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Wheel Offset and Tire Guide

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24 replies to this topic

#1
OFFLINE   25GTurbo

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Here is a compilation of wheel and tire fitments for the Legacy GT.

Legacy GTs bolt pattern is 5x100mm, 17x7 +53mm as stamped on the back of the spokes on you stock wheels.

-OBXT bolt pattern is 5x100mm with +48mm offset (weighing around 20.5 lbs per rim). OBXT wheel is 17"x7".

-2.5i and 3.0R models will need confirmation on stock rim sizes.

-Center bore must have to be 56mm or larger (if the bore is larger than 56mm, use hub centric rings to fit properly to your wheel's center bore, but not always necessary if you have wheels with conical lugnut seating, the wheel will eventually center itself, but that's your call of how you want to go about that).

-SpecB, OBXT, and 3.0Rs can use shorter tire sizes from the GT. But be sure to check and compare the load capacity of the tires. Try to use the same tire load capacities if you can within +/- 100 lbs. You can certainly always go over, but not under (as this requires for you to run higher tire pressures and this could cause more of an issue for tire wear).

-Lug nuts threading are 12mmx1.25mm. Open or Closed End lugs will depend on the mounting thickness of your rim, usually, closed ends (like the stock ones) are fine.

-Here we go, here are your choices for rim widths (regardless of it being 17", 18", 19" or 20" rims):

{offset in BOLD are the closest possible offset to OEM's scrub radius, you'll notice that once you go past 8" wide rims, you will run out of room on the inboard side to put/stuff any more of the wheel/tire to maintain the OEM scrub radius.. 8" and up will increase positive scrub radius}

6.5" (+34mm to +60mm offset, +55) *for 2.5i only
7.0" (+37mm to +57mm offset, +55)
7.5" (+40mm to +54mm offset, +55)
8.0" (+43mm to +51mm offset, +53)
8.5" (+45mm to +48mm offset, +45) *will need to roll the fenders if tires are wider than 255
9.0" (+43mm to +45mm offset, +43) *will need to roll the fenders if tires are wider than 255
9.5" (+38mm to +40mm offset, +38) *will need to roll the fenders if tires are wider than 255

and it also depends on what kind and size of tire you want to run as well (and that can get messy). But to be on the safe side, here is the tire widths you can put on each rim:

195mm = 6.5", 7" and 7.5"
205mm = 6.5", 7" and 7.5"
215mm = 6.5", 7", 7.5" and 8"
225mm = 7", 7.5", and 8"
235mm = 8", 8.5", and 9"
245mm = 8", 8.5", and 9"
255mm = 8.5", 9", and 9.5"
265mm = 8.5", 9", and 9.5"
275mm = 9" and 9.5"
285mm = 9" and 9.5"

Once you decide on the rim size, the tire width you want to run, here are your final tire choices. Note that not all tires are built the same way, so sometimes you'll find two different tire models with the same size (225/45/17), but one can fit on a 7" rim, while the other one will need a 7.5". You'll have to look around the manufacturers' specs on sectional width of the tire.. normally you want your rim width be no more than 1.5" less than the tire's sectional width. For example, if you have a 8" wide rim, your tire's sectional width shouldn't be more than 9.5" or you'll have to deal with the flex on the tire sidewalls. Most performance driving set ups are 1" difference (ie. a 8" wide rim with 9" wide tire). Below I listed for you by rim diameter of which I recommend running with some notes on each tire with notes to go along with them as well:

16 in. rims (for 2.5i, 2005-on) only:

195/60/16 (great for snow rally or snow use)
205/55/16 (OEM sizing which is also good for some non-tarmac surfaces)
215/55/16 (oversized for the rim protection, but very sloppy sidewall handling)
215/50/16 (wider footprint used for more daily driving without harsh gas consumption)
225/50/16 (great for autocrossing, still usable for daily driving all year round)


17 in. rims (for GTs 2005-on):

205/40/17 (only for SUPER FAST acceleration and torque; for autocrossing only, do not use for daily driving)
205/45/17 (only for FAST acceleration and torque; for autocrossing only , do not use for daily driving)
205/50/17 (good for snow rally)
215/45/17 (stock)
225/45/17 (good autocross performance tire size for gearing, more mph per gear)
235/40/17 (good autocross performance tire size for torque, more acceleration)
235/45/17 (tallest tire you could use under the GT due to possible suspension clearance issues, best used with an 8" wide wheel)
245/40/17 (good autocross performance tire size for traction, will need to have a flatter alignment to make use of the grip)
255/40/17 (maximum grip, good for track days, will need a 9" rim to make use of the contact patch and a good alignment as well).

