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18" 235 or 245 Front tyres?

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  • #16
    Originally posted by exdos View Post
    Not all drivers are the same.
    Is this a subtle way of saying I suck
    Ex 2001 S54
    New cars:
    Lotus Carlton
    350Z

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    • #17
      The ACS Flippers are a nice cosmetic addition, nothing more unless perhaps at very high speeds where it would be difficult to detect. Comparing these small bits of plastic to a proper aeroplane that is gliding in the air so can be adjusted with even the slightest of tail movement or a sail to move a [floating] boat is a bit tenuous.

      With the ARB, I would agree that the softest setting is firm enough. I sometimes feel it could do with being a bit softer, somewhere in between the factory roll bar and the H&R and run stiffer springs.

      No point going for too much of a staggered setup if you can fit a 245 fine; fit one if you can (I have run a 245/40/17 up front fine).

      I've swapped the top mounts, turn in in so much better and low speed understeer much reduced. I just wish I didn't have to run so much camber though for the tyres and tramlining (although it's not actually as bad as I thought it'd be).

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      • #18
        Somebody really should do some maths around the effect that the front flippers have. It's a relatively simple problem to look at them in isolation - You just need to find an "average" cross section and do a complex (I.e. imaginary numbers, not difficult!) integration around the whole wing, and then split it with the starting eddy (which drives the downforce calculation) when you move it.

        However, while I can remember the theory, I'll be damned if I can remember how to do the maths. We need to find some maths / fluid mechanics graduate to do it for us. Might even be quite a neat project if we can find a PhD who wants to do some fluid dynamics. Anyone work in a university?

        Jez
        1998 Cosmos Black - Not quite standard ...

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        • #19
          Originally posted by MGR View Post
          Is this a subtle way of saying I suck
          No. If I wanted to say "you suck", I would say so directly in those words.
          /// Exdos ///
          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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          • #20
            Originally posted by c_w View Post
            Comparing these small bits of plastic to a proper aeroplane that is gliding in the air so can be adjusted with even the slightest of tail movement or a sail to move a [floating] boat is a bit tenuous.
            So if the smallest movement of a rudder on the tail, or aileron on a wing, can adjust the attitude of an aircraft, then why does it seem so surprising that relatively small front flippers on a car can have an effect on a car which has its attitude adjusted by turning the steering wheel i.e. an effect on turn in?

            Not only do the front flippers increase the pressure on the upper surface at the front corners of the car relative to the OEM bumper, they also reduce the pressure underneath, so there is a significant pressure change at the front corners of the MC. I've actually measured this, so it's not just wishful thinking on my part. Obviously this is all related to the square of the forward speed of the car and will increase with increase in speed.
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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            • #21
              Originally posted by exdos View Post
              So if the smallest movement of a rudder on the tail, or aileron on a wing, can adjust the attitude of an aircraft, then why does it seem so surprising that relatively small front flippers on a car can have an effect on a car which has its attitude adjusted by turning the steering wheel i.e. an effect on turn in?
              Flying is a very different thing to a car stuck on the ground, they are super sensitive to their shape and rudder changes or power, not least because of the speed but also becasue a plane's only contact point is with air, it becomes weightless so a tiny movement can affect the attitiube a lot. A car is on the ground naturally doesn't have any lift until very high speeds and even then it stays on the ground. Even if the flippers add 20kgs of downforce at speed it isn't much (apart from well into 3 figures).

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              • #22
                I agree that an aircraft is also operating in the third dimension of the vertical plane, which a car doesn't (apart from a bit of lift). But I'm not just referring to lift (+ve or -ve). Surely a car is somewhat affected when the pressure of air on one side of the car is different to the other, as in turning? The air on the side of the turn has far less distance to travel than the air traveling around the side of the car on the outside of the turn (as per aerofoil theory). If the flippers prevent air from escaping under the car and instead, forcing the air to go around the side of the car, then surely this will create lower pressure on the outer side of the car and have some effect on turning? Again, the effect of this will be related to the speed of the vehicle, but it must start at some point and all I am suggesting is that the noticeable point occurs at normal road speeds and not just at speeds above 100mph.
                /// Exdos ///
                "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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