Whats the big deal with 20 inch rims?
05-02-2009, 12:41 AM
#28
RX8 & RX7 owner
Thread Starter
With Width you add another dimension. If you went with a wider tire you could offset the loss of sidewall flex with sheer contact area. Hence my point of relying on contact and compound after a certain point. I was just trying to keep that dimension out of the picture for now. However, as you also said, it really depends on what you want to do and how the driver wants to do it.
Also to your question on price for lower profile. Yes I imagine they have to make it sturdier but that takes in trade the flex that is needed when making a high later g turn.
Also to your question on price for lower profile. Yes I imagine they have to make it sturdier but that takes in trade the flex that is needed when making a high later g turn.
oh:
the point was....
05-02-2009, 12:43 AM
#29
Ok it's bed time so I will say the answer.
Chrome is not the most loved rim choice here because of weight and it usually looks bad on a sports car.
The 20" part is no good because the bigger diameter of the rim makes the majority of that weight farther from its center, even if it is the same weight as a smaller wheel/tire. http://en.wikipedia.org/wiki/Moment_of_inertia http://www.stockcarracing.com/techar...moi/index.html
Chrome is not the most loved rim choice here because of weight and it usually looks bad on a sports car.
The 20" part is no good because the bigger diameter of the rim makes the majority of that weight farther from its center, even if it is the same weight as a smaller wheel/tire. http://en.wikipedia.org/wiki/Moment_of_inertia http://www.stockcarracing.com/techar...moi/index.html
Last edited by J8635621; 05-02-2009 at 12:47 AM.
05-02-2009, 12:51 AM
#31
SARX Legend
iTrader: (46)
This thread fails. If you like dubs, get em'.
20" rims generally weigh more and the performance minded care about that. I was present at a dyno day when a guy with a GTI swapped from 19's back to his stockers (no other changes) and he gained 8 WHP. To me that was an eye opener. But if your into the VIP style then why do you care?
20" rims generally weigh more and the performance minded care about that. I was present at a dyno day when a guy with a GTI swapped from 19's back to his stockers (no other changes) and he gained 8 WHP. To me that was an eye opener. But if your into the VIP style then why do you care?
05-02-2009, 12:51 AM
#32
I don't know for sure, but I wouldn't say that is necessarily true. I know some tires have some sizes that are reinforced while others aren't, but I don't think it is lower profile = more reinforced. I think at least some of the price could be that fewer cars run that size so they have to make up for the quantity with price.
05-02-2009, 01:33 AM
#35
it's an R3 thats why it can have it lol jk idk :/
The only 20s that should be on a sports car is a Nissan GTR "R35" thats just hit me, idk about other cars.
If you want to be a VIP isnt that more for a lexus and other luxary cars? dunno thats just me.
Are cars weren't made for VIP purposes. havn't seen any VIP rx8
If you like your 20s keep them
The only 20s that should be on a sports car is a Nissan GTR "R35" thats just hit me, idk about other cars.
If you want to be a VIP isnt that more for a lexus and other luxary cars? dunno thats just me.
Are cars weren't made for VIP purposes. havn't seen any VIP rx8
If you like your 20s keep them
05-02-2009, 01:43 AM
#37
RX8 & RX7 owner
Thread Starter
Bling? to sell cars? the R3 19's are all polished black, and you say performance wheels arent ever chrome? Yeah right! VOLK, ADVANS, WORKS, RAYS all make CHROME performance wheels!
05-02-2009, 09:24 AM
#40
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Some of the physics up there aren't done very well.
It's a rotational system.
Torque = Moment of Inertia * Radial Acceleration.
T=I*alpha
Different rims distribute the weight of the wheel at a different distance from the center of the wheel. That increase/decreases the radius in the inertia equation, which differs with every shape, but it is a squared term in the formula.
So the lower the moment of inertia (I), the lower the amount of torque at the shaft needed to turn them for the same amount of rotational acceleration (more go fast.)
So, the most important factor is not how much the wheel weighs, but where the weight is placed relative to the center of the wheel.
It's a rotational system.
Torque = Moment of Inertia * Radial Acceleration.
T=I*alpha
Different rims distribute the weight of the wheel at a different distance from the center of the wheel. That increase/decreases the radius in the inertia equation, which differs with every shape, but it is a squared term in the formula.
So the lower the moment of inertia (I), the lower the amount of torque at the shaft needed to turn them for the same amount of rotational acceleration (more go fast.)
So, the most important factor is not how much the wheel weighs, but where the weight is placed relative to the center of the wheel.
05-02-2009, 11:03 AM
#42
Ok it's bed time so I will say the answer.
Chrome is not the most loved rim choice here because of weight and it usually looks bad on a sports car.
The 20" part is no good because the bigger diameter of the rim makes the majority of that weight farther from its center, even if it is the same weight as a smaller wheel/tire. http://en.wikipedia.org/wiki/Moment_of_inertia http://www.stockcarracing.com/techar...moi/index.html
Chrome is not the most loved rim choice here because of weight and it usually looks bad on a sports car.
