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Yellow Goat
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410 Posts
Discussion Starter #1
Is there one set offset that works for an 18x9" wheel with a 275/35/18 tire on the back? I know that mine rub the fenders pretty badly, even with them rolled. I'm sick of it and getting ready to create a stink about it. I want new wheels and I want to know what the correct offset should be for this. My current offset is 43mm and it just has to come in some, 38mm maybe?

With 2 or more people in my car and a dip in the freeway I get a nasty scrape on both sides. It's irritating and embarrassing.

I've had my allignment checked twice and there is nothing wrong with my rear camber.

What is the correct offset to run a 275mm tire on a 9" wheel?
 

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Resident 10-second Priest
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8,959 Posts
1COOLPC said:
My current offset is 43mm and it just has to come in some, 38mm maybe?
As I understand it, it's the other way around. I.e. a 38mm offset will stick out 5mm's further than a 43mm. So you want something closer to the stock 48mm. Alas, there ain't no such animal, as yet, unless you want to have them custom made. I'll let the experts give you the definitive answer.

I had my fenders rolled today. :( Not something I wanted to do, and I still don't know if I'm guaranteed to have no rubbing, and I'm going autocrossing in a couple of weeks.

Padre
 

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One other thing: my vendor "cheated" a little bit and put 265/30-19's on the rear. That bought him some more room, but cost me -1.6% (or so) on the aspect ratio.

Padre
 

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Yellow Goat
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410 Posts
Discussion Starter #5
PadreGTO said:
As I understand it, it's the other way around. I.e. a 38mm offset will stick out 5mm's further than a 43mm. So you want something closer to the stock 48mm. Alas, there ain't no such animal, as yet, unless you want to have them custom made. I'll let the experts give you the definitive answer.

I had my fenders rolled today. :( Not something I wanted to do, and I still don't know if I'm guaranteed to have no rubbing, and I'm going autocrossing in a couple of weeks.

Padre
Good luck on that.

I don't believe you are correct on the offset though. A perfectly centered wheel has an offset of 0mm, as the wheel moves further outwards you get positive offset, the greater the number the farther out it is, or more positive. So a +40mm offset would stick out further towards the outside of the car than a +35mm offset. This is what I've always been led to believe anyway.
 

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1COOLPC said:
Good luck on that.

I don't believe you are correct on the offset though. A perfectly centered wheel has an offset of 0mm, as the wheel moves further outwards you get positive offset, the greater the number the farther out it is, or more positive. So a +40mm offset would stick out further towards the outside of the car than a +35mm offset. This is what I've always been led to believe anyway.
sorry, you are incorrect, as offset gets bigger the wheels move in. You are confusing offset and backspacing. You need an offset of around 54mm for 275 tires but I don't know the exact numbers, and as the good father said, no such animal is currently mass produced. If you talk to Howie he can get you wheels that will fit (arrowhead performance) but I don't think he will tell you the correct offset as he spent considerable time figuring it out and he wants to sell the wheels.
 

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Yellow Goat
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410 Posts
Discussion Starter #8
I stand corrected, thank you. I'm having 4mm shaved off the mating surfaces of my rear wheels on Tuesday. This should bring it in to just the right spot..... I hope.
 

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1COOLPC said:
I stand corrected, thank you. I'm having 4mm shaved off the mating surfaces of my rear wheels on Tuesday. This should bring it in to just the right spot..... I hope.
Good luck on that. Let us know how it works out and how much is involved, for I may want to do the same, despite my rolled fenders.

Padre
 

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Lil Cosmos GTO
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507 Posts
I believe my mass produced chrome wheels have a 56mm offset and they fit well

cjlannoy said:
sorry, you are incorrect, as offset gets bigger the wheels move in. You are confusing offset and backspacing. You need an offset of around 54mm for 275 tires but I don't know the exact numbers, and as the good father said, no such animal is currently mass produced. If you talk to Howie he can get you wheels that will fit (arrowhead performance) but I don't think he will tell you the correct offset as he spent considerable time figuring it out and he wants to sell the wheels.
My title says it all.
 
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