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Tire size. Think I made a decision

Discussion in 'Wheels/Tires/Brakes' started by 8ballBooker, Feb 13, 2019.

  1. 8ballBooker

    8ballBooker Member Established Member

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    Alright guys, after countless hours of searching sizes, reading posts, making a spreadsheet, and playing with the tire calculator, I think I FINALLY figured it out. I really, really want to keep tires under $750 give or take.

    During my quest, ive disassociated with family, lost work productivity, and said good by to long term friends. Its time I admit I have a problem and to seek help.


    20x10 40 offset
    20x9 24 offset

    1.2 vogtland drop

    Drum roll.....
    285/35
    245/40

    Thoughts? Any potential rubbing issues?

    In all seriousness, it's driving me nuts looking at all the different options. Its so damn hard trying to find pictures and getting an idea, because of the angle of pictures and that you cant physically walk around a picture.

    Any help or suggestions are appreciated. Screenshot_2019-02-13-11-54-18.jpeg Screenshot_2019-02-13-11-51-35.jpeg Screenshot_2019-02-13-11-50-37.jpeg

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  2. Discount Tire

    Discount Tire Authorized Vendor Authorized Vendor

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    I don't have any photo's to share from different angles, but from a fitment standpoint, the purposed set-up should fit great.

    What tire/wheel set-up are you running currently?
     
  3. 8ballBooker

    8ballBooker Member Established Member

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    Right now its stock, 225/60 r17, I believe. Think its 27" height.

    Still searching for tires, but have it narrowed down to a few:

    Probably:
    Nitto 555 G2
    Hankook ventus v12 evo2


    Maybe:
    Firestone indy500
    Sumitomo HTRZ
    General gmax as05

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  4. Discount Tire

    Discount Tire Authorized Vendor Authorized Vendor

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    Your O.E. wheels are 7-inches wide with a +40 offset.

    So compared to the stance now, the 20x9 ET+24 will sit just over 1.5-inches further outwards and the 20x10 ET+40 will sit 1.5-inches further outwards.

    You can use these dimensions to gauge where the new assemblies will sit.
     
  5. Norm Peterson

    Norm Peterson Member Established Member

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    255/40 would be a slightly better diameter match for 285/35's.


    Norm
     
  6. 8ballBooker

    8ballBooker Member Established Member

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    Is it normal to have the front tire slighty larger than the rear? I know some guys drop the rear more. The other recommended size was 275/35, 245/40. Id like to balance the car out and have equal wheel gap if possible.

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  7. Norm Peterson

    Norm Peterson Member Established Member

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    The "perfect" diameter match for a 285/35 ends up being something like 250/40, which nobody makes. Either side of 250 - 245 or 255 - would be OK, but most OE staggered setups for UD Domestic cars have been with smaller amount of stagger. Ford has typically used a 30mm nominal difference except for the GT350, Chevy has leaned more toward using 20mm in the Camaro.

    I doubt you'd ever notice the difference in tire to fender gap, as it's only about 3/32" if the tires measure out to exactly what their nominal sizes calculate it out to. It'll change more than that due to tire wear, since staggered setups can't be rotated front to back anyway.


    Norm
     
  8. 8ballBooker

    8ballBooker Member Established Member

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    Norm, since 255/40 is expensive and a difficult size to find, what other options do you think.

    275/35 250/35?
    285/30 250/35?

    Im really starting to doubt staggard, but I got such a killer deal. Just concerned about rubbing while still looking good.

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  9. Norm Peterson

    Norm Peterson Member Established Member

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    Your best bet on tire sizing given your rim widths and the lowering may well be 255/35-20 up front and 285/30-20 out back. Both of those sizes are very close to 27" diameter, which was common for S197 Mustangs (meaning less likely to rub than 28" diameter tires) and within tire industry-recommended tire to wheel fitment guidelines. They're also of identical load capacity to typical S197 OE tire sizes, so there need be no adjustments to the car's recommended inflation pressure.


    Norm
     
  10. 8ballBooker

    8ballBooker Member Established Member

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    Cool, that seems like a pretty popular combo. Question about rubbing, Is it safe to assume people are talking about the tire jumping up and hitting the plastic in the wheelwell, and not the fender? I assume hitting the fender would be very wide tires and could tear them apart unless the fenders are rolled.

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  11. Norm Peterson

    Norm Peterson Member Established Member

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    Where any rubbing might occur depends on several things, amount lowered, wheel width, and offset in particular. Up front, offsets that are too much positive can put the tire or even the wheel into the strut. Not enough positive is what gives "poke", where the rub is on the sheetmetal side (anything from brushing the inner plastic to direct tread to sheetmetal contact). Out back, too little +offset puts the outer edge of the tire outside the fender. Unfortunately, I don't have much feel for what the offsets for 20" wheels should be, or what they could be without rubbing. Or how much clearance you want there to be (except that it's almost certainly more than I'll run).


