I need some assistance, I've been kicking around some ideas for a little while and I need some help in figuring out the math behind wheel offsets and widths.

Say I have a wheel that is currently sized 17x8.5 +38. I'm debating buying new barrels for the wheels that will increase the overall with by 1 inch. I will be retaining the current lips so the outside fender clearance will not change. What would be the new offset for this wheel? I don't believe it's as simple as adding +25mm (roughly an inch) to the offset of the wheel because offset factors in the center line of the wheel which changes when I add width to one side.

Does anyone have any idea what the final offset of this would be? 17x 9.5 +?

If I just added it all up it would be 17x9.5 +63, but I don't think that is right. I want to make sure that if I go through with this I will have adequate clearance for the inner barrels of the wheels.

 

http://www.1010tires.com/Tools/Wheel-Offset-Calculator

Even though you are adding 1" to the inside, it's actually 1/2" on one side of the center line and 1/2" on the other side. In this case you would be adding 12-13mm (1/2") to the offset. The end result would be a 9.5" +50/+51 depending how you round off to the mm.

 

I was thinking that was the case, but until you pointed that out I was mistakenly thinking the face of the wheel equaled the center of the wheel which ovbiously is incorrect. It's funny how as soon as you read someone elses response you know exactly where you were wrong.

So, in that case, Does a 9.5 +50/51 clear the inside on the front of an S2000?

Edit: Using that calculator, the 9.5 +51 inner clearance would be the same as the 10 +45, while it would be 12mm less aggressive against the fender. Does that sound correct? Now I just need to figure out if there are any issues on the inside running a 10 +45.

 

Yes. I am running 9.5" +55 with no issues. I believe SOS determined that a 9" +60 with a 255 tire was the minimum inside clearance required to prevent any kind of issue. I don't have any personal experience but have seen people with the common 9" +63 (255 tire) indicate that it will rub on the inside at full lock.

 

Yeah, I've seen the same thing. That's what I was curious about.

Thank you for all of the help Nate. I should have just sent you a text.

 

 

You won’t have any clearance issues with a 9.5 +51. You could squeeze another half inch on there and make it a 10" +57 if you wanted. I’m running 10”+58 with a 255 and it’s a perfect maximization of the fender space. Otherwise 9.5 +51 is a great fit for either a 245 or 255 as well.

 

He doesn't have fenders flared by junky though so the 9.5 is probably the best way to go.

 

Doesn’t matter, its all going on the inside. He is already running 2mm more aggressive on the outside then I am. That’s why I feel more then comfortable pointing out the option to maximize the inside room he has by going 1.5" additional.