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Old 11-05-2013, 03:23 PM
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QSilver7 QSilver7 is offline
Officially Welcomed to the 'Fest
Location: Northeast Indiana
 
Join Date: Aug 2008
Posts: 5,802
Mein Auto: 1997 740iL / 2006 X5 4.4
You should try to stay within 3% (+/-) the diameter/circumference of the original tire size. This is not just for speedometer & odometer...but the X5's (early) 38/62 AWD ratio & the later 40/60 "variable" xDrive ratio must be considered in the calculations that tie-in ABS/DSC/Traction Control/AWD/xDrive.

Going beyond the 3% limit could (not saying it will) but could have some affect on the way these features work/perform...and could throw them off as well as the speedometer/odometer.

If you want more "cushion" with a 65 aspect ration...you could go to a 235/65/18 tire. This tire would fit an 18" wheel that is 6.5"-8" wide...as well as meet the criteria of being within 3% (+/-) of the orig diameter/circumference.

A quick pull up of a wheel/tire calculator will show you how close you are to the 3% margin. Just google tire calculator, then input the original tire size as the base reference. The narrower the tire, the higher the aspect ration can go. The wider the tire, the lower the aspect ration should go (if you want to maintain the 3% tolerance).
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Q {BMW CCA Member #191509}
2006 E53 X5 4.4i (Sterling Gray) 12/05 mfg date <<~>> 97 740iL (Arctic Silver) 3/97 mfg date
(SOLD)
99 540iT (Orient Blue) <<~>> 95 525IT (Alpine White)
91 735iL (Schwarz Black) <<~>> 85 325e (Bronzit)

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Last edited by QSilver7; 11-05-2013 at 03:25 PM.
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