[Ralph123x]

Hey all,

I've got a base 2018 330i RWD lowered on BILSTEIN B12. It's currently running 397 style rims staggered at 18x8 and 18x8.5. OEM tire size were 225/45/18 and 255/40/18.

I want to do track maybe 2 - 3 times a year and most of my drive is spirited. I also hate how narrow the front is.

I needed new tires after a flat so I placed an order for 245/40/18 and 255/40/18.

But it seems like my most recommended setup for my type of driving is 245/40/18 and 265/35/18. Is that true?

If not, what are your recommended tire size?

P.S. Not looking to get dedicated track tires at the moment as I won't be doing it too often.

[Ralph123x]

Okay after further research, it seems like these two would work better:

F:245/40/18, R: 275/35/18 or
F:235/40/18, R: 265/35/18

Does anyone know if 275/35/18 would fit rear 8.5 wheel if the car is lowered?

[alohasurftoad]

255/40/18 is max recommended width on 18x8.5. any wider is pinching the beads, which bulges the sidewall and reduces sidewall support. on a circuit track the tire performs best when the rim width is slightly wider than the treadwidth, aka light stretch.

with a wider tire pinched on a narrower rim, you don't really gain anything except weight and higher gearing if the tire is taller than OEM.

if you want grip, tire compound plays a more vital role than width, for grip.

for 18x8, 18x8.5 i'd use 245/40/18+255/40/18, max width recommended for each. it's mildly pinched and will have decent curb protection. although each tire width is on their respective minimum recommended rim width, they will still provide the grip and response needed for spirited driving and rare track days.

michelin pilot sport 4S
continental extremecontact sport 02
.

[Ralph123x]

Originally Posted by alohasurftoad

255/40/18 is max recommended width on 18x8.5. any wider is pinching the beads, which bulges the sidewall and reduces sidewall support. on a circuit track the tire performs best when the rim width is slightly wider than the treadwidth, aka light stretch.

with a wider tire pinched on a narrower rim, you don't really gain anything except weight and higher gearing if the tire is taller than OEM.

if you want grip, tire compound plays a more vital role than width, for grip.

for 18x8, 18x8.5 i'd use 245/40/18+255/40/18, max width recommended for each. it's mildly pinched and will have decent curb protection. although each tire width is on their respective minimum recommended rim width, they will still provide the grip and response needed for spirited driving and rare track days.

michelin pilot sport 4S
continental extremecontact sport 02
.

Thanks! I appreciate that. In that case, I'll stick with stock 255/40 in the rear.

But from what you said, isn't the front better at stock 225/45 too? 245 will not provide much more grip and will have a lot less sidewall protection.

Or maybe I understood it wrong

[alohasurftoad]

Originally Posted by Ralph123x

In that case, I'll stick with stock 255/40 in the rear. But from what you said, isn't the front better at stock 225/45 too? 245 will not provide much more grip and will have a lot less sidewall protection. Or maybe I understood it wrong

you understood correctly, however from my own experience, leaving the 255/40/18 at the rear but increasing the front from 225/45/18 to 245/40/18 balances the front and rear grip levels to an almost square set up. imo with 245 up front, understeer of the 225/255 stagger is reduced and it won't push, so you can take a given turn at higher speed.

based on your situation, i feel you'll be quite pleased 245/40/18+255/40/18 vs the OEM sized combo of 225/45/18+255/40/18

this thread, same scenario with OEM 19", 225/40/19 to 245/35/19
https://f30.bimmerpost.com/forums/sh....php?t=1678451
.

[Ralph123x]

Originally Posted by alohasurftoad

you understood correctly, however from my own experience, leaving the 255/40/18 at the rear but increasing the front from 225/45/18 to 245/40/18 balances the front and rear grip levels to an almost square set up. imo with 245 up front, understeer of the 225/255 stagger is reduced and it won't push, so you can take a given turn at higher speed.

based on your situation, i feel you'll be quite pleased 245/40/18+255/40/18 vs the OEM sized combo of 225/45/18+255/40/18

this thread, same scenario with OEM 19", 225/40/19 to 245/35/19
https://f30.bimmerpost.com/forums/sh....php?t=1678451
.

Awesome, I appreciate it tons!