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Old 09-24-2003, 08:39 AM   #76
KC
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Quote:
Originally posted by Rickard
I stand by my equation. I'm not saying an 8" rim will fit - I'm just telling you how to determine what the difference will be.
I make no representations about what fits or what doesn't fit.
I understand what you are saying. "When you increase the width of the wheel, you should keep the outside of the wheel in the same location as stock and send the rest inboard to ensure no rubbing". Did I get that right? You're right... that's a surefire way to gaurentee no rubbing.

HOWEVER... you're missing the whole point on this thread -which is to guide the enthusiast in finding a wheel that WILL fit their car so they can get more rubber to the ground, SAFELY, without damaging parts

Quote:
An eight inch wide wheel with a 59 mm offset will have the outside of the wheel in the same location as the stock STi wheel. It may rub on the inside but the outside will be at the same location as the stock wheel. That's all that I'm saying.
Keeping the outside of the wheel in the same location is not important and has no bearing when finding wheels that actually do fit. The outside of the wheel does not have to be in the same location to avoid rubbing. Due to the way, under load, the suspension compresses, it adds dynamic camber to the wheel/hub and the tire will actually gain more negative camber, tucking it under the lip instead of making it rub. It actually gives more room to play with under the lip of the fender. So you actually CAN add more wheel to the outside of the wheel. (but there's a limit... and by following page ones 1st post measurements, odds are good, not guarenteed, that you will not exceed the limits and will ensure proper operation of the vehicle without destroying bearings.

Here's a great explanatioin and will hopefully help you understand where I'm coming from: http://www.tirerack.com/wheels/tech/offset.htm

--kC
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Old 09-24-2003, 12:45 PM   #77
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Here is a calculator that I think works nicely: Wheel Offset Calculator It has a short explanation with it.

According to this calculator, what the original post shows as the ranges and what KC has been trying to explain is accurate:

For example, if the STi's stock wheels are 7.5 with 53 mm offsets, the ideal offset for an 8" upgrade would be 47 mm, because the the clearences from strut housing to the inside of the wheel would remain the same; however, the wheel would extend 12 mm more towards the outside.

I think the most important part is keeping the inside clearence optimally the same as original while having minimum outside extension of the tire. 12 mm would be roughly 1 in. that seems almost borderline extension to me.
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Old 09-24-2003, 03:23 PM   #78
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Width .... Offset

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

Does this apply to all Subaru's?

If not, what we need is a list of each year and model with the OE offset and wheel size. Then we can all figure out what we should be buying.
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Old 09-25-2003, 03:01 PM   #79
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That got me to thinking about the old "Subaru engineers know what they're doing" line that people use to defend the way stuff comes from the factory. Maybe the engineers only allowed enough room in the fenders for tire/wheel combos that would be safe....

The blistered fenders could have easily been made an inch wider...but they weren't. Maybe the all-knowing Subaru engineers did this on purpose.

The theory goes like this: Subaru engineers know best...nearly any combo that fits is safe...anything wider means going to a widebody which means you're on your own.

Only time will tell if there are common problems with front wheel bearings going bad.
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Old 10-03-2003, 07:59 AM   #80
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Quote:
Originally posted by nhibbert
Width .... Offset

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

Does this apply to all Subaru's?

If not, what we need is a list of each year and model with the OE offset and wheel size. Then we can all figure out what we should be buying.
I can say for certain that list applies to all Imprezas. Whether or not it applies to all Subarus is a different matter all together. Subaru hasn't changed the Impreza design much for the struts, placement, liner, fenderwell since 1993. All we got with the WRX was a new skin and a more strengthend frame/body. Much of the underpinnings and tolerances for mechanicals are the same with a few tweaks here and there.

--kC
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Old 10-03-2003, 11:27 AM   #81
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Is there any ideal offset and wheel size (with tires of course) that wont rub on a GC8?

I mean, would an 18x7.5 and a +50 with a 225/40/18 tire not rub? Or would it?

Would I need something like a +53 ?

