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Will wider rims change off-set? #4563850
11/04/17 10:41 AM
11/04/17 10:41 AM
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
Put on new wheels for my Outback a few weeks ago. These cars are known to have weak wheel bearings and will get upset if the offset is off.

The factory spec wheels are 225/65/17 on 17x7 rims +55 offset. New wheels are 235/60/18 on 18x8.5 rims +55 offset. The 18s weigh about 10lbs more each.

Wheel diameter is 0.59" and Width is 0.39" bigger than stock. We're talking around 1/2" differences here. Will I need spacers or will this set up be fine in the long run? It doesn't rub at full lock and driveabity is fine. I just want to set things up to run within factory specs since don't want any future repairs due to improper modification.

The factory upgrade option is 18x7.5 with 225/60/18s with the same +55 offset.

Last edited by avacado11; 11/04/17 10:50 AM.

2017 Subaru Outback - 0w20 FS - Falken ziex s/tz05
2014 Lexus IS250 - 0w20 FS - Conti Extreme DWS
2014 BMW i3 - Bridgestone Ecopia
Re: Will wider rims change off-set? [Re: avacado11] #4563891
11/04/17 11:23 AM
11/04/17 11:23 AM
Joined: Jan 2013
Posts: 1,414
America's Dairyland
LotI Offline
LotI  Offline
Joined: Jan 2013
Posts: 1,414
America's Dairyland


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Re: Will wider rims change off-set? [Re: avacado11] #4563896
11/04/17 11:35 AM
11/04/17 11:35 AM
Joined: Jun 2013
Posts: 1,125
iowa
Traction Offline
Traction  Offline
Joined: Jun 2013
Posts: 1,125
iowa
If the offset is the same, that's what you want. Both rim flanges are just 3/4 in further away from that measurement, so track width remains the same. Besides, adaptors, and spacers are never a great idea anyway.

Last edited by Traction; 11/04/17 11:37 AM.

Certified Tire Service Instructor since 2009
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Re: Will wider rims change off-set? [Re: avacado11] #4563900
11/04/17 11:37 AM
11/04/17 11:37 AM
Joined: May 2012
Posts: 1,832
The land of USA-made Subies!
SubieRubyRoo Offline
SubieRubyRoo  Offline
Joined: May 2012
Posts: 1,832
The land of USA-made Subies!
What year is your Outback? Outbacks have had a much more robust wheel bearing design than Foresters and Imprezas for a long time now. Unless you are late 90s/early 2000s (I think the design changed around 03-04) you shouldn't have any issues.

Re: Will wider rims change off-set? [Re: SubieRubyRoo] #4563910
11/04/17 11:55 AM
11/04/17 11:55 AM
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
It's a 2017. I've never really messed with anything other than factory wheels for my past 3 Subarus but I've always heard about them going bad. And my 2004 Outback had one go bad, but it was a used and I had no clue what caused it.


2017 Subaru Outback - 0w20 FS - Falken ziex s/tz05
2014 Lexus IS250 - 0w20 FS - Conti Extreme DWS
2014 BMW i3 - Bridgestone Ecopia
Re: Will wider rims change off-set? [Re: avacado11] #4563926
11/04/17 12:25 PM
11/04/17 12:25 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline
Merkava_4  Offline
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Why can't people just keep the stock wheels sizes? I never could understand that. crazy

Re: Will wider rims change off-set? [Re: avacado11] #4563945
11/04/17 12:38 PM
11/04/17 12:38 PM
Joined: Oct 2014
Posts: 12,578
Idaho
CT8 Online content
CT8  Online Content
Joined: Oct 2014
Posts: 12,578
Idaho
Yes, just bigger tires add load on the bearings.


2015 Ford F150 2.7
2018 Ford F350 6.2
Re: Will wider rims change off-set? [Re: avacado11] #4563970
11/04/17 01:08 PM
11/04/17 01:08 PM
Joined: Oct 2010
Posts: 7,097
Michigan
A_Harman Offline
A_Harman  Offline
Joined: Oct 2010
Posts: 7,097
Michigan
If the offset is the same, but the wheel is 1.5" wider, that means the inside rim of the wheel is 1.5" closer to the inside of the car, and that the centerplane of the wheel is .75" further from the wheel mount flange than with the original wheels. This will put more bending moment on the wheel bearing, and will decrease the effective wheel rate of the suspension. To compensate for the 1.5" wider wheel, the offset should be decreased to 36 mm to restore the original dimension between the wheel centerplane and mounting flange.


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Re: Will wider rims change off-set? [Re: avacado11] #4563992
11/04/17 01:25 PM
11/04/17 01:25 PM
Joined: Dec 2008
Posts: 3,116
Occupied Virginia
Bottom_Feeder Offline
Bottom_Feeder  Offline
Joined: Dec 2008
Posts: 3,116
Occupied Virginia
Originally Posted By: A_Harman
If the offset is the same, but the wheel is 1.5" wider, that means the inside rim of the wheel is 1.5" closer to the inside of the car, and that the centerplane of the wheel is .75" further from the wheel mount flange than with the original wheels. This will put more bending moment on the wheel bearing, and will decrease the effective wheel rate of the suspension. To compensate for the 1.5" wider wheel, the offset should be decreased to 36 mm to restore the original dimension between the wheel centerplane and mounting flange.

That's not correct.

