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Discussion Starter · #1 ·
The offset of a wheel is the difference between the wheel's centerline or plane and its mounting plane. Offset is the same as ET (a German abbrev.)

That mounting plane is sometimes defined using backspacing, which can be equated to ET.

Backspacing - (wheel width ÷ 2) = offset

FWD and AWD cars use a positive ET, the ET number is mm, millimeters

The R has a factory ET46 whereas other modern Volvos are 35 or 38.

A smaller ET moves the wheels outboard with the following effects:
- wider track (unless you use a narrow tire)
- altered suspension and steering geometry
- chance for inner fender rub
- increased caliper clearance
If you are using a narrower rim and/or tire, this may be a good thing

A larger ET moves the wheels inboard with the following effects:
- less track (unless you use a wide tire)
- altered suspension and steering geometry
- chance for inner wheel well rub
- less caliper clearance (unless wheel spokes give more)
Not many times to use a larger ET on an R

Adding a wheel spacer to an existing wheel has the same effect as a wheel with a smaller ET.
 

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Re: Wheel Offset Tutorial (JimLill)

Quote, originally posted by JimLill »
A smaller ET moves the wheels outboard with the following effects:
- wider track (unless you use a narrow tire)
- altered suspension and steering geometry
- chance for inner fender rub
- increased caliper clearance
If you are using a narrower rim and/or tire, this may be a good thing
Don't forget:

- increased force on wheel bearings

also the altered steering geometry can modify the turning radius and scrub.

Tom.
 

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Re: Wheel Offset Tutorial (JimLill)

good lord, no wonder we have wheel rub, 8" wide Pegs are ET46...

Since we know that the car looks and handles better with 10mm spacers, I'd think a ET35 wheel would be perfect, and have a better chance of clearing the Brembos.
 

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Re: (traxstarz)

Quote, originally posted by traxstarz »
so r u sayin that you have to run a 10mm spacer on an ET35 wheel? Im still confused. what about fender rub and such?

I would think that if you have to run a spacer for this you are in trouble as it would now be et25, which on an 8" wheel is almost a whole inch further outboard. The 2" increase in track would be cool though.
 

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Re: (vintagemilano)

Quote, originally posted by vintagemilano »


I would think that if you have to run a spacer for this you are in trouble as it would now be et25, which on an 8" wheel is almost a whole inch further outboard. The 2" increase in track would be cool though.

Uno scratches his head becasue he too is confused.


From what has been said here, UNO has interperted that running spacers on a 18 Peg is not a good thing. UNO needs clairification before he gets himself into a bad spot.
 

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Discussion Starter · #9 ·
Re: (UNO_RACING)

From up the page.......

Adding a wheel spacer to an existing wheel has the same effect as a wheel with a smaller ET.

A smaller ET moves the wheels outboard with the following effects:
- wider track (unless you use a narrow tire)
- altered suspension and steering geometry
- chance for inner fender rub
- increased caliper clearance
 

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Re: (JimLill)

Quote, originally posted by JimLill »
From up the page.......

Adding a wheel spacer to an existing wheel has the same effect as a wheel with a smaller ET.

A smaller ET moves the wheels outboard with the following effects:
- wider track (unless you use a narrow tire)
- altered suspension and steering geometry
- chance for inner fender rub
- increased caliper clearance

Jim, I just put on the Heico spcaer(10mm front, 15mm rear).
Should I go to do the 4 wheel alignment?
 

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Discussion Starter · #11 ·
Re: (liu0588)

Quote, originally posted by liu0588 »
Jim, I just put on the Heico spcaer(10mm front, 15mm rear).
Should I go to do the 4 wheel alignment?

I can't see how the spacer offset would change the geometric angles, so no.

Edit: the angles that an alignment would control. There are still changes in some other angles.
 

