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tires How wide on 15x7


Guest oldzman

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JohnC:

 

I may be wrong, but in all the mags/articles I've read a 15X7 wheel is actually 8" wide (bead seat on each side).

 

If this is true, wouldn't 0 offset provide 4" backspacing?

 

If you wanted 3.5" backspacing you would need .5" of negative offset.

 

In case any of you tend to get confused by positive/negative offset, I manage to keep it straight by remembering that front wheel drive cars almost always have POSitive offset (the plane of the hub face moved toward outside of wheel). This goes along with my consideration of front wheel drive cars as Pieces Of Sh*t, because I haven't had/driven one I liked the handling or maintenance requirements on (I keep cars a long time and try to treat them well).

 

Hoping to be enlightened....

 

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The width measurement is from inside bead mounting surface to inside bead mounting surface. The overall width is probably close to 8" but I've got 15 x 7 and 14 x 7 Panasports, 14 x 7 Revolutions, and 15 x 7 Enkies and they all measure 7" from bead to bead.

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The "50" is not the tire width, it's the aspect ratio (lower number = shorter sidewall height).

225 is as wide as you want to put on a 7" wide wheel.

 

My 14X7 Enkeis and 15X7 Panasports are 8" wide total, 7" inside to inside. 4" backspace IS zero offset on a 7" wide wheel, I'm almost certain. Anyway, zero offset is what you want, and no flares or cutting are required to run 225/50-15s, but any higher aspect ratio at that width would likely rub. 205/50, 205/55, or 205/60 should also fit well without rubbing.

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Well... 4" backspace if you're measuring to the outside edge of the wheel, but a zero offset wheel, by definition, would be dead center between the rim halves so the width from the wheel mounting surface to the inside bead mounting surface is 3.5" (7 / 2 = 3.5). The correct way to measure backspace is to the bead mounting surface.

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I would agree with you John that the "correct" or most consistant way to measure backspacing is from the inside of the bead. The thickness of rim beads can very and thus be an inaccurate way to measure.

Although, most are close to 1/2".

 

That being said, when I ordered my wheels from Billet Specialties they measure backspacing from the outside, or extreme inboard edge of the rim. So, according to the guys who made my 15x8 rims with 4 3/4" backspacing, they have a positive offset of 0.25", not 0.75".

 

Just make sure you know how they measure if you plan on ordering custom wheels.

 

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The "correct" and far more practical way to measure backspacing is from the absolute backside of the wheel, outside the bead. Did a quick search to confirm and found: http://www.usacomp.com/Offset.htm

Doesn't prove anything, of course, other than that these guys reference backspacing to the absolute backside, not the bead-seat area. Note they refer to overall widths 1" greater than the inside-bead to inside-bead width, which seems to be standard, as far as I've seen.

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Guest Z-rific

If you get these wheels, jump on those Yokohama AVS Intermediaite tires from TireRack.com. They are on closeout for dirt cheap.

 

I just ordered 4 225/60/zr15's for my 15x8 wheels (3.5" backspacing, but I have flares). They were $44 a piece, totalling $208 shipped to my door. That's an amazing deal on Z rated tires.

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I guess each wheel manufacturer does things their own way. I just spent 18 months ordering custom wheels from BBS, Monocoque, Bogart, Kinesis, and Kodiak. All specify "backspace" from the wheel mounting surface to the tire bead mounting surface and wheel "depth" from the wheel mounting surface to the absolute inside lip of the wheel.

 

BTW... every single one of manufacturers above is a LIAR except for Monocoque and Kodiak. BBS went so far as to give me bogus UPS tracking numbers for wheels they claimed to have shipped.

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