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fc rear backspacing for 10"

Old 04-01-11, 05:43 AM
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fc rear backspacing for 10"

hey guys i am wanting to know what back space to run with a 15x10 rim
i am looking at running a 26x10 or 28x10 and want to know what backspace i need to run.
I do have some wide guards fitted to the car so not worried too much about outside just inside really. thanks guys

also whats the difference in running 26 to 28's?
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Old 04-01-11, 03:31 PM
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http://www.youtube.com/watch?v=dNtplbflhpQ

run a 28x9 mate, unless your planning going sub 8's

26" and 28" will effect final drive ratio and sidewall flex.
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Old 04-01-11, 05:54 PM
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have you tried to fit a 28x9 tyre in the back of a fc without jacking it up 4wd spec
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Old 04-01-11, 06:49 PM
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I run 17x10 +18 offset with my street tires (275/40R17, works out to 10.5" width and nearly 26" dia) and the backspacing is perfect with a fender roll and stock suspension. Works out to roughly 5.75" backspacing, you could get away with less on some aftermarket suspension.

There's no need to go to a 28" tire with stock FC rear end ratios, plus as beefy said, there's no room.
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Old 04-01-11, 08:32 PM
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I tried fitting a 28" tired on my FC. No way without cutting the fenders, A LOT. They are way too tall without fender mods or a min tub and pulling them in.

26x8 is all most need to get into the 9's.
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Old 04-01-11, 09:06 PM
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Obviously depending on tire type. full slick, yes, but if the OP is planning on going with an ET street or drag radial, 26x10.5 or 26x11.5 would be their best bet.
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Old 04-02-11, 07:36 AM
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so stay with a 26x10 as a shop near me has some they trying to unload to me for cheap...
car is nearly ready to hit the damn track and i got no wheels....
i head to USA in 2 weeks so may find some there.

Yes i have nearly 3 inch wide fenders on the rear, no not bolt on these are real metal fenders hand made from scratch and fuken lots of time spent on them. so yeah i can fit bigger on rear than normal fc
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Old 04-02-11, 08:05 AM
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go for wide rims and tyres for sure, but just not 28 inch tyres, too tall they will hit your tubs and front to rear sections , width is not your issue, nor doesn't my missus complain

you may need to invest in a pro guard measuring type kind o guy , thats what i got done when i ordered my weld magnums , give someone some coin they tell me sizes , wish i kept the chart, as he wrote all the combos i could have .
I remember 15x8.5 with 5.5 inch backspace, but i went with 15x8.25, 5 inch backspace, its too close to the outer edge , why didn't i listen to the man i gave money
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Old 04-11-11, 08:12 PM
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Thanks guys so i will go with a 15x10 wheel and a 5" back space by the sounds of it ah.
well hope they fit not too worried about the outside guard hitting as it has a massive widebody guard just worried about the inside of the wheel hitting.
And yes will go with the 26x10 m.t's and a 15x4 front
cheers for all the help guys
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Old 04-12-11, 09:05 AM
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its gonna look mad az bru , get some pics up when you have them fitted
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Old 05-04-11, 08:21 PM
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Hey guys i got our new wheels 15x10 with a 4.5" backspace as they didnt have 5" backspace and we running a 26x10 tyre.
Now how far will these sit outside the guard as it says -25mm offset is this correct as i looked up a tyre convertor site and it says they will sit 118mm outside the guards would that be right?
is this the right Backspace i got or should of got 6"?
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Old 05-04-11, 09:31 PM
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A 6" backspacing would have been equivalent to +25mm offset, and you might have had issues clearing the suspension. A 4.5" backspacing on a 10" wheel would be equivalent to -12.7mm offset. You got the right ones, I'm sure they will fit fine under your wide rear fenders.

If you have stock wheels on it right now, measure 91mm further than the outer edge of a stock wheel. Or, measure 140mm from the hub towards the guard and you'll see where the outside lip of the wheel will be.
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Old 05-04-11, 09:40 PM
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Oh sweet how do you work out the off set as it says -25mm on inside of the rim.
i hope they fit its a long way to get them home if they dont fit.......lol 14hour flight to get them home.
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Old 05-04-11, 09:53 PM
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If you want to calculate back and forth from offset and back-spacing or "front-spacing" (don't know the real word for this) check my thread out here: https://www.rx7club.com/suspension-wheels-tires-brakes-20/fc-wheel-fitment-guide-see-here-before-posting-fitment-thread-950447/

As far as a -25mm offset 15 x 10", that would be a 4" backspacing. They will still clear the inside no problem, but I have no idea how your rear guards are, and whether the tire will fit inside them. It would not fit in a stock fender well, I can tell you that much.

If you want a reference, Slammedblk7 has 17x10 +12 on the rears with 275/40R tires (equivalent to a 25.6" x 10.8") and this is his fitment with only rolled rear fenders:
http://i106.photobucket.com/albums/m...Picture335.jpg
Your wheels will stick out 37mm further than these.
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Old 05-04-11, 10:07 PM
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sweet as mate thanks for that i got 18x10's on there now and a 245 tyre and there is about approx 2" space to guard with out measuring it. but i think the offset as +25

Not sure on the offset on them to be honnest (not stamped) as i tried them on the front and they hit the coilovers
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