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      02-23-2010, 05:13 PM   #1
rmorin49
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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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      02-23-2010, 06:12 PM   #2
Jay Zone
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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.





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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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      02-23-2010, 10:55 PM   #4
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Does anybody know the RFT last for how long? Dealer told me 3 years max or 50000km.

Last edited by Otago; 02-24-2010 at 03:03 AM..
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      02-24-2010, 04:43 AM   #5
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Quote:
Originally Posted by Otago View Post
Does anybody know the RFT last for how long? Dealer told me 3 years max or 50000km.
That's probably a little optimistic. I got about 40,000 Km out of RFTs on 335i and 550i, replaced (full set on both cars) at 25 mos. (what is 'months' in metric? darn - shoulda paid more attention in physics class). Normal city/suburban/hiway miles, no track time.

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, 05:07 AM   #6
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Wow I was lucky to get about 20,000km on my E85.
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      02-24-2010, 08:04 AM   #7
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Wink

Quote:
Originally Posted by nickthegreek View Post
Wow I was lucky to get about 20,000km on my E85.
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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