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Thread: C4 Frame Project

  1. #171
    Registered Member Troy's Avatar
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    I'm just wondering here, I was told years ago when I was racing go karts that a narrower tire with the same weight transfer load would have more load per square inch than a wider tire. This sounds logical. This always seemed odd to me I can see that there would be more load/square inch on the narrower tire causing more grip, but then the wider tire would have less but load there's more area. Is there some point at which the narrow tire would give you more grip?

  2. #172
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    Although an extreme example of track width that is on my "hacked up" 2900 pound Camaro on a 108 in wheelbase, that of course would not work within a stock body Tri-5. It currently has a front track width of 66 inches 75 in overall, and the rear is 3 inches narrower at a track width of 63 in and 72 in overall. Corners very flat with soft springs, and only a 7/8 inch front sway bar. The rear is only narrower because it was a 1975 Frankland quick-change rear end set-up from a dirt car, but seems to work well. It has a 10.5 4.86 ring gear and is very heavy, but it is so easy to change any of like 75+ different gear ratios in minutes.
    Forgot to add, I'm running 15x10 wheels F/R with a 4 inch backspace and 275/60-15 tires.
    Last edited by 55 Rescue Dog; 04-06-2017 at 03:37 AM.

  3. #173
    Registered Member chevynut's Avatar
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    Quote Originally Posted by 55 Rescue Dog View Post
    Assuming this is 4 different rear axels that are cornering, I would say that the 2nd one on drawing "A" both would transfer the same amount of weight, but the wider tire could achieve most grip of the 4 examples. On drawing "B" the narrow tire would have less load transferred, and maybe perform better, because in bottom drawing it looks like it could lift the inside tire off the ground, and tuck the outboard tire under and flip the car.
    I didn't ask you to compare all 4 scenarios. I asked you to compare the tires in drawing A, THEN the tires in drawing B. Try again.

    In diagram A the tires have the same track width...which will perform better (handling) and why, or are they the same?
    In diagram B, the tires have the same outside width, but the large tires have a smaller track width. Which will perform better, and why?

    You seem to be of the opinion that all that matters is track width, independent of anything else, based on your prior comments. I'm trying to show you how wrong that opinion is, with these two drawings.

    As a car turns, the body rolls, and the weight is transferred to the outside tire, plus you have additional loading from centrifugal force. There is a side load on the tires so the sidewall of the tire allows the tire to flex, with the tire wanting to roll along the outboard side of the tire. That's where most of the force is. The further outboard the side of the tread is, the more the car resists roll-over. The more tire contact patch touching the road the better the traction. That's why an IRS with camber gain in the rear handles better than a solid axle with no camber gain. The camber gain compensates at least partly for the tendency of the tire to want to roll under and reduce the contact patch. The body roll tends to cancel that camber gain, and that's why anti-sway bars are important for good handling.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


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  4. #174
    Registered Member chevynut's Avatar
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    Quote Originally Posted by 55 Rescue Dog View Post
    Although an extreme example of track width that is on my "hacked up" 2900 pound Camaro on a 108 in wheelbase, that of course would not work within a stock body Tri-5. It currently has a front track width of 66 inches 75 in overall, and the rear is 3 inches narrower at a track width of 63 in and 72 in overall. Corners very flat with soft springs, and only a 7/8 inch front sway bar. The rear is only narrower because it was a 1975 Frankland quick-change rear end set-up from a dirt car, but seems to work well. It has a 10.5 4.86 ring gear and is very heavy, but it is so easy to change any of like 75+ different gear ratios in minutes.
    Forgot to add, I'm running 15x10 wheels F/R with a 4 inch backspace and 275/60-15 tires.
    All of that info is pretty irrelevant to this discussion, unless someone wants to hack the fenderwell of their tri5. In that case the wider the tires and the farther they stick out the side of the car the better it's going to perform.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  5. #175
    Registered Member chevynut's Avatar
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    Quote Originally Posted by Troy View Post
    I'm just wondering here, I was told years ago when I was racing go karts that a narrower tire with the same weight transfer load would have more load per square inch than a wider tire. This sounds logical. This always seemed odd to me I can see that there would be more load/square inch on the narrower tire causing more grip, but then the wider tire would have less but load there's more area. Is there some point at which the narrow tire would give you more grip?
    Troy, your argument would suggest that a drag car would run better on narrower rear tires which we know isn't true. Looking at if from a purely physics point of view, friction force is simply the coefficient of friction between the two surfaces multiplied by the normal force (downward loading). Area doesn't factor into it so pounds per square inch of loading is irrelevant. There's more going on there than the simple physics would suggest, and we know empirically that larger tires (with less PSI) have better traction.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  6. #176
    Registered Member BamaNomad's Avatar
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    Quote Originally Posted by chevynut View Post
    Troy, your argument would suggest that a drag car would run better on narrower rear tires which we know isn't true. Looking at if from a purely physics point of view, friction force is simply the coefficient of friction between the two surfaces multiplied by the normal force (downward loading). Area doesn't factor into it so pounds per square inch of loading is irrelevant. There's more going on there than the simple physics would suggest, and we know empirically that larger tires (with less PSI) have better traction.
    This is a very interesting subject for discussion. We addressed this in engineering school and proved that the 'coefficient' of friction between a dragster's tires and pavement is actually HIGHER than 1.0... (implying there is an 'interlocking' effect - beyond friction - between the soft tire and the coarseness of the grip surface..?

