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Thread: 255 or 245 17" square vs a wide staggered 18" setup?

  1. #1
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    255 or 245 17" square vs a wide staggered 18" setup?

    This summer we're going to need new summer tires for the M roadster. Going to keep the roadstars and stick some AS3+'s or the like on them for the winter months. for summers.... some re71r's, rival s, ZIII or the like are in order.

    A 255/40r17 square would be great, but I would really want a 9.5 or even better a 10" rim to support this. a 245/40r17 square setup could be run on some 9" rims which should be easier to get my hands on, but what is avaible in the offsets needed for the rear?. The car really feels grip limited on the older 245 pilot super sports in rear (This might just be the age of tire/setup)

    Is there any reasonably priced/ easy to obtain 17x9.5 or 17x10" rims? (the apex rims seem to only be via group buy orders?) or should i stay 17x9?

    The other option is to run 18". If I could fit a ~25.7" od tire, I could share tires with the Porsche/mazda. Either way this opens up 275or285's for the rear. but the front than gets tricky... everything is 25.7" or taller other than the 255/35r18....

    Are there any reasonably priced 18" rims that will work for these cars and tires?


    Track days for fun and setup, once a week commute , and longer joy rides on the street. So don't want to cut fender liners, but i'm down for a fender roll.

    Last time we took it to auto cross it felt like pushed like a pig. Seems like the rear is a bit... playfull... on the real track, and snap over steer on the street has been annoying... in all fairness we only have 1* of chamber in the rear right now, and I think the rear springs settled...

    Hmmm that got a bit long winded. Thanks for any help!

    -Levi

  2. #2
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    I'm 25.9" tall in the rear (285/35-18 on 10.5" Apex PS-7) and lowered...no problems whatsoever. I am only 25.4" tall up front though, and just barely rub a fender liner on a tight bumpy corner. It all depends on your front end setup/geometry/camber, etc.
    Nathan in Denver

    1999 M Roadster, VFE V3 S/C, Randy Forbes Reinforced, Hardtop, H&R/Bilstein, Apex PS-7, Supersprint
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  3. #3
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    The greater the difference in tire sizes from front to rear, the more understeer you have. As such I would maybe bump the front up one tire size and only add as much tire in the rear as is needed... with nice and new tires, stock width is more than enough for an S52, or a 255 if you go 235 in the front to match the profile of the tires f/r

    18"s will be harder to fit, worse so if your car is lowered. If performance is a concern at all its probably easier and better to stay with 17"s. But there are 18" options out there, though I can't imagine many of them working without trimming your fender liners. I had to trim my fender liners when I was lowered on 17"s. Now with 18"s I merely have a suggestion of once having had fender liners...

    People modify the rear sway bars (I think some people jus disconnect them) to help some of our car's weird suspension behavior on the track. I think some track guys will chime in with some help for that, as I'm not sure the problems you are describing are due to tire choice.

    Going into my TENTH YEAR of providing high quality reproduction BMW fabrics!

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  4. #4
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    s8ilver, What size front tire? wheel size and offset?

    I would like to avoid liner rub or cutting, But a fender role and spacer/aggressive offset is fine by me.

    I'm kinda leaning towards the 17x9 and 245 option....

    But its good fun having an over tired car

  5. #5
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    I'm running 17x9et38 w/ 255 on the front. It just polishes the liner at full lock on one side. Your offset has to be exact.


    /.randy

  6. #6
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    Thanks for the fitment info! what do you have on the rear?

    I'll admit that I'm not a fan of pinching a tire on a rim I'd much rather have the rim be .5-1" wider than the tread face though... I'd be down for a 245 on the front with that rim though

    on a square setup It would be nice to run the same rim front and rear (with spacers) to allow rotation.

  7. #7
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    315/35 on 17x11 et19. Again, stock fenders, and they just polish the inner liner at one spot.


    /.randy

  8. #8
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    Randy.......excuse my ignorance, as Im sure u have told us but:


    thats alot of rear tire( frt too..lol).....is car s/c'd or turbo'd?........I hope it aint a stock engined car........

  9. #9
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    The interior is stock. Not much else. Supercharged, 6sp, 3.46, suspension, etc. The sig pic is 10 years old, those wheels are now on the coupe. A more current picture with these wheels. You may understand the inspiration.



    IMAG0161.jpg


    /.randy

  10. #10
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    I run Apex wheels, 17x9.5 ET35 square with 255/40. The front is quite a tight squeeze. Had to add a 5mm spacer and dial in about -3deg camber to make things fit. If I were to do it all over again, I'd just stick with the 17x9 ET30 and 245/40.
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  11. #11
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    Quote Originally Posted by saber63 View Post
    s8ilver, What size front tire? wheel size and offset?

    I would like to avoid liner rub or cutting, But a fender role and spacer/aggressive offset is fine by me.

