[alohasurftoad]

Originally Posted by 440i

That’s why I am struggling with decision. Also the extra wheel gap that will come with the 245s ��

what wheel are you getting? if available, you can lightly stretch a 255/40/18 on 18x9.5" ET35 square setup. in this case the tire shoulder will be 5mm further in than at ET30 and the light stretch provides more sidewall support maximizing tire performance when you are driving at or near limits, 8/10ths+. the negative is less lip protection from curbs since the 9.5" wheel lips are 1/4" more exposed than 9".

link below has 255/35/19 on 19x9.5 ET35, square. although 19", the 255/35/19 tire dimensions are equivalent to 255/40/18 and it, will work on 18x9.5 ET35, square.
https://f30.bimmerpost.com/forums/sh...7&postcount=26

[440i]

Originally Posted by alohasurftoad

what wheel are you getting? if available, you can lightly stretch a 255/40/18 on 18x9.5" ET35 square setup. in this case the tire shoulder will be 5mm further in than at ET30 and the light stretch provides more sidewall support maximizing tire performance when you are driving at or near limits, 8/10ths+. the negative is less lip protection from curbs since the 9.5" wheel lips are 1/4" more exposed than 9".

link below has 255/35/19 on 19x9.5 ET35, square. although 19", the 255/35/19 tire dimensions are equivalent to 255/40/18 and it, will work on 18x9.5 ET35, square.
https://f30.bimmerpost.com/forums/sh...7&postcount=26

I purchased a set of 18x9 et30. So will a 245 be a slight stretch on the 9in wheel like the 255 would be a slight stretch on the 9.5in? Giving me the same performance benefits when really pushing the car?

[alohasurftoad]

Originally Posted by 440i

I purchased a set of 18x9 et30. So will a 245 be a slight stretch on the 9in wheel like the 255 would be a slight stretch on the 9.5in? Giving me the same performance benefits when really pushing the car?

I believe it would. TireRack had an interesting test about this matter, however the vehicle was a BRZ. It would be interesting to see if the results would be the same on our F3/4 series

in their test, the really stretched tire did best, however it is not practical for a daily driver, as you will have slim to no curb protection, less impact protection and harsher ride.

most of the stuff i have read discuss having the wheel width equal to or 0.5" wider than the tire tread(not section) width for best handling, ride, etc. this seems most reasonable and what i mostly try to suggest.
.

[danb1979]

Originally Posted by 440i

That’s why I am struggling with decision. Also the extra wheel gap that will come with the 245s ��

Use the www.willtheyfit.com website for their tyre calculator; that'll give the specs and a diagram too

The extra wheel gap really isn't that bad; it's all about having a decent contact patch on the tarmac, but also not too much sidewall which give a softer feeling to the ride; that's why I'm not keen on 255s fitted to 18x9s - it's just a touch too wide IMO

But that's my personal preference

[440i]

Originally Posted by danb1979

Use the www.willtheyfit.com website for their tyre calculator; that'll give the specs and a diagram too

Yah the fitment of the 245 and 255 are so similar. I am so torn

[danb1979]

Originally Posted by 440i

Yah the fitment of the 245 and 255 are so similar. I am so torn

Only you can make that decision..

The ARC8s with 245/40/18s on the link I added on the previous page look to be a spot on fitment to me; I know tourings do have that bit more generous arch size etc

Equivalency table
Rim width Minimum tyre width Ideal tyre width Maximum tyre width
5,0 Inches 155 mm 165 or 175 mm 185 mm
5,5 Inches 165 mm 175 or 185 mm 195 mm
6,0 Inches 175 mm 185 or 195 mm 205 mm
6,5 Inches 185 mm 195 or 205 mm 215 mm
7,0 Inches 195 mm 205 or 215 mm 225 mm
7,5 Inches 205 mm 215 or 225 mm 235 mm
8,0 Inches 215 mm 225 or 235 mm 245 mm
8,5 Inches 225 mm 235 or 245 mm 255 mm
9,0 Inches 235 mm 245 or 255 mm 265 mm
9,5 Inches 245 mm 255 or 265 mm 275 mm
10,0 Inches 255 mm 265 or 275 mm 285 mm
10,5 Inches 265 mm 275 or 285 mm 295 mm
11,0 Inches 275 mm 285 or 295 mm 305 mm
11,5 Inches 285 mm 295 or 305 mm 315 mm
12,0 Inches 295 mm 305 or 315 mm 325 mm
12,5 Inches 305 mm 315 or 325 mm 335 mm

That table states a 245 or 255 will be perfect, 265 max (far too wide IMO)

So it's down to you which to pick over the other...

