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Old 03-25-2004, 10:57 AM   #126
Decolliber
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Quote:
Originally posted by North Ursalia
[b]
6.5" ....... +53 to +55
7.0" ....... +50 to +53
7.5" ....... +47 to +50
8.0" ....... +43 to +47
I just bought an 04 Forester and want to get some extra wheels for snow tires later in the year. Surbaru tells me that the steel wheels I have now (16x6.5") have 48mm offset. Tirerack tells me that Imprezas use 55mm offset, and I should not try to use Impreza wheels. I am wondering if I can use Legacy/Outback wheels - what is the offset?
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Old 03-25-2004, 11:46 AM   #127
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Stock Legacy GT ( pre-'04, anyway) wheels are 16x6.5 with a 53mm offset.

The aftermarket is rife with wheels in a +48mm offset. As I'm guessing that had been your plan anyway (you already have the steelies for snow tires), I say go for it. Besides, unless you buy used (check out the Forester Forum near the bottom of the Forums list page), aftermarket will be cheaper than stock from the dealer.

  - Eric
    Lil' Red '98 2.5 GT Wagon - Pics
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Old 03-25-2004, 08:08 PM   #128
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i got it now. so this is minimum to actual. for 6.5" the offset should be at a minimum +53mm to an actual of +55mm. so i wonder how close the 7.5 and 8.0 "actual" is? else we're talking wheel bearing problems. looks like staying closest to the "actual" is the way to go. so it looks like a 48mm in an 8" wide would be better than a 48mm in a 7.5" wide. unless of course there is some reason why 1 more mm the other way would mess something up?

6.5" ....... +53 to +55
7.0" ....... +50 to +53
7.5" ....... +47 to +50
8.0" ....... +43 to +47


> Dear Mr. X:
> Thank you for visiting the Subaru Web site and for your message. The only
> tires and wheel specifications that we recommend for the WRX models are:
> 16 x 6.5JJ wheels with an offset of 55 mm and 205/55 R16 tires or 17 x 7JJ
> wheels with an offset of 53 mm and 215/45 R17 tires.
> Thanks for the opportunity to be of assistance. If you need any future
> assistance, please feel free to contact us again.
> Best wishes,
>
> John J. Mergen
> Subaru of America, Inc.
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Old 03-25-2004, 09:26 PM   #129
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SgWRX:

The scale you show, which comes from the beginning of this post, is the reason I've become so involved with this thread.

The offset changes in conjunction with the wheel width changes are increasingly worse. As I've said multiple times...the offset should not change (much). If the ideal offset for the 6.5" wheel is +53 then the ideal offset for the 8.0" wheel is +53. I realize inward clearance becomes an issue but that simply means the wheel is too wide.

Finally, a +48 mm offset works well on most (if not all) Subarus and will give you a nice selection of wheels. Stick with that number (for any width wheel) and you will be happy with your wheel purchase.

HTH,
Eric
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Old 03-25-2004, 10:58 PM   #130
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Default Re: The Offset Information Thread

Quote:
Originally posted by North Ursalia

Width .... Offset

6.5" ....... +53 to +55
7.0" ....... +50 to +53
7.5" ....... +47 to +50
8.0" ....... +43 to +47
Hey guys from what i am understanding that on an 8 in wheel it is ok to have 43 mm offset??
for instance 17 8.5 43 offset is ok for the WRX??

i am asking cause from what i read in the past .. the safety zone is 48mm to 53mm off set for the WRX (wheel bearing life)

please please correct me if i am under the wrong impression
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Old 03-25-2004, 11:06 PM   #131
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Yes, 48 to 53 is the best range (for bearing life, scrub radius, bump-steer, clearance, etc...) for all Subaru wheels.

A 17x8.5 +43 will stick out too far.
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Old 03-26-2004, 09:29 AM   #132
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for example advan rgs come in that fit ment.. would it really stick out too far?
most 8.5 rims have lower offset.

Last edited by wRx14pSi; 03-26-2004 at 12:18 PM.
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Old 03-26-2004, 05:10 PM   #133
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True, some 8.5" wheels have lower offsets to deal with clearance issues. This is cheating, IMHO. Look at the big mfgs. (SSR, O.Z./Prodrive, Rota, Speedline, et al) offering wheels specifically for Subaru and you will find offsets of 48-51mm for our cars.

The SSR comps I'm running are 18X8.5" ET48 with 245/40-18 Michelins. They just clear the strut and the rear fender. Moving the wheel out that extra 5mm will better clear brakes and the strut but then the fender and other issues mentioned repeatedly in this thread come into play.

