After a lot of frustration from both the people answering fitment questions, as well as from those who are looking for fitment advice but don't want to browse through 200+ pages of bickering, opinions on wheel fitment and bullshit, I have decided to write a wheel fitment guide. I did this to benefit some, and relieve the burden from others, so if you notice any problems in my description or have anything to contribute beyond what I’ve written, please feel free to contribute! But for the love of Christ, do not come in to this thread asking if your 17 x 9 +35 wheels will fit. This thread is designed to teach you to be self-sufficient in figuring out offsets and resulting wheel dimensions.

This will be based on simple mathematical formulas to determine from wheel size and offset, what the resulting "Back-spacing" (Distance from hub to inner lip of wheel) and "Front-Spacing" (Distance from hub to outer lip of wheel) are. The significance of knowing these two measurements in reference to the FC's wheel hub is that the "Back-Spacing" determines suspension clearance from the wheel/tire, while "Front-Spacing" determines clearance to fenders. Note now, these measurements will be impacted heavily by tire choice, if you go with a tire much wider than the wheel, you will have to compensate. It will generally not be the wheel that will contact parts of the car, it will be the tire, so that is why this is simply a guide. I know some idiot is going to come on here all up in my **** saying that his 12" wheel fits stock fenders fine at -30 offset and 8* negative camber with a 225 tire stretched on it. Straight up, go **** yourself.

Now that that's out of the way, let's look at HOW to obtain the physical measurements of a wheel from its width and offset!

To determine back-spacing, we take the width of the wheel divided in half to obtain the centerline, then add the offset (or subtract it in the case of negative offset)

Let's take the stock FC TII wheels, 17 x 7 +40mm offset. Mathematically, we take 7"/ 2 = 3.5", multiplying by 25.4 to get mm's gives us 88.9mm (half-point, or centerline) and add 40mm stock FC offset, and we get 128.9mm back-spacing, or 5.07"

To determine Front-spacing (I don't know if this is an actual term, but it is the distance between the hub and the outer lip of the wheel) we divide the width of the wheel in half again to obtain the centerline, and subtract the offset (or add it in the case of negative offset)
Again, let's take the stock FC TII wheels, 17 x 7 +40mm offset. Mathematically, we take 7"/ 2 = 3.5", multiply by 25.4 to get mm's gives us 88.9mm (half-point, or centerline) and subtract 40mm stock positive FC offset to get 48.9mm, or 1.93” “Front-Spacing”, or distance between hub and outer wheel lip.

To verify our calculations, simply add the calculated Back-Spacing and Front-spacing, 5.07” + 1.93” = 7” total wheel width.

Now, Back-spacing limitations on an FC are fairly straight-forward. The space between the suspension and the wheel lip should never change, therefore once you have an offset of wheel that fits, you don't have to worry about it changing during suspension compression/rebound. However, “front-spacing” (distance between outer wheel lip and hub) can be an issue, as changes in camber, changes during compression/rebound as well as turning can affect what wheels/tires will clear a fender and which will not. The trick in wheel selection is generally to get as close to suspension as possible while still leaving sufficient extra room for tire clearance in case you change tire sizes, or even brands as different manufacturers of the same size tire can have slightly different dimensions.

 

Part Two: What kind of space is there between the suspension and outer fender to put wheels in?

Inner clearance limits (AKA maximum back-spacing approximations) Again, tire size will affect these limits, and these figures assume that overall tire width does not exceed rim width by more than 1”or 25mm, so 225 on an 8” wheel, 255 on a 9” wheel, 275 on a 10” wheel, etc. )

-150mm up front on aftermarket suspension, closer to 140mm on stock suspension. I would not personally go over 140mm – 5.5” back-spacing. For the rears, a little more room to play at around ~155mm inner clearance on stock suspension, or 5.9” back-spacing. Possibly more on aftermarket coilovers.

Remember, as ReTed says “it's easier to roll your fenders rather than take the risk of hitting something on the inside.” So err to the side of caution for inner clearance, especially noting that not all tires are created equally.

Outer clearance limits (AKA maximum front-spacing or lip approximations) Again, tire size will affect these limits, and these figures assume that overall tire width does not exceed rim width by more than 1”or 25mm, so 225 on an 8” wheel, 255 on a 9” wheel, 275 on a 10” wheel, etc. ) Note: fender clearance will vary a LOT based on pulling/rolling, camber on suspension compression, tire size, etc. This is just a guideline.
~90mm up front to still allow turning on stock suspension. If vehicle is lowered, pulling/rolling may be required. For the rears, people are much more inclined to pull/roll the fenders, and there is no turning required. As such, you can get away with lower offsets, so outer clearance limits can go up to 110mm “Front-Spacing” with reasonable tire sizes (less than 1” more than wheel diameter) I personally use a 17 x 10 +18 offset, which gives 109mm "Front-spacing" with a 275, and only needed a slight pull/roll.
Over-fenders or replacement wide fenders obviously will increase these outer limits by their measured width, as well as doing heavier pulling of fender.

