Doing abit of work to my car.. new wheels = new brakes?

Discussion in 'OT Driven' started by narcisis, May 17, 2006.

  1. narcisis

    narcisis New Member

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    Hi guys,

    I'm doing abit of work to my car and I'm pretty new to this, so please, excuse my auto-ignorance. You see I'm getting some new wheels soon and I keep hearing because of the increased weight in the rim I'm going to need better brakes. What would this consist of? Just replacing the brake pads and rotors? Or something further?

    Also, most sites I goto only display 17 inch rims for my ride, some display 18, but the point is my car is designed for 17 inches so thats what I usually find on websites after putting in my car info. However I'm getting 19's, do you guys think it'll fit if I just get some lowprofle tires to compensate for the larger rim?

    Many thanks for any help given! [​IMG]
     
  2. Peechka

    Peechka Peaches and Cream

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    Thats a load of Bs they fed you, dude.

    the only reason you would need new breaks, as in larger rotors and reak calipers and shit, is if you increased the powerplant of the vehicle (like adding 100 horses), or significantly increased the weight of your vehicle.

    Keep in mind that cars are designed for a particular size rim and tire. Back when I designed chassis suystems for ford, we used to do wheel jounce studies, which was taking a certain size rim and tire, and putting it into the maximum motions of the suspension. This then gave us a "zone" that the sheetmetal and exterior designers had to stay out of, so all the sheetmetal like the body side, the wheelhouse inner and wheelhouse liner were all designed for that particular tire and rim size.

    So if you change your rim size and tire significantly you could run into trouble in turning radius, when your car hits an extreme pothole, or whatever. But you could use a 19" rim if you keep the tire profile down so that it still fits within the factory wheel and tire space. So just measure the diameter of your stock tire at the centerline, and just dont go over that diameter when you purchase your new rims and tires, or at least try to keep thm close.

    Also your speedometer migt not work correctly. It all depends if your speedometer is driven off of your trans or from one of your front or rear wheels.

    But breaks? I dont think so. The only reson I could think of is the new rim somehow interferes with your breaks somehow, which I doubt.
     
  3. machine81

    machine81 New Member

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    Changing the wheel size will ABSOLUTELY change the way your car handles and brakes. By increasing the wheel's diameter you're messing with its MOI (Moment of Inertia). The mass of the wheel is spinning further from the center of its rotation. Therefore it takes more energy to start and stop it moving. Do you absolutely need bigger brakes? Not necessarily, but they wouldn't hurt. Going from 17" to 19" isn't that big of a jump so it shouldn't impact your braking too much. Will it take you longer to stop, yes, but by how much is a very difficult question to answer.



    Another thing to consider is rolling circumference.

    Circumference = 2*pi*radius

    You need to maintain the original circumference of your wheel-tire combination the best that you can. The engineers at the factory had many things to consider when they determined the car's wheel-tire combination. If you have ABS or traction control these will get screwed up by a different circumference tire. Also, your speedometer could also be affected. And as mentioned before, fitment in the wheel housing is also a concern.
     
  4. narcisis

    narcisis New Member

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    Wow you guys are helpful :)

    Thats a good idea, the measuring my current tires to see if the low profiles will fit with a bigger rim. Whats a good space amount to have between the tire and well wall? I don't want to scrape the walls, I have a few buddies who just HAD to have 20 inch rims, now every turn or bump they hit you hear rubber against well wall.

    Whats your opinion on a wider tire? I really have no knowledge of the subject so I did some research. I've found there's plus 0, 1, 2, and 3.. I think :) . I was thinking around a +2 lowprofile tire - but then again I don't want them sticking out THAT much from the car.

    I was looking to get this.. 19x8
    http://www.discountedwheelwarehouse.com/Store_Detail.cfm?ID=120138&InfoID=2505&ShowLarge=True

    Currently I have this (the top one).. 15x6
    http://www.car-stuff.com/performance/quote.php?make=3&year=1995&model=12&brand=1396&part_name=541&skipped=true

    Look good? :dunno:
     
  5. machine81

    machine81 New Member

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    You're dubbing out a Buick LeSabre? :ugh2:
     
  6. Peechka

    Peechka Peaches and Cream

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    Speaking to a couple of engineers at work, yes you are absolutely right. If the radius is increased it means your hub will be higher off the ground and therefore it will take more force to stop the car. I was totally wrong.

    But they also mentioned that adding 1-2 inches woudnt do crap for breaking performance, other than maybe having to replace your breaks sooner.
     
  7. narcisis

    narcisis New Member

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    haha no - i'm putting 19's on it. :)
     
  8. machine81

    machine81 New Member

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    Cuz that's SO much better :ugh: Not what I'd do, but hey, it's your car.


    So, you're looking to go from a 15" to a 19" wheel? That's a significant jump. You're going to need some seriously low-profile tires on that thing. Buicks have good suspension, but you're really going to harsh-up the ride of that thing.
     
  9. machine81

    machine81 New Member

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    Also, you're talking about going from a 6" width to an 8". I really doubt that wheel would fit in the housing.

    Why not just spend the $2,000 on a better car? :mamoru:


    (I've owned two Buicks so I can't give you too much crap)
     
  10. machine81

    machine81 New Member

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  11. narcisis

    narcisis New Member

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    Well I went outside to measure it, the stock rim is 15 inches, with 5 inches of tire from the wheel edge to the tire edge, so double that for the opposite side.. = 25 inches total diameter of wheel+tire. So if I get a 19 inch rim my tire can be a maximum of 3 inches (for one side, total of 6, 19+6=25). I'd think low profiles are smaller than 3 inches to start with, since my stock was 5.. then again I dont know - is that right? :dunno:

    EDIT: And as for the suspension, I'm getting air-shocks.
     
    Last edited: May 18, 2006
  12. machine81

    machine81 New Member

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    What car, exactly, do you have?
     
  13. narcisis

    narcisis New Member

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    95 Buick LeSabre :bigthumb:
     

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