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Discussion Starter #1
i search tirerack it says
http://www.tirerack.com/wheels/WheelCloseUpServlet?target=runWheelSearch&initialPartNumber=W0171220253B&wheelMake=O.Z.&wheelModel=Ultraleggera&wheelFinish=Black+Painted&showRear=no&autoMake=Mercedes-Benz&autoModel=SLK350&autoYear=2007&autoModClar=&filterFinish=All&filterSize=All&filterBrand=All&filterSpecial=false&filterNew=All&filterWeight=All&sort=Weight

and i know fishtailnz have it on his ex-SLK

so its 18x8 et35 on all 4 but if i want to change the rear from
18x8 to 18x9
, should the offset stay the same or less/more?
Online wheeloffset calculated it will have

Inner Clearance: 13mm LESS
Outer Position: EXTEND an extra 13mm




this is the sideview
 

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anyone?:hail:

or maybe go 18x8.5 on the back to be safe...
It has been a while since I worked this out so I hope I'm remembering it all correctly.

Normally the offset should stay the same. Having the same offset means that any additional wheel/tire width is equally spaced about the load bearing center of the suspension assembly per the original design. This is more important on the front (steering) axel of the car since the offset influences such things as the centering and the over all steering feel.

Given infinite space and clearance in the wheel well, I would always try to keep the offset the same as the OEM design.

That being said, it is normally accepted that +/- 5mm from the OEM design will have little to no effect on the car. (I can not verify this though.) I do know that some manufacturers use slightly off dimensions (I believe my Ford Probe's was 37mm) and the aftermarket wheel makers prefer more even numbers. (Like 40mm, or 35mm.) So you would normally pick the closest one; unless you already know that you have some space issues.

Now, the reason most people change the offset is so that they can fit wider/bigger tires under the car. Generally speaking it is easier to trim the fenders then to move suspension components and mounting points. Certainly within reason this can work, particularly on straight axels, but it can severely increase the wear in the various components (bearing, bushings, etc.) if carried to an extreme. (The more you change it, the more risk there is . . .)

That's just sort of the general information on the topic. (For more detail you might want to find a suspension book like "How to Make Your Car Handle" from HPBooks. Or whatever is current/available . . . my copy is very old . . .)
 

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It has been a while since I worked this out so I hope I'm remembering it all correctly.

Normally the offset should stay the same. Having the same offset means that any additional wheel/tire width is equally spaced about the load bearing center of the suspension assembly per the original design. This is more important on the front (steering) axel of the car since the offset influences such things as the centering and the over all steering feel.

Given infinite space and clearance in the wheel well, I would always try to keep the offset the same as the OEM design.

That being said, it is normally accepted that +/- 5mm from the OEM design will have little to no effect on the car. (I can not verify this though.) I do know that some manufacturers use slightly off dimensions (I believe my Ford Probe's was 37mm) and the aftermarket wheel makers prefer more even numbers. (Like 40mm, or 35mm.) So you would normally pick the closest one; unless you already know that you have some space issues.

Now, the reason most people change the offset is so that they can fit wider/bigger tires under the car. Generally speaking it is easier to trim the fenders then to move suspension components and mounting points. Certainly within reason this can work, particularly on straight axels, but it can severely increase the wear in the various components (bearing, bushings, etc.) if carried to an extreme. (The more you change it, the more risk there is . . .)

That's just sort of the general information on the topic. (For more detail you might want to find a suspension book like "How to Make Your Car Handle" from HPBooks. Or whatever is current/available . . . my copy is very old . . .)

That is really great piece of information first of all. Thanks mate.

Not to hijack the thread but I have the same question.

For ultrareggera's Tirerack says: (Here is the link:)

Size: 18x8
Offset: 35mm
Backspacing: 5.91"
Bolt Pattern: 5-112
Rec. Tire Size: 225/40-18


would be suitable for the car. The question is okey I will buy this with 225/40-18 tires for front.

But what about rear?
Isn t tire size supposed to be somethin like 245/35 or 255/35? I have 255/35 tire at the moment with replica wheels. What model will I use in rear if I purchase OZ?

