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post #1 of 25 (permalink) Old Sep 15th, 2007, 12:31 pm Thread Starter
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Free Magnesium Wheels

How about a free front magnesium wheel with your next tire purchase?

Consider this:

3.5 x 17 Wheel Weights:

Ducati OEM aluminum 5-spoke .... 9.25 lbs
Marchesini magnesium 5-spoke ... 6.80 lbs
Weight Savings ................. 2.45 lbs


120/70ZR17 Tire Weights (Sport Rider Magazine June 2002)

Dunlop D207RR ............... 10.44 lbs
Pirelli Super Corsa............. 8.38 lbs
Weight Savings ................. 2.06 lbs

Dunlop D207RR ............... 10.44 lbs
Bridgestone BT-010 .......... 8.81 lbs
Weight Savings ................. 1.63 lbs

This seemingly small weight difference between the heaviest Dunlops and the lighter Bridgestones is even more important than a larger weight savings at the wheel.

Simply stated, the rotational inertia of a wheel or tire is proportional to the square of the distance the weight is placed from the axle. Because of this square-effect, the tire weight has more effect on the rotational inertia of the wheel-tire combination mainly because of its somewhat greater distance from the axle.

Consequently, a 1.6 - 2 lbs. lighter front tire will give you the same handling improvement that you get by switching from an aluminum to a magnesium wheel.

Looking at it another way, you can negate the handling benefits of expensive light weight wheels by switching to a heavier tire.

This is also the best argument for choosing aftermarket wheels that have carbon fiber rims. When compared to all-magnesium wheels with the same weight, a carbon fiber rimmed wheel will have significantly lower rotational inertia that results in improved acceleration and handling.

(The similar construction of rear tires results in weight savings of less than a pound so you'll see a lesser improvement effect there.)

I'm not saying that tires should be chosen based on weight alone but given the very similar performance of high performance street tires, why not take the free mag wheel?
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post #2 of 25 (permalink) Old Oct 9th, 2007, 9:23 am
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Quote:
Originally Posted by Shazaam
How about a free front magnesium wheel with your next tire purchase?

Consider this:

3.5 x 17 Wheel Weights:

Ducati OEM aluminum 5-spoke .... 9.25 lbs
Marchesini magnesium 5-spoke ... 6.80 lbs
Weight Savings ................. 2.45 lbs


120/70ZR17 Tire Weights (Sport Rider Magazine June 2002)

Dunlop D207RR ............... 10.44 lbs
Pirelli Super Corsa............. 8.38 lbs
Weight Savings ................. 2.06 lbs

Dunlop D207RR ............... 10.44 lbs
Bridgestone BT-010 .......... 8.81 lbs
Weight Savings ................. 1.63 lbs

This seemingly small weight difference between the heaviest Dunlops and the lighter Bridgestones is even more important than a larger weight savings at the wheel.

Simply stated, the rotational inertia of a wheel or tire is proportional to the square of the distance the weight is placed from the axle. Because of this square-effect, the tire weight has more effect on the rotational inertia of the wheel-tire combination mainly because of its somewhat greater distance from the axle.

Consequently, a 1.6 - 2 lbs. lighter front tire will give you the same handling improvement that you get by switching from an aluminum to a magnesium wheel.

Looking at it another way, you can negate the handling benefits of expensive light weight wheels by switching to a heavier tire.

This is also the best argument for choosing aftermarket wheels that have carbon fiber rims. When compared to all-magnesium wheels with the same weight, a carbon fiber rimmed wheel will have significantly lower rotational inertia that results in improved acceleration and handling.

(The similar construction of rear tires results in weight savings of less than a pound so you'll see a lesser improvement effect there.)

I'm not saying that tires should be chosen based on weight alone but given the very similar performance of high performance street tires, why not take the free mag wheel?
Brilliant!!
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post #3 of 25 (permalink) Old Oct 10th, 2007, 12:06 am
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Well there you go... Thanks for that info.. funny how much sense it makes. Pity the comparison was to an BT010 which was supersceeded a while ago.

Shazaam, have you ever weighed into the CF v mag wheel debates ??

Hoping you are the same...


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post #4 of 25 (permalink) Old Oct 11th, 2007, 1:17 am
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Some of the most interesting information that I've read on this board. Great job!




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post #5 of 25 (permalink) Old Jun 3rd, 2009, 8:41 am
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Pirelli lists the weight of each tire they sell in their brochure:
http://www.us.pirelli.com/en_US/brow...LI_FULL_07.pdf

For example, the Diablo Supercorsa:
120/60ZR17: 9.02 lbs
180/55ZR17: 12.76 lbs
190/55ZR17: 13.86 lbs

Supercorsa Pro:
160/60ZR 17: 12.13 lbs

So, going from a 180 to a 190 on the rear will slow you down because there is over 1 pound of very important weight added.

There isn't much difference between the various models within each catagory of tire. For example, there isn't much difference between a 180 Supercorsa and a Corsa III or a plain Diablo. There is a big difference between the Strada line and the Diablo line though.

Last edited by dirkwrong; Jun 3rd, 2009 at 4:26 pm.
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post #6 of 25 (permalink) Old Jun 3rd, 2009, 4:24 pm
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I heard from Dunlop:

Qualifier 120/60-17 8.28 lbs
Qualifier 160/60-17 11.86 lbs

Dang, they are light!
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post #7 of 25 (permalink) Old Jun 3rd, 2009, 6:33 pm
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The moment of inertia is directly proportional to the mass, assuming the tires are the same shape and size. So, we can just use percentages based on the differences in mass of the tires, assuming the wheels are the same.

For the Pirelli vs the Dunlop front tires, there is a 0.74 lb difference. Choosing Dunlop over Pirelli means a (0.74/9.02) = 8% reduction in the moment of inertia. Maybe that's not significant, I don't know.

For the 160 series rear tires there is a 2% difference, with the advantage to Dunlop.

Basically this means that the rear wheel will accelerate 2% faster, and the front wheel will accelerate 8% faster with Dunlops vs. Pirellis. Likewise, I believe that the front wheel will steer with 8% less force as well.
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post #8 of 25 (permalink) Old Jun 8th, 2009, 11:24 am
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OK, I heard from Bridgestone:

BT016 weights:

120/60ZR17 – 7.6lb

160/60ZR17 – 10.7lb

180/55ZR17 – 12.3lb

190/55ZR17 – 15.0lb

wow, some of these are very light!
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post #9 of 25 (permalink) Old Aug 11th, 2009, 10:03 am
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Michlen Pilot Power 2CT:

front: 9.21 lbs
180 rear: 12.62 lbs
190 rear: 14.6 lbs

So, much heavier for the front, but about the same for the rears, as the Bridgestones.
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post #10 of 25 (permalink) Old Aug 20th, 2010, 2:20 pm
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back form the dead.

i weighed the pilot power 2ct and bridgestone bt016 today.

pilot power 2ct
120/70/17
9 lbs 6 oz.

180/55/17
12lbs 0 oz.

bt016
120/70/17
9 lbs 5 oz.

180/55/17
13lbs 12 oz.

they were weighed on a digital hanging scale.i'm glad i could weigh them before buying, cause i thought the Stones were going to be lighter.
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