17x7 O.Z. Superleggera Rims
#21
11-30-2005, 09:33 PM
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Re: 17x7 O.Z. Superleggera Rims
Originally Posted by ftlum
The MPG calculator is really squirley. This morning the overall calculation (since I bought the car) was 51 mpg. This afternoon it was in the 40s. The last tank calculator was in the 40s this morning and in the 30s this afternoon. I find it changes quite a bit througout the day-- much more than I would have expected. I don't think it's working as intended.
#22
11-30-2005, 09:38 PM
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Re: 17x7 O.Z. Superleggera Rims
Originally Posted by coyote
I have a general question about wheel and tire weight, which reveals my ignorance of physics and other such things. Here it is:
How much difference does the weight of the wheel and tire make, considering that the whole car weighs over 2500 pounds more than the scrawny 2-5 pound extra per wheel?
I understand some of the fundamental ideas about why it should make some difference; I just don't know if the difference is significant, or negligible.
How much difference does the weight of the wheel and tire make, considering that the whole car weighs over 2500 pounds more than the scrawny 2-5 pound extra per wheel?
I understand some of the fundamental ideas about why it should make some difference; I just don't know if the difference is significant, or negligible.
On the other hand, I suspect with no ability to prove it, that the spoked wheels mess up the aerodynamics of the car significantly. When you drive at 60 MPH the top of each wheel is moving at 120 MPH. That's a lot of potential drag if the wheels are not aerodynamic.
#23
11-30-2005, 09:45 PM
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Re: 17x7 O.Z. Superleggera Rims
Originally Posted by CGameProgrammer
On the contrary, GreenSeal lists them as having very low rolling resistance in their report. Almost the lowest there is, in fact.
I don't think so... read the report. Your size is not listed, they tested a much smaller tire. 205/55/R16. Try to find the RR for your size and make, it won't be the same as listed in the report. Size of tire will change the RR.
#24
11-30-2005, 09:50 PM
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Re: 17x7 O.Z. Superleggera Rims
Originally Posted by Tim
Stock rims on an 03-05 HCH are 14.2 lbs (I weighed mine after I got new wheels). I have to suspect that the 06 is in the same ballpark - maybe a tad more as it's a 15". The Superleggera's are ones I looked closely at too. Just under 16 lbs is probably very comparable to the stock wheel - within a pound most likely. What I'd look at is the tire weight. I replaced my 185/70R14 with a 195/60R15, and the new tire weighs 18.3 lbs (compared to 17.8 on the stock tire). I found that wider tires - 205, 215, etc. got into the low 20's on weight. Looks like the 225/45R17 tire is 21.3 lbs. Not bad, but may be a pound or so over the stock tires. Tire width may also play a role.
BTW, I got the Continental CV95's (instead of the CH, but same family - just a V rated tire). The mileage for the first 3-400 miles was miserable. I credit this to the "newness" of the tire. They were just plain sticky. I've put about 900 miles on them now, and they're rolling much, much better - easily comparable to the Dunlops they replaced. Just hang in there on the break in period. As you go past 500 miles + things should get much better if they follow the same pattern as mine.
One last thing - your car looks GREAT!!!!
BTW, I got the Continental CV95's (instead of the CH, but same family - just a V rated tire). The mileage for the first 3-400 miles was miserable. I credit this to the "newness" of the tire. They were just plain sticky. I've put about 900 miles on them now, and they're rolling much, much better - easily comparable to the Dunlops they replaced. Just hang in there on the break in period. As you go past 500 miles + things should get much better if they follow the same pattern as mine.
One last thing - your car looks GREAT!!!!
Also keep in mind that the total weight of the rim isn't as important as where the weight is located.
If RIM A and B weigh the same but RIM A has all the weight towards the outer edge, and RIM B has all the weight toward the inner center, then RIM B will perform better as far as FE is concerned.
#25
11-30-2005, 10:00 PM
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Re: 17x7 O.Z. Superleggera Rims
OK, I'll have to fess up to messing up that statistic. I searched for about 40 minutes tonight to find where I got it - I think this was it but it turns out I remembered it incorrectly. Here's the paragraph - link to entire article below.
"The answer, it turns out, depends on how the weight is distributed on the wheel. An extra pound on the tread of a rolling tire has as much kinetic energy as 2 lbs on the floor of the car. As you move toward the center of the wheel, the rotational effect drops until, at the center, a pound is just a pound. The formula I derived to determine the exact relationship between weight on a wheel and weight in the car isn't worth repeating here for one simple reason. It requires that you know the moment of inertia of the wheel, and measuring that is virtually impossible. What you need to know is that changing to tires that are 1 lb heavier will effectively add 8 lbs to the car (four tires, remember) and that adding a pound to the wheels will effectively add somewhere around 6 lbs to the car."
http://www.sportcompactcarweb.com/ed..._technobabble/
"The answer, it turns out, depends on how the weight is distributed on the wheel. An extra pound on the tread of a rolling tire has as much kinetic energy as 2 lbs on the floor of the car. As you move toward the center of the wheel, the rotational effect drops until, at the center, a pound is just a pound. The formula I derived to determine the exact relationship between weight on a wheel and weight in the car isn't worth repeating here for one simple reason. It requires that you know the moment of inertia of the wheel, and measuring that is virtually impossible. What you need to know is that changing to tires that are 1 lb heavier will effectively add 8 lbs to the car (four tires, remember) and that adding a pound to the wheels will effectively add somewhere around 6 lbs to the car."
http://www.sportcompactcarweb.com/ed..._technobabble/
#26
11-30-2005, 10:00 PM
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Re: 17x7 O.Z. Superleggera Rims
Originally Posted by livvie
Also keep in mind that the total weight of the rim isn't as important as where the weight is located.
If RIM A and B weigh the same but RIM A has all the weight towards the outer edge, and RIM B has all the weight toward the inner center, then RIM B will perform better as far as FE is concerned.
If RIM A and B weigh the same but RIM A has all the weight towards the outer edge, and RIM B has all the weight toward the inner center, then RIM B will perform better as far as FE is concerned.
Theoretically that's true. Practically you won't find wheels that differ much in that way. Every wheel has to distribute its strength equally more or less, otherwise it would break at the weak point. And weight is distributed with strength, more or less. For example, if the spokes of a wheel were much thicker near the center than at the edges, then either the edges would be too weak or the center would be unnecessarily heavy. An engineer that designed such a wheel should be fired.
#27
12-02-2005, 05:01 AM
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Re: 17x7 O.Z. Superleggera Rims
Car and Driver magazine has discussed this in many articles. Not only does heavier wheels (unsprung weight) make it slightly more difficult to accelerate, it also has an effect on handling, steering feel, etc.... How does the 17" rims effect your cars ride? Do the stiffer sidewalls contribute much to a bumpier ride? I love the look.
#28
05-09-2006, 08:19 AM
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Re: 17x7 O.Z. Superleggera Rims
I ended up getting these, but in the 17X8 with a different tire. I haven't driven the car much since I put them on, but the handling has improved drastically. The car is sititing since this week I am not driving...car pool. But, will post results as I get them. They really make the car look a lot better.
#29
05-09-2006, 08:40 AM
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Re: 17x7 O.Z. Superleggera Rims
Wow, it looks like those rims are going to act like a fan and be anything but aerodynamic. I think they look fine, but if they are behaving like 4 huge fans blowing air one way or the other that will take quite a bit of energy and lower your mpg substantially.
Please keep us informed of what your actual mileage turns out to be when you fill up at the pump.
Bowdirk
Please keep us informed of what your actual mileage turns out to be when you fill up at the pump.
Bowdirk
