Wheel spacer question

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Mazda CX-9 Grand Touring 2016
Not a Mazda question---a buddy just picked up a 2018 Acura MDX and is looking for snow tires & wheels. The stock Mazda wheels have a 55mm positive offset. That's more than most cars. Our CX9s have 45 mm offset. Aftermarket wheels seem to max out at 40 mm, and I've read that one should shoot for no more than a 5 mm difference from stock. So...what can he do? He can't find used Acura wheels that fit. He won't pay dealer price for new Acura wheels. Non-bolted spacers would require longer lug studs (not practical for switching between stock wheels with summer tires and aftermarket wheels with snows), or bolting the spacer on (probably would require trimming the studs, not good for summer wheels). The car has optional 8Jx20 ET55 wheels, and he wants the standard 8Jx18 ET55 wheels for the snows.

Any good suggestions?


Offset is how far the wheel's mounting face is different from the center of the rim. Positive offset has the mounting face outboard of the rim centerline. Our CX9 wheels have the wheel mounting face 45 mm out from the centerline of the rim. Correct offset is necessary for clearance from suspension parts, brake calipers, and fenders and for proper handling.

8Jx18 ET55 = 8" wide rim. J type bead. 18" wheel diameter. ET55 = 55 mm positive offset
 
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2019 CX-9 GT AWD in Soul Red
20x8 +55 and 18x8 +55 wheels will sit at exactly the same position, so he does not need spacers. The only thing that he needs to figure out is the tire size. Have him check it out at willtheyfit.com and see all the measurements.

Also, I don't think he searched good enough. TireRack has winter tires/wheel packages for the 2018 MDX (I filtered AWD) and there are plenty of choices, even includes a 17" option.
 

sm1ke

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:
Canada
:
'18 CX-9 Signature
https://www.speedwaymotors.com/the-toolbox/understanding-wheel-offset-and-backspacing/30059

Quoted from the article:
"When bolted up to your car this means that a lower offset wheel will stick out farther. If your car was originally equipped with a +50mm offset and you replace it with a +25mm wheel, the wheel will stick out approximately one inch farther."

All other specs the same, the aftermarket wheel (assuming 18x8 ET40) would sit 15mm more outboard than the current wheel. Based on this image, it looks like your friend might be able to get away with the 40mm lower offset. The problem would not be with suspension components making contact with the inner wheel and tire, it would be the clearance between the outer tire and the fender liner. Adding a spacer would only push the wheel out more.

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Tirerack.com has some 18x8 ET45 wheels that I'm sure would fit just fine on the MDX.
 
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Mazda CX-9 Grand Touring 2016
I mixed things up. He wants standard running clearances which he cannot find with aftermarket wheels.

I see, less positive offset will set the wheels even more outboard and throw more winter slop on the sides of the car. Ditto for spacers. I guess what he really needs will be a monthly unlimited car wash plan.
 

sm1ke

Work In Progress..
Moderator
Contributor
:
Canada
:
'18 CX-9 Signature
I mixed things up. He wants standard running clearances which he cannot find with aftermarket wheels.

I see, less positive offset will set the wheels even more outboard and throw more winter slop on the sides of the car. Ditto for spacers. I guess what he really needs will be a monthly unlimited car wash plan.

Pretty much. He might get lucky posting want ads and scouring Craigslist, Facebook Marketplace, and local junkyards.