The 20" part is no good because the bigger diameter of the rim makes the majority of that weight farther from its center, even if it is the same weight as a smaller wheel/tire. http://en.wikipedia.org/wiki/Moment_of_inertia http://www.stockcarracing.com/techar...moi/index.html
Last edited by myriadshalaks; 05-02-2009 at 11:06 AM.
05-02-2009, 11:08 AM
#43
Some of the physics up there aren't done very well.
It's a rotational system.
Torque = Moment of Inertia * Radial Acceleration.
T=I*alpha
Different rims distribute the weight of the wheel at a different distance from the center of the wheel. That increase/decreases the radius in the inertia equation, which differs with every shape, but it is a squared term in the formula.
So the lower the moment of inertia (I), the lower the amount of torque at the shaft needed to turn them for the same amount of rotational acceleration (more go fast.)
So, the most important factor is not how much the wheel weighs, but where the weight is placed relative to the center of the wheel.
It's a rotational system.
Torque = Moment of Inertia * Radial Acceleration.
T=I*alpha
Different rims distribute the weight of the wheel at a different distance from the center of the wheel. That increase/decreases the radius in the inertia equation, which differs with every shape, but it is a squared term in the formula.
So the lower the moment of inertia (I), the lower the amount of torque at the shaft needed to turn them for the same amount of rotational acceleration (more go fast.)
So, the most important factor is not how much the wheel weighs, but where the weight is placed relative to the center of the wheel.
05-02-2009, 11:17 AM
#44
i see a major fail here. i dont believe for a second that the 20" rims were equal in weight.
cant be. first off, i doubt the company that made your rims cares about weight. 22lbs for 18" rims is actually pretty damn light. im going to guess that your 20" rims weigh about 28lbs and that your scale is off. some tires are lighter than others, but im going to say that the thinner tirewall has to be stiffer and will add weight so the a 225/45 and a 225/35 will not have a huge weight difference.
second point i want to make about inertia, the rim size DOES matter because the cylindrical portion of the rim (arguably a lot of the weight of the rim is here) is pushed out another inch. that does make a difference. especially coupled with the point that i said about tires not being a big deal here.
so, you said your rims were 50lbs, ok, im going to assume no more than a few pounds is added by the air. and im also going to say your rims were more like 55lbs. so lets say your set up weighs 7lbs more than stock.
we have already discussed how inertia is actually an issue here. the farther out an object is pushed, the "heaver" it becomes. to test this, put a 10lb weight 1 foot from your chest and hold it for 30 seconds. then, put it out at arms length.
a good rule of them is the x5 method for rotating mass. so take your 7lbs and multiply them by 5. thats 35lbs that you have effectively added PER corner. so thats 140lbs you've added to your car.
now tell me, do you notice a difference in acceleration when someone is sitting in your car with you?
cant be. first off, i doubt the company that made your rims cares about weight. 22lbs for 18" rims is actually pretty damn light. im going to guess that your 20" rims weigh about 28lbs and that your scale is off. some tires are lighter than others, but im going to say that the thinner tirewall has to be stiffer and will add weight so the a 225/45 and a 225/35 will not have a huge weight difference.
second point i want to make about inertia, the rim size DOES matter because the cylindrical portion of the rim (arguably a lot of the weight of the rim is here) is pushed out another inch. that does make a difference. especially coupled with the point that i said about tires not being a big deal here.
so, you said your rims were 50lbs, ok, im going to assume no more than a few pounds is added by the air. and im also going to say your rims were more like 55lbs. so lets say your set up weighs 7lbs more than stock.
we have already discussed how inertia is actually an issue here. the farther out an object is pushed, the "heaver" it becomes. to test this, put a 10lb weight 1 foot from your chest and hold it for 30 seconds. then, put it out at arms length.
a good rule of them is the x5 method for rotating mass. so take your 7lbs and multiply them by 5. thats 35lbs that you have effectively added PER corner. so thats 140lbs you've added to your car.
now tell me, do you notice a difference in acceleration when someone is sitting in your car with you?
05-02-2009, 02:15 PM
#47
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I think people tend to snicker a bit when they see a nice car like the 8 defiled with huge chrome rims; especially when the driver thinks he's made an improvement.
Of course people will hate on you for this. What did you expect?
I wouldn't have the ***** to show pics of my car on here if I had done that to it, so I guess I do owe you props for that.
Oh my looks like I posted another negative, insulting, pompous comment. What a surprise.
Of course people will hate on you for this. What did you expect?
I wouldn't have the ***** to show pics of my car on here if I had done that to it, so I guess I do owe you props for that.
Oh my looks like I posted another negative, insulting, pompous comment. What a surprise.
05-02-2009, 03:56 PM
#49
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