SPD Tuning Service
Page down for detailed information. Suggestions, comments and questions are always welcome.
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SPD Tuning Service Page down for detailed information. Suggestions, comments and questions are always welcome.
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Why are 16 and 17 aftermarket rims associated with poor steering and often rubbing tires? There are two issues here. The first is that wide, stiff, high performance tires tend to have poor directional stability compared to passenger car tires. The better the tire grips and turns, the less stable it will be. A second and overlooked factor is the rim offset. Subaru is built to a 15x6 +55mm and 16x7 +53 offset and if you install +45 or god forbid, +40 or +35 offsets, the steering becomes very squirrelly. As my sister said, "You have to drive it more." Pzeros on a +55 offset are not that bad. They move all over on a +45 offset. For 205/45-17 you may use a 17x7+55 and a 215/40 will use a +50. These numbers are from Prodrive. That is about the limit before the hammers come out of the tool box....a +45 rim will need the inner lip of the rear fender opening bent up and in if you expect to use FULL wheel travel. This cracks the paint, which is not the end of the earth, but needs tending to. They also start to touch on the front fender opening...again when using the tire for its intended purpose. Best get the correct offsets. Every month I get a comment from an owner who has bought "bargain" wheels, only to find that tires touch or the car steers funny or want to know why the tires rub. This is one of many reasons we offer only low pressure cast, heat treated and inspected wheels made expressly for the Subaru. As to comments the understeer goes away with high performance tires, this is not exactly the case. What goes away are the wide slip angles associated with low-tech tires. In addition, the actual cornering forces have now gone way up. The understeer is still there. You just have to drive a lot harder to find it. And when you do find it, it still takes a huge lift of the throttle to kill it. |
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Send mail to mshields@spdusa.com with
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