[fortythirtyfive]

I currently run an 8.5j set on all 4 wheels, mainly because I was inpatient at the time of ordering my current wheels (they kept pushing back on 10j lead times for 3 months) however it's left me with a predicament now that I need new tyres.

I don't want a super stretched or round look. I currently run 235/35 & 255/30, as I have recently installed monoball control arms and have my coilovers setup pretty harsh though I decided maybe it's time to go up to 235/40 & 255/35? Especially as I bent a rear wheel last year running the 30's.

Last time I ran a 255/35 on an 8.5j it was on the verge of looking super square/almost round.

Do I need to keep within the 2% diameter considering I'm RWD, or this that purely an X-Drive requirement?

I'm just trying to decide whether I'll have any negative impacts if I ran something like 235/40 & 245/35. Apart from a slightly less accurate speedometer will that setup do affect the drive? Or maybe I run a squared setup..

I really wish I had held out for the 10j rears now but then again I could have been waiting months and months. As for acquiring a new set that isn't possible, I had to import them from Germany and paid close to £800 in taxes and shipping.. they held me ransom when they came to importing

[johnung]

Originally Posted by fortythirtyfive

I currently run an 8.5j set on all 4 wheels, mainly because I was inpatient at the time of ordering my current wheels (they kept pushing back on 10j lead times for 3 months) however it's left me with a predicament now that I need new tyres.

I don't want a super stretched or round look. I currently run 235/35 & 255/30, as I have recently installed monoball control arms and have my coilovers setup pretty harsh though I decided maybe it's time to go up to 235/40 & 255/35? Especially as I bent a rear wheel last year running the 30's.

Last time I ran a 255/35 on an 8.5j it was on the verge of looking super square/almost round.

Do I need to keep within the 2% diameter considering I'm RWD, or this that purely an X-Drive requirement?

I'm just trying to decide whether I'll have any negative impacts if I ran something like 235/40 & 245/35. Apart from a slightly less accurate speedometer will that setup do affect the drive? Or maybe I run a squared setup..

I really wish I had held out for the 10j rears now but then again I could have been waiting months and months. As for acquiring a new set that isn't possible, I had to import them from Germany and paid close to £800 in taxes and shipping.. they held me ransom when they came to importing

Not sure what RWD car you have. Are you talking about 18x8.5” wheels? What offset?

I’d be inclined to run a square setup with 255/40-18. Looks great, handles great, comfortable because of the width and the stock 26.0” tire diameter, and they can be rotated front to back so wear is perfectly even throughout the lifespan of expensive performance tires.

Oh, and XDrive spec is no more than 1% diameter difference between front/rear tires which translates to 0.2” or less diameter difference.

[alohasurftoad]

rwd's have no f&r diameter difference issues

235/40/19(26.3")-245/35/19(25.8") is a reversed rake diameter stagger. Rear sidewall is smaller than front, thus rear wheel gap more than front.

while there's nothing wrong with staggered tire sizes on square rim widths, square (non-directional) tires on square rim widths is much more practical, for rotatability, sidewall appearance and handling.

255/35/19(26") most grip
245/35/19(25.8"), quicker steering
245/40/19(26.7"), best impact protection and ride comfort
235/40/19(26.3") happy medium, but least dig traction.

since you have coils and dont want stretch or bulge, 245/35/19 square would be most suitable.
.

[fortythirtyfive]

Originally Posted by johnung

Not sure what RWD car you have. Are you talking about 18x8.5” wheels? What offset?

I’d be inclined to run a square setup with 255/40-18. Looks great, handles great, comfortable because of the width and the stock 26.0” tire diameter, and they can be rotated front to back so wear is perfectly even throughout the lifespan of expensive performance tires.

Oh, and XDrive spec is no more than 1% diameter difference between front/rear tires which translates to 0.2” or less diameter difference.

Sorry I should have added. It's an F32 435i RWD.

They're 20" 8.5j ET35 - however I run a 10mm spacer up front and 12mm in the rear, this might sound pretty aggressive but they sit pretty much perfectly, the front rub when cornering pretty hard at speed but I guess that's because I've taken the offset down to an ET25 with the spacer combined.

Right now I run 235/35/20 upfront and 255/30/20 in the rear and they appear almost identical, mainly because of the 30 profile on the rear stretching it a tad

Originally Posted by alohasurftoad

rwd's have no f&r diameter difference issues

235/40/19(26.3")-245/35/19(25.8") is a reversed rake diameter stagger. Rear sidewall is smaller than front, thus rear wheel gap more than front.

while there's nothing wrong with staggered tire sizes on square rim widths, square (non-directional) tires on square rim widths is much more practical, for rotatability, sidewall appearance and handling.

