Big ass 21 inch wheels on GTR.

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I dont think my math is wrong I just simply coverted the Diameter in inches to Diameter to mm and my conversion of inches to mm is accurate as far as I can tell. Once again the overall moment of inertia will have very little effect on the whole thing when you take into account the wheel + tires and how the overall diameter is nearly identical and how the mass is not only reduced for the wheels but for the tires and the mass farthest from the hub which is tires is still less then in previous configuration.

Kayani - even with the supposedly reduced weight, your new inertia is still higher.

BTW, your math above in calculating the diameters of your tires is wrong.

[Danish]

I think his figures came directly from tire rack.

Manufacturer's nominal tires sizes are just that: nominal, they give themselves certain leeways on way or another. For instance: the Dunlop 205s on my Civic are 6 mm wider than the Goodyear 205s on the Caddy.

Also, calculating tire diameter via width and sidewall aspect leaves out tread depth as another variable.

You're right.... I guess I can end this by saying that in the end, diameter and weight still increased.

Greg, Dan, Dave, Koko, I've learned my lesson and I'm through with this thread

[Danish]

A lot of trouble, yes. But it does go to the heart of the rotational inertia argument.

Unfortunately, it would be almost impossible to get hard numbers without a FEA program, and if you did, it would likely be misunderstood.

Amen.

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I was not aware of where you got that I was saying wheel size has something to do with the contact patch that is why I was asking .

Now here at the bottom I was not being sarcastic but rather talking how going from 245/45/19 to 265/30/22 for front and 275/40/19 to 295/25/22 effectively increased the overall contact patch of the tire due to much wider foot print and that is what I was refering to at the bottom. So going with bigger/wider wheels allowed me to go with wider tires. For the each wheel and its width the ideal width tire is suggested by people like tire rack for example it will be hard to fit 295 size width of tire on a 7 inch wide rim but the ideal width for such wide tire is wider wheel such as 9.5 to 10" wide. The biggest tire that I could have fitted on 19X9" rim as recommended by tirerack would have been 255/45 and for 19x9.5 the ideal recommended size is 275/40. So that was pretty much where it stands however going with 9.5" wide in front and 10" in rear allowed wider recommended tires. I think you are misunderstanding certain things I said. I hope this clears that.

Yes I agree that you can get 12x10 inch wide custom aftermarket wheels. However, I was talking in general that most of the time 12" tires are not 10" wide but rather stock cars equipped with 12" tires will barely bee 6" wide. You will rarely see a 20 inch wheel that is 6 inch wide most of them are any where between 8.5-10 inch wide. Now that doesnot mean you cant get them in 6 inch in aftermarket.

So I never disagreed with that part and I still dont. That is why I didnot understand what you were talking about.

"Last but not least? the overall, weight of the wheel + tire is taken into account as the whole package and not independent of one another and the overall diameter of? wheel + tires is what matters not just the wheel itself. Even though few people pretend that only the wheel matters and as if the tire doesnot exist. Bottom line is the ability to reduced unsprung mass and greater contact patch for enhanced grip and lateral acceleration as well as the ability to fit huge brakes is a great advantage. On the other hand it has few negatives just like you have with any performance enhancing upgrade. There is no win win situation in anything there are postives and negatives of everything."

This is your statement, no? Were you being sarcastic at this time, it sure doesn't sound like it. At least you finally admitted there was no connection.

Oh and this statement, this one you just made: "Most of the time larger wheels are also wider and smaller wheels are usually less wider."

That is also horribly incorrect. There is no relationship between diameter and width. You can get 14x15 inch wheels and 40x6 inch wheels.

[sportyaccordy]

Really though you should be taking r as the diameter of the wheel, or at least the centerline of the wheel and tire, not the rolling radius of the tire. The metal rim is where there is the highest concentration of mass, and consequently, unless you put monster truck tires on your old rims the larger diameter rims will have a higher moment of inertia.

Plus in any case, again, I'm still waiting for the racing league where 22s are favored over 19s, etc.

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I think the overall diameter of both wheels + tires have to be taken into account not to mention the construction and design of the wheel as well as other factors. The amount of weight you shave while keeping the diameter the same allows for the moment of inertia to be not effected by much if any. According to most sources each pound of unsprung mass reduced is almost effectively reducing equal of 10 Ibs of the car itself. I think that in it self is far greater benefit with the ability to go with wider tires in my case.

As for racing leagues they are governed by rules and the wheel and tire size is not the choice of each individual team but rather mandated by the governing body.

Also in my case I like the way bigger wheels look on a car that is 7er size. If I can make the car look better while effectively reducing unsprung weight and going with wider tires I feel I have done well. I am fully aware that I could have gone with 19" 3 piece forged if I wanted to make them even more lighter but I wanted to improve the looks and reduce weight. So if you dont like bigger wheels good for you I like them and I think I did well over all in keeping the weight increase to minimum.

[Eye of the Tiger]

I think the overall diameter of both wheels + tires have to be taken into account not to mention the construction and design of the wheel as well as other factors. The amount of weight you shave while keeping the diameter the same allows for the moment of inertia to be not effected by much if any. According to most sources each pound of unsprung mass reduced is almost effectively reducing equal of 10 Ibs of the car itself. I think that in it self is far greater benefit with the ability to go with wider tires in my case.

As for racing leagues they are governed by rules and the wheel and tire size is not the choice of each individual team but rather mandated by the governing body.

Also in my case I like the way bigger wheels look on a car that is 7er size. If I can make the car look better while effectively reducing unsprung weight and going with wider tires I feel I have done well. I am fully aware that I could have gone with 19" 3 piece forged if I wanted to make them even more lighter but I wanted to improve the looks and reduce weight. So if you dont like bigger wheels good for you I like them and I think I did well over all in keeping the weight increase to minimum.

Encased in this massive heaping pile of shit, Kayani actually admits the truth: the only good thing he got out of his $6000 investment is that he thinks they look better. There. End of story. Stop with the bullshit now, Kayani, you can't change your story any more.

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What I said is different then what you are pretending but what is new you only like to read what you want and ignore the rest in your typical immature fashion .

Encased in this massive heaping pile of shit, Kayani actually admits the truth: the only good thing he got out of his $6000 investment is that he thinks they look better. There. End of story. Stop with the bullshit now, Kayani, you can't change your story any more.

[Eye of the Tiger]

What I said is different then what you are pretending but what is new .

Like I said before, you are a bigot.

[Soup DeVille]

I think the overall diameter of both wheels + tires have to be taken into account not to mention the construction and design of the wheel as well as other factors. The amount of weight you shave while keeping the diameter the same allows for the moment of inertia to be not effected by much if any. According to most sources each pound of unsprung mass reduced is almost effectively reducing equal of 10 Ibs of the car itself. I think that in it self is far greater benefit with the ability to go with wider tires in my case.

As for racing leagues they are governed by rules and the wheel and tire size is not the choice of each individual team but rather mandated by the governing body.
Also in my case I like the way bigger wheels look on a car that is 7er size. If I can make the car look better while effectively reducing unsprung weight and going with wider tires I feel I have done well. I am fully aware that I could have gone with 19" 3 piece forged if I wanted to make them even more lighter but I wanted to improve the looks and reduce weight. So if you dont like bigger wheels good for you I like them and I think I did well over all in keeping the weight increase to minimum.

Most of the time that is correct, but DTM and JGTC cars (and perhap even Speed GT) have no wheel diameter limits in their rules; yet it's rare to find anything larger than 19": and if their rules allowed inboard brakes they'd be much smaller.