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Thread: juanone 289 carbuild 17

  1. #21
    Hi Ralph:

    Rick and I will leave Louisville at about 7:15 on Sunday and however long it takes to get there. I will talk to Rick tomorrow.

    Juan

    Juan Lopez-Bonilla
    Kentucky Cobra Club
    2432 Crittenden Drive
    Suite 201
    Louisville, KY 40217
    502-635-5711
    juanlb@lbrllc.net

    http://www.kentuckycobraclub.com

  2. #22
    Join Date
    May 2004
    Location
    Clinton, TN, USA.
    Posts
    1,287
    Juan, Pulling a trailer I'll figure on 10:30 -- 11:00 Look forward to seeing you hope I can make it and nothing comes up.

    Ralph

  3. #23
    Join Date
    Nov 2003
    Location
    Mississippi Gulf Coast and Central Florida
    Posts
    2,153
    Rick,

    Great points, but as I mentioned, "I will be checking to see if" they fit, and I would use 295/50s not 295/60s (are 295/60s available?). Interestingly, I suspect that the 295/50s, though wider, will fit better than the 275/60s, due to their smaller diameter. However, I realize that either just might not fit...

    If it is an engineering issue, then they likely have put that spec in place with some amount of "safety factor," but the question is, "How much?" You point out the empirical evidence that points to it working for many FIA cars. No question about that. Though, as an engineer I just have to wonder how close it is to tolerance. I have worked in "life-safety" situations in the past, and I can tell you that it can keep you awake at night wondering if you've crossed every T and dotted every I.

    I asked Maurice about wider tires on the FIA car, and if I recall correctly, he said that wider tires will fit in the rear, though I cannot remember exactly what size he mentioned. Thoughts Alan?

    Also, Lynn Park suggested the 275/60s for the rear (is that what he has on his original?)

    It seems that I recall, somewhere on this site, a discussion about someone running 295/50s on the FIA car without issue. This would be a great time for anyone with first-hand knowledge of this to speak up .




    Paul

    289 FIA

    2899464

    408 Windsor

    Toploader (wide)

    3.07 rear


  4. #24
    Join Date
    Dec 2003
    Location
    Rogers, AR, USA
    Posts
    577
    Paul,
    Above when I mentioned that 275's wouldn't "fit" I was referring to keeping the tire inside the line of the fenderwell. A 295 tire will physically work on the car, but you'll get that low rider look with the tire outside the well.



    Brian Carlson

    Unique 9122 - 289 FIA Cobra - The Legendary "Spence" Car

  5. #25
    Join Date
    Nov 2003
    Location
    Mississippi Gulf Coast and Central Florida
    Posts
    2,153
    Sorry for such a long post[8D]!

    I called and spoke to an engineering guy at Yokohama, and while he could not tell me exactly why it was bad practice, he indicated that both performance and safety would suffer. He admittedly was unable to indicate how much. He asked me to submit the query through a written question via email to provide time for him to do some research on the subject. I will post his response when I receive it.

    In the meantime, I have been examining the Yokohama document I referenced above for some indication of the way they are determining the rim width range specs. It appears that on the 60 series tires they are pretty consistent with the width range of 1/2" less and 1.5" more than the measuring rim width to get the range spec (see below for an explanation of measuring rim), though there is some variation to this.




    Here is what Tire Rack says about rim width range (By the way, the measuring rim is a standardized rim width that comes from the Tire and Rim manufacurer's ASsociation, or TPA, for a specific tire size. Each tire size has a standardized measuring rim.):

    Rim Width Range
    Because tires have flexible sidewalls, a single tire size will fit on a variety of rim widths. A tire's rim width range identifies the narrowest to the widest rim widths that the tire is designed to fit. The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim. NOTE: Because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.

    The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".

    For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its range, the tire's approximate section width would change as follows:

    Difference from---|--Rim Width--|---Approximate Tire
    Measuring Rim----|-------------|----section width
    __________________________________________________ ______
    0.5" narrower-----|---5.5"------|-------8.03"
    Measuring Rim----|---6.0"------|-------8.23"
    0.5" wider--------|---6.5"------|-------8.43"
    1.0" wider--------|---7.0"------|-------8.63"
    1.5" wider--------|---7.5"------|-------8.83"

    Because of the different wheel widths used in the above example, there is a 8/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages

    Additionally, some vehicle manufacturers and tire companies have permitted rim widths that are not within the tire's original approved rim width range. For example: BMW has combined 235/40R17 sized tires on 17x7.5" rims (which are 0.5" less than the narrowest 8.0" wide rim listed for the size) on certain M3 models; and Chevrolet has combined P255/50R16 sized tires on optional 16x9.5" rims (which are 0.5" wider than the 9.0" wide rim now listed for the size) on certain Corvette models. While these applications have received the approval of the vehicle and tire manufacturers, staying within the approved rim width range helps assure that the tire's internal stresses are within its design parameters.


    Back to me... it appears that the change from the 9" to the 9.5" rim on the 255/60s would only increase the section width of the tire from 11.1" to 11.3", which hardly seems it would be an issue. We'll need to hear from Yokohama on this.

    Anymore thoughts?

    Anyone running larger tires on the back of the FIA?


    Paul

    289 FIA

    2899464

    408 Windsor

    Toploader (wide)

    3.07 rear


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