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Sedans Ultimate AWD Sports Sedans
828 messages, Last post on Oct 03, 2009 at 9:40 PM
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Replying to: bruceomega (Mar 19, 2008 9:14 am) I think it's safe to say if the stagger was offered as an option, it's OK but I am not qualified to comment on adding a staggered wheel/tire arrangement to the 2 cars you mentioned. Regards, OW |
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Replying to: bruceomega (Mar 19, 2008 9:14 am) In spite of the fact that BMW recommends against rotating tires (especially staggered ones for obvious reasons), I found that tire noise could be dramatically reduced and tire life could be nominally increased by rotating the tires on my BMWs. Best Regards, Shipo
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Replying to: bruceomega (Mar 19, 2008 9:14 am) If we think about an extreme case, where you have small tires up front and much bigger tires in the rear, the front axle would be spinning a lot faster than the rear axle, and that would confuse the AWD system, which might try to "correct" for that difference. I'm sure that's why tires are not staggered on the AWD models. Even if the circumference is the same, you would still have to account for things like tire wear and sidewall deflection. Given the better AWD systems are designed to react very quickly to differences in axle speeds, the tire circumference has to be very close, i.e. the tolerances are much smaller vs. cars with only one axle being powered. |
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Replying to: shipo (Mar 19, 2008 10:45 am) I have always rotated my tires but still do not understand BMW's direction regarding this. Regards, OW |
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Replying to: ateixeira (Mar 19, 2008 10:49 am) Exactly. Some manufacturers of AWD vehicles state that if your tires are over 25%-50% worn you should allways replace them in sets of four because of the difference in circumference. Ditto for the tires on an axle equipped with a LSD. |
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Replying to: ateixeira (Mar 19, 2008 10:49 am) But they are. consider the following: 2008 328xi Sedan offers a $300 upgrade to the Sport Package. Said upgrade includes: - - 17 x 8.0 front, 17 x 8.5 rear; 225/45R-17 front, 255/40R-17 rear run-flat performance tires. 2008 328xi Sport Wagon offers a $300 upgrade to the Sport Package. Said upgrade includes: - - 17 x 8.0 front, 17 x 8.5 rear; 225/45R-17 front, 255/40R-17 rear run-flat performance tires. 2008 328xi Coupe offers a $600 upgrade to the Sport package. Said upgrade includes: - - 18 x 8.0 front, 18 x 8.5 rear; 225/40R-18 front, 255/35R-18 rear run-flat performance tires. 2008 335xi Sedan offers a $600 upgrade to the Sport package. Said upgrade includes: - - 18 x 8.0 front, 18 x 8.5 rear; 225/40R-18 front, 255/35R-18 rear run-flat performance tires. 2008 335xi Coupe offers a $600 upgrade to the Sport package. Said upgrade includes: - - 18 x 8.0 front, 18 x 8.5 rear; 225/40R-18 front, 255/35R-18 rear run-flat performance tires. 2008 535xi Sedan offers a $600 upgrade to the Sport package. Said upgrade includes: - - 18 x 8.0 front, 18 x 9.0 rear; 245/40R-18 front, 275/35R-18 rear run-flat performance tires So, it would seem that every AWD version of the 3-Series and 5-Series save the 528xi can be had with staggered rubber. Go figure. Best Regards, Shipo
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Replying to: shipo (Mar 19, 2008 12:54 pm) I'm thinking that BMWs AWD system may get tweaked when staggered tires are fitted. Either that or the tires have an identical circumference. Otherwise the system would detect the difference in wheel rpm and interpret it as slippage.
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Replying to: roadburner (Mar 19, 2008 1:14 pm) I'll get my handy-dandy circumference calculator out and report back in a few minutes. Best Regards, Shipo |
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Okay, here's how diameters lay out for the upgraded SP package tires on the "xi" models: The 328xi Sedan and Sport Wagon: - - 225/45 R17 -- 24.97" (Front) - - 255/40 R17 -- 25.03" (Rear) - - Difference ------ 0.06" The 328xi Coupe, 335xi Sedan and 335xi Coupe: - - 225/40 R18 -- 25.09" (Front) - - 255/35 R18 -- 25.03" (Rear) - - Difference ------ 0.06" The 535xi Sedan: - - 245/40 R18 -- 25.72" (Front) - - 275/35 R18 -- 25.59" (Rear) - - Difference ------ 0.13" I'm thinking that as the worst (from a difference perspective) of the above cars is thirteen-hundredths of an inch, they can be considered virtually identical as far as their overall diameter is concerned.  Best Regards, Shipo |
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Replying to: shipo (Mar 19, 2008 6:06 pm) BTW, what's the difference in performance between 17" and 18" wheels on the 3 series from your point of view? Regards, OW
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