Determine Wheel Offsets.

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brown_fv

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Hey, does anyone have a guide or a good write up that will help me determine what offsets i need? ive been looking at tons of wheels lately (mostly sporty wheels; Volks, Work, etc) and i have NO CLUE what to look for regarding offsets.

stock wheels are 18x8 or 20x8 with a 40mm offset.

if i moved up to lets say 19x9 or 19x9.5 what would be a similar offset? or maybe 20x9 or 20x9.5. also with the stock wheels we can add up to a 20mm spacer so would that still have to be added onto the new wheel that we chose?
Just a wild example; if the new wheels i chose had a +22 offset which lets just say in this scenario was equal to the stock in terms of fitment, would i then need to make the offset +2 for it to sit flush on the fender?

i am so lost...
 
Offset is a little goofy to get right away but it's pretty simple.

Offset is based on the centerline of the wheel. 10" wide, centerline is at 5" They do it in mm cause inches or fractions would be crazy to try to determine. Plus metric makes more sense anyways. :tongue:

8" wide wheel, centerline is at 4".The mounting point of the wheel is +40mm closer to the outside of the wheel than the centerline of the wheel. 8" +0 would mean the mounting point of the wheel is at exactly 4" and you have 4" of wheel on either side, so the difference with a 8" +40 and a 8"+0 is 40mm wider offset.

Get it?

Offsets change based on the wheels width.
8" +0 is the same as 10" +25
 
The calculators are awesome, I use them all the time. The thing most of those don't tell you is the sidewall bulge beyond the lip of the wheel. Which in some cases is a lot.
 
Oh ok ok i kind of get it know, its pretty straight forward haha. i guess the next part would be how to determine sizing differences once you know the offset, but having to deal with sidewall bulge?

OK, so this is what ive been looking at lately; VOLK wheels. if i go 19's, i will either way 19x9 all around or 19x9.5 all around. not really wanting to deal with staggered set-ups and not being able to rotate the tires and what not.

with either 19x9 or 19x9.5 i would be using 285-45/19 (makes sense, right?) or 295-45/19? 295-45/19 would be closer to the stock radius than the 285's so my speedo will be less off. not sure which way i should go with that one.
 
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To go more aggressive you go to a lower offset to push the outer edge of the wheel out more. You see FXers running 25mm spacers all the time, this puts the stock 8" +40 to 8" +15. Looking at the sidewall bulge of the OEM GYs, I would guess there's almost an inch of sidewall bulge depending on how much air is in there.

25mm more than stock is relatively safe, beyond 25mm you want to make sure the tire width doesn't bulge more than the OEM GYs. My 10" +22 was 43mm wider than stock, the Axis Orden 9" +15 is 38mm wider than stock.
 
Hmm...i see alright ill try to get the hang of this one. The wheels so far i have selected are from this list so far (volks only for now):

Volk GTS - 19x9.5
Volk GTC - 20x9.5
Volk R57GT - 20x9.5
Volk RE30 - 19x9

i think these have the best chance of looking good on an SUV. now down to the offsets! I looked over Alexus1's thread over on the .org before trying a go at this

Volk GTS - 19x9.5 +28 or +30
Volk GTC - 20x9.5 +31 or +32
Volk R57GT - 20x9.5 +25 (cutting it a bit too close?)
Volk RE30 - 19x9 +25 (would possibly require a 5mm spacer?)

i am not looking to have my wheel wells trimmed down or anything like that, just looking for a decent fitment. i dont want to go TOO aggressive and possibly have camber issues. i would not want to go any further than how a stock 20x8 +40 with a 20mm spacer looks on an FX.

Sorry if i was completely wrong and it seems like i didnt pay attenion from everything you have just said in this thread. i have a 50% midterm on sunday (business) and ive been studying all day i feel like my brain is fried.
 
Alexus wheels were very close to being outside of the wheel wells, had he put anything larger than the 285/45-19 on the 10.5" he had in the back it would have stuck out further. The shorter tire helped as well in not rubbing.

What tire did you have in mind for the 19s?
 
With the 19s i was thinking either 285-45/19 or 295-45/19. the 285s would work with the offsets on most of those wheels right? the 295's would have a closer radius to the stock wheels (speedo will be less off)
 
295 would be closer to the oem height, 285 lets you play a little bit more with offsets. The Nismo rears are a 9.5" +30, using that rear size tire it would be very close to rubbing.
 
True. i am not too worried about keeping it close to the OEM height anymore, its just the price i have to pay to have nice wheels haha. does the Cipher from uprev allow me to adjust my settings to put my recalibrate my speedo? because i might be getting one of those (i have a few plans involving it).

regardless, going with the 285-45/19 mated with a wheel for example the GT-S (19x9.5, offsets +28 or +30) will they fit fine? i dont want it to be VERY aggressive but not ultra conservative at the same time lol
 
very good information here.

I want to chime in and say that I also like to look at the manufacturer's website (of the tire that is) and get the actual dimensions of the tire and also the recommended wheel width. For example a tire I'm looking at has 30.1 inch diameter, 8-9.5 inch wheel width recommended. This should give you a ballpark of the sidewall bulge. If it's recommending 9.5-11 inch wheel width and you're putting it on a 9 inch wheel width, you're clearly going to have a big side bulge, how much varies.

I like to stay closest to OEM diameter and the recommended wheel width for the tire I choose, but a larger side bulge can give it a more aggressive look and protection for your wheel.
 
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