Kendy Posted December 5, 2012 Report Share Posted December 5, 2012 Hello all! I'm new to the Forum and I have a question for everyone. I have a 2011 Ford Edge and in the spring the PCM needed to be replaced (covered by warranty). The day it failed, coincidentally, was the day my winter tires were removed and my spring ones put on. My spring tires are the original 18" tires that came with the vehicle and my winter ones (with rims) are 17". Could this difference have caused the PCM to fail (there was no diagnosis on why the PCM failed)? Does anyone know if I have the smaller winter tires on (which does effect my speedometer), does it void any warranties? Any help or ideas out there would be greatly appreciated! Quote Link to comment Share on other sites More sharing options...
akirby Posted December 5, 2012 Report Share Posted December 5, 2012 Could this difference have caused the PCM to fail (there was no diagnosis on why the PCM failed)? Does anyone know if I have the smaller winter tires on (which does effect my speedometer), does it void any warranties? Absolutely not in both cases. The PCM is a piece of electronics. They fail due to a fault in the circuit board or one of the components or because it got wet, etc. Other than getting it wet or shorting it out you can't cause it to go bad. Are you sure the 17" tires are smaller? They can have a smaller wheel diameter but maintain the overall circumference in which case the speedo won't be off. Find a tire size calculator and check both sizes. Even if they are smaller it won't hurt the warranty. The only wheel/tire related problem would be a bearing failure from running wheels that are too large/too heavy. Quote Link to comment Share on other sites More sharing options...
Kendy Posted December 5, 2012 Author Report Share Posted December 5, 2012 Thank you very much for the info. This will be my second winter with the 17" tires and I did notice the speedo off last season. I wanted to reach out and ask before I put the tires on again this season. It seemed such a coincidence that it happened when it did in the spring, I didn't want to cause another failure and therefore be held responsible. Thanks again!! You've set my mind at ease! Quote Link to comment Share on other sites More sharing options...
ls973800 Posted December 5, 2012 Report Share Posted December 5, 2012 Enter your 17" and 18" tire sizes into this calculator to see how much of a difference there really is between the two sizes. This will show you sidewall amount, height, width, RPM's, speedometer readings, etc. http://www.miata.net/garage/tirecalc.html When I was deciding to stay with the factory 20" wheels which came on the Edge or to replace them with a factory 18" set, I was surprised to see there was almost a ZERO difference between the two sizes! It's all because of the tire ratios and tire sizes which Ford uses. This results in no need for different gearing in the trans-axle or transmission as in past years. Heck, I could have even gone down to a 17" factory setup without too much difference from the 20" to worry about. Quote Link to comment Share on other sites More sharing options...
Waldo Posted December 5, 2012 Report Share Posted December 5, 2012 Having formerly worked in automotive electronics, the fact is that the vast majority of the times an electronic module like a PCM is replaced, the electronics aren't actually bad at all It's far more likely that the real issue is a bent pin or a poorly made connection somewhere. There's no chance that changing your tires caused your PCM to fail. Quote Link to comment Share on other sites More sharing options...
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