Keith
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Old 10-04-2003, 02:20 PM   #82
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what offset would you suggest for a 17x8.5
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Old 10-12-2003, 12:16 PM   #83
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Yep, KC is right!
I have a question of my own, though. I have heard of problems with the 18x7.5s rubbing with a +48 offset. I have been recommended a +44 offset. I don't know what tires they were using, and they could be the problem. Has anyone else heard about this from people that have tried it, and not from dealers? I am looking at getting the 18x7.5 Volk CE28 or LE28s.
Thanks-
Nevin
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Old 10-14-2003, 07:03 PM   #84
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Quote:
Originally posted by WhiteHotWRX
Yep, KC is right!
I have a question of my own, though. I have heard of problems with the 18x7.5s rubbing with a +48 offset. I have been recommended a +44 offset. I don't know what tires they were using, and they could be the problem. Has anyone else heard about this from people that have tried it, and not from dealers? I am looking at getting the 18x7.5 Volk CE28 or LE28s.
Thanks-
Nevin
I was just told the same thing as I am trying to order my CE28N's and they said it was 18x7.5 and +44. I was told it will be perfect. True?
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Old 10-14-2003, 10:56 PM   #85
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Quote:
Originally posted by WReX'n'Effect
I was just told the same thing as I am trying to order my CE28N's and they said it was 18x7.5 and +44. I was told it will be perfect. True?
The folks at Ronal set me up with 17x8 wheels with an offset of 40. I really like the fitment and look of the wheels......this is what they recommended for my car. However, there is room for a higher offset. Personally, it makes more sense to me to keep the offset as close to factory specs as possible (to avoid any potential issues).

- Kean
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Old 10-15-2003, 07:15 AM   #86
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Yeah, that's kind of what I figured. I know 44 is still right around the "nirvana" range. Thanks for your help!
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Old 10-16-2003, 12:38 AM   #87
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yeah this "nirvana" range is gonna make me pull a Kurt Cobain. so what are we sayin here.....that 18x7.5 with +44 is gonna be safe or what?
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Old 10-16-2003, 04:20 AM   #88
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Yes, they should work. The guy that told me this actually has them on his car with the +44 offset.
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Old 10-16-2003, 06:27 PM   #89
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excellent....now if I can just find a place that stops telling me they have them in stock when they really don't. Do these people not like money???
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Old 10-21-2003, 05:44 PM   #90
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Ok guys, after reading this post I have more knowledge about the correct wheel/offset issue, but I'm also a little confused. Could you please let me know if this combo would work on my '02 WRX sedan:

5 Zigen Super Six wheels 18x7.5 w/ 48mm offset
P235/40ZR-18 tires (not sure of the brand yet)
My car is lowered approximately 1.5 in the front and 1.4 in the rear w/ H & R springs.

Thanks so much for any advice. My main point of concern is the offset and the tire size, should I go with P225 instead of P235?
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Old 11-06-2003, 01:58 PM   #91
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Default Re: The Offset Information Thread

Quote:
Originally posted by North Ursalia
I'll sticky this for a little bit, then move it to "FAQ/Threads of Note"


Please people, do not just quote random specs- offset is directly related to rim width- you can certainly use a +55 6.5" wide rim on most late model Subarus, but you cannot use a +55 8" wide rim! Offset Nirvana is within a few millimeters of:

Width .... Offset

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

Anything within sighting distance of these ranges is happiness for your wheel bearings. I reserve the right to be corrected on the ranges, but they are about 95% accurate .


Brian
http://www.subaruwrxparts.com
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When you say wheel bearings, you mean the ball bearings in the CV joints (half shafts), right?
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Old 11-06-2003, 03:57 PM   #92
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Also, is 8.0" wide the widest we can safely go on the wheel bearings???
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Old 11-08-2003, 03:00 PM   #93
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Anybody got a picture of the wheel bearings? This thread is worthless without pix.
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Old 11-08-2003, 09:01 PM   #94
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Quote:
Originally posted by JDMSubaru
When you say wheel bearings, you mean the ball bearings in the CV joints (half shafts), right?
No. He is referring to the bearings pressed into the steering knuckle. Basically, they are what the splined end of the half shafts (at the knuckle) turns in. I can't find any decent pics at this time, but I hope this explaination helps.