255/35/19(26") most grip
245/35/19(25.8"), quicker steering
245/40/19(26.7"), best impact protection and ride comfort
235/40/19(26.3") happy medium, but least dig traction.

since you have coils and dont want stretch or bulge, 245/35/19 square would be most suitable.
.

Ah okay.. so the ultimate staggered setup there would be 245/35 upfront for quicker steering and 255/35 in the rear for best potential grip?

I am tempted to run a squared setup it's just the fronts do occasionally rub from time to time if I'm pushing the car and cornering.. I get the dreaded screech noise and a nice groove stuck into the top of my sidewall.

Are there any handling differences with a staggered reverse rake setup compared to a squared setup? I kinda deleted the reverse rake on my car by adjusting the heights..

I'm very tempted to pull the trigger on 245/35/20's all round, I just wanna be dead sure this time as it's pretty much £1000 in rubber

[alohasurftoad]

Originally Posted by fortythirtyfive

Sorry I should have added. It's an F32 435i RWD.

They're 20" 8.5j ET35 - however I run a 5mm spacer up front and 10mm in the rear, this might sound pretty aggressive but they sit pretty much perfectly, the front rub when cornering pretty hard at speed but I guess that's because I've taken the offset down to an ET30 with the spacer combined.

Right now I run 235/35/20 upfront and 255/30/20 in the rear and they appear almost identical, mainly because of the 30 profile on the rear stretching it a tad

Ah okay.. so the ultimate staggered setup there would be 245/35 upfront for quicker steering and 255/35 in the rear for best potential grip?

I am tempted to run a squared setup it's just the fronts do occasionally rub from time to time if I'm pushing the car and cornering.. I get the dreaded screech noise and a nice groove stuck into the top of my sidewall.

Are there any handling differences with a staggered reverse rake setup compared to a squared setup? I kinda deleted the reverse rake on my car by adjusting the heights..

I'm very tempted to pull the trigger on 245/35/20's all round, I just wanna be dead sure this time as it's pretty much £1000 in rubber

disregard my previous reply as it was based on 19" tire sizes, i didn't know you have 20".

235/35/20 is 26.5" and 255/30/20 is 26", so your front tire is taller than the rear although it is difficult to notice, visually. 235/40/20 would be way too tall at 27.4"

245/35/20(26.8") square will work but you will need to remove the front spacer because it will rub the fenderwell liner when turning full lock at ET30. for handling, i would remove the rear spacer as well but if you just care about appearance than leave it.

here is 245/35/20 square...
https://f30.bimmerpost.com/forums/sh...d.php?t=849595
.

[fortythirtyfive]

Originally Posted by alohasurftoad

disregard my previous reply as it was based on 19" tire sizes, i didn't know you have 20".

235/35/20 is 26.5" and 255/30/20 is 26", so your front tire is taller than the rear although it is difficult to notice, visually. 235/40/20 would be way too tall at 27.4"

245/35/20(26.8") square will work but you will need to remove the front spacer because it will rub the fenderwell liner when turning full lock at ET30. for handling, i would remove the rear spacer as well but if you just care about appearance than leave it.

here is 245/35/20 square...
https://f30.bimmerpost.com/forums/sh...d.php?t=849595
.

If I was to keep them staggered then both fronts and rears would go up by 5mm in sidewall, so that would be a 27.4" and 27" setup.

On my old 405M's I ran a 225/35/20 with a 12mm spacer up front, that used to rub on the fender liner on full lock. The rubbing I currently have however is the actual metal work of the fender edge.

It'll be tough to ditch the spacers as they really finish the wheels for me

With:


Without:

[alohasurftoad]

oem diameter = 26"

if it fits within the fenderwell, i believe the outer shoulder of a 27.4" dia. tire at ET30 will destroy the front fenderwell liner or lip edge, while turning full lock. your 27" rear tire is also heightening the gearing(at pavement), which would affect acceleration by some small value, though it may not be significant enough to notice. let us know how it works out.

[fortythirtyfive]

Okay.. sorry to throw a complete spanner in the works but I may have a solution here.

So my current alloys are brushed and thanks to the poor powder coat job from factory they are in dire need for a refurb, however I've just spotted I can get 9j versions of them but in gloss black from a UK seller.. even better they're only £230 each.

Here's my thoughts, if I'm going to refurb them why not buy x2 9j versions in gloss black and have them all refurbed together, that way they'll match. It also allows me to increase the rear width slightly so that the 255 doesn't bulge too much?

I am sort of sold on the 245 squared setup, however I am also running the most power I can get out of a stock N55 turbo, so maximum grip is kind of key for me.