18 in. rims (for GT 2005-on):

215/35/18 (only good for autocrossing use, do not use for daily driving)
225/35/18 (only good for autocrossing use, do not use for daily driving)
215/40/18 (uncommon tire size, close to OEM overall tire diameter, good for daily driving)
225/40/18 (typical sizing, most popular size, GREAT for daily driving)
235/40/18 (very large, but great for pot-hole city driving, may need fender rolling)
235/35/18 (rare size, but closest to OE tire sizing to keep the spedometer reading correctly)
245/35/18 (common autocross, performance size, very good for daily driving)
255/35/18 (very good daily driving size, even better on the track)
265/35/18 (very good daily driving use, but the car wont be able to use all 265mm of tread for the track)
275/30/18 (tallest tire you can mount without fender clearing issues on a 2" lowered car if you get the right offset)
285/30/18 (aka, the "STREETS OF DREAM" setup... the widest you can go.. this is the next tire size I am going for and a rim to match it)

18 in. rims (for Spec B.2006-on, 3.0Rs 2008-on):

225/40/18 (common tire to use and gives a better acceleration since it's 0.5" shorter)
235/40/18 (rare size to find, but near stock height for proper gearing)
245/40/18 (popular tire size for the larger cars)

19 in. rims (for GT 2005-on):

225/35/19 (common typical sizing for 19" for our cars)
235/35/19 (tallest tire you can mount without fender clearing issues on a 2" lowered car if you get the right offset)
245/30/19 (rare size, but also tallest tire you can mount without fender clearing issues on a 2" lowered car)

Use at your own risk.

Ive got to thank xenonk many times over for allowing me to use his guide on Offsets, sizes for rims and tires.

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Measuring Backspace
The easiest way to measure backspace is to lay the wheel face down onto the ground so the backside of the wheel is facing up. Take a straight edge and lay it diagonally across the inboard flange of the wheel. Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub mounting pad of the wheel. This measurement is backspace. The above photo shows three wheels with 2",3", & 4" backspace.



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Measuring Wheel Offset
To calculate offset you'll need the following measurements:

Wheel backspace
Wheel Width
Wheel Center line (outboard flange to inboard flange measurement / 2)

Subtract:

Wheel center line from Wheel backspace to get offset. If backspace is less than the wheel centerline the offset is negative
if backspace is greater than the wheel centerline the offset is positive

Tip:
To convert from inches to mm multiply by 25.4
To convert from mm to inches divide by 25.4


Backspace to Offset Conversion Chart
The table on the right is q quick reference for finding offset, pick the rim width and follow the row over to the backspace of your wheel.

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Determine Wheel Caliper Clearance
Ensuring proper caliper clearance inside the wheel is important. The following chart should enable you to have the dimensions required by most wheel manufactures.

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A. Caliper Overhang Distance Used to determine if wheel dish is adequate (in some cases a spacer is required for clearance)

B. Diameter of Hub Center Required if wheels are hub centric

C. Wheel Stud Diameter Required along with bolt circle

D. Height of Hub Center
E. Length of Lug and Thread Type (Fine or Coarse) Required to determine if longer studs are necessary

F. Distance from CL of Hub to Caliper Used with A to determine if a spacer is required for proper fitment

G. Width of Caliper Used with F to determine if wheel ID is adequate to clear rotor/caliper package

H. Diameter of Hub Mounting Face Used to determine if hub is adequate to support wheel/spacer

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#2
OFFLINE   MAINIAC XV

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Really useful tire & rim info , Carter should make this a sticky :cool:

It ain`t over till the fat lady sings ( for those too young it`s a Yogi saying )


#3
OFFLINE   25GTurbo

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it was a sticky when you posted! :cool:

#4
OFFLINE   MAINIAC XV

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it was a sticky when you posted! :D


Oh dam , must be time for new glasses again :cool:

It ain`t over till the fat lady sings ( for those too young it`s a Yogi saying )


#5
OFFLINE   inski

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thanks!

#6
OFFLINE   25GTurbo

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n/p hope you find it informative

#7
OFFLINE   mainewrx09

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I am still confused. lol I want this sweet looking rim that is 18x8 but only comes in a +38mm offset. I am keeping my suspension stock and will later add eibach springs. Will that offset be hard on my wheel bearings with that rim width. Or scrub? I will still probably run 225/40/18 on them? They are sweet and are blue and black 2 tone to match my paint.
Any help would be great.

#8
OFFLINE   scooby RS

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i have a quik question, that i should know being a mechanic in all. but i'm not tire professional. i am putting the one ince impreza lift off dirtyimpreza.com. and i am putting 205-75-15 general grabber. i'm just trying to figure out what offset i have to get to clear my struts... i was also looking at 215-75-15 BFG a/t but those are pretty wide. i was also thinking of just putting wheel spacers in..? i don't know just need an oppinion i suppose before i go dropping all the money. i'll make it happen one way or the other.

