[MakkaRound]

Hi everyone- apologies if this is a duplicate question as I’m new on the site

I have a 2018-g31 530d xdrive and it was factory set up with 20 inch staggered wheel set up. 275/30/20 on rear and 245/35/20 front. + run flats
Looks great but it’s super harsh ride

I’m looking for a more comfy set up and so willing to change the wheels and tyres. Can I do this without messing with the differentials? (It’s m sport non adaptive suspension)

Can I also go square set up?

Image shows the options that online car company thinks I can do with tyres and I’m seen various wheels for sale set up to accommodate. I’m happy to go non run flat as well

If I go square 19 or 18 am I going to kill my car? Any advice warmly welcome😎

[SonD]

Depends on your brake calliper spec if you can go 18”, you certainly can do 19” with M spec callipers.
Square is an option, as is non run flat - I have done just this.
Utterly transforms the ride quality IMO.

[MakkaRound]

Thanks SonD!! Yes they are m spec callipers on my car. Think I’ve possibly found a solution and will see how it rolls. Pics attached are 8jx18 widdtg offset et30 wheels from 2021 g31 (not my car but very similar and the car pic seems to also show m spec callipers )- tyres will be 245/45/18 with tmps sensors still fitted. and my car computer is happy to make adjustment.

Will keep my old rims/tyres for a while to see it goes in case she doesn’t like it but I’m hoping for a lovely and comfy ride!

Appreciate the response ☺️

[G30M]

go square 245 40 19 or 245 45 18

[MakkaRound]

Thanks G21. I think the guy has square 19s like you say so will check them both out tomorrow! I think changing to non rfts will also be the game changer!

[G30M]

Originally Posted by MakkaRound

Hi everyone- apologies if this is a duplicate question as I’m new on the site

I have a 2018-g31 530d xdrive and it was factory set up with 20 inch staggered wheel set up. 275/30/20 on rear and 245/35/20 front. + run flats
Looks great but it’s super harsh ride

do you have adaptive suspension?

[MakkaRound]

Non adaptive M suspension. That’s why I think- or hope!- it should be ok

[G30M]

18" would be best if the wheels can clear your calipers

[MakkaRound]

Thanks and that’s the plan. Probably daft question but can I check this caliper measurement without putting the wheels on? The plan was to buy tonorrow (assuming theyre scuff/mark/crack free) and then get them properly put by my own garage peeps next week

[G30M]

if someone can tell me your rotor (not caliper) diameter i can tell you if it will clear the 18"

[MakkaRound]

Ok thanks- will look into it. Alternatively, Can I do this via a vin decoder? Bimmer work and/or mdecoder pull up stats on my car but can’t see anything precise regarding rotor size. Sorry for the follow up questions but as you can tell I’m slowly learning my way around it all😝 it is a darn nice car though

[MakkaRound]

Final point to add. The 18 inch square wheels I am looking at are (supposedly) bmw OeMs from another g31. I suppose the question is without physical measuring (which I think I’m gonna have to do now) is are the discs/rotors the same for every build of that specific model regardless to whether the 1st customer of car requests 18 or 19 or 20 inch wheels in their build? It’s a bloody minefield🤨

[G30M]

just take a ruler and measure.

[G30M]

Originally Posted by MakkaRound

Final point to add. The 18 inch square wheels I am looking at are (supposedly) bmw OeMs from another g31. I suppose the question is without physical measuring (which I think I’m gonna have to do now) is are the discs/rotors the same for every build of that specific model regardless to whether the 1st customer of car requests 18 or 19 or 20 inch wheels in their build? It’s a bloody minefield🤨

brakes depends on the country and the packages not wheel size option.

[MakkaRound]

Gonna measure 100% thanks!!

[KyivanRus]

Originally Posted by g21

go square 245 40 19 or 245 45 18

If the car came with 20 inch wheels, 35 profile front, 30 profile rear, won’t going with 245 45 18 square not affect speedometer reading? Shouldn’t front be 245 45 18, but rear’s 245 40 18? Thanks

[G30M]

Originally Posted by KyivanRus

If the car came with 20 inch wheels, 35 profile front, 30 profile rear, won’t going with 245 45 18 square not affect speedometer reading? Shouldn’t front be 245 45 18, but rear’s 245 40 18? Thanks

no your math is not correct

[HighlandPete]

Originally Posted by KyivanRus

If the car came with 20 inch wheels, 35 profile front, 30 profile rear, won’t going with 245 45 18 square not affect speedometer reading? Shouldn’t front be 245 45 18, but rear’s 245 40 18? Thanks

I guess you are thinking staggered, where the rear will be a 275 section to drop the profile to a 40.

[KyivanRus]

Originally Posted by HighlandPete

I guess you are thinking staggered, where the rear will be a 275 section to drop the profile to a 40.

The car in question is 550i with staggered 20 inch wheels. 35 profile front, 30 rear. Moving down to 18 inch wheels should increase tire profile by 10: front 45, rear 40. If I’d go square, with 45 profile tires all around, the rear’s wheel+tire overall diameter will be larger than original, and thus affect speedometer reading, no? Where am I wrong?

Thanks

[HighlandPete]

Originally Posted by KyivanRus

The car in question is 550i with staggered 20 inch wheels. 35 profile front, 30 rear. Moving down to 18 inch wheels should increase tire profile by 10: front 45, rear 40. If I’d go square, with 45 profile tires all around, the rear’s wheel+tire overall diameter will be larger than original, and thus affect speedometer reading, no? Where am I wrong?

Thanks

The diameter and RC stay the same, by having the 45 profile on the 18" rim. Doesn't change the speedo at all.

The 18" setup would be:

Staggered: 245/45 R18 Front, 275/40 R18 Rear. Both tires RC of 2065 mm.
Square: 245/45 R18 Front & Rear.

Keep in mind the staggered setup drops a profile on the rear, to compensate for the wider section, which at the same profile would be a larger diameter.

[KyivanRus]

Originally Posted by HighlandPete

The diameter and RC stay the same, by having the 45 profile on the 18" rim. Doesn't change the speedo at all.

The 18" setup would be:

Staggered: 245/45 R18 Front, 275/40 R18 Rear. Both tires RC of 2065 mm.
Square: 245/45 R18 Front & Rear.

Keep in mind the staggered setup drops a profile on the rear, to compensate for the wider section, which at the same profile would be a larger diameter.

Now it makes sense! I looked up through a tire size calculator, the difference is indeed minuscule. Thanks!

[roggggggg]

Hi, how did you get on with this in the end? I've got the same issues of a super hard ride on my 540i. I've found a set of 19's locally that I would wrap in non run flats, but not sure how much it'll improve the ride/change the image of the car.

The combo of 20" + low profile run flats is a killer on UK roads, i've had 5 tyres replaced in the two years of owning the car and it's between £250-£300 a tyre!