- Jan 7, 2015
- 10
In France, we must get European certifications with CE tags on our sidewalls tires, but there is not a too much choice regarding dimensions, even less GT factory size who are not available anymore.
First choice has been 245/40X18 in front and 325/30X19 in rear (Michelin pilot sport cup 2) to not lose too much thickness, alas this choice was bad and the car entered in Limp mode, It took me a long time to understand where the problem came from.
Today, i swap the four wheels from another GT with Stock wheels and tire, go for a long road test in fact to be sure ; no limp go home problem anymore ! It was realy incorrect tires size who enter limp mode.
Ford factory sizes are 235/45X18 front = 669 mm diameter and 315/40X19 = 735 mm. The ratio between front and rear is 1.098 (9.8%)
GT friend's sizes are 245/40X18 front = 653 mm diameter and 325/30X19 = 678 mm. The ratio between front and rear is 1.038 ( 3.8%)
My personal GT sizes are 235/30X20 front = 649 mm diameter and 345/30X20 = 715 mm . The ratio between front and rear is 1.101 (10.1%)
Normaly, factories tolerance regarding ABS moudules are 5% up or 5% below, so 1.098 - 1.068 = 0.06 (6%) outside factory tolerance!
I know SCT tuners, who are able to correct speedo reading when you change tires heigth or differential gear ratio ,* I don't think they could resolve the problem because the speedo sender signal is not the same signal than the ABS wheels sensors.
Can anyone confirm or refute my reasoning ?
Thank you
First choice has been 245/40X18 in front and 325/30X19 in rear (Michelin pilot sport cup 2) to not lose too much thickness, alas this choice was bad and the car entered in Limp mode, It took me a long time to understand where the problem came from.
Today, i swap the four wheels from another GT with Stock wheels and tire, go for a long road test in fact to be sure ; no limp go home problem anymore ! It was realy incorrect tires size who enter limp mode.
Ford factory sizes are 235/45X18 front = 669 mm diameter and 315/40X19 = 735 mm. The ratio between front and rear is 1.098 (9.8%)
GT friend's sizes are 245/40X18 front = 653 mm diameter and 325/30X19 = 678 mm. The ratio between front and rear is 1.038 ( 3.8%)
My personal GT sizes are 235/30X20 front = 649 mm diameter and 345/30X20 = 715 mm . The ratio between front and rear is 1.101 (10.1%)
Normaly, factories tolerance regarding ABS moudules are 5% up or 5% below, so 1.098 - 1.068 = 0.06 (6%) outside factory tolerance!
I know SCT tuners, who are able to correct speedo reading when you change tires heigth or differential gear ratio ,* I don't think they could resolve the problem because the speedo sender signal is not the same signal than the ABS wheels sensors.
Can anyone confirm or refute my reasoning ?
Thank you