Minimum wheel save strength for an E90/E92?

skow · 11-08-2009, 12:05 AM

In another post, the rating of 1200 lbs/wheel of the forgestar f14s was called in to question. As that comment wasn't folowed up, nor the topic of the thread, i felt something safety related was deserving of its own thread. So what would you say is the minimum safe wheel rating?

If I'm at 3800lbs/4 = 950lbs, how much more would i need? I would assume a tolerance is put into a wheel strength rating, so it likely can take more, but the absolute minimum it could fail at is the rating amount?

perrymaxima · 11-08-2009, 08:27 AM

Good tread going to subscribe to this one...

skow · 11-09-2009, 08:23 PM

No one has any input?

bantam · 11-09-2009, 08:46 PM

The actual solution to this problem is rather complex, as it would require a simulation of the loading that the wheel is to experience (either in a lab or using a FEA system). Aluminum (unlike ferrous materials) will progressively lose yield strength as the number of loading cycles that it is subjected to increases.

Thats not all, but the bottom line is that you cant just do a simple stress calculation.

Each wheel manufacturer probably has some proprietary rule of thumb that they use in order to provide the wheel with a safety factor.

If you're that worried, buy OEM.

Shazmonkee · 11-09-2009, 10:10 PM

Take a look here. A heated debate i'd say..pretty interesting..makes you think twice about the forgestar though lol

http://www.m3post.com/forums/showthread.php?t=316081

skow · 11-10-2009, 01:17 AM

Quote:

Originally Posted by Shazmonkee

Take a look here. A heated debate i'd say..pretty interesting..makes you think twice about the forgestar though lol

http://www.m3post.com/forums/showthread.php?t=316081

Ahh, thanks for the link, that is a good read. From what i read the 19" are 1500lb/wheel rated, which sounds sufficient, but yes the 1200/wheel on the 18" is pretty sketchy. The 18" tires weighing so little, 5 lbs per wheel less than the 19" sounded nice, but simply not worth such a risk or a wheel failing.

And yes, temperature, car balance & suspension, prior stress, etc all impact a failing of a wheel, but from what was said on that thread, a safe rule of thumb is 1.5 times the cars weight per tire. (1450/950 = 1.52).

jayhudson · 11-10-2009, 10:57 AM

All of this is very interesting. I wonder what the rating is on 17x8.5" Kosei K-1s? I've bent several and broken the spokes on 2 on the race car. Just figured it was the stresses of the track and racing. I know they're a cast wheel and are pretty light at around 17lbs.

Does anyone know the rating for the K-1?

Thanks - Jay

ALUFELGEN · 11-10-2009, 11:04 AM

For any BMW wheel you`d want something in between 1450 - 1600lbs per corner or 660kg - 710kg. VIA/JWL certifications will require above 1500lbs per corner. Anything lower than that means that the wheel will not be certifiable by them.

These are guidelines established for your own safety.

11-08-2009, 12:05 AM	#1
skow First Lieutenant 20 Rep 310 Posts Drives: 2016 F36 Gran Coupe xDrive Join Date: Mar 2009 Location: Oregon iTrader: (1)	Minimum wheel save strength for an E90/E92? In another post, the rating of 1200 lbs/wheel of the forgestar f14s was called in to question. As that comment wasn't folowed up, nor the topic of the thread, i felt something safety related was deserving of its own thread. So what would you say is the minimum safe wheel rating? If I'm at 3800lbs/4 = 950lbs, how much more would i need? I would assume a tolerance is put into a wheel strength rating, so it likely can take more, but the absolute minimum it could fail at is the rating amount?
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11-08-2009, 08:27 AM	#2
perrymaxima Lieutenant 27 Rep 482 Posts Drives: E70 X5 M Sport Join Date: Sep 2009 Location: Oahu, HI iTrader: (7)	Good tread going to subscribe to this one...
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11-09-2009, 08:23 PM	#3
skow First Lieutenant 20 Rep 310 Posts Drives: 2016 F36 Gran Coupe xDrive Join Date: Mar 2009 Location: Oregon iTrader: (1)	No one has any input?
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11-09-2009, 08:46 PM	#4
bantam Private First Class 20 Rep 144 Posts Drives: 2009 335i Join Date: Sep 2008 Location: Dallas, TX iTrader: (2)	The actual solution to this problem is rather complex, as it would require a simulation of the loading that the wheel is to experience (either in a lab or using a FEA system). Aluminum (unlike ferrous materials) will progressively lose yield strength as the number of loading cycles that it is subjected to increases. Thats not all, but the bottom line is that you cant just do a simple stress calculation. Each wheel manufacturer probably has some proprietary rule of thumb that they use in order to provide the wheel with a safety factor. If you're that worried, buy OEM.
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11-09-2009, 10:10 PM	#5
Shazmonkee 116 Rep 2,455 Posts Drives: BMW E92 Join Date: Feb 2007 Location: United States iTrader: (11) Garage List 2007 BMW 328i E92 C ... [0.00]	Take a look here. A heated debate i'd say..pretty interesting..makes you think twice about the forgestar though lol http://www.m3post.com/forums/showthread.php?t=316081
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11-10-2009, 10:57 AM	#7
jayhudson Ex-CCA racer 3 Rep 183 Posts Drives: '08 328i Join Date: Jul 2009 Location: Grants Pass, OR iTrader: (0)	All of this is very interesting. I wonder what the rating is on 17x8.5" Kosei K-1s? I've bent several and broken the spokes on 2 on the race car. Just figured it was the stresses of the track and racing. I know they're a cast wheel and are pretty light at around 17lbs. Does anyone know the rating for the K-1? Thanks - Jay __________________
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11-10-2009, 11:04 AM	#8
ALUFELGEN 175 Rep 2,056 Posts Drives: E92 M3 Join Date: Nov 2008 Location: South Florida iTrader: (5)	For any BMW wheel you`d want something in between 1450 - 1600lbs per corner or 660kg - 710kg. VIA/JWL certifications will require above 1500lbs per corner. Anything lower than that means that the wheel will not be certifiable by them. These are guidelines established for your own safety.
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