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How to Install Maximum Motorsports Low Profile IRS Subframe Bolts on your Mustang

Installation Time

15 minutes

American Muscle
Shop Parts in this Guide

Thank you for buying the Maximum Motorsports Low-profile IRS Rear Sub-frame Bolts. These bolts provide the maximum space possible for inside tire clearance on IRS-equipped cars. The head on our low-profile bolt is 30% shorter than the stock bolt. In addition, the rounded shape will be more gentle on the tire sidewall should a little bit of tire rub occur.

Read all instructions before beginning work. Following instructions in the proper sequence will ensure the best and easiest installation.

Warning: The Maximum Motorsports Low Profile IRS Subframe Bolt is metric. Installation of this metric bolt requires an 8mm hex key (Allen head) tool. Do NOT use a standard SAE hex key tool. Use only a quality metric 8mm hex key tool. A poorly fitting hex key tool will round out the internal hex of the bolt. An 8mm hex key tool with a square drive will allow use of a torque wrench for proper tightening. Be sure to fully seat the hex tool in the head of the Low Profile IRS Subframe Bolt before applying tightening torque.

Warning: Do not use any air tools on the Low Profile IRS Subframe Bolt. This increases the danger of rounding out the head of the bolt. Use hand tools only for installation.

1. Jack up the rear of the car, and place it safely on two jack-stands. Support the car at the rear frame rails, NOT the IRS Sub-frame.

2. Remove the rear tires.

3. Start at the Driver Side of the car. Locate the rear IRS sub-frame mounting bolt.


4. Remove the bolt.

Note: The sub-frame may drop slightly during this process. If the bolt binds up or becomes difficult to pull out, use a floor jack under the lower control arm. Jack it up until the sub-frame crush sleeve aligns properly with the mounting hole.


5. Place one of the provided Grade 8 washers on the low profile bolt.

6. Install the bolt and torque to 76 ft-lb.


7. Repeat Step 3-6 on the Passenger Side.

8. Re-install the rear tires. Torque the lug nuts to the wheel manufacturer’s specifications.

9. Safely lower the car to the ground.

10. Drive and enjoy.

This kit includes:

2 Low Profile IRS Subframe Bolt (12mm-1.75)
2 G8 Flat Washer​

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