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Re: (vintagemilano)

Quote, originally posted by vintagemilano »


I would think that if you have to run a spacer for this you are in trouble as it would now be et25, which on an 8" wheel is almost a whole inch further outboard. The 2" increase in track would be cool though.

Uh, no. A 10mm spacer would move the whell 10mm further out. Using a spacer on both sides would increase track by 20mm or ~3/4".

/edit/ My bad, that 10mm spacer would be in addition to the 10mm 'gained' by going from an ET45 wheel to an ET35 wheel. So, 40mm total increase in track, or ~1.5".
 

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Re: (Mk1Racer)

I tried searching for the offset in the other forums but I haven't found the results I'm looking for.

I still have a set of the 17x7.5 "Thor" wheels from my last 60. (The winter tires/rims were on it when it was totaled).

Where can I look up the offset on those rims? I'd like to use them on an SR
 

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Re: (bohem3006)

Quote, originally posted by bohem3006 »
I tried searching for the offset in the other forums but I haven't found the results I'm looking for.

I still have a set of the 17x7.5 "Thor" wheels from my last 60. (The winter tires/rims were on it when it was totaled).

Where can I look up the offset on those rims? I'd like to use them on an SR

Josh, the offset should be stamped inside one of the spokes.
 

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Re: (bohem3006)

What I can't figure out is why Volvo released a set up that scrubs with the inner wall? What gives? Why weren't the wheels spaced out correctly to give you no scrub at full turn?
 

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Re: Wheel Offset Tutorial (JimLill)

I'm in the process of looking for 17" wheels for next winter (I went through my 18" tire tread like nothing here in CO with all the snow this yr).
I would like to get a rim with around an ET35 so I can avoid spacers and get close to, if not eliminate wheel rub at full lock.
I would like to see some wheels that fit the R that have an ET35 or close to it. All of the wheel forums on this site mention very little about rims with this offset.
What are my options?

I wish the 19" Peg replicas had an ET35.
 

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Discussion Starter · #18 ·
Re: Wheel Offset Tutorial (art_werks)

If you are serious about the snow, Get 7 or 7.5" rims and a tad narrower tire. Snows tend to be wide at the should which compounds the rub issue.

I run 17X7.5 rims in ET38 and 215/50-17 snows. No rub


 

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Re: Wheel Offset Tutorial (JimLill)

Quote, originally posted by JimLill »
The offset of a wheel is the difference between the wheel's centerline or plane and its mounting plane. Offset is the same as ET (a German abbrev.)

That mounting plane is sometimes defined using backspacing, which can be equated to ET.

Backspacing - (wheel width ÷ 2) = offset

FWD and AWD cars use a positive ET, the ET number is mm, millimeters

The R has a factory ET46 whereas other modern Volvos are 35 or 38.

A smaller ET moves the wheels outboard with the following effects:
- wider track (unless you use a narrow tire)
- altered suspension and steering geometry
- chance for inner fender rub
- increased caliper clearance
If you are using a narrower rim and/or tire, this may be a good thing

A larger ET moves the wheels inboard with the following effects:
- less track (unless you use a wide tire)
- altered suspension and steering geometry
- chance for inner wheel well rub
- less caliper clearance (unless wheel spokes give more)
Not many times to use a larger ET on an R

Adding a wheel spacer to an existing wheel has the same effect as a wheel with a smaller ET.


Regarding this tutorial... just to be clear....

we currently have a 46 offset...

so if i buy a 40 offset wheel.. what does that mean?

Do i have enough clearance because the number is smaller.. or do i need a spacer?
 

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Re: Wheel Offset Tutorial (Jersey R)

Quote, originally posted by Jersey R »


Regarding this tutorial... just to be clear....

we currently have a 46 offset...

so if i buy a 40 offset wheel.. what does that mean?

Do i have enough clearance because the number is smaller.. or do i need a spacer?
The center of the wheel will now be 6mm farther outboard.

It may work fine depending on wheel width and tire size, but a spacer would only make it "stick out" farther.
 
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