I never really understood wheel offset and backspacing, so I am asking you... The expert! When I get the money from the city for my rim they destroyed I would like to pick up some 18x9's with 0 offset and 5" backspacing. How will these differ from stock?
Procomp 7031
stryker125
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I never really understood wheel offset and backspacing, so I am asking you... The expert! When I get the money from the city for my rim they destroyed I would like to pick up some 18x9's with 0 offset and 5" backspacing. How will these differ from stock?
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Thanks rbt, I'll be running stock for the time being, then to 35s after another 1.5" of lift.
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Stock backspacing is 5.5". That's the flat section that bolts to the rotors/hub, to the back lip of the rim. So by running a 5" BS'd rim, it'll stick out by another half inch.
Just FYI, I know you've seen my setup and stared... :lol: but the BS'ing on my rims is 4.75". Offset is just another way to describe what I just did, IIRC.
Just FYI, I know you've seen my setup and stared... :lol: but the BS'ing on my rims is 4.75". Offset is just another way to describe what I just did, IIRC.
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just to warn you be prepared to do some trimming to fit 35's with that much offset.
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Yea I'm not worried about it, shouldnt take much.... a stock pro4x will take a 295-70-18 easy, so another 3" should help a bunch with a real 35". We'll see, but pwm is no biggie!
Btw, is that really considered to be THAT much different than stock?
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Offset is the distance to the rim's mounting surface, from the centerline of the wheel, (so with 0mm offset the mounting surface is half way between the inside and the outside of the rim), while backspacing is the distance from the mounting surface to the inside edge of the rim.
But with a 9" rim and 0mm offset you would expect 4.5" backspacing instead of 5", (half of 9"), but rims are actually about an inch wider than their advertised width, because they don't count the flanges, (which are about half an inch each).
Measured width is an inch wider than "width":
![Image]()
Offset from centerline:
![Image]()
To convert offset mm to inch:
25.4 mm is the same as an inch: so +/-18 mm is about 3/4" from centerline; +/-12 mm is about 1/2"; and +/-6 mm is around 1/4".
But with a 9" rim and 0mm offset you would expect 4.5" backspacing instead of 5", (half of 9"), but rims are actually about an inch wider than their advertised width, because they don't count the flanges, (which are about half an inch each).
Measured width is an inch wider than "width":
Offset from centerline:
To convert offset mm to inch:
25.4 mm is the same as an inch: so +/-18 mm is about 3/4" from centerline; +/-12 mm is about 1/2"; and +/-6 mm is around 1/4".
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Thanks Norcal, but I'm still a little confused.... haha its still all mumbo jumbo to me? rbt said it should be about 38mm more than stock, and an online calculator told me that is about 1.5", correct?Offset is the distance to the rim's mounting surface, from the centerline of the wheel, (so with 0mm offset the mounting surface is half way between the inside and the outside of the rim), while backspacing is the distance from the mounting surface to the inside edge of the rim.
But with a 9" rim and 0mm offset you would expect 4.5" backspacing instead of 5", (half of 9"), but rims are actually about an inch wider than their advertised width, because they don't count the flanges, (which are about half an inch each).
![Image]()
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Sweet description.
As for 1.5 inches. There are 25.4mm for every inch. 38/25.4 = about 1.5 inches. If stock is 5.5", you want 5", and your rim is 1" more, you'll get 1.5" or 38mm more to the outside of the fender than stock or 1.5" more to the outside. Curbs will be closer to your ties than your fender than before.
Unless... I'm wrong...:bangit:
I'm watching SOA and drinking beer... so...
As for 1.5 inches. There are 25.4mm for every inch. 38/25.4 = about 1.5 inches. If stock is 5.5", you want 5", and your rim is 1" more, you'll get 1.5" or 38mm more to the outside of the fender than stock or 1.5" more to the outside. Curbs will be closer to your ties than your fender than before.
Unless... I'm wrong...:bangit:
I'm watching SOA and drinking beer... so...
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Yep. 5" BS is 1/2" less BS than stock's 5.5", and then an inch wider of a rim means it will stick out 1.5" more.
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Ok sweet thanks! So Im going to assume that I will be good to go with the stock tires, however do you think the pwm would be able to take care of any rubbing issues with 35's? I know it wouldnt be an issue with stock wheels, but I'm not sure about the additional 1.5".
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Yep. PWM will be needed. My Black Rocks only stuck out 1" and with 34" LT305/70R17 Terra Grapps, I needed to remove the front mudguards, trim the metal behind where they were, do the pinch weld and pull back the plastic fender liner and reattach. I had on my backup set of Bilstein HD's with a 2.5" leveling kit for the trimming, which is 1/2" taller than recomended for my year and model. So you will be trimming for 35's ...
See the Pinch Weld Mod link in my sig.
You said, (above), another 3". Do you have 5100's in addition to the 1.5" leveling kit?
O.k. I see you plan to add another 1.5" before 35's. That will help, but it still might rub. I had mine at 4" shortly after the trimming with the HD's and 2.5" PRG leveling kit, and it didn't look like much more clearance at the pinch weld. To clear without the pinch weld mod, the bottom of the fender needs to be at more like 2 o'clock instead of around 3 o'clock.
See the Pinch Weld Mod link in my sig.
You said, (above), another 3". Do you have 5100's in addition to the 1.5" leveling kit?
O.k. I see you plan to add another 1.5" before 35's. That will help, but it still might rub. I had mine at 4" shortly after the trimming with the HD's and 2.5" PRG leveling kit, and it didn't look like much more clearance at the pinch weld. To clear without the pinch weld mod, the bottom of the fender needs to be at more like 2 o'clock instead of around 3 o'clock.
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I am familiar with the PMW, I did it on my last T. I have just a 1.5" level currently, but will be adding 5100's set on the middle setting (in addition to aftermarket uca's) when I'm ready for 35's.
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