z51vette
02-11-2007, 12:37 AM
I Got an 07 sport pack and was looking to improve the handling and the look of the car. So I decided to get the 06 staggered 192M wheel option by purchasing two 18x9" rims for the rear. As some of you know in 07 they killed the 18" staggered wheel option and replaced it with a 19" staggered option. I didn't want to have 19s on my car and needed all season tires so I ordered it from the factory standard with 18x8" 192M wheels and 235/50 18 AS tires all around. Stock tires were Michelin Pilot HX MXM4 235/50 18 all around. Ride comfort with stock tires was OK even with the sport pack but handling is only so so. With noticeable body roll and a bit of unresponsiveness.
Since then I've tried three sets of tires on it. Reading great reviews from tirerack I ordered Kumho Ecsta ASX in 235/50 18 front and 255/45 18 rear per 06 Specs. Installed the tires and was very disappointed in them. The ride went to crap. Absolutely unbearable. Very harsh riding tire, Very noisy. Handling better but with such bad ride that becomes irrelevant. Also a weird driveline wine at certain engine speeds and gears and got Automatic Transmission shifting problems. The whine is not related to balancing. I thought it might be due to slightly shorter overall diameter of the tires. The stockers 235/50 18 Michelins are 27.5" OD (overall diameter) and 759 revolutions per mile. The Kumhos are 27.3" OD front and 27" OD rear. Could not find Revolutions per mile on this tire anywhere in the specs. The whine sounds like gear whine, short duration for a few seconds at a time and could be present at any given time and speed. Just from standstill or going 65 on the highway.
At first I thought it was the tires so I got a set of Michelin Pilot Sport AS in the same 235 front 255 rear sizes. After mounting them on the car the whine went away completely. The ride improved but still harsher than Pilot HX. A bit too harsh for my taste. Much quieter than Kumhos and possibly even quieter than stockers on the highway but not over bumps and expansion joints. Handling is fantastic. Feels like a different car. Response is immediate with absolute absence of body roll. What I hate about this tire is the width of the rear 255/45 18 tires. I don't know what Michelin was thinking but they decided to make 235/50 18 and 255/45 18 dimensionally identical. Meaning they are the same width. It looks weird on a 9" wide rim and looks too skinny in the back. Really kills the staggered look. They are both 27.2" OD and 762 revs per mile. Very close to stock (759 revs per mile). Less than 1/3 of a percent deviation from stock OD. Since the whine disappeared I thought to myself maybe it was the difference in diameters of the Kumhos 27.3" front, 27" rear or even a problem with the tires themselves.
Back to Michelin Pilot Sport AS. Unhappy mostly with the look of the rear tires and after getting a few complaints from rear seat passengers about ride quality I went on a new tire search. Now looking for identical or very close diameter front to rears and the ultimate in width rear tire. I came up with Pirelli P-Zero Nero MS in 245/45 18 front and 275/40 18 rear. Specs say these tires will work fine on 18x8 and 18x9 wheels respectively. They are 26.7", 26.6" OD and 780, 782 revolutions per mile front/rear. They are within 2% of the stock diameter. And I thought to myself a worn stock tire would be close to the diameter of these. So I got the tires. Which, mind you was not an easy thing to do. The 275/40 18 is on national back order. No one had these tires. Had to get them shipped from Pirelli directly after a few favors. Got them installed. From the rear the car looks fantastic. This is what the sport pack X3 should look like. Very meaty and mean look to it, though the tires seem to fill the wheel well a little less due to the smaller diameter. Driving impressions: The tire is supremely quiet. Quieter than Pilot Sport AS or the Stock Pilot HX tires. Comfort is better than Pilot Sport but maybe not as forgiving and Pilot HX. After all this is a Z rated tire and the stockers are H rated. Handling is great though responsiveness not as sharp as Pilot Sport AS. Possibly due to the wider 275 tire on the same 9" rim as the 255 Pilot Sport AS. On the Negative Side. The driveline/gear whine is back. Also the AT shifting problems are back. I think the speedometer is way off now by as much as 10MPH at 60. However I wasn't able to verify this. Maybe they are just so quiet that I think I'm going slower. After all 2% difference in size should yield only about 1.5 MPH difference going 60. Now I know for certain that changing tire size will cause all sorts of computer related problems even if it is only a very minor change.
Here is my dilemma. Can the computer be reprogrammed to compensate for tire size? Spoke to a few dealers they tell me, NO, only the factory can do that. Kind of hard to imagine the dealer can't reprogram for tire size. It is very simple to do even with basic hypertech programmer on almost all GM cars. Why would BMW only reserve that for the factory? If I'm not able to get the car reprogramed I will probably have to put my stock 235/50 18 Pilot HX MXM4 tires back on. That would be a shame, not to be able to keep the best tires for the car after spending all this money just because of dealer incompetency in reprogramming the ECU.
