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02-23-2010, 05:13 PM | #1 |
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OEM Runflat: May be 3G after all?
Having not read too many complaints about a bone jarring ride from E89 Z4 owner I decided to do a little research.
Seems Bridgestone has now released the 3rd generation of their runflat tires. See this article: http://www.autoblog.com/2009/07/06/r...ck-out-of-run/ Went to TireRack website and found that this tire is listed as the OEM tire for BMW: http://www.tirerack.com/tires/tires....0&autoModel=Z4 sDrive30i&autoModClar=Sport Package It is noted as being "New" so I am thinking that BMW is fitting the latest Z4 with the 3rd Gen runflats. If this is true this may explain why the ride is not near as rough as many 3 series owners, 07 and 08, are complaining about. However, it still gets mediocre reviews when compared with other high performance tires. Now my question is: There are two different ratings listed for the 225-40-18 size in this tire on the TireRack website. 88Y is the one listed as the OE tire. The other is 88W. Is this referring to a load rating or a speed rating? I think it is speed and the Y rating is one level below Z. Is this correct?
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Colonel (Retired), US Army/Hagerstown, MD
2016 518ixdrive/MSport AW/Ivory White ED-01-10 2010 Z4s30i AW/Beige/Burl/ 6MT/SP/PP/CWP/NAV/ipod/USB/CA (retired) 2011 335d BS/Oyster/PP/CWP/NAV/ipod/USB(Daily Driver) 30+ mpg(retired) |
02-23-2010, 06:12 PM | #2 |
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Nice catch. I suspected mine were 3G. Thanks for the TireRack link my 07 335i tread is almost due for the upgrade.
RFT are still inferior to the best High performance tires. If I was aiming for higher performance I would definitely go for the non-RFT. But I think the difference is not really noticeable unless you track your car. Or live in a state where you can really drive your Z without laser guns on every corner. JZ |
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02-23-2010, 09:50 PM | #3 |
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Lots of info here:
http://www.tirerack.com/tires/tirete....jsp?techid=35 Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110. Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below: L 75 mph 120 km/h Off-Road & Light Truck Tires M 81 mph 130 km/h N 87 mph 140km/h Temporary Spare Tires P 93 mph 150 km/h Q 99 mph 160 km/h Studless & Studdable Winter Tires R 106 mph 170 km/h H.D. Light Truck Tires S 112 mph 180 km/h Family Sedans & Vans T 118 mph 190 km/h Family Sedans & Vans U 124 mph 200 km/h H 130 mph 210 km/h Sport Sedans & Coupes V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities. W 168 mph 270 km/h Exotic Sports Cars Y 186 mph 300 km/h Exotic Sports Cars While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed. 225/50ZR16 in excess of 149 mph, 240 km/h 205/45ZR17 88W 168 mph, 270 km/h 285/35ZR19 99Y 186 mph, 300 km/h Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below: 285/35ZR19 99Y 186 mph, 300 km/h 285/35ZR19 (99Y) in excess of 186 mph, 300 km/h As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.
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2011 E89 Z4 M Sport (Euro Delivery, Performance Center redelivery), Extended Nappa leather, Eisenmann Sport Exhaust 2003 E46 325i Touring |
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02-24-2010, 04:43 AM | #5 | |
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Quote:
Keep a close eye on the sidewall/tread junction inside the front tires. Cannot see problem just looking at the tread - reach around and feel the inside sidewall. On both cars, failure was pretty severe. Lost tire pressure, inside sidewall pretty much shredded, zero warning. But also had zero ride/handling issues with the RFTs. In all much an improvement over conventional tires IMHO. YMMV. |
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02-24-2010, 08:04 AM | #7 |
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It's that "down under" asphalt. Much rougher than what we have north of the equator, LOL. And you guys all drive like you stole it@
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Colonel (Retired), US Army/Hagerstown, MD
2016 518ixdrive/MSport AW/Ivory White ED-01-10 2010 Z4s30i AW/Beige/Burl/ 6MT/SP/PP/CWP/NAV/ipod/USB/CA (retired) 2011 335d BS/Oyster/PP/CWP/NAV/ipod/USB(Daily Driver) 30+ mpg(retired) |
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