Tyre size recommendation for e86 coupe

[thetenksi]

Hi all, deciding to get rid of the run flats and i'm unsure if my options would cause any rubbing issues.

I'd like more comfort and my wheel arches to be 'filled out' more so I've gone with a higher aspect ratio so the tyre is larger in diameter. I'm aware my speedo will read wrong my a few mph and I don't mind this:) Suspension is all stock and i have no plans on lowering the car either so any advice would be appreciated!

Wheels are 8jx18 et47 front and 8.5jx18 et50 rear, stock tyres are 225/40r18 front and 255/35r18 rear (635mm diameter)

Options:

square: 1) 255/45r18 (686mm diameter)
2) 255/40r18 (660mm diameter)

staggered: 3) 225/45r18 front, 255/40r18 rear (660mm diameter)
4) 235/45r18 front, 265/40r18 rear (668mm diameter)
5) 245/45r18 front, 275/40r18 rear (678mm diameter)

[buzyg]

Interested to know why you are looking to fit such wide tyres?

Standard fit on the ///Ms18inch 224s are:-

225/45r18 front
255/40r18 rear

Nice a comfy and more than enough grip for 343 hp

[thetenksi]

Just purely for aesthetic reasons, hoping the tires are more flush with the wheel arches, and I've found they're not too much more expensive either! I've heard 275 on 8.5 wheels would be a massive stretch

[Zedtastic]

I fitted your option 3 above (225/45/18 at the front, and 255/40/18 at the rear). This is the tyre size used on M models, though mine is a 30Si. Firstly, the comfort level is greatly improved. Secondly , they do fill the arch gap better (mine is standard ride height with 5mm spacers at the front, and 12mm at the rear). Lastly, and most surprisingly, the speedo actually reads more accuratly now. With the standard tyre size the speedo was over-reading (when compared to my GPS), but with the new tyres its still over-reading, but now only by about 1 or 2%. Hope this helps you make up your mind.

[z4pilot]

Just purely for aesthetic reasons, hoping the tires are more flush with the wheel arches, and I've found they're not too much more expensive either! I've heard 275 on 8.5 wheels would be a massive stretch

Option 3 is the sensible one. You are trying to solve 2 problems though. When viewed from side on, increasing the sidewall ratio will help to reduce the arch gap. When viewed from head on (or rear on), the only effective way to change the offset and bring the outer face of the wheel to be more flush with the arches (assuming you're sticking with original wheels) will be to add spacers. 12mm or 15mm at the front and 20mm rears will do it. Might also be worth saying if your car is on M Sport or SE springs?

[mr wilks]

Option 6 225 45 18 front / 245 40 18 rear

[Ed Doe]

I have 10J rears on my M with 265/40/18s - that tyre size on a narrower wheel will look a bit s**t imo. Also my arches have been slightly rolled to accommodate, and the arch liners have rubbed away a little (admittedly probably from the bottom of paddock Hill at Brands..!) Not a problem for me as I don't drive the car in winter but worth considering if you're dailying...

IMG-20181216-WA0020.jpg (142.88 KiB) Viewed 1511 times

IMG_20181117_124456.jpg (352.26 KiB) Viewed 1511 times

[mmm-five]

I posted this in your other thread before I spotted it here.
-------------------

Before I say anything, I have seem some really wide fitments on e46 M3s at the Ring, but they've been stupidly lowered as well and have difficulty getting over the smallest speed bumps - and you can see dents in the arches where the tyres have hit. But they're track cars, so not a big issue.

#1 - Don't think 255/45 would fit on the front - as it's adding 50mm to the diameter. Even if you fitted the 'correct' profile (probably a 35 profile to keep it the same as OE) you'd still have problems with steering lock and rubbing.

#2 - Think 255/40 would also be very tight on the front - and it's adding 25mm to the diameter.

#3 - I believe they're they OE M sizes, and I know people run those sizes on non-Ms.

#4 - Possibly the largest 'safe' size you'd get away with, and have seen this size run on both Ms and non-Ms.

#5 - I'd rule that out completely as the rears are not just too wide (which will rub, catch and wear out your tyre and arch liner), it's also too high a side profile - which will knock out the speedo and make performance/fuel economy worse. I go through a set of arch liners every couple of years in my Z4MC and I'm only running 265/40r18. I can't change the offset to bring it in as the tyre is only about 5mm away from the suspension strut.

For reference, this is my Z4MC on 225/45r18 and 265/40r18 (only the rears are slightly wider), but being slightly lowered (about an inch) on Bilstein B16/PSS10 fills the arches nicely, and still gives me a good compromise between road & track use.







Wouldn't want the tyre any more outset...

[thetenksi]

thank you for all the replies! I think i'll go with the general consensus of option 3, and I'll add spacers on later on to make it more flush with the arch liners seen as though the wider tires are £110 more so expensive all the pictures really helped too so thank you again , beaut cars!

[Mind Bomb]

I fitted your option 3 above (225/45/18 at the front, and 255/40/18 at the rear). This is the tyre size used on M models, though mine is a 30Si. Firstly, the comfort level is greatly improved. Secondly , they do fill the arch gap better (mine is standard ride height with 5mm spacers at the front, and 12mm at the rear). Lastly, and most surprisingly, the speedo actually reads more accuratly now. With the standard tyre size the speedo was over-reading (when compared to my GPS), but with the new tyres its still over-reading, but now only by about 1 or 2%. Hope this helps you make up your mind.

hope this isnt hijacking a thread, but is that with sport or SE springs?

[Zedtastic]

I fitted your option 3 above (225/45/18 at the front, and 255/40/18 at the rear). This is the tyre size used on M models, though mine is a 30Si. Firstly, the comfort level is greatly improved. Secondly , they do fill the arch gap better (mine is standard ride height with 5mm spacers at the front, and 12mm at the rear). Lastly, and most surprisingly, the speedo actually reads more accuratly now. With the standard tyre size the speedo was over-reading (when compared to my GPS), but with the new tyres its still over-reading, but now only by about 1 or 2%. Hope this helps you make up your mind.

hope this isnt hijacking a thread, but is that with sport or SE springs?

Sport springs.

[Ed Doe]

Wouldn't want the tyre any more outset...

I do reckon they look their best with chunky tyres on. Looks far more purposeful than any of this rubber band/stretch s**t people put on performance cars these days. And rides better too! Win win in my book

[Mind Bomb]

I fitted your option 3 above (225/45/18 at the front, and 255/40/18 at the rear). This is the tyre size used on M models, though mine is a 30Si. Firstly, the comfort level is greatly improved. Secondly , they do fill the arch gap better (mine is standard ride height with 5mm spacers at the front, and 12mm at the rear). Lastly, and most surprisingly, the speedo actually reads more accuratly now. With the standard tyre size the speedo was over-reading (when compared to my GPS), but with the new tyres its still over-reading, but now only by about 1 or 2%. Hope this helps you make up your mind.

hope this isnt hijacking a thread, but is that with sport or SE springs?

Sport springs.