What I Learned About Run Flats and 2002 C5 Wheels
07-04-2002, 04:26 AM
#1
Racer
Thread Starter
What I Learned About Run Flats and 2002 C5 Wheels
Hi,
1) Tire weight comparison
2) Wheel weights
3) Wheel & tire inertias
4) Effective weight ratios
I changed my EMT’s for Bridgestone S03’s. I expected to lose about 6lbs per tire based on Net Roomers. This is the weight comparison:
275 EMT = 32.5lbs (3k miles)
275 S03 = 33lbs (new) (+0.5lbs each!)
245 ETM = 29.5lbs
245 S03 = 27lbs (-2.5lbs each)
For a grand total of 4lbs lighter! Rats! What happened to the 24lb reduction with non-EMT? Do you have any tire data?
I weighed each wheel as the tires were being changed. These are WCC chromed stock GM 2001, 5-spokes. The weights are:
#1 17x8.5 front = 18.5lbs
#2 17x8.5 front = 19.5lbs!
#1 18x9.5 rear = 20lbs
#2 18x9.5 rear = 21lbs!
I guess I figured that they would be within several ounces of each other.
I also took the time to measure the inertia of the wheels and tires to add to my Vette math model. The method I used came from Van Valkenburgh’s book, “Race Car Engineering & Mechanics”. This method uses a rotational pendulum with the wheel & tire as the mass. You get the tire to oscillate and measure the period. I hung some rope from the ceiling and leveled the tire before the test.
The results are:
Stock front wheels & EMT's = 1.19 ft-lb-sec^2
Stock rears = 1.38 ft-lb-sec^2
So why is this interesting? Because it tells you how much the effective weight of the wheel & tire is. This is the weight plus the equivalent weight of the rotational inertia.
For the front wheels & EMT's the weights are:
Weight = 49.5
Added weight due to inertia = 32.5
Total or Effective weight = 82.0lbs!
That’s a ratio of 1.66.
For the rears:
Weight = 55.5
Added weight due to inertia = 36.3
Total or Effective weight = 91.8lbs!
That’s a ratio of 1.65.
This is why I was hoping for a 24lb weight reduction with the S03’s.
The inertia calculation is:
I (ft-lb-sec^2) = r^2 * t^2 * wt /(473 * L)
The effective weight calculation is:
Equivalent added weight = 9.8 * t^2 * wt / L
Where:
r is the radius of the test rig (the tire)
t is the period of oscillation (time 20 cycles for an average)
wt is the weight
L is the length of the pendulum
Bye for now,
Steve
:seeya
1) Tire weight comparison
2) Wheel weights
3) Wheel & tire inertias
4) Effective weight ratios
I changed my EMT’s for Bridgestone S03’s. I expected to lose about 6lbs per tire based on Net Roomers. This is the weight comparison:
275 EMT = 32.5lbs (3k miles)
275 S03 = 33lbs (new) (+0.5lbs each!)
245 ETM = 29.5lbs
245 S03 = 27lbs (-2.5lbs each)
For a grand total of 4lbs lighter! Rats! What happened to the 24lb reduction with non-EMT? Do you have any tire data?
I weighed each wheel as the tires were being changed. These are WCC chromed stock GM 2001, 5-spokes. The weights are:
#1 17x8.5 front = 18.5lbs
#2 17x8.5 front = 19.5lbs!
#1 18x9.5 rear = 20lbs
#2 18x9.5 rear = 21lbs!
I guess I figured that they would be within several ounces of each other.
I also took the time to measure the inertia of the wheels and tires to add to my Vette math model. The method I used came from Van Valkenburgh’s book, “Race Car Engineering & Mechanics”. This method uses a rotational pendulum with the wheel & tire as the mass. You get the tire to oscillate and measure the period. I hung some rope from the ceiling and leveled the tire before the test.
The results are:
Stock front wheels & EMT's = 1.19 ft-lb-sec^2
Stock rears = 1.38 ft-lb-sec^2
So why is this interesting? Because it tells you how much the effective weight of the wheel & tire is. This is the weight plus the equivalent weight of the rotational inertia.
For the front wheels & EMT's the weights are:
Weight = 49.5
Added weight due to inertia = 32.5
Total or Effective weight = 82.0lbs!
That’s a ratio of 1.66.
For the rears:
Weight = 55.5
Added weight due to inertia = 36.3
Total or Effective weight = 91.8lbs!
That’s a ratio of 1.65.
