swelling-259575/
"Delrin absorbs water[hydroscopic?] and grows. Can be enough to put you out of tolerance. I had a project where I made small gear pump/housings and when they would test run water throught the pump, the gears would swell and jam. We had to open up the tolerances to accomodate. Delrin is a very nice material but it doesnt do so well with exposure to weather and UV. JinNJ"
Swollen Delrin bushing that caused a control arm to lock up and break apart.
Mystic SVT
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So I installed FTBR's differential bushings on my '96 cobra (03 IRS equipped) and could not be happier! Reduced wheelhop by 50% just by doing the differential bushings. A couple of weeks later I installed MM's polyurethane differential bushings on my buddy's Bullitt that I was doing an IRS swap into. He chose the bushings not me so I installed what he wanted.
Fast forward almost 2 years later and long behold, I'm doing a header and clutch install on the Bullitt and the MM bushings are falling apart. Had to swap in my factory bushings that I managed to find by pure luck, I thought I threw them away.
I should have taken pictures to post up here on this thread but I was too busy installing those piece of crap BBK headers.
Cobraracer46, I'm not saying that polyurethane didn't do wonders for you but please stop trying to make everyone believe that Delrin bushings are crap, especially Full Tilt Boogies. I've installed a complete set of FTBR's bushings on an '03 cobra and the owner was very happy to say the least. Also to your surprise, no noticeable gear whine or suspension noise increase. Car was still quiet on the inside, and the car still had the factory catback.
BTW, that picture of the broken control arm you posted looks like that thing would have fallen apart if the vehicle would have hit a pebble.
FTBR's bushings are greasable so a seized bushing shouldn't be an issue.
Fast forward almost 2 years later and long behold, I'm doing a header and clutch install on the Bullitt and the MM bushings are falling apart. Had to swap in my factory bushings that I managed to find by pure luck, I thought I threw them away.
I should have taken pictures to post up here on this thread but I was too busy installing those piece of crap BBK headers.
Cobraracer46, I'm not saying that polyurethane didn't do wonders for you but please stop trying to make everyone believe that Delrin bushings are crap, especially Full Tilt Boogies. I've installed a complete set of FTBR's bushings on an '03 cobra and the owner was very happy to say the least. Also to your surprise, no noticeable gear whine or suspension noise increase. Car was still quiet on the inside, and the car still had the factory catback.
BTW, that picture of the broken control arm you posted looks like that thing would have fallen apart if the vehicle would have hit a pebble.
FTBR's bushings are greasable so a seized bushing shouldn't be an issue.
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cobraracer46
Active Member
Thanks for posting in My IRS poly bushing thread. I wrote this thread to showcase the fact the Delrin and Aluminum IRS bushings such as the Full tilt parts are a mistake for a street driven Cobra while Poly bushing are the best solution for a mostly street driven Cobra and to debunk all the myths about poly IRS bushings with solid tech. For NVH, cost and durability on a mostly street driven Poly IRS bushings From Prothane, Maximum Motorsports and Steeda is the best solution.
Oy
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cobraracer46
Active Member
Now that we know just how good Maximum Motorsports, Prothane and Steeda Poly IRS bushings really are and that for a street driven Cobra, POLY is the way to go; I will talk about something I plan on doing to the IRS in my Cobra later on down the Road: cooling the oil.
Maximum Motorsports offers a IRS oil cooler kit, but I will look into making my own kit. Stay tuned.
Maximum Motorsports offers a IRS oil cooler kit, but I will look into making my own kit. Stay tuned.
How the hell did I miss this wtf?
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cobraracer46
Active Member
Hope you enjoyed reading the whole thread.
Back to the IRS tech.
One company, run by Ford engineers offers a IRS oil cooler, but it's pricy at $1300.
http://www.rehagenracingproducts.co...RS-DIFFERENTIAL-COOLER-PRO-KIT-RRIRSDCPRO.htm
The Maximum Motorsports cooler is priced the same at $1300 as well
http://www.maximummotorsports.com/store/index.php?main_page=product_info&products_id=1077
if only someone here worked for a plastics company!!!! ARGGGG!
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