  7. #177
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    Quote Originally Posted by chevynut View Post
    I didn't ask you to compare all 4 scenarios. I asked you to compare the tires in drawing A, THEN the tires in drawing B. Try again.

    In diagram A the tires have the same track width...which will perform better (handling) and why, or are they the same?
    In diagram B, the tires have the same outside width, but the large tires have a smaller track width. Which will perform better, and why?

    You seem to be of the opinion that all that matters is track width, independent of anything else, based on your prior comments. I'm trying to show you how wrong that opinion is, with these two drawings.

    As a car turns, the body rolls, and the weight is transferred to the outside tire, plus you have additional loading from centrifugal force. There is a side load on the tires so the sidewall of the tire allows the tire to flex, with the tire wanting to roll along the outboard side of the tire. That's where most of the force is. The further outboard the side of the tread is, the more the car resists roll-over. The more tire contact patch touching the road the better the traction. That's why an IRS with camber gain in the rear handles better than a solid axle with no camber gain. The camber gain compensates at least partly for the tendency of the tire to want to roll under and reduce the contact patch. The body roll tends to cancel that camber gain, and that's why anti-sway bars are important for good handling.
    I don't know Cnut, but it has been an interesting discussion, and has made me think of a few things I hadn't considered like the effect wheel width has on track width regardless of tire size. I checked the front of my C4 that has some temporary 7 in wide zero offset wheels on it, and it also has an outside width of 68 inches, but the track width is 61 inches. So, that has me re-thinking my wheel width choices, since that has a direct impact on track width for any given tire size. In my case if I go with a 255/45-18 tire that has a rim width range of 8-9.5 inches I think it would work better with the 8 in wheel versus the 9.5. Maintaining an overall width of 68 inches, the track width would be 60 inches with an 8 inch wheel. With a 9.5 in wheel the track width would decrease to 58.5 inches with the same width tire. I never really thought about it that way before. So, without testing, it will be a compromise, or lucky guess. Running the stickiest tire you can get is another piece of the puzzle, along with the most important part...the driver.
    Sway bars are a completely different discussion, since they increase spring rate and load the outboard tire too.
    Last edited by 55 Rescue Dog; 04-06-2017 at 02:47 PM.

  8. #178
    Registered Member chevynut's Avatar
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    You need to quit getting hung up on track width alone imo. What does a car "flip" around? It's the outside of the outside tire. The best performance is going to be with the stickiest rubber on the widest tire with the tire edge pushed out as far as you can go. That's really what you did on your Camaro. We have to work within the confines of the body too, unless you're willing to cut it up which most guys aren't. Track width is just another measurement, but where the tire actually contacts the road is what matters.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  9. #179
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    Quote Originally Posted by chevynut View Post
    You need to quit getting hung up on track width alone imo. What does a car "flip" around? It's the outside of the outside tire. The best performance is going to be with the stickiest rubber on the widest tire with the tire edge pushed out as far as you can go. That's really what you did on your Camaro. We have to work within the confines of the body too, unless you're willing to cut it up which most guys aren't. Track width is just another measurement, but where the tire actually contacts the road is what matters.
    I could have used a little more track width on my VW GTI at an autocross when I had both inside tires 3 feet in the air. I somehow managed to save it, but it sure got my attention. And my point was that within the confines of the body, the wheel width affects track width regardless of tire size, and it wouldn't matter if the tire was 2 feet wide if it totally unloads the inside tire off the ground and over you go.
    In my case I had way too much grip on skinny 185/60-14 DOT autocross tires. I understand how tires look is important, but from the side view they all look the same width to me.
    Last edited by 55 Rescue Dog; 04-06-2017 at 03:30 PM.

  10. #180
    Registered Member BamaNomad's Avatar
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    A lot of people would say that a 'narrow' car, with obviously narrower track width, has an advantage in an autocross (at least most of them I've seen which seem to be set up for narrow/small Euro cars)... I know that the big butt C4 Corvettes (ZR1s) are at a disadvantage regardless of the wider track width!

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