Anyone running 18x9 front and 18x10 rear wheels - What tire sizes are you running

[bmw m3 s50]

I’m running 18x9.5 front and 18x10.5 rear with 265/35/18 and 285/35/18 rear. Had to shave the rear fenders to eliminate rubbing.

Those wheels look great. If I had the 9.5 in the front, then the 265 would be a no-brainer.

[bmw m3 s50]

Only if you lower the pressures.

Are you asking for street use or track use?

Keeping everything else constant, for a given tire compound, grip is determined by pressure (lower pressure = more grip).

Wider tires let you run lower pressures for a given heat level, so they can indirectly allow for more grip (and are necessary on heavier cars that heat tires more). But, for street use, heat capacity isn't something most people worry about in tires (and most people aren't optimizing their pressures for grip for street use).

Wider tires come with a bunch of trade offs- worse steering feel, tram lining, increased drag, heavier, more expensive, etc. If you don't need to increase the heat capacity (aka, for street use), wider tires are worse.

I remember reading this in one of your posts. Can you elaborate on this a little more? Is the lower pressure allowing for a wider contract patch via shape of the tire as it contacts the ground or is it due to the tires getting to operating temperatures quicker?


What are the optimal tire pressures for the street?

[Obioban]

Agreed but 255/40 and 285/35 would be even more grip, no?

Only if you lower the pressures.

Are you asking for street use or track use?

Keeping everything else constant, for a given tire compound, grip is determined by pressure (lower pressure = more grip).

Wider tires let you run lower pressures for a given heat level, so they can indirectly allow for more grip (and are necessary on heavier cars that heat tires more). But, for street use, heat capacity isn't something most people worry about in tires (and most people aren't optimizing their pressures for grip for street use).

Wider tires come with a bunch of trade offs- worse steering feel, tram lining, increased drag, heavier, more expensive, etc. If you don't need to increase the heat capacity (aka, for street use), wider tires are worse.

[Calb]

I’m running 18x9.5 front and 18x10.5 rear with 265/35/18 and 285/30/18 rear. Had to shave the rear fenders to eliminate rubbing.

[bmw m3 s50]

For what's it's worth, BMW put 9"/10" wheels (ZCP) on e9x and they went with 245/265(40) or 255/285 (GTS). People often usize to 255/275 though that does stray from what DSC expects. And e9x expects a larger diameter rear tire where e46 dsc expects them to be basically equal so I don't know how much value there is in this comparison.

This is a good point about the GTS sizing being 255/285. Tire heights are pretty similar so it should work with the e46 DSC.

The more I think about it, I may just try this size out and report back.

[Tbonem3]

For what's it's worth, BMW put 9"/10" wheels (ZCP) on e9x and they went with 245/265(40) or 255/285 (GTS). People often usize to 255/275 though that does stray from what DSC expects. And e9x expects a larger diameter rear tire where e46 dsc expects them to be basically equal so I don't know how much value there is in this comparison.

[MTiz]

I was 19x9 and 19x10 and ran 245/265 and it felt great

[9kracing]

Has anyone tried a 255/40 275/35 setup on a 9/10 set? Rears will be slightly shorter but it's only 1.5%.

Firestone Firehawk

245/40/19 - 26.7"

285/35/19 - 26.89"


That's what I run, but I'm on a 8.5 front wheel. I'd imagine you could still run it on a 9" wheel though.

[DJAM3]

Has anyone tried a 255/40 275/35 setup on a 9/10 set? Rears will be slightly shorter but it's only 1.5%.

[bmw m3 s50]

I was going to say, Dinan used 275 front and 285 rear, correct?

Yes, that is correct. The issue is that Dinan’s wheel setup was 9.5 in front and 10 rear would makes 275 front and 285 rear a good fit. My issue is that I have a 9 in the front not a 9.5, this makes selecting the tire size more tricky.

I am thinking that a 265 on a 9” wide wheel might not fit properly but not really sure.

[9kracing]

I was going to say, Dinan used 275 front and 285 rear, correct?

[bmw m3 s50]

This.

Of many setup ups I've tried over the last decade+, the 9.5 et35 and 10 et25 really work well with this chassis.

DINAN showed me the way and apex offers those sizes standard on all their wheels


Sent from my iPhone using Tapatalk Pro

As I mentioned, I completely agree. If I had the choice the would have been the 9.5 et35 and 10 et25. I came across this setup and trying to select the best size size using these specs.

I was hoping others ran a similar setup to give me feedback.

[Chas3n]

I'd do 245/275 with most tires, though 236/265 with something wide like a052 or nankang. I ran 245/275 ps4s.

I have to say, I hated 9/10, much happier with 9.5/10". 9/10 felt no better than typical 8.5/10 plus the tire math is worse. Don't do it imo. Plus the stretch of the 235 or 245 tire on 9" wheel was offputting imo.

This.

Of many setup ups I've tried over the last decade+, the 9.5 et35 and 10 et25 really work well with this chassis.

DINAN showed me the way and apex offers those sizes standard on all their wheels


Sent from my iPhone using Tapatalk Pro

[bmw m3 s50]

More is not always better especially if you want an M3 with a good balance of grip and slip. 235/265 CSL setup for the street is plenty IMO unless you are FI and need the extra traction of a 275 or 285.

Well, to be fair the CSL just upsized 10mm over the standard m3 tire sizes but the biggest difference is effect on grip was the tire compound of the Pilot Sport Cup tires. One could argue going from a PS2 or Supersport compound to a Pilot Cup compound could potentially be the equivalent of upsizing 20mm or 30mm via street summer compound tire.

For me, I am about the grip not so much the slip. I am not really a fan of sliding the car and would prefer the stability of grip in the corners.

[Slideways]

Agreed but 255/40 and 285/35 would be even more grip, no?

More is not always better especially if you want an M3 with a good balance of grip and slip. 235/265 CSL setup for the street is plenty IMO unless you are FI and need the extra traction of a 275 or 285.