    Norm
     
  12. Chuckieduck

    Chuckieduck Member Established Member

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    I would not do less than a 275 on the front. If you drive your car often your going to want to rotate your tires so going squared would be the best option. You can fit a 285/35-20 on the front with a 20x10 with a 40 offset. That is what I currently run on the front right now and only have rubbing at full lock. I ran 285 squared set up until I changed to 315s on the back.
     
  13. 8ballBooker

    8ballBooker Member Established Member

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    Yeah, I have staggard, 20x10, 20x9. In hindsight, I would've/should've gone square, and less than 20'. BUT, I got the foose rims for $78 each on black friday. All together, this set up is running me less than $1100 for everything brand new. Ot was kinda this or nothing since I couldnt afford $2000.

    I played around with calculators last night and with Norm's suggestion, and the offset, 285/30, 255/35, will be even all around. Just hoping with the 1.2 drop, it will take care of the 4x4 look and not look goofy and lifted with 20's.

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  14. KBBoss302

    KBBoss302 Active Member Established Member

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    Did I miss why are you so concerned with having the tires the exact same height? If it was an AWD car, I would understand. Maybe you should consider the 255/35 front and 285/35 rear combo.

    Heck, you could even do 275/35 front and 285/35 rear which keeps the diameters close. I know a 275 is maybe slightly wide for a 9" wheel and might give you less than optimal steering feel, but it's within spec for the tire.
     
  15. Norm Peterson

    Norm Peterson Member Established Member

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    The ABS system only has so much tolerance, and the number most commonly mentioned seems to be 3%, which is enough to cover replacing worn-out tires at one end of the car at a time.

    What can happen is that the ABS module could see the front wheel rpms dropping too fast relative to the rear wheel rpms if the new amount of tire stagger is too much different from whatever the ABS system was calibrated to. In a hard stop, that might mean releasing the front brakes at a particularly bad time if the ABS system didn't take itself offline (usually this throws the ABS light in the instrument panel at you, but I wouldn't want to have to count on this always being the case).

    Some cars are more sensitive about this than others, but this very situation came up recently on another forum that I belong to. The guy ended up having to change out his new set of tires.


    Norm
     
  16. KBBoss302

    KBBoss302 Active Member Established Member

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    Hey Norm - thank you for that reply but there are a ton of guys running things like 305/35/20 and even 315/35/20 with much shorter front tires and no ill effects. On my Boss, I have personally run a 285/30/20 and 305/30/20 combo with zero issues and even tried out a 285/30/20 and 285/35/20 combo for a while (the PSS 305s were rubbing with 10.5 ET45 wheels and lowered about 1.5" on KW V3 coilovers).

    I do not know what the size differential threshold for triggering ABS issues but I suspect it's much greater than we realize.
     
  17. Norm Peterson

    Norm Peterson Member Established Member

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    Exactly. We don't know where it is, and those in a position to know aren't saying.

    We just don't know what the tolerance is, what design conditions result in it stepping in, or how constant it might be from one year to the next, or among different trims in the same year. Straight line braking? Braking while steering? Don't forget that on the 2011-up you've got stability control placing additional demands on the ABS calibration.

    Except for those who actually have encountered this problem - and this has happened - we're somewhere between guessing and hoping here. Though 3% does have some legitimate backing (meaning from sources more reliable than marque-centered car forums such as this one).


    Norm
     
  18. 8ballBooker

    8ballBooker Member Established Member

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    I think im in a position where Id like to get the tire gap much lower than stock and close to even with the front while not having a ton of (or any) rake. The 1.2 drop seems to be pretty conservative. I find suspension and tires to be a tad frustrating, because the end result seems to be a guessing game unless you are at a car show or find a friend that has close to the same set up that you are looking to do.
    At least with that, you can see it from all angles, get down on one knee, etc...

    Sadly, pictures can only do so much.

    I know this, on a staggered set up with a 20x9 rim, I think 255/35 is a safe bet. The rear is tough tough. I know companies make drop packages where it drops the rear more than the front. Mine is going to be 1.2 all around, just down want a huge gap where the tire just looks to small in the rear.

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  19. Gunney

    Gunney New Member Established Member

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    Hello Norm, I read your January post on tire sizes!
    Jeez, it gives me little brain a headache.
    I’m looking at a set of Foose chrome wheels and 20”
    Tires all around on line and they are: 255/35/20 for the front and : 285/30/20 for the rear and that’s what you say will work. Agree?
    Thanks, Ray
     
  20. Norm Peterson

    Norm Peterson Member Established Member

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    Depends on the widths of your wheels, where you'd want to keep a 1" difference in width.

    That'd be a good choice for 9" & 10" wide wheels. At least OK with 9.5" and 10.5" wides.

    255/8.5" and 285/9.5" would be technically "do-able", but those are "minimum recommended" wheel width/tire combinations - not something I'd ever recommend for a sporty/muscle car.


    January post???

    Norm
     
    Last edited: Jul 20, 2019

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