This is why I was hoping for a 24lb weight reduction with the S03’s.
The inertia calculation is:
I (ft-lb-sec^2) = r^2 * t^2 * wt /(473 * L)
The effective weight calculation is:
Equivalent added weight = 9.8 * t^2 * wt / L
Where:
r is the radius of the test rig (the tire)
t is the period of oscillation (time 20 cycles for an average)
wt is the weight
L is the length of the pendulum
Bye for now,
Steve
:seeya
07-04-2002, 11:57 PM
#9
Le Mans Master
Member Since: Apr 2001
Location: Ex-SF Bay Area; now happily Denver area
Posts: 8,133
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Re: What I Learned About Run Flats and 2002 C5 Wheels (NewVetteLover)
I got a headache after just a few sentences... :D
[Modified by FunDriver, 7:58 PM 7/4/2002]
[Modified by FunDriver, 7:58 PM 7/4/2002]
07-05-2002, 01:14 AM
#11
Racer
Thread Starter
Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
By popular demand, here is a Less Taxing Version:
Lighter is better, (axiom requiring no proof)
Lighter tires are way-more better, (see above)
Non-run flats are not always lighter, (ibid)
Non-run flats may only be just better. (speculative assertion)
Part of the joy of sharing with my fellow Vette owners is there kind and sometimes- enlightening replies.
Bye,
Steve
:seeya
Lighter is better, (axiom requiring no proof)
Lighter tires are way-more better, (see above)
Non-run flats are not always lighter, (ibid)
Non-run flats may only be just better. (speculative assertion)
Part of the joy of sharing with my fellow Vette owners is there kind and sometimes- enlightening replies.
Bye,
Steve
:seeya
07-05-2002, 01:24 AM
#12
Melting Slicks
Member Since: May 2000
Location: Portland OR
Posts: 2,375
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Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
Steve,
Had you included your last post in your original thread posting you would have gotten through to many more of us readers. :rolleyes:
Had you included your last post in your original thread posting you would have gotten through to many more of us readers. :rolleyes:
07-05-2002, 04:08 AM
#14
Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
I'm just a dumb sales guy and I got it. This is good info. You should post it on the racing forum as it will probably be of interest over there. Thanks for your effort!
07-05-2002, 07:51 AM
#15
Melting Slicks
Member Since: Mar 2001
Location: New Milford CT
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Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
SNW Vette, please tell us how you like the S0-3's. That is my next vette tire of choice also.
07-05-2002, 10:40 AM
#16
Safety Car
Re: What I Learned About Run Flats and 2002 C5 Wheels (CJS)
SNW Vette, please tell us how you like the S0-3's. That is my next vette tire of choice also.
Way stickier than the GS-C Z06 tire.
07-05-2002, 10:58 AM
#17
Instructor
Member Since: Jun 2001
Location: Tipp City Ohio
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Re: What I Learned About Run Flats and 2002 C5 Wheels (Richin Chicago)
I've got them and they are great! Quiet and smooth on the highway and the stickiest tire we saw at the roadcourse.
Way stickier than the GS-C Z06 tire.
Way stickier than the GS-C Z06 tire.
07-05-2002, 11:36 AM
#19
Race Director
Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
SNW
very interesting!
for comparison my 15" steel wheels weigh 25, and my 255x60x15 weigh 30, for a total of 55. Sounds just as heavy, but with a 15" wheel, wouldn't the effective mass be lower, thus it would be easier to accelerate my combo on my 72, even with steel wheels?
my 61 has 235x60x15 rear, weighs 39 total(with aluminum wheel) just step on the gas and it spins 'em even at just 1500 rpm in 1st
very interesting!
for comparison my 15" steel wheels weigh 25, and my 255x60x15 weigh 30, for a total of 55. Sounds just as heavy, but with a 15" wheel, wouldn't the effective mass be lower, thus it would be easier to accelerate my combo on my 72, even with steel wheels?
my 61 has 235x60x15 rear, weighs 39 total(with aluminum wheel) just step on the gas and it spins 'em even at just 1500 rpm in 1st
07-05-2002, 11:52 AM
#20
Re: What I Learned About Run Flats and 2002 C5 Wheels (SNW Vette)
Here's what you do....
Leave the laptop at home.
Cut out the fries.
Drink diet soda only...No beer.
That should make up the difference.
:D :D ...GeorgeC
Leave the laptop at home.
Cut out the fries.
Drink diet soda only...No beer.
That should make up the difference.
:D :D ...GeorgeC