So, with this in mind, we can back-calculate to see the largest theoretical wheel size with optimal offset for front and rear on stock suspension, stock (or mildly modified) fenders. For the fronts: 140mm inner clearance + 90mm outer clearance = 230mm total width, or 9” wide wheel. Centerline of a 9” wheel is 115mm, so offset would be +25. For rears: 155mm inner clearance + 110mm outer clearance = 265mm, or 10.5” wheel. Centerline of a 10.5” wheel is 132.5mm, so offset would be 22.5.

Note: I'm not saying you cannot or should not put a tire more or less than 1" greater than wheel width, I'm just saying for the sake of my figures in these posts, if you do go larger you have to take that into consideration. If you go smaller, well, I'll save my opinion on that.

If anybody has used higher back-spacing, go ahead and list what the wheel size, offset, tire size and suspension type is to add to the data. Same thing with outer wheel clearances.

 

Good writeup!

 

I like it. Thanks for taking the time to write this!

 

Nice!

 

thank gooooodness.. u are THE MAN!..
that wheel fitment thread is trash..

this is the ****!

 

It's not the be-all end-all, but it's a start and with some more feedback it could be a worthwhile piece of info. Glad it could help you.

 

Bumping this up, hopefully more people read it instead of posting in the fitment thread.

 

Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

Theres a link to a site to see changes real time. Helps see why some **** wont fit lol.

 

Hoping one of the mods can correct my initial post, I had 17x7 +40 for stock TII rims, was supposed to read 16x7 +40. Anyone who's ran wheels closer to suspension or with lips further out towards fenders post the results, and I can change the maximum clearance figures on FC's

 

I have 142.65mm on the inner (back spacing) front and 98.65 on the outer front with stock suspension, front fenders are rolled with lowering springs and factory shocks, so what your telling me now is that these 9.5" rims will fit?

http://www.ebay.com/itm/130899727612?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_sacat%3D0%26_from%3DR40%26_nkw%3D130899727612%26_rdc%3D1&autorefresh=true

 

Very nice wheels!

I think fitment would be close, the inner suspension might clear, albeit tightly w/ suspension if wheel/tire is kept 'normal' - under 26" in diameter, but I've never run that close. The biggest wheel I had on front stock suspension (not even lowered) was a 17x9 +22 and 255's, giving 136.3mm backspacing. You could always get away with a 5mm spacer between wheel and hub if you needed to, or go with a coilover setup for more clearance.

Outer clearance to fender you would probably be better off with aftermarket fenders, I'm not sure if the roll alone will be enough to clear, it would have to be aggressive. See here: https://www.rx7club.com/suspension-w.../#post11474021 where a gentleman was sporting 17x9 +12, giving 102.3mm front-spacing, and it looks close, and very cambered with stretched tires, and your wheels are 18" vs his 17. Look at that and make the decision for yourself.

The offset is very ideal, but again the outer fit will be tight. You are sticking out ~50mm further than stock wheels, I think it will take a hell of a roll to not rub on rebound/turning. If you do try these wheels, please update this post to let us know what you were able to fit on factory type suspension, because these will be pushing the limits, and again the offset is pretty much perfect to situate the wheel. Being 18" will definitely make it even tighter, so I can't make you any guarantees. Either way you won't be fitting very wide a tire on these, I'm not sure if you are after a stretched/super cambered look or want actual performance out of your car, that should definitely influence your decision.

Rears will fit without a problem with a healthy pull/roll, I've had 17x10 +18's running 275's on stock rolled-pulled fenders.

 

No I do not want the stretched camber look, the rears are my concern, it's the front. Sounds like I should play it safe and just go with 9 inches max up front. I want to keep the stock fenders

 

I'm running 255/40-17s on 17X9 +35s and it works fine, but I'm running a coilover with a long spindle mounting ear. I also clearanced the inside of the fenderwell ~1/4" and performed a light pull on the fender lip.

 

What about wheel width measurement? I have 18x10 ccw wheels on my FD and the last time I measured it, it was more than 10 inches wide, maybe 11 inches. So that impact the wheel clearance when you order 10 inches rim and you received 11 inches. I'm a bit confused about this, maybe it depends of the wheel manufacturer or maybe I took the measurement incorrectly.

 

To add a common question and answer to what Trots*88TII-AE* already posted up here;

Front over Fender +30mm would look like this;
Inner clearance = 140mm
Outer clearance = 120mm (90mm OE + 30mm Aftermarket Fender)
Total = 260mm Which is a 10" (254mm) Wheel width
Centreline of the 10" (254mm) Wheel is 127mm
Inner Clearance - Centreline = 140-127 = +13mm offset

So ideally for many reasons the ideal wheel Tyre Setup (tyre width matches rim width) with a car with OE rear fenders and front +30 aftermarket fenders would be (knowing that these would be custom wheels as it would be tough to find these offsets);

FRT = 18x10 +13 Wheels with 255/35R18 Tyres
RR = 18x10.5+23 Wheels with 265/30R18 Tyres