Interchangeable Wheels?

[shawnee]

Hi everyone,

As you may all know, I own a 2016 CX-9 equipped with the factory 20-inch wheels. I’m considering installing the 21-inch wheels from the CX-70 and wanted to confirm compatibility. From what I understand, both vehicles share the same 5x114.3 bolt pattern, but I’m unsure about other potential fitment issues such as offset, hub bore, brake caliper clearance, and overall wheel-well clearance with the larger diameter.

In addition, would the existing lug bolts and wheel locks from my CX-9 work with the 21-inch CX-70 wheels, or would I need different hardware?

Has anyone attempted this swap or looked into whether the CX-70 wheels are a direct fit on the CX-9 without requiring spacers or modifications? Any insight on whether the OEM tire sizes would work without rubbing would also be appreciated.

Thanks in advance,
Shawnee

 

[leeharvey418]

My biggest concern is that the CX-70 has a 9.5” wide wheel with a 45 mm offset. That’s going to give you about 179 mm / 7.05” of wheel backspacing. I’m not familiar with how much kingpin clearance the CX-9 has, but I’d bet that the CX-70 wheels are going to test it.

 

[youri]

According to wheel-size.com

The CX-9 20 inch wheels are 8.5J x ET 45
CX-90 21 inch are 9.5J x ET 45

When you compare the wheels the CX-90 rim will stick out 1/2 inch on both side (towards the outside and the inside). That is probably fine but check the clearance on your CX-9.

I don’t recommend using the CX-90 tires size though, you can search on this forum what size people are using for their 21 wheels.

Also, OEM wheels are typically really expensive, you can probably find some good alternatives for a better price or higher quality for the same price ( unless someone is selling their OEM wheels)

Rim & Tire Size Calculator. Custom Offsets

Tire Tech Information - The Wheel Fitment, Tyre Stretch, Rolling Radius and Speedometer Error Calculator. Play with specs, try different settings, compare results

www.wheel-size.com

 

[leeharvey418]

I rescind my previous statement of reservation. Tire Rack will sell you a 22 x 10" wheel with a 42 mm offset. That's 182 mm / 7.17" backspacing, or another 1/8" more than what you'd have with the CX-70 wheel.

 

[N7turbo]

20x9.5 +45 will just fit on a CX-5 so it should fit on the CX-9, but a lot depends on the tire. If you go with really beefy tires (relative to OEM), don't be surprised if you get rubbing.

 

[shawnee]

20x9.5 +45 will just fit on a CX-5 so it should fit on the CX-9, but a lot depends on the tire. If you go with really beefy tires (relative to OEM), don't be surprised if you get rubbing.

I was planning on getting OEM spec tires (OEM to the CX-70).

 

[youri]

if you do your speedometer will read low, but not by much. I think you will be driving 1 or 2 mph faster than indicated

 

[shawnee]

if you do your speedometer will read low, but not by much. I think you will be driving 1 or 2 mph faster than indicated

Is that because I would be using a wider tire?

 

[N7turbo]

Is that because I would be using a wider tire?

It is based on the tire diameter. You will want to find a tire with an aspect ratio that results in the same diameter.

This site has been very useful to me: Tire Size Comparison

 

[leeharvey418]

It is based on the tire diameter.

This always gets stated, but there’s a far simpler and more accurate measure that will give you speedometer error. Practically every tire on the market will give you a revs per mile rating. If you want to know how much a tire will throw off your speedometer, just divide the revs per mile of your tires by that of the replacement tire. You’ll get the actual number - not the estimate from some theoretical formula.

 

[N7turbo]

This always gets stated, but there’s a far simpler and more accurate measure that will give you speedometer error. Practically every tire on the market will give you a revs per mile rating. If you want to know how much a tire will throw off your speedometer, just divide the revs per mile of your tires by that of the replacement tire. You’ll get the actual number - not the estimate from some theoretical formula.

I haven't seen that advertised on tires before, but if you're referring to that site as using a theoretical formula, it is doing just as you describe using revs per mile.

 

[leeharvey418]

Look at any tire listing on Tire Rack - almost all of them publish revs per mile.

And that site’s numbers are way off. OE tires on a CX-5 have a rating of about 724 - they give a number closer to 700. Same for a CX-90’s tires, where they say about 650, and the real number is about 670. They’re taking the theoretical circumference of a tire that’s “perfect” according to the size, when that’s not actually how it works. The biggest thing is that tires squat, which is most of the difference between their number and reality. Another problem is that tires are very rarely theoretically “perfect” - they’re sized so that 20 mm of width ends up being more like 25 when it gets multiplied by the aspect ratio, just so that plus- and minus-sizing work better. Sometimes you’ll see where the system breaks down, and they have to adjust the numbers to get back to what it should be in theory. Going from a 275/45R21 to a 255/55R20 is way off according to that calculator, but they’re a dead match if you compare actual tire specs.

 

[N7turbo]

Interesting, I will remember that next time I use it.

 

[youri]

Is that because I would be using a wider tire?

Width does not affect it. It is because the combination of the wheels diameter (21 inch) + the tire thickness does not equal the same total diameter as the CX-9 20 inch wheels + the CX-9 tire diameter.

If wheel and tire combine to be a larger diameter, then the wheel will turn more slowly for the same distance driven. (Revolution per miles as states above).

In a car, speed is calculated based on how fast your wheels are turning, so if you install bigger diameter tires which makes your wheels turn slower than the original wheel, then the car measured speed is slower than the speed you are actually travelling at.