Keep in mind that an 8.5" wheel should get a tire 235 or wider to keep the sidewall in line. Even then the 235 will not protect the lip of the rim. A 245 would be ideal but then with that offset you will surely scrub the rear fenders.

If you really want the lower offset, decrease the wheel width to 8.0" or 7.5". A 235 would be ideal on an 8.0" and OK on a 7.5".

Your choice but there is a huge selection in proper offset for our cars.

HTH,
Eric
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Old 03-27-2004, 12:41 AM   #134
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FWIW GRM has a good art. on the subject of offset, scrub radius and such. Issue April 04, page 167-170
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Old 03-28-2004, 09:19 PM   #135
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Now that I think about it, the Subaru offsets that are over 50mm are probably trying to take advantage of the narrow wheels that are being used. If Subaru, for example, spec'd a 6 inch wide wheel...then they might choose to use a 60mm offset. Why? Several reasons. First, steering feel is improved as the scrub radius is decrease (or eliminated). Second, toe change under power or braking is decreased (or eliminated).

The question really should be "How can the aftermarket build struts that increase clearance from the strut body and the inside lip of the rim?".
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Old 03-30-2004, 01:02 AM   #136
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on the rayswheels.co.jp website (volk wheels) they have a 19x8 ce28n in 5x100 with an offset of +35.
i think that would be flush with the fenders, i have tein coilovers and can bring in the camber so i was wondering if i might have any other problems? and what they might be?
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Old 03-30-2004, 06:31 PM   #137
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If Tein recommends an 18mm decrease in offset to match some geometry change in their set up, I'd say go for it. Otherwise, a wheel with +35mm offset is definately going to hit the fender. But, only if you put a tire on the wheel.

Bump-steer and other possible clearance issues will certainly occur.

Isn't the same wheel available in a +48 for Subaru?
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Old 03-30-2004, 06:36 PM   #138
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yeah, but i want the wheel to look flush with the fender, i also thought i heard jdm junkyard or someone say that the rear will fit a +30 offset no problem, i cut all the fender lining out of the front fenders already cuz it was all chewed up before. i have been debating on the +43 or +35 for the last couple days. i have a friend with the same wheels on his sti in +43 but i dont think they come out far enough.
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Old 03-30-2004, 06:47 PM   #139
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Quote:
Originally posted by sc00by25rs
yeah, but i want the wheel to look flush with the fender, i also thought i heard jdm junkyard or someone say that the rear will fit a +30 offset no problem, i cut all the fender lining out of the front fenders already cuz it was all chewed up before. i have been debating on the +43 or +35 for the last couple days. i have a friend with the same wheels on his sti in +43 but i dont think they come out far enough.
I'm attaching a pic of my 17x8 Ronal wheels that have an offset of +40. The tires are Pirelli PZero Neros M+S 225/45's. They're pretty flush and I haven't experienced any rubbing issues even under load with passengers. I wish I had better angles for you........sorry for the size of the pics. Hope this helps in some way:


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Old 03-30-2004, 07:01 PM   #140
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I have 18" X 8.5" +48 SSR Comps and they are just about flush with the fender. They look nice when you look down the side of the car (STi). The tires (245/40-18) barely clear the fenders with 1.3 degrees negative camber.

An 8.0" wide wheel with a +42 offset would fit with the outer lip in almost the same position. A 235 width tire on such a wheel should fit quite nicely while a 245 would barely clear like mine.

That said, a +42mm offset is really not right for Subaru.

EDIT: My SSR Comps do NOT stick out as far as pics from Kean.

Last edited by EHobron; 03-30-2004 at 07:09 PM.
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Old 03-30-2004, 07:04 PM   #141
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Quote:
Originally posted by EHobron
That said, a +42mm offset is really not right for Subaru.
.....agreed.
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Old 04-03-2004, 01:06 AM   #142
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Quote:
Originally posted by aspera
I haven't ever seen any threads on wheel bearing failures, but it does make sense that numerically small offsets would increase bearing problems over time. Cornering hard should also be avoided...hahaha.

moving on...

I'm not a suspension guru, but I think something is being overlooked. I think you'd call it torque steer, but I'm not sure if that is the *real* name.

Let's assume that a USDM WRX sedan can fit 245's all around with ZERO offset for a moment. I know this is fantasyland, but bear with me.

In the front, stepping on the gas will toe the wheels inward. It will also lift them up slightly, depending on caster. They will also creep forward of their normal location. Slamming on the brakes will toe the wheels out greatly. Since the WRX tends to dive, the toe out will be extreme.

