Upgrade Your Classic Mustang with a Heidts Independent Rear Suspension (IRS)
Transform Your ’64½–’70 Mustang’s Ride, Handling, and Performance
Modern Performance for a Classic Icon
At Stang-Aholics, we’re passionate about helping Mustang enthusiasts blend timeless design with modern performance. If you own a 1964½–1970 Mustang, you already know that the original suspension — a solid rear axle with leaf springs — was built for simplicity and durability, not precision handling.
The Heidts Independent Rear Suspension (IRS) Kit changes that. This complete bolt-in system gives your classic Mustang the handling, comfort, and road manners of a modern performance car — while keeping the spirit of your vintage pony intact.
Why Upgrade from the Stock Live Axle and Leaf Springs?
Classic Mustangs came equipped with an 8-inch or 9-inch live axle and multi-leaf spring rear suspension. While iconic and reliable, this setup has limitations that modern drivers quickly notice.
1. High Unsprung Weight
A live axle means the entire rear differential moves with the wheels, creating extra unsprung mass. That results in a rougher ride and less precise handling over uneven roads.
2. Limited Suspension Geometry
Leaf springs both locate the axle and support the car’s weight. This limits adjustability — making it difficult to fine-tune alignment settings like camber or toe.
3. Reduced Cornering Stability
When one wheel hits a bump, the entire axle moves, unsettling the opposite wheel. That reduces traction and stability in corners or on rough pavement.
For enthusiasts who want more than straight-line performance, a Mustang independent rear suspension upgrade is the answer.
The Heidts IRS Kit: Designed for Real-World Performance
The Heidts Independent Rear Suspension Kit, available from Stang-Aholics, brings your classic Mustang into the modern era of handling and comfort — without extensive fabrication or chassis modification.
Key Features:
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Tubular Upper and Lower Control Arms – Allow each rear wheel to move independently, improving traction and handling.
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Adjustable Coil-Over Shocks – Fine-tune your ride height, damping, and comfort to match your driving style.
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Outboard Disc Brakes – Enhance braking performance and cooling, ideal for high-performance builds.
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Heavy-Duty CV Half Shafts – Handle modern horsepower levels with smooth, reliable power transfer.
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Mostly Bolt-In Design – Fits ’64½–’70 Mustangs with rear frame rail modification and some trunk floor modifications and a near-stock 58” track width.
This IRS setup is engineered for both strength and precision, offering a massive leap in handling quality over stock.
The Benefits of an Independent Rear Suspension
1. Smoother Ride Quality
Each wheel moves independently, absorbing bumps without transferring harshness across the axle. The result is a more composed, comfortable ride.
2. Sharper Handling and Better Grip
Independent suspension geometry keeps both tires planted through corners, dramatically improving traction, steering response, and overall control.
3. Reduced Body Roll
The IRS keeps your Mustang level and predictable through corners, making it far more confidence-inspiring at speed.
4. Tunable Performance
With adjustable coil-overs, you can set your ride height and damping for cruising comfort, autocross precision, or track performance.
5. Ready for Modern Power
Built strong, the Heidts IRS is designed to handle today’s high-torque engines — from small-blocks to modern 5.0 Coyote swaps — without compromise.
Independent Rear Suspension vs. Live Axle: The Real Difference
| Stock 8" or 9” Live Axle | Heidts Independent Rear |
|---|---|
| Harsh over bumps | Smooth and composed |
| Limited traction in turns | Superior grip and control |
| Fixed geometry | Fully tunable (camber, toe, ride height) |
| Heavy unsprung mass | Reduced unsprung weight |
| Drum or Limited Disc options | Outboard Modern Performance Disc brakes |
| Factory look and install | Modern Look and more complicated install |
Final Thoughts:
For drivers who love the look of a classic Mustang but want modern handling, comfort, and control, this is one of the most rewarding upgrades you can make. The Heidts IRS Kit gives your car the composure of a new performance vehicle while maintaining its vintage personality.
We’ve installed and supported countless Heidts systems, and we can confidently say — once you experience how your Mustang drives with an independent rear suspension, you’ll never go back.
Installation & Support
The Heidts IRS kit is designed for a mostly bolt-in installation with minimal cutting and welding to your existing rear frame rails. It fits your stock frame rails with a welded-in frame section and allows the stock rear fuel tank to be retained. Because of the complexity of the suspension design, exhaust is best routed to exit out the side at the rocker or to terminate right after the muffler in front of the suspension. For high-horsepower builds, we recommend adding subframe connectors for maximum rigidity.
If you’d like installation assistance or setup recommendations, our Stang-Aholics team is always here to help — from initial planning to final tuning.
Ready to Modernize Your Mustang?
Take your classic pony to the next level with the Heidts Independent Rear Suspension Kit, available now from Stang-Aholics.
Shop the Kit Here:
Heidts 1964½–1970 Mustang Independent Rear Suspension (Outboard Brakes)
Do you have questions about fitment, installation, or setup?
Contact our expert team today at stang-aholics.com — we’re always happy to help you build the Mustang of your dreams.
IMAGE GALLERY OF KIT INSTALLED IN A CLASSIC MUSTANG CHASSIS:
Heidts Independent Rear Suspension Installed in a Classic Mustang Chassis - View from Rear with Stock Fuel Tank Installed
Heidts Independent Rear Suspension Installed in a Classic Mustang Chassis - Shows the Exhaust System Routing and Drive Shaft Routing through 3rd Member Support Structure
Heidts Independent Rear Suspension Shown Installed in a Classic Mustang Chassis - Close-up shows Lower Control Arms, CV Shafts, and how Exhaust Exits in Front of the Suspension
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