Tech: Energy Suspension 2015 Mustang Bushing Install

The 2015 Mustang hit the streets running at its release, and it seems to be another hit for Ford. However, for performance enthusiasts the return of the independent rear suspension was met with justified hesitation.

That’s because every IRS-equipped Mustang ever produced has suffered from excessive wheel hop during aggressive driving, such as what might occur at the drag strip. Early indications are the 2015 model suffers from the same issue. Energy Suspension and Joey Granatelli worked together on this 2015 Mustang GT owned by Granatelli Motor Sports. To establish a baseline, they did a series of drag launches with the stock tires. “One of the biggest things I noticed was the significant amount of wheel hop,” says Energy Suspension’s R&D Engineer Ben LaHatt.

Wheel Hop

Wheel hop is when the suspension is unable to keep the tires in constant contact with the pavement. The rubber bushings allow the IRS to bounce back and forth within the subframe assembly. Wheel hop can damage your IRS’ half-shafts, and your teeth if not fixed. The Energy Suspension Polyurethane bushings we cover here are designed to provide a more rigid connection between the IRS and the subframe assembly to remedy wheel hop.When it came to past IRS-equipped Mustangs, the answer to help eliminate wheel hop was the installation of polyurethane bushings within the IRS’ subframe and differential assembly…or swapping out the IRS for a solid axle. Energy Suspension is one company that has always been at the forefront of bushing development, and the 2015 Mustang is no different. Before this writing, there wasn’t a fix for wheel hop associated with 2015 Mustangs. However, Energy Suspension says it has the answer with these bushing kits for both the front and rear of the 2015 Mustang.

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The 2015 Mustang polyurethane bushings from Energy Suspension that were used in this installation are still in development. We guess you could call them prototype bushings as of right now. The company is still in final testing before these bushings are released to the public. The bushings Energy Suspension is developing are for the subframe kit, differential mount kit, rear suspension kit, rear sway bar kit, shifter kit, front lower control arm kit, and front sway bar kit.

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“For the subframe and differential mount kit, the goal is to help reduce, or eliminate the wheel hop,” LaHatt says. “Polyurethane helps to stiffen it up. Polyurethane is a performance upgrade. The polyurethane will also last significantly longer than any rubber bushing, to extend the life of the car, and the components.” Lahatt also said the bushings present a more cost-effective way of upgrading the suspension without buying new suspension components.

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However, the polyurethane comes at a cost. Most of us already know the polyurethane is stiffer than the rubber bushings they replace. A durometer is the instrument used to measure the hardness of a visco-elastic material such as rubber or polyurethane. The higher durometer reading the stiffer the material, which also means there is less deflection, as well. That increased stiffness can cause an increase in NVH over the factory rubber bushings, but that’s where the performance increase comes from. Remember, the rubber bushings are there to keep NVH levels low, and provide a quiet ride. The OEM bushings are a trade off between high performance and what most consumers consider tolerable NVH levels. They aren’t meant to be the best for performance. They are meant to be the best for NVH standards.

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With a more rigid IRS assembly thanks to Energy Suspension’s polyurethane bushings, you’ll be able to use your ’15 Mustang the way it was intended. When the bushings hold up their end of the job, handling is enhanced, drag strip performance is improved, and you won’t lose your teeth in the process.

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