BTW, they can't be removed or installed at home unless you have a hydraulic press.
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Old 11-19-2003, 02:08 AM   #95
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"Wheel bearings" - the rotating support for the wheel hub(that thingy with 5 bolts sticking out that you bolt your wheel to). Now these bearings have a load rating of (educated guess-check my name) somewhere in the neighborhood of 1600 to 3000 lb load, and there are two of them at each corner. as long as the centerline of the tire stays the same, you could put on a 20" wide tire and not change the load. Changing the centerline with more or less offset will change the leverage, but 5mm is only .2" and would be relatively nothing to the bearings. Clearance, both inside and out is the rub(pun intended). That said what I need is someone with experiance to let me know if I can get away with lowering 1.8 in front and going with a 17x7 with yokohama 215-45 on my wagon.
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Old 11-19-2003, 02:28 AM   #96
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T-WREXX,

I haven't heard of any problems with the 5zigen wheels, so 48 should be correct. The whole 44 thing was with the CE28N and LE28N wheels only.
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Old 11-24-2003, 04:10 PM   #97
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Quote:
Most often you will see wheels with oh so close offset, these are usually VW wheels remarketed for subaru owners who dont know any better.
Doh! Looks like a bunch of us who bought some winter tires and rims from a group buy are poached! We bought 16" steel rims stamped "VW/MATRIX" on it that the owner told us last year would fit same a stock. oh well.
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Old 12-08-2003, 08:13 PM   #98
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For those interested, the formula for calculating offset is:

[(Back Space - 0.5) - (wheel width / 2)] *25.4

Back spacing will change while offset should remain fairly constant. Not the other way around. That is how proper suspension geometry is maintained.

Back spacing is measured from the outermost edge of the back of the wheel (including the lip) to the mounting surface of the wheel. Use a straight edge across the back of the wheel and a tape rule to measure the distance to the mounting surface. Measure your factory wheel to get offset. Use that offset number, plus or minus 3mm, and you should have a proper fitting wheel.

Changing backspacing or offset to clear brakes may work short term, but bearing, ball joint, and tire wear will be dramatically increased. The wheel needs to be designed with proper spoke clearance and offset to work correctly on the car.

Hope this helps.
EAH
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Old 12-09-2003, 12:19 PM   #99
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Quote:
Originally posted by EHobron
For those interested, the formula for calculating offset is:

[(Back Space - 0.5) - (wheel width / 2)] *25.4

Back spacing will change while offset should remain fairly constant. Not the other way around. That is how proper suspension geometry is maintained.

Back spacing is measured from the outermost edge of the back of the wheel (including the lip) to the mounting surface of the wheel. Use a straight edge across the back of the wheel and a tape rule to measure the distance to the mounting surface. Measure your factory wheel to get offset. Use that offset number, plus or minus 3mm, and you should have a proper fitting wheel.

Changing backspacing or offset to clear brakes may work short term, but bearing, ball joint, and tire wear will be dramatically increased. The wheel needs to be designed with proper spoke clearance and offset to work correctly on the car.

Hope this helps.
EAH
Are you saying anything more than 3mm (1/8") variance from the stock offset is going to drastically cut short the life of suspension components, tires, etc? I'm not trying to start an argument, but there seems to be a lot of conflicting info regarding offsets on this forum. I'm just curious as to where your information came from.

- Kean
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Old 12-09-2003, 11:17 PM   #100
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Kean:

I can appreciate your question. That is how I learned.

No, I don't think 3mm will cause "drastic" problems in any specific area. The degree of deviation from a specification is proportional to some negative result. In other words, a wheel offset difference of 12mm might cause greater problems than one differing by only 3mm. Keep in mind that a wheel sticking out and added 1/2 inch has greater leverage and will change handling characteristics and increase wear.

The offset calculation formula originally came from Weld Wheel Industries' website, a couple of years ago. It is however the standard. It was provided as a guide and for those who needed to find offset for their wheels.

As far as my assesment of wear, I've driven dozens of cars and trucks over the years and have noticed differences in driving feel and parts wear with offset differences of only 5mm.

As somone mentioned in an earlier response, a major difference in offset might cause a dealer to refuse warranty coverage of wheel bearing repairs.

The bottom line is, wheel offset should remain as close to OEM design spec as possible for best results. Differing wheel widths and back spacing can change since those aspects really only effect clearance of some parts.

Thanks,
Eric
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