I bought a small tire to put on a 9 inch rim

thelastofthem23004

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I remembered hearing somewhere that anything bigger than 225 would rub on my inner fenders and whatnot so I bought 2 225 45 r17 pirelli tires. I didnt even think about my rims being 9 inches wide until the tire shop had them aired up. They look like ass! Now for whatever reason they don't ride like ass. They are a huge improvement from the old 255s that came off of them. Here's the issue. I do plan on buying a different set of tires or maybe 8 inch rims, but for now I'm stuck with them. They were a great deal at 80 bucks a peice and unfortunately that was one of the selling point of these tires. I'm probably a month out from switching tires or rims. In the meantime: am I ok to run these without blowing one off a rim and ending up in the ditch or something worse? Curbs are a mortal enemy for me until I get things straightened out, but I understand that risk. Thanks in advance for anything you might have to say. Thanks. Also I heard rumors that once upon a time there were such a thing as 8inch 03 cobra style rims. I have 03-04 cobra rims and would like to keep the theme alive but I can trade them off if it has to happen
 

lwarrior1016

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I can tell you for sure, you can go much wider than 225 without rubbing. I was running 275/40-17 all the way around mine and I never had a rubbing issue. What is making you want to go to a narrower rim? I think you should just get a different set of tires for you current wheels. Also, as far as blowing the tire off the rim, I guess you are more at risk doing that now because the tires are stretched out to seat the bead. I think you will be ok if you don't drive like an idiot and understand your hazard areas (curbs, potholes, ect.).
 

thelastofthem23004

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Its a 94 GT thats been lowered. My 255s left rub marks on my inner fender and sway bar! Oh and on the ride height, I'm low enough that low profile jacks DO NOT fit. I usually have to be on blocks or start lifting on the tranny mount to fit a jack under it. So am I right to fear hard corners or are huge bumps the only thing I should fear?
 

Caboose302

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They don't look like this, do they? Lol
81270db779deecea1520dba9480e4508.jpg


What wheels do you have? They're probably the incorrect backspacing.
 

lwarrior1016

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I would look out for hard corners also, just because you don't want to stress that stretched sidewall too much. As far as your rub marks from 255's, that seems to be a backspacing issue. I have 17x9 saleens with 275's all the way around and I wouldn't rub lock to lock. I was lowered about 2".
 

thelastofthem23004

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I have 03-04 cobra STYLE rims from AFS. I only learned this when we went to put the tires on. and no if my tires had looked anything near that I would have just left the weather rot specials on the rims.
 

lutter94

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What wheels do you have? How low is your car? Have any pics of anything? I have 275's up front and 285's out back. It rubs on the front during hard right turns. The back is fine.

This is backspacing
backspace_offset.jpg
 

RichV

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Do you have a pic of your setup?

I have a 94 GT and ran 17x9 OEM 03 Cobra wheels with 275 tires, no rubbing, even 1.25" spacers in the rear.
 

lwarrior1016

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Wheel Offset and Backspace Explained

Wheel Offset and backspace are essentially two different ways of looking at the same thing. They determine the location of the wheel and tire assembly when bolted to the vehicles hub (how far in – tucked, or how far out they will sit).
Wheel Offset is the measured distance between the hub mounting surface and the wheels center line.
With X being the determined offset, the hub mounting surface on positive offset wheels is X amount forward from the wheel center line. The hub mounting surface on negative offset wheels is X amount backwards from the wheel center line. The hub mounting surface on 0 offset wheels is the wheel center line.
Wheel Backspacing is the measurement from the hub mounting surface to the back edge of the wheel.
backspace_offset.jpg

Typically speaking, the higher the offset/backspace, the more the wheel will tuck inward towards the suspension or away from the fender. The lower the offset/backspace, the more the wheel will push out away from the suspension or towards the fender.
For Example:

  • If the offset on a 9″ wide wheel is +12 mm, the hub mounting surface will be 12 mm forward from the wheels center line. Measuring from the hub mounting surface to the back edge of the wheel, the backspacing is 5.5″.

  • If the offset on a 9″ wide wheel is -12 mm, the hub mounting surface will be 12 mm towards the back of the wheel from the wheels center line. Measuring from the hub mounting surface to the back edge of the wheel, the backspacing is 4.5″.
Here’s how to calculate the backspacing using the rim width and offset:
First – add 1″ to the rim width and then divide by 2 to find the wheels center line (you have to account for the wheel flange which is why you add 1″ to the rim width). Second – convert the offset which is in millimeters into inches (there is 25.4 mm in 1 inch so divide the offset by 25.4). Lastly – add the converted offset to the wheels center line (if the offset is positive) for the correct backspacing or subtract the converted offset to the wheels center line (if the offset is negative) for the correct backspacing.
For Example:
17×9 +12 mm offset

  • 9″ rim width + 1″ = 10″

  • 10″/2 = 5″ (wheels center line)

  • +12 mm offset/25.4 = 0.47″ (0.50″ rounded up)

  • 0.50″ + 5″ = 5.50″ Backspace
17×9 -12 mm offset

  • 9″ rim width + 1″ = 10″

  • 10″/2 = 5″ (wheels center line)

  • -12 mm offset/25.4 = 0.47″ (0.50″ rounded up)

  • 0.50″ – 5″ = 4.50″ Backspace
*Please note that the wheels center line is the backspacing for 0 offset wheels*
 

lwarrior1016

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Oh no not at all, I google searched "backspacing explained" and that was the first website that came up. I copy and pasted it, I cannot take credit for that and still consider myself an honest man.
 

thelastofthem23004

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https://www.facebook.com/photo.php?...843278.-2207520000.1426167500.&type=3&theater
https://www.facebook.com/photo.php?...843278.-2207520000.1426167500.&type=3&theater
https://www.facebook.com/photo.php?...843278.-2207520000.1426167500.&type=3&theater
https://www.facebook.com/photo.php?...843278.-2207520000.1426167500.&type=3&theater
https://www.facebook.com/photo.php?...843278.-2207520000.1426167500.&type=3&theater

Those are the pictures I have. The face of the rim (outside) is against the wheel hub. The car is pretty low and the only description on the lowering springs used is as follows: Drag springs. That was the description on the post when I went to buy it. It sounds dumb, but I have no reason to not believe it as I have never driven anything that was made specifically to drag. I also have never driven anything meant to road course race either. The suspension doesn't lean when I take corners and when launching I can't feel a whole lot of weight transfer. To compare I guess I'd have to use my 94 cougar which under hard acceleration will kick the front end up a bit and the back end down a bit.
 

lutter94

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sorry pics don't work. Did you click the image button and paste the link in there?

On fb, right click on the photo, then click copy image location. Dump that link into the
coding. It will work.
 

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