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Thread: Tire Sizes: Help a Noob!

  1. #1
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    Tire Sizes: Help a Noob!

    Tell me about tire sizes: Is a "staggered" setup a good thing on the track? If not, what about equal tire widths all the way around?

    What is the cost/benefit of having unequal tire sizes?

    I know at the very least, it doesn't make economic sense to purchase two different sizes of tires...

    Any other tips or curiosities I couldn't even think of?

  2. #2
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    On a BMW, a staggered is almost always worse than a square setup. They want the street cars to understeer on purpose to keep shitty drivers alive longer.

    Plus a square setup allows you to rotate tires around the car easily to maximize wear. You can even rotate the spare into things. I even ran equal tires on staggered rims. It's what I had. That would still handle better and I could remount them to move them around the car.

    Don't go for an overly wide tire for the rim. The more you stretch the tire on the rim, the less sloppy the handling, and the less camber it will require.

    I would look for separate rims as wide as will fit. Then choose a tire that it not crazy wide for the rim. You will probably need aftermarket wheels for this. Check out Apex Arc-8s. Very inexpensive with a lot of sizes available. If you car is staggered already, check eBay to see if you can get two more rear wheels.
    Last edited by PCarroll; 04-10-2012 at 08:02 AM.
    Peter Carroll - http://www.driversmeeting.com/pcarroll
    BMW Club Instructor & Club Racer, 1997 BMW M3 GTR #321
    2008, 2009, & 2011 BMW CCA National C-Mod Champion

    Videos channels at:
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  3. #3
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    Quote Originally Posted by PCarroll View Post
    On a BMW, a staggered is almost always worse than a square setup. They want the street cars to understeer on purpose to keep shitty drivers alive longer.

    Plus a square setup allows you to rotate tires around the car easily to maximize wear. You can even rotate the spare into things. I even ran equal tires on staggered rims. It's what I had. That would still handle better and I could remount them to move them around the car.

    Don't go for an overly wide tire for the rim. The more you stretch the tire on the rim, the less sloppy the handling, and the less camber it will require.


    I would look for separate rims as wide as will fit. Then choose a tire that it not crazy wide for the rim. You will probably need aftermarket wheels for this. Check out Apex Arc-8s. Very inexpensive with a lot of sizes available. If you car is staggered already, check eBay to see if you can get two more rear wheels.
    I'm sorry, do you mean, "the more sloppy the handling" instead?

  4. #4
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    Don't go for an overly wide tire for the rim. The more you stretch the tire on the rim, the less sloppy the handling, and the less camber it will require.
    Quote Originally Posted by MikeLenoch5 View Post
    I'm sorry, do you mean, "the more sloppy the handling" instead?
    Peter is correct, if I may recapitulate his thoughts: The same size tire on a slightly wider rim will result in more crisp handling (less sloppy handling) and require less negative camber compared to the same size tire on a narrower rim. "The more you stretch the tire on a (wider) rim" means placing a tire on a wider rim than it is normally fitted. This is stretching the beads apart (left to right). The contact patch of the tire is about the same size, but the sidewalls will have additional support.

    I hope I explained this to Peter's satisfaction.

  5. #5
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    You in the Chicago area..come along to the Car control clinic and Autocross school with the BMWCCA. You will have several E30 owners to show you some options.

    http://www.windycitybmw.com/

  6. #6
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    The contact patch of the tire is about the same size, but the sidewalls will have additional support.
    In fact... the contact patch will be slightly wider on a stretched tire. By pulling the bead outward, you are laying more of the tread on the road for a wider contact patch. Conversely, if you pull the bead in on a narrow rim, you are pulling the tread up off the road making it an effectively narrower tire.

    For more on this concept... see: http://www.autotek.fi/pdf/PSCTires.pdf
    Peter Carroll - http://www.driversmeeting.com/pcarroll
    BMW Club Instructor & Club Racer, 1997 BMW M3 GTR #321
    2008, 2009, & 2011 BMW CCA National C-Mod Champion

    Videos channels at:
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  7. #7
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    Quote Originally Posted by SunzOut View Post
    You in the Chicago area..come along to the Car control clinic and Autocross school with the BMWCCA. You will have several E30 owners to show you some options.

    http://www.windycitybmw.com/
    Been there done that... no joke! Besides, they don't want people there who've done it before!

    I'll be at Majestic Star Casino in South Bend, Indiana for an SCCA Autocross this coming weekend. Went to the Tire Wall Day/free track day at Blackhawk this weekend, and went to Putnam for a track day last weekend.

    Building up my credentials!

    Edit: In fact, SunzOut, were you at the Car Control Clinic last year with your yellow Z3? If so, I saw you there then!

    Quote Originally Posted by davejff50 View Post
    Don't go for an overly wide tire for the rim. The more you stretch the tire on the rim, the less sloppy the handling, and the less camber it will require.


    Peter is correct, if I may recapitulate his thoughts: The same size tire on a slightly wider rim will result in more crisp handling (less sloppy handling) and require less negative camber compared to the same size tire on a narrower rim. "The more you stretch the tire on a (wider) rim" means placing a tire on a wider rim than it is normally fitted. This is stretching the beads apart (left to right). The contact patch of the tire is about the same size, but the sidewalls will have additional support.

    I hope I explained this to Peter's satisfaction.
    I just thought it was a typo because wouldn't you want a less sloppy-handling car?
    Last edited by MikeLenoch5; 04-10-2012 at 07:11 PM. Reason: Automerged Doublepost

  8. #8
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    I just thought it was a typo because wouldn't you want a less sloppy-handling car?
    Nobody wants sloppy handling. I think you're misreading my point...
    Peter Carroll - http://www.driversmeeting.com/pcarroll
    BMW Club Instructor & Club Racer, 1997 BMW M3 GTR #321
    2008, 2009, & 2011 BMW CCA National C-Mod Champion

    Videos channels at:
    http://vimeo.com/pcarroll/videos
    http://www.youtube.com/user/pc270


  9. #9
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    Quote Originally Posted by PCarroll View Post
    Nobody wants sloppy handling. I think you're misreading my point...
    That's what I said! "Less sloppy-handling," non-sloppy handling! I don't know how else to express this! I know it is preferable to NOT HAVE SLOPPY HANDLING!

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