How important is wheel offset, really?

saCusa

Active member
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May 20, 2020
Location
USA
TDI
mk.IV Golf BEW M5
Hi.

TLDR:
Does the center point of my aftermarket wheel have to be in the same position as the center point of the stock wheel?

Long:
I purchased a set of 16"x7" (.5" wider than stock) +40mm offset wheels that are lightweight. The inside of the wheel is going to be .4" closer to the suspension assembly, and the outside of the wheel will remain in the same position as my stock steel wheels (assuming +35mm offset). This is according to the online wheel offset calculator on the tiresize website. If I put a 5mm spacer in with my new wheels (essentially making them +35mm offset instead of +40mm offset), this would cause the inside of the wheel to be .2" closer to the suspension, and the outside of the wheel to be .2" farther out (closer to the fender). That essentially places the center of the wheel on the same plane as the original steel wheels, right? Is that what I want with aftermarket wheels, in order to keep the steering geometry the same?

I have read everywhere that offset is very important for the handling of a vehicle, and having incorrect offset can adversely affect the handling, but none of these places mention what is important about it and why.. Is it simply getting it to clear other objects in the fender well that is important? Is it keeping the center of any wheel in the same plane as stock? What exactly is so important about offset?
 
Last edited:

saCusa

Active member
Joined
May 20, 2020
Location
USA
TDI
mk.IV Golf BEW M5
Could really use some guidance here... Can't mount the wheels until I understand the importance of wheel offset and what can go wrong if it's not perfect. What is perfect, anyways?
 

Windex

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Apr 1, 2006
Location
Cambridge
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05 B5V 01E FRF
Offset is important - you want the centerline of the wheel to line up with the centerline of the wheel bearing/hub assembly. To far to one side or the other and the bearing will be loaded (bearing weight) unevenly.

That said, small differences in offset (from centerline) are not that big a deal. Heck, I've had 15mm and 20mm spacers on my passat for 6 years now, and no issues at all with the wheel bearings. If as your post implies, the differnce to offset is in the 1/4" range, I would install and not worry about it.
 

Mongler98

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Mar 23, 2011
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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
No. Not even close. Offset needs to be what it is for clearance. Want more or less poke depending on clearance add or subtract.
 

saCusa

Active member
Joined
May 20, 2020
Location
USA
TDI
mk.IV Golf BEW M5
Offset is important - you want the centerline of the wheel to line up with the centerline of the wheel bearing/hub assembly. To far to one side or the other and the bearing will be loaded (bearing weight) unevenly.

That said, small differences in offset (from centerline) are not that big a deal. Heck, I've had 15mm and 20mm spacers on my passat for 6 years now, and no issues at all with the wheel bearings. If as your post implies, the differnce to offset is in the 1/4" range, I would install and not worry about it.
I believe that if I used a 5mm spacer on +40 offset wheels, this essentially makes the offset +35 which will put the centerline of the wheel in the same plane as the centerline of the stock steel wheel (if the steel wheel is truly +35mm offset). Am I understanding this part correctly? I wouldn't think that a 5mm space would hurt the bearings too much.

Quote fromMongler98:
No. Not even close. Offset needs to be what it is for clearance. Want more or less poke depending on clearance add or subtract.

So the offset has no bearing whatsoever on the steering geometry? I went from 15" Steels to 17" Ariettas and the MPG drop was god awful. I'm sure it was a combination of weight + tire width, but perhaps the offset was causing issues as well, since it was +38? That part I'm not sure of, which is why I'm obsessing over this topic right now because I do not want to go back to that horrible fuel economy (39 at best, versus 52 at best with stock wheels).
 

Andyinchville1

Veteran Member
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Apr 7, 2016
Location
Virginia
TDI
2003 Jetta TDI wagon, 5 sp, 226K miles
HI,

Just Curious but how much weight was added with the 17s vs the factory steelies?

What tires were you running on the steelies / what tires are you running now?

Andrew
 

Instigatr

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Sep 4, 2016
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NE WA State
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03 Golf 2 door MTM
My golf has some sort of factory vw 17" wheels on it for the summer. Factory steelies for winter. I can say with no doubt the 17" alloys are heavier, by I'd guess 15-20%
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
My Jetta came from the factory with 15x6" Avus wheels, offset 38mm.