Anyone know how to reprogram the ECU for tire size?
I will post pictures of Michelin Pilot Sport AS and Pirelli P-Zero Nero On my car shortly.
Since then I've tried three sets of tires on it. Reading great reviews from tirerack I ordered Kumho Ecsta ASX in 235/50 18 front and 255/45 18 rear per 06 Specs. Installed the tires and was very disappointed in them. The ride went to crap. Absolutely unbearable. Very harsh riding tire, Very noisy. Handling better but with such bad ride that becomes irrelevant. Also a weird driveline wine at certain engine speeds and gears and got Automatic Transmission shifting problems. The whine is not related to balancing. I thought it might be due to slightly shorter overall diameter of the tires. The stockers 235/50 18 Michelins are 27.5" OD (overall diameter) and 759 revolutions per mile. The Kumhos are 27.3" OD front and 27" OD rear. Could not find Revolutions per mile on this tire anywhere in the specs. The whine sounds like gear whine, short duration for a few seconds at a time and could be present at any given time and speed. Just from standstill or going 65 on the highway.
At first I thought it was the tires so I got a set of Michelin Pilot Sport AS in the same 235 front 255 rear sizes. After mounting them on the car the whine went away completely. The ride improved but still harsher than Pilot HX. A bit too harsh for my taste. Much quieter than Kumhos and possibly even quieter than stockers on the highway but not over bumps and expansion joints. Handling is fantastic. Feels like a different car. Response is immediate with absolute absence of body roll. What I hate about this tire is the width of the rear 255/45 18 tires. I don't know what Michelin was thinking but they decided to make 235/50 18 and 255/45 18 dimensionally identical. Meaning they are the same width. It looks weird on a 9" wide rim and looks too skinny in the back. Really kills the staggered look. They are both 27.2" OD and 762 revs per mile. Very close to stock (759 revs per mile). Less than 1/3 of a percent deviation from stock OD. Since the whine disappeared I thought to myself maybe it was the difference in diameters of the Kumhos 27.3" front, 27" rear or even a problem with the tires themselves.
Back to Michelin Pilot Sport AS. Unhappy mostly with the look of the rear tires and after getting a few complaints from rear seat passengers about ride quality I went on a new tire search. Now looking for identical or very close diameter front to rears and the ultimate in width rear tire. I came up with Pirelli P-Zero Nero MS in 245/45 18 front and 275/40 18 rear. Specs say these tires will work fine on 18x8 and 18x9 wheels respectively. They are 26.7", 26.6" OD and 780, 782 revolutions per mile front/rear. They are within 2% of the stock diameter. And I thought to myself a worn stock tire would be close to the diameter of these. So I got the tires. Which, mind you was not an easy thing to do. The 275/40 18 is on national back order. No one had these tires. Had to get them shipped from Pirelli directly after a few favors. Got them installed. From the rear the car looks fantastic. This is what the sport pack X3 should look like. Very meaty and mean look to it, though the tires seem to fill the wheel well a little less due to the smaller diameter. Driving impressions: The tire is supremely quiet. Quieter than Pilot Sport AS or the Stock Pilot HX tires. Comfort is better than Pilot Sport but maybe not as forgiving and Pilot HX. After all this is a Z rated tire and the stockers are H rated. Handling is great though responsiveness not as sharp as Pilot Sport AS. Possibly due to the wider 275 tire on the same 9" rim as the 255 Pilot Sport AS. On the Negative Side. The driveline/gear whine is back. Also the AT shifting problems are back. I think the speedometer is way off now by as much as 10MPH at 60. However I wasn't able to verify this. Maybe they are just so quiet that I think I'm going slower. After all 2% difference in size should yield only about 1.5 MPH difference going 60. Now I know for certain that changing tire size will cause all sorts of computer related problems even if it is only a very minor change.
Here is my dilemma. Can the computer be reprogrammed to compensate for tire size? Spoke to a few dealers they tell me, NO, only the factory can do that. Kind of hard to imagine the dealer can't reprogram for tire size. It is very simple to do even with basic hypertech programmer on almost all GM cars. Why would BMW only reserve that for the factory? If I'm not able to get the car reprogramed I will probably have to put my stock 235/50 18 Pilot HX MXM4 tires back on. That would be a shame, not to be able to keep the best tires for the car after spending all this money just because of dealer incompetency in reprogramming the ECU.
Anyone know how to reprogram the ECU for tire size?
I will post pictures of Michelin Pilot Sport AS and Pirelli P-Zero Nero On my car shortly.