Pounding the Pavement
A behind-the-scenes look at BMR Suspensionâ€™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. Letâ€™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.
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.
â€œBMR 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,â€ Pete Epple, Marketing Tech at BMR Suspension, said. â€œThe 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.â€
Hereâ€™s a look at some of the companyâ€™s wheel hop testingâ€¦
â€œWe just put cameras under the car and watched what everything did. It was obvious that everything was moving,â€ Brett Rocky of BMR Suspension explained. â€œI didnâ€™t expect the whole wheel to be moving forward and backward. It was Â¾ of an inch in some cases.â€
While that testing and development is ongoing, the BMR team is confident they are zeroing in on the causal factors and finding solutions.
â€œI think the automotive aftermarket is still figuring out the S550 chassisâ€”especially the IRS. Through all of BMRâ€™s testing, weâ€™ve found there is significant wheelhop. In our first round of testing, we literally chased wheelhop from part to part,â€ Pete said. â€œEach 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.â€
Of course, the challenge is sharpening the carâ€™s performance without detracting from the refinements bestowed on it by Ford.
â€œWhen 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 thatâ€™s what the aftermarket is for. That being said, the rubber bushing in the IRS cradle and differential mounts do nothing for performance,â€ he added. â€œThe 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.â€
So far the improvements have been significant, but there is no single, magic bullet for sharpening the performance of the S550 suspension.
â€œâ€¦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,â€ Pete said. â€œLowering 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.â€
â€œBMRâ€™s parts for eliminating wheel hop make equally significant improvements, but sometimes the â€˜feelâ€™ of the changes is much more subtle. Eliminating wheel hop will allow you to get more power to the ground as aggressively as possible,â€ he added. â€œAnother 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.â€
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.
â€œâ€¦Weâ€™ve already seen how strong the S550 is at the drag strip. BMRâ€™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,â€ Pete said. â€œThe 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 itâ€™s so new that people havenâ€™t realized it yet. Once people get over the stigma that the IRS wonâ€™t work at the drag strip, weâ€™re going to see some very fast S550s!â€
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 hereâ€¦
Now that we have had a look behind-the-scenes at BMRâ€™s S550 development, we canâ€™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.