Tech: BMR 2015 Mustang Development

0 BMR S550 Development Featured

Pounding the Pavement

A behind-the-scenes look at BMR Suspension’s S550 product development

By Steve Turner
Photos by Steve Turner and courtesy of BMR Suspension

With each new generation of Mustang, Ford continues to significantly improve upon the last iteration. When it was first announced that the new Mustang GT would upstage the Boss 302 on the road course, we wondered how much room for improvement was left in the new platform. Let’s face it. The Performance Pack-equipped Mustang GT is pretty good. However, after studying how the 2015 Mustang reacts to hard launches, BMR Suspension has discovered a number of upgrades that will take the new car to another level.

See those gaps in the tire tracks? That’s evidence of wheel hop from the stock 2015 Mustang independent rear suspension. The crew at BMR Suspension have tested the latest Mustang with a variety of hard launches to document the unwanted movement of the stock gear. After locating the trouble spots, the BMR team worked at bolstering each weak link.
See those gaps in the tire tracks? That’s evidence of wheel hop from the stock 2015 Mustang independent rear suspension. The crew at BMR Suspension have tested the latest Mustang with a variety of hard launches to document the unwanted movement of the stock gear. After locating the trouble spots, the BMR team worked at bolstering each weak link.

To do so, the company took its in-house 2015 Mustang tester out and hit the pavement hard with 5,000-rpm launches, rolling launches, and any torture test they could think come up with. Sure this was fun, but they also documented how the new suspension reacted to this treatment to see where improvements could be made.

“BMR has always been dedicated to making high-quality, affordable parts for the street and track that will help you outperform the competition. That mentality goes into every part we develop, and the S550 is no different. BMR has had a huge amount of success in the S197 world, and much of what we have learned over the last 10 years designing and manufacturing parts for that car has already gone into the design of our S550 parts,” Pete Epple, Marketing Tech at BMR Suspension, said. “The IRS certainly makes things interesting. Luckily for BMR, the fifth-gen Camaro is another strong platform for us, and a lot of what we have learned developing those parts can be applied to the S550 IRS. With the combination of bushings and hard parts already released and in development, BMR will have a complete solution that greatly increases performance and eliminates wheelhop for any form of performance driving.”

Here’s a look at some of the company’s wheel hop testing…

“We just put cameras under the car and watched what everything did. It was obvious that everything was moving,” Brett Rocky of BMR Suspension explained. “I didn’t expect the whole wheel to be moving forward and backward. It was ¾ of an inch in some cases.”

You wouldn’t think that the factory IRS cradle would move around. After all, it is bolted to the frame. However, as evidenced by these marks on the chassis, the cradle definitely moves around. Those concessions to OE noise, vibration, and harshness standards mean that the cradle definitely shifts when it is shocked by a drag launch.
You wouldn’t think that the factory IRS cradle would move around. After all, it is bolted to the frame. However, as evidenced by these marks on the chassis, the cradle definitely moves around. Those concessions to OE noise, vibration, and harshness standards mean that the cradle definitely shifts when it is shocked by a drag launch.

While that testing and development is ongoing, the BMR team is confident they are zeroing in on the causal factors and finding solutions.

“I think the automotive aftermarket is still figuring out the S550 chassis—especially the IRS. Through all of BMR’s testing, we’ve found there is significant wheelhop. In our first round of testing, we literally chased wheelhop from part to part,” Pete said. “Each time we eliminated deflection we thought was the cause, something else deflected causing more wheelhop. The great part about this is that we really learned a lot about what each part of the IRS was doing dynamically. This allowed us to isolate the function of each part and make very effective upgrades to eliminate the causes of wheelhop.”

Of course, the challenge is sharpening the car’s performance without detracting from the refinements bestowed on it by Ford.

Hard at work for months developing its full line of upgrades for the latest Mustangs, BMR Suspension is building a fully tested line of robust gear. Here is a mixture of the stock parts and the new BMR parts undergoing development at the company’s Florida facilities.
Hard at work for months developing its full line of upgrades for the latest Mustangs, BMR Suspension is building a fully tested line of robust gear. Here is a mixture of the stock parts and the new BMR parts undergoing development at the company’s Florida facilities.

