Wider rear track (or wheel & tire) Bad Idea for racing?

Discussion in 'Suspension And Brakes' started by Alberto521, Jan 10, 2017.

  1. Alberto521

    Alberto521 Well-Known Member

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    164
    Location:
    Chicago, IL
    Vehicle Model:
    Civic Si
    Body Style:
    Coupe
    Hello guys

    My current settup is 17x9 + 35 (plus 25mm spacers, so technically +10) offset. 255/40R17 on front, 235/45R17 on rear.

    As some of yall may know, I got some fender flares (wide zg 3.25in front, 3.75in rear) , i love the fitment on the front, but the back could "use some work".

    i already attempted getting smaller flares for the rear (2.75) but it created absolutely terrible wheel gap, and i could not move it down more because the cuts on the rear fender area would be visible.

    Some people are telling me to get wheels with a more aggressive offset to make them poke out more, or even wider wheel and tire too (or a combination of all)... however, this isnt a show car for stance shows, i actually do track days and autox, eventually i wanna do time attack street preped.

    Would running a wider track on the back create more understeer and make the car harder to rotate?

    Thanks

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  2. Nix
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    Nix J├Âtunn Moderator

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  3. Safe Gabe

    Safe Gabe Well-Known Member

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    Location:
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    Sorry for the late reply -- I'm not as active online these days cause I'm prepping my own car for Global Time Attack in April.

    I wouldn't run anything too aggressive in the rear. I run a 225. It will take 255 forever to heat up and yes, it will take away your car's ability to rotate as it sits. I would recommend maybe running a lower offset in the rear if you're looking to fill the fenders.
     
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  4. Alberto521

    Alberto521 Well-Known Member

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    164
    Location:
    Chicago, IL
    Vehicle Model:
    Civic Si
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    Coupe
    Hey Gabe, thanks for reply.

    So in other words: skinnier tire on rear is good (i run 255 front, 235 rear, 17x9 wheels)

    But my main concern is the overall track width, if my rear is "wider" do you think it will increase understeer? Right now both offsets are +10 (+35 with a 25mm spacer)
     
  5. Safe Gabe

    Safe Gabe Well-Known Member

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    Location:
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    Civic Si
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    Yes, it will increase understeer. The other concern (which you shouldn't really have because of aero, but for the sake of information) is high speed braking. Because you are removing weight from an already light rear end, under high speed braking, you will experience rear end instability. If you watch any of the lapping of the new Civic Type-R, you will notice that upon initial braking and down shift, the driver is fighting the wheel to keep it straight. This problem only gets worse once you've jumped to a staggered setup.

    I think running that +10 front would be fine and something like a +20 in the rear will be enough of an offset to induce oversteer.
     
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  6. Civi9

    Civi9 Well-Known Member

    Messages:
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    Location:
    Houston
    Vehicle Model:
    Si
    Body Style:
    Coupe
    I'd like to revive this thread because I am considering swapping my front brakes to Spoon Sports calipers and 2 piece lightweight rotors. I track 2-4 times yearly, and like to take curves fairly aggressively during daily driving(when safe).

    I have 17x9 +45 RPF1's, and would likely have to use a 20-25mm spacer up front to clear the calipers.

    I've talked with Andy Chen and he warns about the scrub radius becoming too positive with the use of spacers in general, which could affect stability during high speed braking.

    Any other comments on this?
     
  7. webby
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    webby Administrator

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  8. Safe Gabe

    Safe Gabe Well-Known Member

    Messages:
    323
    Location:
    San Francisco, CA
    Vehicle Model:
    Civic Si
    Body Style:
    Sedan
    Sorry for the late reply! I've actually been parting out my car.

    It sounds like you're overdoing it for 2-4 times a year. There was a point where I was driving 2-3 a month, and I was using stock setup. Hell, even competing in Global Time Attack and Super Lap Battle, I was on stock calipers. The car sat on podium at several events on stock calipers. The price for that setup (roughly $1,300 just for the caliper) does not justify if you are only going to be running so little events per year. This cannot be stressed enough - Good tires, brake pads, and fluid. I get that the Spoon setup looks mad tight yo!, but at the end of the day, you should spend that $1,300 on more track days and/or an instructor.
     
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  9. webby
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    webby Administrator

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    Really? Selling the car, or going back to stock,...or??
     

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