Here are options

18" Superleggera


7.00 x 18 4x100 ET42
7.00 x 18 4x108 ET42
8.00 x 18 5x100 ET35
8.00 x 18 5x100 ET48
8.00 x 18 5x112 ET35
8.00 x 18 5x112 ET50
9.00 x 18 5x114.3 ET35
8.00 x 18 5x114.3 ET35
8.00 x 18 5x114.3 ET45
9.00 x 18 5x114.3 ET55
9.00 x 18 5x120 ET40
8.00 x 18 5x120 ET40


It was a colorful post I know but I put a lot of work into it. :biglaugh:

Hope the forum gurus will answer my question so I can buy a nice set of OZ. Will share the pictures afterwards on my black car.


One last thing:
Isnt it BEAUTY? :Beer:
 

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. . . For ultrareggera's Tirerack says: (Here is the link :) . . .
I'd put a lot of faith in Tire Rack's info, but they really only address "stock" configurations. If I can redirect the nature of your question a bit . . . You got the rims (which have an offset, and also MUST clear your suspension components) and then you have the tire which is what really drives the need for bigger rims. (And which also do most of the bumping and rubbing in the wheel well if too big or not fitted well.)

What TR can not address is whatever else you do to your car! (Such as with lowering, brakes, etc.) I would mostly likely bet that any 225/245s tires of 24.5-25" max dia will normally fit (under an SLK) while using a recommended rim width and stock offset. Rim widths should all fall within the tire's recommended range, but there is some room to work here. (i.e. to keep all the rims the same (front to back) is helpful, but not a necessity.) If you want to go with greatly wider tires (which need wider rims) that is where the potential problems start to crop up; mostly in wheel well rubbing while going over bumps or turning.

If you go too much wider than OEM and keep the original offset, the tire/wheel might rub on the suspension components on anything less than a smooth road going in a straight line. This will be made worse if the car has been lowered. To solve this problem, most people will change the offset to move the wheel/tire more outboard, (to stop the "inside" rubbing) and then work on the fenders (bulging, flares, cutting, etc.) a bit to keep down the outside rubbing . . .

Hope that helps a bit . . .

Since I can't afford BBS RGRs, I'd settle for ASA GT5s. :Beer:
 

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One last thought . . . .

If you go with a rim that is in the slightly narrower range for the tire, your tires will tend to protect the edges of the rims more from rubbing against the curbs.

The trade off is that the ride won't be quite as precise. Normally the wider the rim is in the range, the more vertical and stiffer the tires' sidwalls will be.

From the rear though, the tires will look equally as wide, and from the side, well, no one can tell how wide the rims are anyway . . . (Well most of us can't. lol)

If its standing still, it's all about the looks. If its moving at everyday speeds, no one can tell. If you are racing, who cares what they look like as long as they help you go faster!! :biglaugh:
 

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Discussion Starter #9
Thanks for the feedback!

need to bring this up,

the slk is wearing the ultraleggera now (i will post the pic later)

but because im on carlsson bodykit which the side skirt is quite wide,
it make the rear wheel look really sunken in compare to an amg kit(pic above)

since the OZ wheel need centering ring to fix on the oem hub
so im asking if a 10mm H&R hubcentric spacer which(if im not wrong) hub is the same size to the oem hub will the centering ring be fix on the H&R?

Base on my calculation and a pic i think it will work!
but i need opinions from u gurus.



btw the center ring is very snugly fix on the hub, the last time i took the wheel off i need a - sign screwdriver and a hammer to knock it out:tazz:
im asking since the oz center ring is spec to fix on the slk hub, and the h&r spacer hub is design to be the same size as the oem hub, will the center ring be able to fix on the h&r?
i need a confirmation from u guys before i order the h&r. ;)
 

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Discussion Starter #10
7.00 x 18 4x100 ET42
7.00 x 18 4x108 ET42
8.00 x 18 5x100 ET35
8.00 x 18 5x100 ET48
8.00 x 18 5x112 ET35
8.00 x 18 5x112 ET50
9.00 x 18 5x114.3 ET35
8.00 x 18 5x114.3 ET35
8.00 x 18 5x114.3 ET45
9.00 x 18 5x114.3 ET55
9.00 x 18 5x120 ET40
8.00 x 18 5x120 ET40
we can only fix on pcd which is 5x112, so we can only get the 8"
 
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