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MM News

New! MM Technical Services: MM’s Engineering Team will provide setup recommendations specifically tailored for your Mustang. Get help choosing options for a Maximum Grip Box, deciding on coil-over spring rates, selecting a brake master cylinder, and advice on converting your Fox to Hydroboost.

New! Swapping a Coyote into a Fox Mustang? MM's Hydroboost Conversion Kits allow easy installation of a 1996-2004 Mustang Hydroboost power brake assist unit into a 1979-1993 Mustang.

New! Swapping an IRS into your Fox Mustang? MM makes it easier with a brake line kit made just for this conversion. Bolts-in, with no cutting or flaring of brake lines. Designed to fit standard IRS brake hoses.

New! MM now offers a tool for the giant nut securing a Mustang Hydroboost. This MM socket fits the 1-7/8" nut holding the Hydroboost to the firewall mount. Required when changing a Hydroboost unit.

New! MM's billet aluminum Pedal Box Spacer for Fox Mustangs. Replace the breakage-prone OEM plastic spacer when converting to manual brakes or Hydroboost.

Canadians! Please read the latest about ordering from Canada/shipping to Canada.

We've posted the parts list and link to the video of MM's Mustang in /DRIVE Tuner car Shootout

Urethane IRS Subframe Bushing Kit, 1979-98
Actual product may differ from photo.


  • Item # MMIRSU-2
  • Manufacturer: Maximum Motorsports
Add subframe bushing removal tool?
Add 12mm installation hardware?


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Kit designed for swapping a 1999-2004 IRS into the 1979-98 Mustang chassis. Reduces wheel hop and improves handlingover the extremely compliant stock subframe bushings.

  • Smaller crush sleeves fit the 12mm holes of the 1979-98 chassis.
  • Greatly reduces the deflection allowed by stock rubber bushings.
  • Reduces wheel hop because deflection is greatly reduced.
  • Improves alignment stability because the reduced bushing deflection keeps the IRS subframe properly located to the chassis.
  • Handling is much more predictable because the IRS cradle no longer moves relative to the chassis.
  • NVH remains virtually stock, unlike bushings made of harder materials.
  • Exclusive to MM, this bushing fits all IRS subframes. Other companies do not know that Ford had two different designs of the IRS subframe mounting bushings, so their bushings fit only one design, at best.
  • Easier to install than bushings made of harder materials.
  • Unique MM tool makes installation much easier.
  • Use new 12mm mounting hardware.

Not all IRS subframe bushings are created equal! Other companies sell their own urethane or aluminum bushings. Unless they are reselling the MM-brand bushing, they are simply selling urethane originally designed for a different application as their IRS mounting bushings. Their urethane bushing sort-of-fits, and they consider that to be good enough. That was not good enough for us. We designed a urethane bushing specifically for this application. It fits both IRS subframe versions properly, and is easier to install than the "sort-of-fits" urethane offered by others.

We do not offer aluminum bushings because:

  • They are extremely difficult to install. The receiving tubes on the subframe are not round; they are always distorted from the welding done during manufacturing of the subframe. Aluminum bushings require custom fitting all four bushings to each subframe tube.
  • The multiple mounting points on the two welded structures (chassis and IRS subframe) never align perfectly. Trying to slip the four mounting bolts into position becomes a nightmare when solid bushings are used.
  • The very small amount of deflection allowed by urethane accommodates the oval-shaped bushing shells, as well as the typical misalignment of the subframe to the chassis.
  • Urethane bushings remove 80% of the deflection allowed by rubber bushings, without the headaches caused by aluminum bushings.