You will be absolutely fine with both

[440i]

Originally Posted by danb1979

Only you can make that decision..

The ARC8s with 245/40/18s on the link I added on the previous page look to be a spot on fitment to me; I know tourings do have that bit more generous arch size etc

Equivalency table
Rim width Minimum tyre width Ideal tyre width Maximum tyre width
5,0 Inches 155 mm 165 or 175 mm 185 mm
5,5 Inches 165 mm 175 or 185 mm 195 mm
6,0 Inches 175 mm 185 or 195 mm 205 mm
6,5 Inches 185 mm 195 or 205 mm 215 mm
7,0 Inches 195 mm 205 or 215 mm 225 mm
7,5 Inches 205 mm 215 or 225 mm 235 mm
8,0 Inches 215 mm 225 or 235 mm 245 mm
8,5 Inches 225 mm 235 or 245 mm 255 mm
9,0 Inches 235 mm 245 or 255 mm 265 mm
9,5 Inches 245 mm 255 or 265 mm 275 mm
10,0 Inches 255 mm 265 or 275 mm 285 mm
10,5 Inches 265 mm 275 or 285 mm 295 mm
11,0 Inches 275 mm 285 or 295 mm 305 mm
11,5 Inches 285 mm 295 or 305 mm 315 mm
12,0 Inches 295 mm 305 or 315 mm 325 mm
12,5 Inches 305 mm 315 or 325 mm 335 mm

That table states a 245 or 255 will be perfect, 265 max (far too wide IMO)

So it's down to you which to pick over the other...

You will be absolutely fine with both

Thanks for this. You’re right, both will be great choices just have to pick one

[keithyo88]

Originally Posted by danb1979

Use the www.willtheyfit.com website for their tyre calculator; that'll give the specs and a diagram too

The extra wheel gap really isn't that bad; it's all about having a decent contact patch on the tarmac, but also not too much sidewall which give a softer feeling to the ride; that's why I'm not keen on 255s fitted to 18x9s - it's just a touch too wide IMO

But that's my personal preference

Thank You, that tyre calculator is the best

[danb1979]

Originally Posted by keithyo88

Thank You, that tyre calculator is the best

Yes it's really good; a good tool to save to your bookmarks

It helped me when I was deciding on tyre sizes for the 18x8.5 and 18x9.5 LMs I ran on a previous Jap import E39 touring; everything was saying 235/40 and 265/35; but 245/40 and 275/35s worked the best:

[alohasurftoad]

https://f30.bimmerpost.com/forums/sh...&postcount=311
https://f30.bimmerpost.com/forums/sh...&postcount=313

the links above show obzen's F36 rwd 255/40/18 on 9 ET30 at m-sport height. at stock height your x-drive gaps will be bigger. if you go with 245/40/18 increase gaps 3.8 mm.

with either size(but moreso with 245) you'll want to get lowered to reduce the gap and inherently tuck the upper shoulder of the tires slightly more. i suggest Eibach Pro-Kit E10-20-031-05-22 with F80 bumpstops over Koni SA dampers and rest of the bits comprising the strut/shock assembly.
sorry to have opened "another can of worms", lol.

[440i]

Originally Posted by alohasurftoad

https://f30.bimmerpost.com/forums/sh...&postcount=311
https://f30.bimmerpost.com/forums/sh...&postcount=313

the links above show obzen's F36 rwd 255/40/18 on 9 ET30 at m-sport height. at stock height your x-drive gaps will be bigger. if you go with 245/40/18 increase gaps 3.8 mm.

with either size(but moreso with 245) you'll want to get lowered to reduce the gap and inherently tuck the upper shoulder of the tires slightly more. i suggest Eibach Pro-Kit E10-20-031-05-22 with F80 bumpstops over Koni SA dampers and rest of the bits comprising the strut/shock assembly.
sorry to have opened "another can of worms", lol.

Would that setup be similar to a bilstein b14 or kw v1 coilover? In terms of handling, lowering ability, and cost?

[alohasurftoad]

Originally Posted by 440i

Would that setup be similar to a bilstein b14 or kw v1 coilover? In terms of handling, lowering ability, and cost?

