[turbobeagle]

I know there have been a few threads on this already but this may be a bit different and could use some help.

My G30 5 series lease ends tomorrow and I’ll have a set of Style 634 18 inch wheels spare. I’d like to know whether I can mount these onto the M40i. I know that OE BMW wheels are not officially certified for the M40i but Tirerack will happily sell you aftermarket 18 inch wheels that they guarantee to fit. And Bimmerpost members have confirmed fitment.

So I test fit the 634 wheels on the front. It seems like there’s quite a lot of clearance, but I’m not a wheel expert. Some pictures attached. I would replace the tires with 245/55/18 to hit expected diameter. The wheels are 8 inches wide, 30 offset, 5x112 bolt pattern, and 66.6 bore.

My question is whether I can run these? If not, I’ll have to buy a set of 18s/19s elsewhere. It would save me some money if I just used these. Thanks!

[COM40]

That clearance looks fine, I'd have no problem running those.

[turbobeagle]

Originally Posted by COM40

That clearance looks fine, I'd have no problem running those.

Thanks! I guess I’ll check the rears too just to be safe.

I do wonder why BMW doesn’t certify any 18 inch wheels for this though. I guess the offset and width is not quite right in this case, since it’s meant for a 5 series. But tirerack is willing to put a figment guarantee around those exact same specs.

[COM40]

Originally Posted by turbobeagle

Thanks! I guess I’ll check the rears too just to be safe.

I do wonder why BMW doesn’t certify any 18 inch wheels for this though. I guess the offset and width is not quite right in this case, since it’s meant for a 5 series. But tirerack is willing to put a figment guarantee around those exact same specs.

I think the older 30i had 18s as the base wheel. So I guess it's not load related, although I suppose that may vary by wheel (but while the X3 is heavier than a 5 series, it's still in the same ballpark).

Maybe BMW thinks the sidewall flex of a 55 tire is not appropriate for an "M Lite" car handling wise. Or they want to bake in price increases by having a larger wheel as standard.

[turbobeagle]

Originally Posted by COM40

I think the older 30i had 18s as the base wheel. So I guess it's not load related, although I suppose that may vary by wheel (but while the X3 is heavier than a 5 series, it's still in the same ballpark).

Maybe BMW thinks the sidewall flex of a 55 tire is not appropriate for an "M Lite" car handling wise. Or they want to bake in price increases by having a larger wheel as standard.

Regarding weight, the wheels actually first came off of a 2018 530e which is 4266 lbs, which is just spitting distance from the M40i at 4392 lbs.

Or if we go by gross axle weight, it’s 5470 lbs vs 5556 lbs GVWR. So hopefully I’m ok there?

[COM40]

Originally Posted by turbobeagle

Regarding weight, the wheels actually first came off of a 2018 530e which is 4266 lbs, which is just spitting distance from the M40i at 4392 lbs.

Or if we go by gross axle weight, it’s 5470 lbs vs 5556 lbs GVWR. So hopefully I’m ok there?

For sure. Idk what safety factor they engineer the wheels with but it's a lot more than ~2%. And with thicker sidewalls there should actually be less impact force going through the wheels.

[ZQUANT]

Don’t worry about it. I have the style 618 18inch wheels. They are ugly but works.

[turbobeagle]

Originally Posted by ZQUANT

Don’t worry about it. I have the style 618 18inch wheels. They are ugly but works.

Nice. Just curious - what tire size are you running there? I was thinking of doing 245/55/18 to match stock diameter.

[ZQUANT]

Originally Posted by turbobeagle

Nice. Just curious - what tire size are you running there? I was thinking of doing 245/55/18 to match stock diameter.

The wheels are 18x7 and tires are 225/60/18 came from the factory. It’s the size for the base model 2020 x3 30i.

My wheels are too narrow for 245 tires. Check your wheel width.

[turbobeagle]

Originally Posted by ZQUANT

The wheels are 18x7 and tires are 225/60/18 came from the factory. It’s the size for the base model 2020 x3 30i.

My wheels are too narrow for 245 tires. Check your wheel width.

Thanks. My wheel is 18x8.

[sikedsyko]

I've been running 18" Enkei wheels on my M40i for 2 years now and about 40k miles, with no real issues. I'd say my caliper clearance looks similar to yours. There's definitely been a few rocks get caught between the barrel and the caliper, I've never noticed it while driving, but I've got a few scars inside the front wheel barrels, only superficial damage though.

[turbobeagle]

Originally Posted by sikedsyko

I've been running 18" Enkei wheels on my M40i for 2 years now and about 40k miles, with no real issues. I'd say my caliper clearance looks similar to yours. There's definitely been a few rocks get caught between the barrel and the caliper, I've never noticed it while driving, but I've got a few scars inside the front wheel barrels, only superficial damage though.

Appreciate the confirmation. I found your pick with the Enkei wheels. Looks nice.

[turbobeagle]

A follow-up question on tires:

I'm thinking of going with a 245/45/18 Conti DWS 06+ which seems like it matches stock diameter, and is a reasonable match for the 8 inch wide wheels.

But these tires are rated as 103W SL. Is that ok for the M40i?

Other size options would allow me to get back to XL, but some compromises:

• 225/60/18 - The Conti DWS isn't available (and in general tire choice seems to be worse), and maybe too narrow for 8 inch wheels.
• 235/60/18 - Increases diameter by 1.7%.
• 255/55/18 - Increases diameter by 1.4%, maybe too wide for 8 inch wheels.

I see in this chart here from wheel-size.com that the 20-inch winter tire spec is 103V. Does that mean I'd be ok with 103W? I didn't know if it could be applied to alternate wheel sizes like that.

[sikedsyko]

I ran 245/55/18 on an 8" wheel at first at the recommendation from Tire Rack. Ended up going with a 255/55/18 the second time.

The V and W are speed ratings (149 and 168mph respectively). The 103 is the load rating, 1923lbs.

[turbobeagle]

Originally Posted by sikedsyko

I ran 245/55/18 on an 8" wheel at first at the recommendation from Tire Rack. Ended up going with a 255/55/18 the second time.

The V and W are speed ratings (149 and 168mph respectively). The 103 is the load rating, 1923lbs.

1. Do you happen to remember what tire you ran for 245/55/18 ?

2. Any reason in particular you bumped up to 255/55/18, and I assume no issues so far with that?

[sikedsyko]

Originally Posted by turbobeagle

1. Do you happen to remember what tire you ran for 245/55/18 ?

2. Any reason in particular you bumped up to 255/55/18, and I assume no issues so far with that?

Both sizes were Conti DWS06+. The 245 didn't come in an XL load rating, but the 255 does. Not that you theoretically need the XL load rating, but all the factory tires are XL. Given that I tow a decent amount with the X3 I figured it would be good to have some slightly more robust tires, plus the 255 give a better looking stance IMO.

[turbobeagle]

My thanks again for help confirming this. I finally had a chance to get the tires on (Conti DWS 06+ 255/55/18) and mounted the wheels myself today. Nothing has exploded so far and I haven’t heard/felt anything funny, even at full steering angle. And I think it doesn’t look half bad. I think it’ll look even better once the brake dust paints it to a nice gunmetal grey.

[internalaudit]

Anyone know if the 18" 618 wheel will fit with the M Sport Brake add-on?

Thinking of buying a used winter tire set.

[harryo2b]

Originally Posted by internalaudit

Anyone know if the 18" 618 wheel will fit with the M Sport Brake add-on?

Thinking of buying a used winter tire set.

I'm curious as well since I already have a set but moved up to an M40i since.