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245 40 18inch ok??

Caballito

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Hi guys so i want to run a hankook rs4 on my stock 18 inch rim i believe width is 8 inches. The size am looking at is 245x40 by 18inch mainly am concerned with the profile is it too thin? Am gonna use this for track work. Stock is 235 50 18. Thanx
 

Zathras

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The issue with 245/40 R18 is that the tire diameter (and circumference, etc.) is gonna be a lot smaller than the stock 235/50 size. (The tire height or diameter for 235/50 is 27.3 inches, for a 245/40 it's only 25.7 inches.) That means there will be a lot of gap and open space between the tire and the body of the car. Also, the smaller diameter will make the speedometer read high by several MPH, and throw the odometer off. But if this is just for track work, you might not care about the speedometer accuracy, or the "wheel gap."

If you go with a 245/45 tire, that would be closer to the original size. That's probably what I'm going with.
 

Caballito

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The issue with 245/40 R18 is that the tire diameter (and circumference, etc.) is gonna be a lot smaller than the stock 235/50 size. (The tire height or diameter for 235/50 is 27.3 inches, for a 245/40 it's only 25.7 inches.) That means there will be a lot of gap and open space between the tire and the body of the car. Also, the smaller diameter will make the speedometer read high by several MPH, and throw the odometer off. But if this is just for track work, you might not care about the speedometer accuracy, or the "wheel gap."

If you go with a 245/45 tire, that would be closer to the original size. That's probably what I'm going with.
Yea thats kinda the stuff i had in mind but like you said its only reallyfor track work dont mind the gap my question will it hurt something? Like limited slip or is the tire to thin for the rim and when cornering will it mess the tire up etc.. any thoughts? Looks dont bother me
 

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You will have a 5.9% speedometer difference. So if your odometer says you drove 100,000 miles, you will have driven 94,000 miles....this is negligible. Don't worry about the diameter difference.
It will have no negative affect on your diff.
You actually want a smaller sidewall tire for the track to essentially make it more rigid. You want to avoid sidewall flex at the track and other than getting tires with a stiffer sidewall (RS4 will have stiff sidewall) you can get this with a shorter sidewall. You're good.
 

Caballito

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upload_2020-2-14_8-43-7.png

You will have a 5.9% speedometer difference. So if your odometer says you drove 100,000 miles, you will have driven 94,000 miles....this is negligible. Don't worry about the diameter difference.
It will have no negative affect on your diff.
You actually want a smaller sidewall tire for the track to essentially make it more rigid. You want to avoid sidewall flex at the track and other than getting tires with a stiffer sidewall (RS4 will have stiff sidewall) you can get this with a shorter sidewall. You're good.
Thanks for the input bro! It might look a lil funny but am sure it will help with my time compared to my last years time with the stock crappy tires, i have my eye on those sp2 wheel or the drift if i want to go cheaper but i have to wait for right now. What track u run at??
 

Ewheels

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Thanks for the input bro! It might look a lil funny but am sure it will help with my time compared to my last years time with the stock crappy tires, i have my eye on those sp2 wheel or the drift if i want to go cheaper but i have to wait for right now. What track u run at??
I do all the Socal tracks. Chuckwalla, Autoclub, Willow Springs, & Buttonwillow. I'm going to Chuckwalla this weekend actually.
 

Caballito

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I do all the Socal tracks. Chuckwalla, Autoclub, Willow Springs, & Buttonwillow. I'm going to Chuckwalla this weekend actually.
awesome! if your ever out here in the thunderhill track hit me up we should be outhere march 7th
 

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