18" front wheels with a wide tire

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by dcozzi, Sep 5, 2020.

  1. dcozzi

    dcozzi Veteran Member

    Messages:
    4,232
    Likes Received:
    1,202
    Joined:
    May 1, 2002
    Location:
    Phoenix, AZ
    Who has them and how did you get them to fit? I am in the 115 degree garage with a sizing tool and they do not seem to fit because the large diameter of 18" tires. Most are 26"+ and they will hit the back and front of the painted body. I am trying to fit a 275/40/18 but the section width makes it too wide to clear.
    I see all sorts of guys running 275/35/18s and stuff with stock sub frames but, did they have to cut the bottom corners off like when you put big tires on a truck?
    I have no issues cutting or removing the inner fender but, I really do not wish to cut any painted surfaces.
    The car is not aligned yet. Maybe set the alignment with as much caster as i can get first then try to size the tire/wheel combo?
    I know I could use a smaller tire and call it good but, I can fit a 335/30/18 rear so a 235 front is no bueno unless you want to push so hard you'll need a turning brake.
    Also, does the wheel clear the UBJ or do you have to stop there on the backspacing?
    Any input is appreciated.
     
  2. dcozzi

    dcozzi Veteran Member

    Messages:
    4,232
    Likes Received:
    1,202
    Joined:
    May 1, 2002
    Location:
    Phoenix, AZ
    I was told 9 inches is probably max for a wheel. Tire will have to follow suit.
     
  3. Schubitzky

    Schubitzky Veteran Member

    Messages:
    354
    Likes Received:
    23
    Joined:
    Mar 10, 2003
    Location:
    Maryland
    I have run 275/35/18 on a 9.5" wheel w/ 6" BS on the front. I did not have to modify the inner/outer fender at all other than I use pan head bolts to hold them together. The car does have PTFB upper and lower control arms and other than a slight rub on the sway bar (which I could fix because those arms have adjustable steering stops), no other interference. I have run up to 10 degrees of caster, but with the new 8 degree spindles I put on this year, I'm running 7.5 to 8 degrees. I am running about -3 degrees of camber. Hope that helps.

    edit: I ran one event with a 285/30/18 on the same 9.5 wheel, but I didn't like it. Too pinched and the inner fender was slicing into the sidewall slightly.
     
    Last edited: Sep 8, 2020
  4. G72Zed

    G72Zed Veteran Member

    Messages:
    3,099
    Likes Received:
    1,556
    Joined:
    Sep 8, 2015
    Location:
    Canada
    Sorry for the highjack dcozzi.

    Schubitzky, may I ask who makes those spindles, would assume they are the PTFB.com ones?

    Bet you have killer front grip on turn entry with 8* + Caster and 3* - camber....nice set up, and the quote I would use is "proof is in the pudding" in this case.

    Now back to the regular scheduled program
     
  5. Schubitzky

    Schubitzky Veteran Member

    Messages:
    354
    Likes Received:
    23
    Joined:
    Mar 10, 2003
    Location:
    Maryland
    Yes Sir, they are the PTFB spindles. New castings, bigger later year bearings, 8* KPI, and improved Ackerman. They can also be ordered already modified for bigger brakes.

    Front grip is awesome. I had to build a big spoiler to help with the balance because the front grips so good.
    118531658_10101508042976980_434534307759285235_n.jpg

    */end thread hijack
     

    Attached Files:

    G72Zed likes this.
  6. dcozzi

    dcozzi Veteran Member

    Messages:
    4,232
    Likes Received:
    1,202
    Joined:
    May 1, 2002
    Location:
    Phoenix, AZ
    What brand tire are you running? Looks, like going from a 40 aspect to 35 makes a tire like the Firestone Firehawk Indy 1.1 inches shorter . That would help a lot.

    Unfortunately, mixing aftermarket parts, like you and me are both doing makes accuracy real difficult. I made it even worse since I have Lateral Dynamics UCAs and RideTech LCAs with stock spindles. It's a suspension melting pot down there.

    I was told to run 7-8* Caster with -2* camber and 1/32 to 1/16 toe in. Pretty close to your settings.
     
    Last edited: Sep 9, 2020
  7. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

    Messages:
    16,485
    Likes Received:
    1,270
    Joined:
    Mar 25, 1999
    Location:
    San Jose, CA, USA
    The contact point for tires tends to be the lower rear of the front fender, especially when turning the wheels.
    I ran a 265/45/16 (~10" width and ~26" diameter) on 16x10 with 5" BS the front of my car and had all sorts of contact issues on the street.
    The 285/35/18 is bigger in all directions

    I'd be looking at something like a 245/40/18 on the front - same size as the Standard C7 front tire, so you know they'll be around for a while.
     
  8. Schubitzky

    Schubitzky Veteran Member

    Messages:
    354
    Likes Received:
    23
    Joined:
    Mar 10, 2003
    Location:
    Maryland
    I ran the Bridgestone RE-71 in a 275/35 and now the Yokohama A052 in the 265/35, although they're basically the same size physically.

    You should be good with those settings, especially if you plan to autocross. Its usually better to run 0 toe or slightly out for autocross. for a street car only, that may be a bit aggressive on the camber, try more like -1.
     
  9. dcozzi

    dcozzi Veteran Member

    Messages:
    4,232
    Likes Received:
    1,202
    Joined:
    May 1, 2002
    Location:
    Phoenix, AZ
    These are the suggested settings I got from Mary Pozzi. They may be for autocross.
    "toe-in for the front (1/16" to 1/32"), about 2* negative camber, and as much positive caster as you can get (usually about 6.5-7.5*)"
    She was nice enough to point me in the right direction on dealing with my stock sub-frame limitations. The 265 and 275 35 series are pretty beefy with about 10" of tread so, I'm sure they will do the job. Thanks for the recommendations.
     

Share This Page