“When Ford designs a car, even a performance-based car like a Mustang, it has to appeal to the masses. This means NVH and the overall comfort of the vehicle is more important than high levels of performance. But that’s what the aftermarket is for. That being said, the rubber bushing in the IRS cradle and differential mounts do nothing for performance,” he added. “The voids in the bushings do a great job of reducing NVH, but large amounts of deflection makes them one of the biggest causes of wheel hop. This is why BMR has developed multiple cradle and differential bushing options (polyurethane, Delrin, and billet aluminum), giving S550 owners the ability to increase performance with a level of NVH that they are comfortable with.”

So far the improvements have been significant, but there is no single, magic bullet for sharpening the performance of the S550 suspension.

The front lower control arm bushings in the factory IRS are rubber, while the rears are spherical. Upgrading the rubber bushing with a spherical unit really helps minimize wheel hop. The units BMR tested were press fit, but they are planning to offer a machined insert to ease installation for consumers.
The front lower control arm bushings in the factory IRS are rubber, while the rears are spherical. Upgrading the rubber bushing with a spherical unit really helps minimize wheel hop. The units BMR tested were press fit, but they are planning to offer a machined insert to ease installation for consumers.

“…We have parts in development that will help the car handle better, and we have parts that will reduce or eliminate wheel hop and unwanted IRS deflection. In a perfect world, someone would upgrade as much as possible, which would make an incredible S550,” Pete said. “Lowering springs and adjustable sway bars always make a big difference as far as feel. That comes from changes in spring rate, a lower center of gravity, and higher sway bar rates. These give huge increases in handling capabilities, and these changes are obvious when you drive the car.”

“BMR’s parts for eliminating wheel hop make equally significant improvements, but sometimes the ‘feel’ of the changes is much more subtle. Eliminating wheel hop will allow you to get more power to the ground as aggressively as possible,” he added. “Another benefit to eliminating wheel hop is the reduced risk of breaking parts. For anyone who wants to take the car to the drag strip or road course, these will be significant and necessary mods.”

BMR purchased a complete S550 IRS cradle and suspension so they could mock up and test its products. We used this out-of-body cradle to get a closer look at the prototype versions of the company’s forthcoming S550 parts.
BMR purchased a complete S550 IRS cradle and suspension so the company could mock up and test its products. We used this out-of-body cradle to get a closer look at the prototype versions of the company’s forthcoming S550 parts.

While we once worried about the performance potential of the latest Mustang at the drag strip, the cars have proven quite potent with limited modifications, and the BMR team is confident that the latest Mustang will only get better as more of its products come to fruition.

“…We’ve already seen how strong the S550 is at the drag strip. BMR’s supercharged drag-race test car has already gone 10.16 at 139 mph with a 1.52 60-foot. And this was with only a few select BMR test pieces and good tires,” Pete said. “The IRS is going to allow racers to keep the tires planted evenly, giving you maximum traction. Without wheel hop, the IRS becomes an advantage, but it’s so new that people haven’t realized it yet. Once people get over the stigma that the IRS won’t work at the drag strip, we’re going to see some very fast S550s!”

With a conservative tune and just shy of 700 rear-wheel horsepower, that BMR car is definitely impressive. You can watch its 10-second run right here…

Now that we have had a look behind-the-scenes at BMR’s S550 development, we can’t wait to see the whole package come together. When it does, we will make a return visit to follow the installation of the production parts and, with any luck, take the upgraded car for a spin to see how it feels, so stay tuned to the SVTP Front Page.