#9
OFFLINE   GClark

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Stock wheels would work fine. I run 215/65/16 on my car and that's as big as you want to go. Go to the Miata tire calculator and try to get as close to mine as possibe. Go with the Grabbers, I love mine. Perfect for on and offroad.
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#10
OFFLINE   SUBARUDE

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i have a quik question, that i should know being a mechanic in all. but i'm not tire professional. i am putting the one ince impreza lift off dirtyimpreza.com. and i am putting 205-75-15 general grabber. i'm just trying to figure out what offset i have to get to clear my struts... i was also looking at 215-75-15 BFG a/t but those are pretty wide. i was also thinking of just putting wheel spacers in..? i don't know just need an oppinion i suppose before i go dropping all the money. i'll make it happen one way or the other.

if this is for your rs then the 205/75/15 grabbers will not fit a 205/70/15 might but i already tried the 205/75/15 grabbers on my 2000 obs with almost 2" in the rear and a 1" in the front on a 38mm offset wheel in the fron they rub just a light but on the rear they touch the strut and the rocker panel in front of the rear tire.your best bet is to run a set of forester wheels which are a 48mm offset in a 17" forester rim the biggest tire you can run is a 215/55/17 and in a 16" forester rim the biggest you can run is a 215/60/16 and last is the 15" forester rim the biggest tire you can run is a 205/70/15.oh and you probably want to pick up some butt sag spacers to add to the rear of your car
hope this helps

#11
OFFLINE   scooby RS

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hey, yah that helped a lot, thanks both of you. i have a set of 17's with a 48mm offset. i just don't know if i trust the spoke design.. it doesn't look very sturdy. i wanted to buy a set of 15' steelies, yah that strut was my initial problem, i have 215 55 16 and they just barely don't rub... if you say the forester rims will work, i'll get a replica steelie for a forester in a 15 and see if i can find an aggresive tire in that size.. any recomendations? again, i appreciate the help.

#12
OFFLINE   SUBARUDE

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i would just go with something for a snow tire it semi aggressive and look mean

#13
OFFLINE   scooby RS

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yah i was thinking that to... only thing is they wear like a sun of a b**ch in the summer.. i think i'll end up doing that though, thanks a lot man. i'll put up pics when i finally get it all done. heard any bad things about the jackson racing 1 ince kit?

#14
OFFLINE   IBratmanI

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That's what both of us have on our OBS's and have no complaints. If Gabe remembers the tire that's on my OBS, those wear damn good, I have been running them all summer and they don't wear too fast

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#15
OFFLINE   SUBARUDE

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the jackson lift even with my added spacers has kept everything in subaru factory alignment spec nothing is out of the green which surprised the guy that did the alignment on mine and snows tires don't wear that hard on the gc body style cause they aren't that heavy of a car for the size tire you will be running

#16
OFFLINE   scooby RS

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alright, so i've been doing non stop research since we talked last night. my rims (stock wrx rims) are a 52 mm offset, and you say i need a 48, so i ordered 5 mm wheel spacers (closest i could find) and i'm going to run the 215/60-16 yoko geolanders. and you say i should use the saggy butt spacers with the jackson lift? and you stayed in green without cam bolts? haha i'm sorry for so many questions... just trying to get a grasp on things.. appreciate your help pal.

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OFFLINE   GClark

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I don't know how different your RS is from my wagon, and I'm sure Gabe knows, but I just put on my spacers and my 215/65/16 General Grabbers and have had zero problems. Maybe because it's an OBS? I'm not sure... Either way, it's a wicked fun setup and you'll love it. The Geolanders are great tires, you'll have to make sure to come to our next dirty meet to try them out.
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#18
OFFLINE   scooby RS

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i think clearance would be no problem... the only problem i think i'm going to run into is the strut itself.. the 215 55 16 that i have on right now... just barely don't touch.. i don't think the 5 mm i'm gunna add to it will clear a 10 percent increase in side wall... luckily i work at vip so i can mount a tire off the shelf onto one of my rims and see if she clears once i get the whole set up installed. i'm hoping i can clear a 65 due to the fact that i want to run grabbers... if not i'm glad i heard someone say the geolanders are a good tire, i havn't heard much but bad from them... but they look like a solid tread design... hell yah i'll come out to the meet lifted or not. what size spacers are you running?

#19
OFFLINE   SUBARUDE

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yes in the green with no camber bolts and the reason gclark can fit the bigger tires is cause the newer obs's have a bigger wheel well and the strut perch is a little higher on the strut.the butt sag spacer are just to give it a more level look and if you carry anything heavy in the back it will help keep anything from rubbing

#20
OFFLINE   scooby RS

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yes in the green with no camber bolts and the reason gclark can fit the bigger tires is cause the newer obs's have a bigger wheel well and the strut perch is a little higher on the strut.the butt sag spacer are just to give it a more level look and if you carry anything heavy in the back it will help keep anything from rubbing


awesome. thanks a lot guys. we'll see how she goes.





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