I bought a set of Kumho Ecsta ASX tires, sized 235/45R17 front and 285/40R17 rear from Performance Plus Tire in Long Beach, California. These tires were about 1⁄2 inch shorter than the tires they replaced, giving the Vic even more of a 4x4 stance. I bought a set of Kumho Ecsta ASX tires, sized 235/45R17 front and 285/40R17 rear from Per I fixed the stance issue by trimming two coils from the rear springs. I also needed to recalibrate my speedometer using the SCT X3 power programmer, which has provisions for speedo calculations based on revs per mile, 805 in the case of these tires. I fixed the stance issue by trimming two coils from the rear springs. I also needed to rec “Holy s*#@! That thing looks siiiick! K.J. Jones, Tech Editor, 5.0 Mustang Checking Offset/Backspace There are a variety of ways to determine just how wide a wheel and tire package you can fit on your car. Here is process I used. I found a good tire size comparison tool online at RimsNTires.com/specs.jsp that allows you to compare prospective wheel and tire combinations to what's on your car now. For this to work, you need to know your tire size (no biggie-it's molded into the tires) and the diameter, width, and offset of your existing wheels. Tire Rack will have specs for your stock wheels. Using the tire comparison tool, I plugged in my stock specs and then tried several combinations of section widths and aspect ratios to come up with a tire that was about 2 inches wider and within an inch of overall diameter of my stock tires. In my case, the 225mm section width is approximately 8.9 inches wide. A 285mm tire is approximately 11.2 inches wide. To determine the correct offset and backspace for the new wheels, I used Tire Rack's specs for my stock wheels: 16x7 ET50 (ET50 means 50mm positive offset-the hub flange is 50 mm outboard of the wheel's centerline). According to the tire comparison tool, this is equivalent to a 5.9-inch backspace. Knowing I could increase the overall package by about an inch inboard, and factoring a 285/40 tire mounted on a 17x9 wheel, a 37mm offset equates to 6.5 inches of backspace. I measured the space around the stock tire with the wheel mounted to the axle, figuring I could safely add at least 1 inch to the front and back of the centerline of the stock tire. I measured the space around the stock tire with the wheel mounted to the axle, figuring I Know that these are general figures that must be verified before having a set of wheels made and buying tires of a certain size. I checked my calculations with this Wheelrite tool made by Percy’s. Different brands of tires will have more sidewall bulge than others do, and that can throw off your calculations. Be conservative with your figures, however, and you will still be able to fill your wheelwells with a serious-looking wheel and tire combination that won’t rub over every bump in the road. End Know that these are general figures that must be verified before having a set of wheels ma Parts List Description PN Source Price 17x7.5 10-slot wheel (set of four) STL03670 Rock Auto $383.16 Widening two steel wheels to 9 inches N/A Pico Wheel & Tire 180.00 Kumho Ecsta ASX 245/45R17 (pair) N/A Performance Plus 266.00 Kumho Ecsta ASX 285/40R17 (pair) N/A Performance Plus 360.00 Mount and balance four tires N/A Performance Plus 79.00 Wheel alignment N/A Just Tires 79.00 Total $1,347.16 SOURCES Performance Plus Tire & Automotive 3910 Cherry Ave Long Beach CA 90807 562-988-0211 www.performanceplustire.com Rock Auto 6680 Odana Road Madison WI 53719 866-762-5288 http://www.rockauto.com Pico Wheel & Tire North Hollywood CA 818-982-0375 « | 1 | 2 | View Full Article By John McGann Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!