The extra offset will give the tire more leverage to move around in the bushings. It will also give the tire more leverage to steer. If you press on the gas pedal when exiting a corner, the outside front tire will steer INTO the curve. Since the car is leaning during a corner, the tire will climb forward and UP! This is extra understeer that an AWD doesn't need.

Like I said, I'm no expert (I probably got parts wrong), but my point is that all kinds of wacky suspension gremlins are waiting to pounce on "wider is more gooder" guys.

You're presuming what we call "bump steer" here and that's the key flaw in the analysis. Bump steer comes when the tie rods go through an arc on suspension compression - if you're going straight ahead this only affects the toe, but if you're cornering it affects the steering angle. Most cars are well designed to have a minumum toe change through the range of suspension compression, although lowering your car changes this paramenter (NOTE THIS - that's the main handling problem of lowered cars, besides spring jounce).

Torque steer, by contrast, is caused by different wind-up of unequal-length half shafts, something that Subaru is not plagued with. But look at a transverse-engined car with the gearbox on the side and you'll see something interesting -- the shorter shaft is way thinner. That's to ALLOW it to twist as much as the longer thicker shaft under acceleration. The problem is that this design presumes a single torque figure through both axles - less torque (easy acceleration) doesn't usually twist the axles much and so isn't a problem, but high torque, especially with modified engines, does make a profound difference. The wheels simply want to go a different distance, and this twists the wheel out of your hands. That's torque steer.

Wheel offsets? The original post is the genius post here. I think the Forester people have slightly different parameters is all. But note that as you move away from ideal offset (and TRUE offset of the load centre of the wheel is a SINGLE number for each model, it's just that different wheel offsets are necessary to achieve that number with different widths which is what this thread is really about) you will wear the wheels bearings more. So in rally we do what's necessary to clear our 5 inch rims with 4 inch wide tires (winter) to our 8 inch rims with 245s for tarmac, but we replace our wheel bearings twice (or more) a year! Stay near the first post above and i think your bearing will last reasonably well.

ACP
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Old 04-05-2004, 03:41 AM   #143
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Is there anyway of increasing the Offset on a rim? I found some 6.5's I'd love to use, but they are +40. What kinda damage would I be looking at if I used them? Also, this isnt for a WRX, its for a '92 Legacy TurboSedan.

Thanks
-Brian
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Old 04-07-2004, 07:34 PM   #144
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I have a 2004 WRX and want to replace the wheels (16x6.5) with the stock STi silver BBS wheels (17x7.5). What is the offset on the STi wheels and will they work ok with no issues on the WRX?

Thanks!
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Old 04-07-2004, 09:14 PM   #145
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The stock STi BBS wheels will fit your car perfectly! Several people have done this already.

HTH,
Eric
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Old 04-07-2004, 10:50 PM   #146
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Thanks. I'm a little confused about this "offset". The factory BBS 17 in. x 7.5 STi wheel has an offset of +53. This is outside the previously posted range for this size wheel of +47 to +50. Why is this? Also, if you look at Tire Racks website for the 17x7.5 BBS wheel it has an offset of +48 (perfect according to the posted ranges). Which would be better? I'm so confused
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Old 04-08-2004, 07:26 PM   #147
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The +53mm offset is the correct stock offset for the STi and many other Subaru models. This is the "ideal" offset for any wheel you put on the vehicle.

The Tire Rack offers most if not all of their wheels for Subaru applications in +48mm offset. While it is not exact, it is close enough offering the best compromise in a variety of wheel widths.

Some believe, rather strongly, that offset changes as wheel width changes and that is the reason for the range list. IMHO, the list is not really correct.

In my experience over the years, keeping offsets as close to stock as possible yields the best results.

Bottom line, the +48mm offset wheels offered by Tire Rack and others will work well on your car. The STi BBS wheels with +53 will be even better.

Eric

Last edited by EHobron; 04-08-2004 at 07:32 PM.
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Old 04-08-2004, 09:42 PM   #148
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I dont quite understand this...

would a

17x7 Enkei Rim for a WRX fit a Legacy Sedan, w/ a 44mm offset?

Also, tire size: 225/45/17
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Old 04-13-2004, 02:00 PM   #149
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this is interesting..

so advan made the RG's in 17 8.5 +43 offset. now i dont see any other cars that fit the 100 bolt pattern and stuff.. so i assume Advan made this size for subaru..

so would it fit our car with no probs? i am sure they know what they are doing.. .


anyone with insights please help .. i need to buy rims!!
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Old 04-13-2004, 02:23 PM   #150
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My '84 Fiero uses a 5x100 bolt pattern. Offsets seem to run from 35 to 42. VW also runs the same wheel.

Lew
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