For the last 10 years I have run 17x7.5" 32mm offset Audi TT wheels in summer and 15x6" 43mm offset Speedline2 wheels in winter.

I prefer the narrower track of the Speedlines in winter conditions and the wider stance of the TTs looks sweet in summer. I have not had any wheel bearing or handling issues. Fuel economy doesn't vary, I guess the narrower tires compensate for winter blend fuel.
 

gforce1108

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Aug 2, 2006
Location
Newburgh, NY
TDI
04 Jetta GLS BEW, 14 Audi A7 V6 TDI
You aren't making a large enough change to make a difference. I run 17x8" on my 04 and they are still "tame" compared to many on vwvortex. As long as it's a positive offset, it'll be close enough.

FYI - the centerline of the wheel isn't lined up with the hub or it would have had a ET0 (no offset). Most front wheel drive cars have a relatively large offset due to the suspension design.
 

Andyinchville1

Veteran Member
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Apr 7, 2016
Location
Virginia
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2003 Jetta TDI wagon, 5 sp, 226K miles
HI,

If my brain was not as tired as it is now after work I would try to digest this for you BUT offset and tire height etc affects scrub radius which can affect things in the front end...

Maybe somebody can summarize this until my brain gets some rest ...HA

see link :


Andrew
 

saCusa

Active member
Joined
May 20, 2020
Location
USA
TDI
mk.IV Golf BEW M5
HI,

Just Curious but how much weight was added with the 17s vs the factory steelies?

What tires were you running on the steelies / what tires are you running now?

Andrew
I'm not entirely sure about this, but it's significant enough to where I can feel myself struggling to mount them as opposed to the lighter wheels. When I get my steelies off, I will weigh both and let you know.



You aren't making a large enough change to make a difference. I run 17x8" on my 04 and they are still "tame" compared to many on vwvortex. As long as it's a positive offset, it'll be close enough.

FYI - the centerline of the wheel isn't lined up with the hub or it would have had a ET0 (no offset). Most front wheel drive cars have a relatively large offset due to the suspension design.
Yes I agree, the centerline of the wheel isn't lined up with the face of the hub or my wheel would stick out well beyond the fenders, and that would look a bit silly. All I am looking to do is:

1. Confirm that the steel wheels that come with these cars are in fact ET35 (is it 38? I don't know!)

2. Keep the center line of my new wheels in the same plane as the center line of my old wheels as to not upset the steering geometry too much.

The 5mm spacer will do just that (provided that the stock is actually 35 offset, please somebody confirm this), and they'll look a bit better in the process. I tend to overthink things, even moreso when I'm having a hard time understanding conflicting data throughout the web.


HI,

If my brain was not as tired as it is now after work I would try to digest this for you BUT offset and tire height etc affects scrub radius which can affect things in the front end...

Maybe somebody can summarize this until my brain gets some rest ...HA

see link :


Andrew
I took a read, and I understand what they're saying. So.. I decided to go with 205/60/R16 tires, which will increase the height of my tires from stock slightly. Being that the wheels are ET40, they're already pushing inwards a bit, in combination with a taller tire, this will create quite a bit more scrub and road feedback from the stock setup. I want to keep the feel of the stock setup roughly the same. I like smooth. So to counteract this increase in scrub (assuming the scrub was very small to begin with from the factory), then I should most definitely add a spacer in there to compensate, if not an even bigger spacer than 5mm. I will stick to 5mm, though.
 

gforce1108

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Aug 2, 2006
Location
Newburgh, NY
TDI
04 Jetta GLS BEW, 14 Audi A7 V6 TDI
1. Confirm that the steel wheels that come with these cars are in fact ET35 (is it 38? I don't know!)
Only 1 of my 5 mkiv cars had steel wheels and I didn't keep them on it long enough to record the size. I see two 15" sizes listed - 6Jx15 ET38 and 6.5Jx15 ET35. There is a bigger variance in the OE wheel specs than what you are looking to do.
 
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