The manufacturer says its Sport Springs are progressive-rate wherever the application allows, so the spring rate increases as the coil compresses. That makes this H&R 51655-500 set a practical street-and-track lowering option for the 2007-2010 Ford Shelby GT500 and GT500 Convertible V8. Owners on user forums describe the springs as German-made and good quality.
The main reason to choose this set over stock is the combination of stance and ride. Owners on user forums report that H&R rear springs leveled their GT500s with a full tank of fuel and rode better than the factory setup, and one owner reported dropping the car exactly 1" in both the front and back. Because published drop figures differ between sources, confirm the lowering number with H&R before you buy, especially if you want a fender-gap change without harsh ride.
Fitment is the key question for this GT500 lowering spring. One owner on a forum says H&R told them the Sport Springs do not suit 10-and-up Shelbys, while another reports fitting them on a 2010 car, so verify application before ordering. For the DIY side, you should measure your ride height before and after suspension installation. Alignment should be checked after any suspension ride height modification.
Sources conflict. One owner on a user forum says H&R told them the Sport Springs were not intended for 10-and-up Shelby GT500s, while another owner reports fitting them on a 2010 GT500. Confirm the application with H&R before ordering.
The manufacturer states that alignment should be checked after any ride height modification, and that the factory service manual guidelines should be followed to get as close to factory specification as possible.
Owners on user forums report that H&R sells rear springs separately and that rear-only swaps leveled their cars. One owner noted that taller-than-stock tires offset much of the drop, so tire size affects the result.
H&R publishes an installation and safety instruction PDF for its springs through its customer service resources, so review it before you start. Measure ride height before and after the swap to confirm the change, and plan on a wheel alignment afterward. It will take about a 1/2 hour to install these is how one owner on a user forum described a rear-only job, while another reported that the install time took me about 1.5hrs from start to finish. Full front-and-rear swaps will take longer than these rear-only accounts.