Offset is the difference between the center of the wheel and the actual mounting surface. It is not affected by wheel width. His new wheels have identical offset from the stock ones, and since they are 1.5" wider then that difference is going to be split evenly between the inside and outside, .75" each.

The only thing detrimental to his wheel bearings in this case will be added tire/wheel weight and any increased cornering loads a 'better' tire may allow the car to generate. The tire/wheel centers will be the same.

Re: Will wider rims change off-set? [Re: Bottom_Feeder] #4563999
11/04/17 01:36 PM
11/04/17 01:36 PM
Joined: Oct 2010
Posts: 7,097
Michigan
A_Harman Offline
A_Harman  Offline
Joined: Oct 2010
Posts: 7,097
Michigan
Originally Posted By: Bottom_Feeder
Originally Posted By: A_Harman
If the offset is the same, but the wheel is 1.5" wider, that means the inside rim of the wheel is 1.5" closer to the inside of the car, and that the centerplane of the wheel is .75" further from the wheel mount flange than with the original wheels. This will put more bending moment on the wheel bearing, and will decrease the effective wheel rate of the suspension. To compensate for the 1.5" wider wheel, the offset should be decreased to 36 mm to restore the original dimension between the wheel centerplane and mounting flange.

That's not correct.

Offset is the difference between the center of the wheel and the actual mounting surface. It is not affected by wheel width. His new wheels have identical offset from the stock ones, and since they are 1.5" wider then that difference is going to be split evenly between the inside and outside, .75" each.

The only thing detrimental to his wheel bearings in this case will be added tire/wheel weight and any increased cornering loads a 'better' tire may allow the car to generate. The tire/wheel centers will be the same.


Oops, you're right. I forgot the definition of offset while I was typing the note.


1985 Z51 Corvette track car
2002 Camaro Z28 LS1/6-speed
2001 Dodge Ram 2500 diesel
1972 GMC 1500 shortbed project truck
Re: Will wider rims change off-set? [Re: avacado11] #4564535
11/05/17 07:00 AM
11/05/17 07:00 AM
Joined: Feb 2003
Posts: 3,476
Somewhere in the US
CapriRacer Offline
CapriRacer  Offline
Joined: Feb 2003
Posts: 3,476
Somewhere in the US
If I remember correctly, when you go to a wider wheel, they tend to try to keep the distances the same on the inside - so the offset increases (or decreases if you started off positive) by half the amount of the width change.

Note: I may have the sign wrong on the offset. But both Discount Tire and Tire Rack can set you up with proper fitting wheels - and that's what I would recommend doing.


CapriRacer

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Re: Will wider rims change off-set? [Re: Merkava_4] #4564844
11/05/17 12:32 PM
11/05/17 12:32 PM
Joined: Sep 2013
Posts: 10,680
Indiana
dlundblad Offline
dlundblad  Offline
Joined: Sep 2013
Posts: 10,680
Indiana
Originally Posted By: Merkava_4
Why can't people just keep the stock wheels sizes? I never could understand that. crazy


What?

I thought you said the first thing you did to your Buick was upgrade to those spinny bro wheels?


03 Jeep WJ 4.0 202k Castrol Edge 10w40 HM Fram XG16
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Re: Will wider rims change off-set? [Re: Merkava_4] #4564861
11/05/17 12:50 PM
11/05/17 12:50 PM
Joined: Sep 2010
Posts: 7,486
Texas & Global
4WD Online confused
4WD  Online Confused
Joined: Sep 2010
Posts: 7,486
Texas & Global
Well when I ran 265s on my Canyon it was pretty limited then I tried 285s:



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Re: Will wider rims change off-set? [Re: Merkava_4] #4578771
11/19/17 09:39 AM
11/19/17 09:39 AM
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
Originally Posted By: Merkava_4
Why can't people just keep the stock wheels sizes? I never could understand that. crazy


With the width of the rim I couldn't run the factory 225. Even if I ran a stretched tire the rim would still be wider then OE. I could have done a 18x7.5 rim except they were all aftermarket trash lol(didn't like the 18" upgrade wheels). These 18x8.5s came off a STI


2017 Subaru Outback - 0w20 FS - Falken ziex s/tz05
2014 Lexus IS250 - 0w20 FS - Conti Extreme DWS
2014 BMW i3 - Bridgestone Ecopia
Re: Will wider rims change off-set? [Re: CapriRacer] #4578786
11/19/17 09:49 AM
11/19/17 09:49 AM
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
avacado11 Offline OP
avacado11  Offline OP
Joined: Aug 2015
Posts: 128
Central NY/Arkansas
Originally Posted By: CapriRacer
If I remember correctly, when you go to a wider wheel, they tend to try to keep the distances the same on the inside - so the offset increases (or decreases if you started off positive) by half the amount of the width change.

Note: I may have the sign wrong on the offset. But both Discount Tire and Tire Rack can set you up with proper fitting wheels - and that's what I would recommend doing.


I did a quick search on tire rack with a 18X8.5 rim set up on my car and it's showing 45mm-50mm depending on what rim I buy frown

I'm gonna hope Subaru updated the bearing design(bolt patterns 5x114 and not 5x100 like they used to be). Otherwise I'll throw my factory wheels back on and run the wheels as a winter set up.


2017 Subaru Outback - 0w20 FS - Falken ziex s/tz05
2014 Lexus IS250 - 0w20 FS - Conti Extreme DWS
2014 BMW i3 - Bridgestone Ecopia

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