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04-11-2011, 08:16 AM | #24 |
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I was in for tire number 7 and the dealer saw a bubble on another tire.
Number 8 being installed this week. One of the salesmen said that he went through 12 tires. I had Porsches before my Z4 and never tires go like this even with NYC potholes. At least they are covered by insurance. |
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04-11-2011, 09:13 AM | #25 |
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Another reason not to use RFT
Quick comparo of tire weight on the Tire Rack's website:
255/35-18 rear tire: Bridgestone Potenza RE050A RFT (OEM tire): 27 Lbs Michelin Pilot Sport PS2 ZP (RFT): 29 Lbs Michelin Pilot Sport PS2 (same as above, not RFT): 24 Lbs Michelin Pilot Super Sport (non RFT): 25 Lbs That's anywhere from 2 to 5 more pounds of unsprung weight per wheel. Also, the RFT are up to $100 more per tire!
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04-11-2011, 09:36 AM | #26 |
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[QUOTE=cdeslandes;9336970
Here's a teaser, will post pics in the photo sections one mounted on the car with the new Michelin Pilot Super Sport (non-run flat) just ordered from the Tire Rack![/QUOTE] Good looking wheel, well done I don't think you have to worry about cracks in the new wheels they look very strong. What the parts manager told you is very interesting. I am wondering how many people just put the money on the table and believe the BMW story about having driven thru potholes. Then just pay the bill and never tell anyone. I maintain the 296 wheel is weak and there is some sort of a design flaw.
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04-11-2011, 05:01 PM | #27 | |
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I am not sure about RFTs contributing. I've always read that extra tire pressure causes less energy to go into the rim deflection and more into the suspension deflection. The RFTs should maximize the energy transfer into the suspension.
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04-11-2011, 06:53 PM | #28 | |
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So perhaps the negative side might be lower pressure? Also if a person has a flat driving 80 KM (50 Miles) certainly cannot be very healty for the inner wheel rim the sidewall of the RFT is reinforced with steel shims now inflicting more pressure to the inner outer rim due to the 2.5 degree camber.
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04-12-2011, 12:19 PM | #29 |
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I am neither an engineer nor physicist, so take the following with a grain of salt. It has not been supported by any form of testing or experimentation and therefore has no more basis in fact than unicorns selling bridges for a low low price and extra whitening power for your gear teeth. YMMV.
Seems like pressure could be the exact problem. Think about the air pressure in the tire and the pressure on the rim from hitting a bump separately. With increased air pressure, you may be transferring X pounds of force, but it's being distributed over a large surface area, the entire inside of the wheel and even the inner sidewalls of the tire...so the pressure, in pounds per square inch on the wheel, of a bump is pretty small when it's distributed by all the air in the tire. But if the force is distributed over a much smaller area, such as would be the case when a bump is transferred by the stiff sidewalls of a runflat to only the area of the rim in contact with the sidewall, the result is much higher pressure on that smaller portion of the rim taking the impact. Even though the pressure from the bump was the same, the ratio of pressure to square inches was higher because there were fewer square inches. Low tire pressures may very well be exacerbating the problem. Are BMW's recommended tire pressures for the 296 wheel any different than the other wheels? It may actually require more pressure. |
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04-12-2011, 01:16 PM | #30 | |
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There are more factors that can amplify the 296 wheel problem, so what about using the sport+ mode with the adaptive suspension? Last edited by zEdP; 04-12-2011 at 02:01 PM.. |
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04-13-2011, 03:35 PM | #31 |
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Here is my theory Gentleman ....
-RFT ... detrimental to the soft alloy wheels -Low Air Pressure ... will transfer more stress to the inner outer rim. -The 2.5 degree camber contributes to the overall mess. -Air Pressure control is very important -Watch what you put in the trunk when the roof is down you need more air pressure to take care of the extra weight Feel free to add to the list Forged wheels, different tires, change the camber on the rear wheels to 1 degree negative. A new car (makes sense when you add the cost for new wheels, tires and changing the camber). As I said it depends on the pocket book and how secure you want to be when you go on a trip. Try finding a wheel or a replacement RFT when you are in small town USA. I've been there done that and have no plans to do it again. Solutions ... well it all depends on your pocket book My cracked wheels gave me nightmares and I kicked myself for ever changing from my original M3 to a 2008 Z4 30is then to the 2009 Z4 35i (perhaps if I would have stuck with the 2008 I would not be typing this right now).
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04-13-2011, 03:40 PM | #32 | |
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Did you ever Google "Cracked wheels BMW" you will come across a link to "UK Watchdog" there are a lot of people in England with cracked wheels. BMW simply tells the customer "Sorry you went thru a pothole" You are right when you say "There are more factors that can amplify the 296 wheel problem" I bet BMW knows all about it only they are not telling the customer.
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04-13-2011, 10:34 PM | #33 |
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My 294's with non run flats Michelin Pilot Super Sport are on and they look and feel GREAT!
It's amazing how sharp the handling is, and how smooth the ride is now! Will takes pics when the rain stops and will post feedback in a new thread. ^ I'm happy!
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04-17-2011, 04:56 AM | #34 |
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If I get a crack in one of my 296's, replacing the damaged one will not solve the problem. The problem will come back.
Switching over a non RFT could reduce the change, but I guess that you have to buy two new rear wheels and not use wheels that ran many miles/kms with RFT. Even then, we have no prove the 296 with a non RFT is a solid combination. Switching over to the 294 will be very expensive. Trading in the E89 MY09 for a new one, 35i N55, 294 wheels, somewhere next year could be an option. |
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04-18-2011, 09:25 AM | #36 |
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Eric ... Moderator Thank!
Thanks Site Moderator
For putting up the Sticky on the BMW 296 Wheels
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Life will take us to some interesting places, fortunately The ///M3 will too with a many of us know this very well, now my C6.3 AMG with 487 HP does it too ---> Click here for some good stuff I found Last edited by Mr. ///M3 RD; 04-18-2011 at 09:52 AM.. |
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