    I'm kinda leaning towards the 17x9 and 245 option....

    But its good fun having an over tired car
    18x8.5 up front w/ 235/40. Went 285 out back due to the supercharger, else would have been content with a 255 or 265 for a bit more neutral handling. It still corners pretty darn well.

    Same exact wheels and tire sizes as this article from Apex:

    https://www.apexraceparts.com/blog/p...mw-z3-m-coupe/
    Last edited by s8ilver; 04-16-2018 at 09:32 AM.
    Nathan in Denver

    1999 M Roadster, VFE V3 S/C, Randy Forbes Reinforced, Hardtop, H&R/Bilstein, Apex PS-7, Supersprint
    1999 Z3 2.8 Coupe, Headers, 3.46, Manual Swap, H&R/Koni, M Geometry/Brakes, M54B30 Manifold, Style 42

  12. #12
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    Quote Originally Posted by rf900rkw View Post
    The interior is stock. Not much else. Supercharged, 6sp, 3.46, suspension, etc. The sig pic is 10 years old, those wheels are now on the coupe. A more current picture with these wheels. You may understand the inspiration.



    IMAG0161.jpg
    ahhhhh...those wheels......dare I say halibrand?........ol skool......shelby etc etc etc ..............

    - - - Updated - - -

    Quote Originally Posted by Tim95M3 View Post
    I run Apex wheels, 17x9.5 ET35 square with 255/40. The front is quite a tight squeeze. Had to add a 5mm spacer and dial in about -3deg camber to make things fit. If I were to do it all over again, I'd just stick with the 17x9 ET30 and 245/40.
    255/40 up frt......Im not saying thats wrong but visually Id say it just looks tooo fat.....no?

  13. #13
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    I have 255/40 on the front. I wouldn't want to track or autocross with these clearances, but they do work fine on the street. The car was setup for me and my wife to enjoy, no one else. Hint, the wife's first born is named Shelby.

    Yes, 427 Cobra Halibrand "clones". Or as close as you can get with five lug where the original was a pin drive with 6 pins.


    /.randy

  14. #14
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    very very nice




    always hunting for a used ERA 289 FIA car....

  15. #15
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    255/40 on a 9" rim not "pinching" the tire in anyway. keeps the weight down as well compared larger rim widths

  16. #16
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    Look at 2Forge ZF1 wheels, they are lightweight, cheap and custom order sizes by default.

    Z3 & E36 RamAir systems, send private message for more information.

  17. #17
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    All great discussions!

    I have one question, with most 17x9 wheels in the ET40 range. is it ok to run a ~30mm spacer on the rear? if so what type? (I'll go looking for answers on my own after work)

    Yes, a 255/40r17 on a 17x9 is bang on the recommend wheel width, not really pinched. But my wife and I have found for our personal taste running a rim that is .5-1" wider than the measured tread width gives a much better feeling car than running a narrower rim, Even if it is in the allowed or recommend width. The narrower the rim it is the worse the response is, makes the car feel detached from the road / floaty (in our use cases so far). The wider tire might have better peak grip or lap time.

  18. #18
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  19. #19
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    I would never run spacer, it is not the right way to do it and it is a compromise and there are risks.
    Why not just buy wheels that fit from the get go, you also get the right looks then with proper amount of lip, spokes etc..
    Especially now when custom wheels are super cheap, and when most of the stock wheels can be had anyway with multiple different et's.

    Z3 & E36 RamAir systems, send private message for more information.

  20. #20
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    Quote Originally Posted by Remotion View Post
    I would never run spacer, it is not the right way to do it and it is a compromise and there are risks.
    Why not just buy wheels that fit from the get go, you also get the right looks then with proper amount of lip, spokes etc..
    Especially now when custom wheels are super cheap, and when most of the stock wheels can be had anyway with multiple different et's.
    Using a spacer to allow you to run the same size/spec wheel front and back is great advantage. You r free to rotate wheels, even out wear, etc.

    Also it's almost impossible to get wheels with the correct offsets. And I've never seen "Super cheap" custom wheels.

  21. #21
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    255/40/17 square setup looks and drives like badass IMO. Faster around the track too.

  22. #22
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    My latest set up is 245-40-18 front and 265-35-18 rear, turn in is nice and doesn't snap over steer.

  23. #23
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    I would not worry about using a spacer up to 18mm on rack if you are also using studs. I have been running 5 to 15mm spacers for 17 years on track with zero issues. I use 90mm studs.
    FYI, Amazon has a very good 5 and 10mm spacer kit with studs and nuts for 90 bucks. There was some sort of discount applied. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 The nuts were too long for my needs. Price was right even at full price. Spacers were top grade finish and fit. If you are looking for just a little room, the kit is as good as you will find. I am not related to the seller in any way.
    Dan "PbFut" Rose

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