Discussion
There is no way it will affect the gearing by 10%.
Mate is running 255/40x18 on his with no problems.
Try any wheel/tyre combo in this gear ratio calc and see.
www.geocities.com/z_design_studio/transmission_z28_6.html
Your diff is 3.46, tyre size is obvious.
Your gear ratios are slightly different, I dont have them off hand. But 4th is always the same, so easy to use it as an indicator.
>> Edited by stevieturbo on Saturday 26th November 22:16
Mate is running 255/40x18 on his with no problems.
Try any wheel/tyre combo in this gear ratio calc and see.
www.geocities.com/z_design_studio/transmission_z28_6.html
Your diff is 3.46, tyre size is obvious.
Your gear ratios are slightly different, I dont have them off hand. But 4th is always the same, so easy to use it as an indicator.
>> Edited by stevieturbo on Saturday 26th November 22:16
Ask yourself the question "how informed was the person that commented the rear tyres were too large?"
This comment is based on visualy comparing the apparent tyre size front to rear because you still have the original bridgestone potenza re040 235/40x18 fitted on the front.
The wheel rim is 55mm from the road on 235/40x18
The wheel rim is 65mm from the road on 245/40x18
while 10mm looks a large difference v8hsv correctly points out that the tyre circumference is the important point, being only 1.2% different.
I also use a RA2 which proved the speedo was 1-2% high on original 235/40x18.
Since fitting 245/40x18 on the rear the speedo now matches the RA2 perfectly!
This comment is based on visualy comparing the apparent tyre size front to rear because you still have the original bridgestone potenza re040 235/40x18 fitted on the front.
The wheel rim is 55mm from the road on 235/40x18
The wheel rim is 65mm from the road on 245/40x18
while 10mm looks a large difference v8hsv correctly points out that the tyre circumference is the important point, being only 1.2% different.
I also use a RA2 which proved the speedo was 1-2% high on original 235/40x18.
Since fitting 245/40x18 on the rear the speedo now matches the RA2 perfectly!
The garage have a duty of care to point out potential issues with your car that fall outside the std factory settings. They would have someone check the car and report all visual 'faults' as they saw it.
They have reported, correctly, that your tyres are too large for std fit items. If u had had tyres fitted somewhere else and they had put the wrong size on, u may nit have even known. The service garage are being diligent and reporting.
They have reported, correctly, that your tyres are too large for std fit items. If u had had tyres fitted somewhere else and they had put the wrong size on, u may nit have even known. The service garage are being diligent and reporting.
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