Cobraracer46 Posted February 8, 2015 Report Share Posted February 8, 2015 (edited) Over a year ago, finally performed a major upgrade and overhaul to the IRS in my 2001 Cobra to address a scary instability issue under hard acceleration. It turns out that after I fitted a set of 335/35/17 Micherlin PS2 tires on Fikse FM 10 wheels, I started to feel an extreme side to side back end movement under hard acceleration that would start at 85 MPH and steadily get worse.. I looked into going with all Polyurethane into the IRS. At the end of 2012 after a lot of thought, I decided to go with Poly for all of the IRS bushings to avoid any NVH issues and to save some money as well. Some people might say that poly "sucks" or that poly is "cheap" and "crappy." Don't believe it. Some numbers Pulled out of a discussion from a mustang site to show that Polyurethane is a perfectly acceptable bushing material for use in the Cobra IRS suspension. After upgrading the IRS in my car with poly, the handling has noticeably improved, without having to make painful sacrifices in NVH. from Here is what I did during the big IRS suspension overhaul: From Maximum Motorsprts: Complete IRS urethane differential mount kit with a removal tool for $56 that will transmit ZERO gear noise to the passenger compartment. IRS differential mounts, urethane, complete kit, 1999-04 Cobra [MMIRSB-45] : Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! A complete IRS urethane control arm bushing kit for $65 shipped that will preserve some level of ride quality over broken pavement. 1999-04 Mustang Cobra Prothane Irs Control Arm Bushing Set at LRS - Free Shipping! Urethane Subframe mounts for $49.95 Urethane IRS Subframe Bushing Kit, 1999-04 [MMIRSU-1] : Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! $16 for 14 MM sub frame bolts, Metric, not a "pretty-close" English-size. Use metric bolts for installation. 14mm hardware kit for IRS subframe & RLCA mounting, 1999-04 [MMF-4] : Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! A complete IRS tie rod kit for to replace the original ones that are shot and causing the wheels to wiggle back and fourth. IRS Adjustable Complete Tie Rod Conversion Kit, 1999-04 Cobra [MMIRSTR-3] : Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! I thought about this one long and hard and since I had the IRS totally apart, I stepped up and installed a $254 Ford racing diff cover as well with the money I save by not buying an IRS kit with Delrin and Aluminum bushings. 1999-04 Mustang Ford Racing 8.8" Irs Rear Differential Girdle, M-4033-G3 at LRS - Free Shipping!. I spent about $445 for IRS bushings and tie rod kit , plus another $250 for the Ford Racing Cover. Not too bad. A few pics of the install that I did my self in my home garage. drilling out the factory rubber subframe bushings and getting ready to use the Maximum Motorsports removal tool.Fully cleaned lower A arm bushing shell ready for a Prothane IRS poly bushing Cleaning out the bushing shells subframe bushing I ended using a the Maximimum IRS subframe bushing tool and a smaller disc from a Lise bearing race driver kit to remove the lower A arm factory rubber bushings along with a little heat from a propane torch. (no need to light the bushings on fire, just get the rubber warm.) I also made sure to Use plenty of anti size lube on the MM tool threads and not to use any power tools with the MM removal tool since the MM IRS subframe bushing removal tool had to survive and work double duty on the sub frame and lower control arm bushings. Many people by mistake have used an Impact gun with the MM removal tool, only to destroy the threads on the tool before all of the factory rubber sub frame bushings were removed. Compared to the lower control arm bushings, The factory rubber upper control arms easily come out with just a little bit of drilling, cutting and nothing else. Maximum Motorsports IRS poly rear diff mount installed. Maximum motorsports IRS toe links replacing the trashed stockers Fully upgraded IRS all cleaned up, filled with RED Line synthetic gear lube and ready to be reinstalled. ( 2003 Terminator cobra Half shaft and knuckle assemblies were left off to make the IRS easier to raise into position since I only had a floor jack to work with) Checking Bump steer with my home made gauge set up. After pulling my hair out, trying to get Zero toe change readings during the bumpsteer procedure, I called Maximum Motorsports and was advised that up to .040'' bump in compression and rebound was acceptable. The best reading I was able to get was around .008" Close enough. I made sure that the IRS only bumped in. One tip I picked up from another Cobra owner who upgraded a Cobra IRS with poly in the control arms was to mix the Supplied Prothane grease with a bit of Anti size and not to apply grease to the outside of the bushings. You only want the bushings to rotate around the bolts, not the shells so thats what I did. Properly greasing the poly IRS bushings during installation eliminates the need to occasionally lube them and it eliminates the need to weaken the control arms by drilling into them to install grease fittings. As for the subframe, I did apply a bit of grease to the outside of the Poly sub frame bushings and with just an aluminum floor jack, the IRS assembly popped back into the car really easy. Since I avoided installing Delrin or aluminum bushings on the IRS subframe there was no need at all to spread the torque boxes or deal with other head aches to reinstall the IRS subframe back in the car. I was expecting the ride to become a bit more harsh with poly replacing all of the rubber, but I'm in shock that I can't seem to notice any increased harshness. - - - Updated - - - will add that to use the the Maximum motorsports IRS subframe bushing removal tool to remove thefactory rubber IRS lower control arm bushings, you will need to a Lisle race bearing driver kit pictured below- - - Updated - - - It only took me a year, but the Cobra IRS Brembo brake conversion is done. Surprisingly, about the only performance difference I have noticed so far is that the parking brake works better than before. Edited February 10, 2015 by 95riosnake Non-tech info removed from post. Remaining post shows how to install the MM IRS bushings. This is a how-to section, and this is now a how-to thread. 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95riosnake Posted February 10, 2015 Report Share Posted February 10, 2015 Thread cleaned up. This is a how-to section, and now this is a how-to that shows members interested in the MM kit how to do the install, because the MM kit is a very nice kit and a viable option for any IRS owner. This is not Royal Rumble where flaming and bashing is allowed. This is in our tech section and will be treated as such. Members with more than 100 posts gain access to view and post in the Royal Rumble section. Link to comment Share on other sites More sharing options...
Sleeperstang1994 Posted February 10, 2015 Report Share Posted February 10, 2015 Thread cleaned up. This is a how-to section, and now this is a how-to that shows members interested in the MM kit how to do the install, because the MM kit is a very nice kit and a viable option for any IRS owner. This is not Royal Rumble where flaming and bashing is allowed. This is in our tech section and will be treated as such. Members with more than 100 posts gain access to view and post in the Royal Rumble section.im feeling like i missed something that went down in here. gotta love the source and our no nonsense approach to only knowledge! with that being said... how about a little more how to on that brembo caliper hanging out in the back! Link to comment Share on other sites More sharing options...
95riosnake Posted February 10, 2015 Report Share Posted February 10, 2015 im feeling like i missed something that went down in here. gotta love the source and our no nonsense approach to only knowledge! with that being said... how about a little more how to on that brembo caliper hanging out in the back! If you check out his welcome thread he went into a little detail about the brakes Link to comment Share on other sites More sharing options...
Sleeperstang1994 Posted February 10, 2015 Report Share Posted February 10, 2015 If you check out his welcome thread he went into a little detail about the brakes am I blind? Can't find the thread Link to comment Share on other sites More sharing options...
95riosnake Posted February 10, 2015 Report Share Posted February 10, 2015 am I blind? Can't find the thread http://www.sn95source.com/topic/4762-welcome-to-sn95sourcecom-cobraracer46 Link to comment Share on other sites More sharing options...
