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I posted this in the tire and wheel forum and just got a bunch of laughs, hoping you guys understand what I'm getting at better...

I'll be autocrossing my new 2001 330i sport package this season.

My co-driver is convinced we can fit 275/45/17 V710's or Hoosiers on the 7.5" front wheels. I think he's crazy, but we've seen pictures of 285's on 8" wide rims, and he used to do tire mounting for a living at a tire shop.

Anyway, assuming we can actually fit the goofy things on the tires, will they fit in the wheel wells? I'm guessing we're looking at a fair amount of bulge out since the rims will be so much smaller, so the total width might be more like that of a 285 on a more normal wheel.

What do you think? Will they rub? (can't roll/cut the wheel wells, stock class)

What do the DSP guys run?
 

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While the tire may fit on the wheel, I'm not sure that combo will be able to turn without hitting something. If you want to take your wheel off, you can measure the distance from your hub to the inner fender.

That's my best advice, regarding body roll, gonna have to risk it and if it's rubs, then bump up to SM or something.

Ron
 

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lot of the DSP guys are running 285s on wider wheels. 275 on 7.5 is doable. did it in the 350z. ofcourse, the 350z has enough room for clearance. may think that the 275 on a e46 will not work. at most with stock fenders, i think 255 is max from lock to lock.
 

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Woah woah woah!!!!

Fitting a wide tire on a narrow rim is a horrible recipe for LESS surface contact. The contact patch is bowed (narrowed) by the sidewalls being pinched inwards.

The other issue is that you are looking to use a tire that works best with some heat in it. Running a large sectional width decreases the heat introduced into the tire, which in turn can make it have LESS grip than a narrower tire.

So...am I talking out of my a$$ on this? Nope. I run 275s on the back of my car for road racing, but for autocross I now run 255s for heat reasons.
 

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Woah woah woah!!!!

Fitting a wide tire on a narrow rim is a horrible recipe for LESS surface contact. The contact patch is bowed (narrowed) by the sidewalls being pinched inwards.

The other issue is that you are looking to use a tire that works best with some heat in it. Running a large sectional width decreases the heat introduced into the tire, which in turn can make it have LESS grip than a narrower tire.

So...am I talking out of my a$$ on this? Nope. I run 275s on the back of my car for road racing, but for autocross I now run 255s for heat reasons.
Couldn't you counteract the bowing by reducing tire pressure? I don't know if it would still seat on the rim, but it's one option.

Ron
 

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Woah woah woah!!!!

Fitting a wide tire on a narrow rim is a horrible recipe for LESS surface contact. The contact patch is bowed (narrowed) by the sidewalls being pinched inwards.

The other issue is that you are looking to use a tire that works best with some heat in it. Running a large sectional width decreases the heat introduced into the tire, which in turn can make it have LESS grip than a narrower tire.

So...am I talking out of my a$$ on this? Nope. I run 275s on the back of my car for road racing, but for autocross I now run 255s for heat reasons.
You are correct about the wheel/tire fittment, but I have seen crazier things.

BUT as far as 275's NOT being a good choice for autocross (with proper fittment) you are DEAD wrong.

HEAT! What are you talking about?? With 2 drivers and V710's he will have a problem with them OVERHEATING during the summer. Need lots of cold water and a sprayer between runs.

My car is at least 400lbs lighter, and my 275's will overheat and get quite greasy with 2 drivers.
 

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booo for body roll.
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Another reason I run such a wide tire on a narrow rim is it helped camber challenged cars from cording the tires. ie. with a 245, i corded the tires within 20 runs, which is typical for a 350z that runs hoosiers. with a 275, it would not cord until the tire was dead.

ofcourse, since the v710 has alot more "built in" camber, i haven't really noticed any issues with cording these tires. but the tire size to have in BS whether you are in an rx8 or a 350z is a 285. look at the national results. if the people were not running 285s, they said they would be next year. i drove a car with 245s this year on 8F 8.5R and it was just not enough tire for the car. tire stretching or not, a 285 on an 8 will be faster regardless. also, i do not have any problems building up heat in my tires, even if i am driving solo.
 

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58mm of Bliss
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You are correct about the wheel/tire fittment, but I have seen crazier things.

BUT as far as 275's NOT being a good choice for autocross (with proper fittment) you are DEAD wrong.

HEAT! What are you talking about?? With 2 drivers and V710's he will have a problem with them OVERHEATING during the summer. Need lots of cold water and a sprayer between runs.

My car is at least 400lbs lighter, and my 275's will overheat and get quite greasy with 2 drivers.
Something else to consider is the length of the run. In events close to me, it's rare to have a time over 1 minute; the course sizes aren't that big. That's probably a big part of my heat issue, and also ambient temps which are much lower up here.

Under the conditions you highlight, I agree with your take on running 275s or 285s.
 
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