[Resjudicata]

In the M850i the 20" p zero are stock tires.
245/35R20 and 275/30R20. I know people put 21" and lowering springs, so I'm guessing stock - you can probably gain an fraction sidewalls?

Does anyone know if 245/40-20 and 275/35-20 will run without problems?

[FBMWWINS]

As far as the variance goes (40 vs 35 on FRONT and 35 vs. 30 on REAR), below are the results.

FRONT

Will fill out the wheelwell by extra 12 mm. Acceptable for most cars

Negative scrub radius (about -4 mm). Almost no difference. Please be aware that calculated value is approximate.

When speedometer reads 60 km/h actual speed will be 62.2 km/h

REAR

Will fill out the wheelwell by extra 14 mm. Make sure that you have enough room under the fender. If not, consider lower profiles or smaller rims

Negative scrub radius (about -5 mm). Scrub radius will be changed by -5 mm, this may affect the car's handling. Please check manufacturer recommendations. Please be aware that calculated value is approximate.

When speedometer reads 60 km/h actual speed will be 62.5 km/h


I usually turn to this site it's very precise and you get the decisive values and parameters in regard to variance between stock and the desired setup:

https://www.wheel-size.com/calc/

Also consider there will be added weight as well.


Technically you can drive it and should not have any issues as scrub radious is minimum and many cars (setup) come with a slight negative scrub radius already. Though, I'd ask a professional tire/car shop just to be 100% on the safe side before installing.

[Resjudicata]

Originally Posted by FBMWWINS

As far as the variance goes (40 vs 35 on FRONT and 35 vs. 30 on REAR), below are the results.

FRONT

Will fill out the wheelwell by extra 12 mm. Acceptable for most cars

Negative scrub radius (about -4 mm). Almost no difference. Please be aware that calculated value is approximate.

When speedometer reads 60 km/h actual speed will be 62.2 km/h

REAR

Will fill out the wheelwell by extra 14 mm. Make sure that you have enough room under the fender. If not, consider lower profiles or smaller rims

Negative scrub radius (about -5 mm). Scrub radius will be changed by -5 mm, this may affect the car's handling. Please check manufacturer recommendations. Please be aware that calculated value is approximate.

When speedometer reads 60 km/h actual speed will be 62.5 km/h


I usually turn to this site it's very precise and you get the decisive values and parameters in regard to variance between stock and the desired setup:

https://www.wheel-size.com/calc/

Also consider there will be added weight as well.


Technically you can drive it and should not have any issues as scrub radious is minimum and many cars (setup) come with a slight negative scrub radius already. Though, I'd ask a professional tire/car shop just to be 100% on the safe side before installing.

As always, thank you my friend!! Thanks buddy.

[BeamerandBimmer]

Originally Posted by Resjudicata

As always, thank you my friend!! Thanks buddy.

Did you try this setup?

[Resjudicata]

Originally Posted by BeamerandBimmer

Did you try this setup?

yes, it's running fine and awesome so far.

[Jim-Bow]

This is a genuine question, apologies if I seem dumb, what's the benefit of running oversized tyres? Have the wrong speedo reading would drive me OCD crackers but I obviously don't get the whole picture.

[Resjudicata]

Originally Posted by Jim-Bow

This is a genuine question, apologies if I seem dumb, what's the benefit of running oversized tyres? Have the wrong speedo reading would drive me OCD crackers but I obviously don't get the whole picture.

Looks. It looks like you put lowering springs or bigger wheels on it. Gives the appearance of a full wheel well. 21" vs 20" tires.

[Andycam]

Originally Posted by Resjudicata

Looks. It looks like you put lowering springs or bigger wheels on it. Gives the appearance of a full wheel well. 21" vs 20" tires.

Have you also noticed any difference in road noise, comfort and handling?

[Resjudicata]

Originally Posted by Andycam

Have you also noticed any difference in road noise, comfort and handling?

I think it handles better, but I haven't tracked it with the new tires.

[unfoundnemo]

Originally Posted by Jim-Bow

This is a genuine question, apologies if I seem dumb, what's the benefit of running oversized tyres? Have the wrong speedo reading would drive me OCD crackers but I obviously don't get the whole picture.

Don't worry, it's wrong anyway. I think there's something like a 5% tolerance. You could also tell iDrive you have a bigger wheel to try to offset the bigger tire, but I believe you're getting some free miles on the odometer if you don't as well.

[RNemesisN63]

Originally Posted by Resjudicata

I think it handles better, but I haven't tracked it with the new tires.

Debating going 21" or 20" with bigger tires. I know you decided to go with the bigger tire option, any pics?

[ArcticWhite]

Originally Posted by Jim-Bow

This is a genuine question, apologies if I seem dumb, what's the benefit of running oversized tyres? Have the wrong speedo reading would drive me OCD crackers but I obviously don't get the whole picture.

Also, if you live in a pothole town, the larger sidewall protects the rim a bit more from damage.

[ve7mma]

Originally Posted by ArcticWhite

Also, if you live in a pothole town, the larger sidewall protects the rim a bit more from damage.

You need a good memory to be remember where are the potholes in town.

I am currently running stock 20" non run-flat.

[__AD__]

Originally Posted by ve7mma

You need a good memory to be remember where are the potholes in town.

I am currently running stock 20" non run-flat.

I feel like if I squint really hard when I hit a big pothole, it prevents the tire/wheel from getting damaged 😅

[Tenac]

Originally Posted by __AD__

I feel like if I squint really hard when I hit a big pothole, it prevents the tire/wheel from getting damaged 😅

Way better to lift your feet off the pedals and floor and pinch real tight.

[Mgrae456]

snowbimmer

[Accentu8]

I still have stock 20” wheels, but replaced the stock run flat summers with Continental ExtremeContact DWS06+ with 40 front/35 rear sidewalls. Looks a lot better, rides better and is much quieter. No decrease in handling. Had the setup for 10 days.

[Accentu8]

Better shot I did today. After her first foam bath and wax.

[bloozemanAZ]

Excellent and as previously stated my next go to when the new set of P Zeros run their course. Always ran Continentals on my prior sport sedans with all the grip needed for every day plus spirited driving. Plus throw in the extra tread life and a total win-win.

[bloozemanAZ]

Originally Posted by Tenac

Way better to lift your feet off the pedals and floor and pinch real tight.

Hit one yesterday in an unknown areas of town which was more of a crack in the street vs a pothole so didn't see it until too late. Friend in the car with me got an ear full of WTF and a couple of further rants. He has no clue what a pothole can do on 20" rims with little rubber between them and the road.

[bloozemanAZ]

Originally Posted by unfoundnemo

Don't worry, it's wrong anyway. I think there's something like a 5% tolerance. You could also tell iDrive you have a bigger wheel to try to offset the bigger tire, but I believe you're getting some free miles on the odometer if you don't as well.

Which brings up a point from older threads in which oversized tires caused issues with X drive and the dealers not wanting to cover the drive train issues due to that. Is this setup of sizing immune to that?

[Mgrae456]

Originally Posted by bloozemanAZ

Which brings up a point from older threads in which oversized tires caused issues with X drive and the dealers not wanting to cover the drive train issues due to that. Is this setup of sizing immune to that?

Did you bend a rim? The upsize in tire has been no issue from my dealership (bmw of Manhattan) they did it for me and suggested it.