Maximum Motorsports IRS Rear Grip Package - "The Basics", 1999-04 Cobra MMRG-20

Maximum Motorsports
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Reduce IRS wheel hop and improve handling with this Delrin Control Arm Bushing Package for upper and lower control arms. Fits 1999-2004 Mustang Cobra

  • Eliminates deflection allowed by stock rubber upper and lower control arm bushings.
  • Greatly reduces wheel hop because there is no bushing deflection.
  • Precisely locates the upper and lower control arms for improved dynamic alignment.
  • Handling is greatly improved because there are no unpredictable camber changes caused by bushing deflection.
  • NVH and ride comfort virtually unchanged.
  • Much easier to install than urethane control arm bushings.
  • Installation tools included.
  • This package includes MMIRSB-1 and MMIRSB-2.

Innovative designfeatures:

  • Stainless steel shims included for custom-fitting each bushing and arm combination to the subframe. This accommodates the very large OEM production tolerances in the fore and aft position of the control arm mounting tabs on the IRS subframe. The distance between the forward and rearmost tabs for the lower control arms can vary by over 1/4"!This works fine for the pliable factory rubber bushings, but not when trying to improve performance with precision-machined bushings. Our custom-fitting process uses stainless steel shims to ensure that the control arms cannot shift forward or rearward because of the factory production tolerances. This is yet another MM innovation copied by those lacking MM's engineering and design talent.
  • The shims are installed under the shoulder of the bushing to allow easy installation of the assembly into the subframe.
  • Delrin bushing shoulders are chamfered for ease of installation, and to reduce sliding-friction contact area with the subframe tabs.
  • For the highly loaded lower control arms, double-shouldered front and rear bushing sets are used to evenly spread acceleration and braking loads into the subframe. Thrust forces, caused by braking and acceleration, highly load the lower control arms along the pivot axis of the bushings. These loads are taken up by the bushing shoulders and passed into the control arm mounting tabs. The MM lower arm bushings have a shoulder on both sides of each bushing set. This lets both bushing sets on each control arm transmit these thrust loads into the subframe. For the upper control arms we are able to utilize less expensive single-sided bushings because the thrust loads into the bushings are much lower than the loads coming from the lower control arms.
  • Lower control arm bushings have crush sleeves made of thick-walled aluminum, and are hard anodized to reduce wear.
  • Upper control arm crush sleeves are made of zinc-plated steel.
  • Tab straightening tools, designed by MM, are included to assist in flattening the subframe tabs before reinstalling the control arms with the new Delrin bushings. The mounting tabs are always distorted by the original installation of the control arms on the assembly line. Tab straightening is a critical step that ensures that the control arms pivot freely, without binding.
  • Tooling is included to easily remove the original bushings. Designed by MM, these tools make bushing removal an easy job of only a few minutes, instead of an hours-long nightmare.
  • PTFE-based lubricating grease is included. This is one of the best greases in the world, and is successfully used in applications a thousand times harsher than Mustang control arm bushings.
  • Gloves are included to keep the super-sticky grease off your hands.

For more details and technical information, scroll down. 

IRS Mustang Tech: Q&A 

Handling is improved and wheel hop reduced by eliminating deflection allowed by the stock rubber control arm bushings. These Delrin bushings precisely locate the rear control arms, and maintain rear wheel alignment in a manner that is impossible with the compliant stock rubber bushings. Rubber bushings provide barely adequate suspension control, albeit the best noise and vibration reduction, but they cannot accurately position the control arms well enough to achieve maximum performance from the suspension. 

Wheel hop is a major complaint about IRS-equipped Mustangs. The un-damped compression of the rubber bushings in the rear suspension is the primary cause of wheel hop. That un-damped movement is amplified by repeated loss of traction. Wheel hop occurs because the rear tires continually oscillate between losing and then regaining traction. The extremely soft stock rubber bushings are the biggest contributor to this oscillation. The rubber compresses easily and then springs back, over and over again. To reduce wheel hop the stock rubber bushings must be eliminated.