New Tire Question

BeerHerder · 12-29-2023, 02:46 PM

It's time to replace my RFT OEM tires and I want to go with Michelin PS5. Stock size is 225/45R18 and PS5's don't come in that size, they have 1 size larger diameter 235/50R18 or one size smaller 235/40R18. The 10mm wider width I don't think I need to be worried about. My speedo runs slow; at 65mph on my dash, I'm actually going about 61-62 per those radar speed signs. My advanced google skills tell me that it'll be 1.28 inches taller in diameter which will result in the speedometer reading just about accurate for once. That's also less than inch in radius, so I don't think I need to worry about rub.
Anything else I need worry about? Will these mount with no issue?
I was perusing through the forum and someone said that it absolutely must be the OEM size or you'll have an issue with x-drive, but I can't figure how that's true... it's a square setup.

Any insight and advice is welcome. Or just tell me to get the PS4S and call it a day...

jmanB45 · 12-29-2023, 05:54 PM

235/50/18 is far too tall and will look goofy. It's 5% bigger, you wanna stay within 3%. Ideal alternatives to the stock size are 245/40/18 or 235/45/18. I would just get the PS4S.

https://tiresize.com/calculator/

235/40/18 looks ok if you're lowered and like the smaller sidewall (diameter less by 2.3%)

https://f30.bimmerpost.com/forums/sh...27&postcount=4

alohasurftoad · 12-29-2023, 08:32 PM

235/45/18 on OEM 18x8 ET34 is best for unlowered x-drive.

https://f30.bimmerpost.com/forums/sh...1634952&page=2

and yes, PS4S call it a day... ^^
.

BeerHerder · 12-31-2023, 12:21 PM

Thanks my dudes. I'll keep it simple and looks like I'll go a little wider.

12-29-2023, 02:46 PM	#1
BeerHerder Lieutenant 251 Rep 426 Posts Drives: F30 335, G01 X3, Victory Vegas Join Date: Mar 2019 Location: IL iTrader: (1)	New Tire Question - Michelin PS5 It's time to replace my RFT OEM tires and I want to go with Michelin PS5. Stock size is 225/45R18 and PS5's don't come in that size, they have 1 size larger diameter 235/50R18 or one size smaller 235/40R18. The 10mm wider width I don't think I need to be worried about. My speedo runs slow; at 65mph on my dash, I'm actually going about 61-62 per those radar speed signs. My advanced google skills tell me that it'll be 1.28 inches taller in diameter which will result in the speedometer reading just about accurate for once. That's also less than inch in radius, so I don't think I need to worry about rub. Anything else I need worry about? Will these mount with no issue? I was perusing through the forum and someone said that it absolutely must be the OEM size or you'll have an issue with x-drive, but I can't figure how that's true... it's a square setup. Any insight and advice is welcome. Or just tell me to get the PS4S and call it a day... __________________ Glacier Silver Metallic 335i X-Drive - Can't leave well enough alone... Fabspeed DP, Wagner Evo Comp II IC, ER CP, BM3 Stage 2 93 OTS, Bimmertech Amp (more to come... always more) Graphite Metallic X3 (nothing yet, but... you know)
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12-29-2023, 05:54 PM	#2
jmanB45 Private First Class 146 Rep 125 Posts Drives: 2018 BMW 330iX Sedan Join Date: Apr 2022 Location: Toronto, ON iTrader: (0) Garage List 2018 BMW 330iX Sedan [0.00]	235/50/18 is far too tall and will look goofy. It's 5% bigger, you wanna stay within 3%. Ideal alternatives to the stock size are 245/40/18 or 235/45/18. I would just get the PS4S. https://tiresize.com/calculator/ 235/40/18 looks ok if you're lowered and like the smaller sidewall (diameter less by 2.3%) https://f30.bimmerpost.com/forums/sh...27&postcount=4
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12-29-2023, 08:32 PM	#3
alohasurftoad Brigadier General 3082 Rep 4,333 Posts Drives: 440i gran coupe w/mppsk Join Date: Apr 2015 Location: hawaii iTrader: (0)	235/45/18 on OEM 18x8 ET34 is best for unlowered x-drive. https://f30.bimmerpost.com/forums/sh...1634952&page=2 and yes, PS4S call it a day... ^^ . Last edited by alohasurftoad; 12-29-2023 at 08:43 PM..
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12-31-2023, 12:21 PM	#4
BeerHerder Lieutenant 251 Rep 426 Posts Drives: F30 335, G01 X3, Victory Vegas Join Date: Mar 2019 Location: IL iTrader: (1)	Thanks my dudes. I'll keep it simple and looks like I'll go a little wider.
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