B14/B16 have monotube shocks and ride is stiff
KW V1 better product

eibach pro kit + koni SA would be about the same price as B14 but cheaper than KWV1. eibach/koni will ride much better than both and be lowered just the right amount, since max recommended front lowering for x-drive is about 1.5" or 38mm. this is due to stresses put on the half shafts since the angle into the front differential changes when lowered.

if you have the money for KWV1 and prefer the height adjustability, get that since the ride is better than the B14.

although the eibach/koni setup is non height adjustable, the lowered ride height is just right(imo), reverse rake is addressed, handling is sporty yet compliant, since the spring rates are just 10% firmer than stock. for an idea of the drop, smak168 has the eibach on his F36xdrive, here...
https://f30.bimmerpost.com/forums/sh...&postcount=158

here's one of a few koni/eibach threads in the suspension sub-forum
https://f30.bimmerpost.com/forums/sh....php?t=1901058

[440i]

Originally Posted by alohasurftoad

B14/B16 have monotube shocks and ride is stiff
KW V1 better product

eibach pro kit + koni SA would be about the same price as B14 but cheaper than KWV1. eibach/koni will ride much better than both and be lowered just the right amount, since max recommended front lowering for x-drive is about 1.5" or 38mm. this is due to stresses put on the half shafts since the angle into the front differential changes when lowered.

if you have the money for KWV1 and prefer the height adjustability, get that since the ride is better than the B14.

although the eibach/koni setup is non height adjustable, the lowered ride height is just right(imo), reverse rake is addressed, handling is sporty yet compliant, since the spring rates are just 10% firmer than stock. for an idea of the drop, smak168 has the eibach on his F36xdrive, here...
https://f30.bimmerpost.com/forums/sh...&postcount=158

here's one of a few koni/eibach threads in the suspension sub-forum
https://f30.bimmerpost.com/forums/sh....php?t=1901058

I think I will play it safe and order a set of extreme contact sport 02 in 245/40/18. Less poke on the et30 and easier fitment!

[440i]

Side note - alohasurftoad will 245 squared be enough tire for a stage 2 tuned car? Just wondering if the 255 will provide a significant amount of difference compared to the 245 when I’m not stock power. Thanks

[alohasurftoad]

Originally Posted by 440i

Side note - alohasurftoad will 245 squared be enough tire for a stage 2 tuned car? Just wondering if the 255 will provide a significant amount of difference compared to the 245 when I’m not stock power. Thanks

all things equal 255>245 but 285/35 on a 10" would've been more appropriate.

if you want traction from a tire, compound>width. of course i understand running a 200TW extreme performance summer is not practical for a daily driver

if you really wanna talk traction for stage2, an LSD should be in the convo before all of this...LSD+255's>"one legged" 285

[440i]

I didn’t realize our cars could fit a 285! Yes I was debating a 200tw tire but like you said not good for a DD also I get a lot of rain here in the summer. How much would a LSD be with install roughly?

[alohasurftoad]

Originally Posted by 440i

I didn’t realize our cars could fit a 285! Yes I was debating a 200tw tire but like you said not good for a DD also I get a lot of rain here in the summer. How much would a LSD be with install roughly?

https://f30.bimmerpost.com/forums/sh...07&postcount=2
above is strawhatdan running 255/40/18(26") on 18x9 ET30 front, 285/35/18(25.9") on 18x10.5 ET40 rear. fyi, this staggered size combo would work with an x-drive as well.

the cheapest LSD is M-Performance, part# 33-10-8-659-989. $2330 USD plus ship and speculating install cost of $800-$1200 USD or more? idk... but yes OUCH! this'll hurt your wallet something fierce. Quaife or Wavetrac LSD's are best and cost even more!

[Voodoo18]

I just ordered a set of ARC8's 18x9 et30 today for my GC, and this thread was extremely helpful in my decision with wheel spec and tire sizing.

Thanks to all who contributed, especially Alohasurftoad. His knowledge and links provided were much appreciated.

[danb1979]

Originally Posted by Voodoo18

I just ordered a set of ARC8's 18x9 et30 today for my GC, and this thread was extremely helpful in my decision with wheel spec and tire sizing.

Thanks to all who contributed, especially Alohasurftoad. His knowledge and links provided were much appreciated.

[440i]

Originally Posted by Voodoo18

I just ordered a set of ARC8's 18x9 et30 today for my GC, and this thread was extremely helpful in my decision with wheel spec and tire sizing.

Thanks to all who contributed, especially Alohasurftoad. His knowledge and links provided were much appreciated.

What tire size are you going with?

[Voodoo18]

Originally Posted by danb1979

Gimme a week or so

[Voodoo18]

Originally Posted by 440i

What tire size are you going with?

255/40/18 all the way around. Not sure which tire yet. Ill sort that out later.

I don't mind the slight extra poke. I actually really like that look and prefer it over the extra gap from the 245s. And I don't want to go with 19s, this is my dd and I live in the NE.