BMR has tested both cradle bushings and differential bushings. Both help control unwanted movement, but if you are working your way up the ladder, you’ll want to start with the cradle bushings.
BMR has tested both cradle bushings and differential bushings. Both help control unwanted movement, but if you are working your way up the ladder, you’ll want to start with the cradle bushings.
Depending on the intended use and the location of the bushing, BMR will offer both delrin, elastomer, and polyurethane bushings. The elastomer units are far more durable but don’t introduce any more NVH. For example, they opt for 95-duramoter poly bushings to corral the hot differential, but even stiffer Delrin bushings to secure the cradle. If you don’t care about NVH, BMR will also offer billet aluminum diff bushings, which will totally eliminate movement of the carrier.
Depending on the intended use and the location of the bushing, BMR will offer Delrin, elastomer, and polyurethane bushings. The elastomer units are far more durable but don’t introduce any more NVH. For example, they opt for 95-duramoter poly bushings to corral the hot differential, but even stiffer Delrin bushings to secure the cradle. If you don’t care about NVH, BMR will also offer billet aluminum diff bushings, which will totally eliminate movement of the carrier.
A unique aspect of BMR’s forthcoming adjustable toe links is this new mount. Rather than reusing the factory eccentric bolt, which could move under load, BMR utilizes this robust mount to secure the link to the chassis and lock out the factory adjustment.
A unique aspect of BMR’s forthcoming adjustable toe links is this new mount. Rather than reusing the factory eccentric bolt, which could move under load, BMR utilizes this robust mount to secure the link to the chassis and lock out the factory adjustment.
You won’t need that factory adjustment, which is difficult to access, when you use the new BMR toe links. They will offer up to 1 ½ inches of range, which can be adjusted on the car. That level of adjustment will come in handy if you lower your new Mustang significantly with coil-overs.
You won’t need that factory adjustment, which is difficult to access, when you use the new BMR toe links. They will offer up to 1 ½ inches of range, which can be adjusted on the car. That level of adjustment will come in handy if you lower your new Mustang significantly with coil-overs.
As BMR solidified each aspect of the rear suspension it exposed the next weakest link. To further control the IRS movement, BMR developed a replacement, billet vertical link. The production versions will employ a give-free spherical bushing on one end and a Delrin bushing on the other. This combo is said to eliminate deflection while keeping noise down.
As BMR solidified each aspect of the rear suspension it exposed the next weakest link. To further control the IRS movement, BMR developed a replacement, billet vertical link. The production versions will employ a give-free spherical bushings.
BMR put in a lot of testing work to dial in just the right rates for its spring package, and the new coils should be available soon.
BMR put in a lot of testing work to dial in just the right rates for its spring package, and the new coils should be available soon.
For those that don’t want to swap out the cradle bushings, BMR is experimenting with billet bushing supports, and for either application they will offer these bolt on cradle braces. Not only with the brace further support the cradle, but it offers another jacking point. Speaking of that, BMR will also offer bolt-on jacking rails that will allow you to jack up the car from any point between the wheels.
For those that don’t want to swap out the cradle bushings, BMR is experimenting with billet bushing supports, and for either application they will offer these bolt on cradle braces. Not only with the brace further support the cradle, but it offers another jacking point. Speaking of that, BMR will also offer bolt-on jacking rails that will allow you to jack up the car from any point between the wheels.
We couldn’t really mock them up on the out-of-car cradle, but BMR is also offering upgraded front and rear sway bars, 35mm in front and 25mm in back. These bars offer adjustable stiffness via three mounting positions that results in a 28- to 70-percent increase in sway bar rate in front and a 63- to 208-percent increase in the rear.
We couldn’t really mock them up on the out-of-car cradle, but BMR is also offering upgraded front and rear sway bars, 35mm in front and 25mm in back. These bars offer adjustable stiffness via three mounting positions that results in a 28- to 70-percent increase in sway bar rate in front and a 63- to 208-percent increase in the rear.
For months, BMR has been testing and designing its products for the latest Mustang. These parts are created using computer-aided design. This is the CAD drawing of the billet vertical link. The real-world production version will feature a combination of spherical and Delrin bushings and wear a powercoat finish.
For months, BMR has been testing and designing its products for the latest Mustang. These parts are created using computer-aided design. This is the CAD drawing of the billet vertical link. The real-world production version will feature spherical bushings and wear a powercoat finish.

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