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C8, will it also have the Ackerman effect?

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  • C8, will it also have the Ackerman effect?

    The hopping and grinding noise scared me when I first had a chance to drive a C7 in cold weather. Do you think the engineers will fix it this time around since there's more in the steering area to deal with the issue. (I presumed that it wasn't fixed in the C7 because of the complexity and space required in the FE).

    You'd imagine a flagship car wouldn't have such an issue (an issue that's been already been solved over a hundred years ago).
    Last edited by khanmark; 05-31-2019, 02:02 AM. Reason: grammar

    Mark

    - Brave men run in my family -

    3LT - Accelerate Yellow - Performance Exhaust - High Wing - Torch Red Seat Belts - Yellow Stitching - Bright Red Calipers - Black Side Rockers - Splash Guards - Carbon Flash Mirrors & Spoiler - Front End Lift - Carbon Flash Open Spoke Wheels

  • #2
    Ackerman can easily be changed in the current space available. Simple geometry, steering arm length and angle to the tie rods. My opinion of the hopping noise is due to the width and cold temp hardness of the tire.

    Comment


    • #3
      Good thread question khanmark! As I come out of my garage, I make the identical, sharp turn every time. In the summer, there is zero tire chattering. As it gets colder, the shuddering progressively returns in direct relationship to the dropping temps. The first time I drove my 2014 Z06, on December 26th at 33 degrees at the dealership, when I was driving from where it was parked outside where the service manager had parked it in a protected space over to the wash rack, even though I knew all about the Ackerman effect and had explained it to many new 2014 C7 owners, each telling them “not to worry,” I thought the front end of my Z was going to fall off.

      Racer86 is correct that it is majorly due to the width and the cold temp hardness of the tire. However, might the ME’s front end suspension, especially since it will not longer have the 450 pounds of the motor on top of it, and as its suspension is significantly changed, if nothing else with adjustable coil overs instead of transverse leaf composite springs, and/or with the improved PS4’s, singularly or together significantly reduce or even outright eliminate shuddering???

      GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5ZZ high wing; 5VM vis CF ground effects pkg; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards. Separately getting from my dealer RCC Edge Red engine cover and 5JR vis CF mirror caps.

      Lifetime, annual contributors, and 20+ year members of National Corvette Museum.

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      • #4
        Never bothered me once i heard it was part of the vehicles design..

        barely ever popped up as an issue...

        i imagine it will continue but just a guess...
        Torch Red exterior/ black interior z51 FE4 2LT or 1LT depending on when i get the call..Ill flip a coin at that moment..same for E60

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        • #5
          Several MEs still actually do this, mostly due to the width and nature of summer tires, but also the reduced weight on the front. Complaints on the McLaren Forum come to mind..

          Comment


          • #6
            Originally posted by khanmark View Post
            The hopping and grinding noise scared me when I first had a chance to drive a C7 in cold weather. Do you think the engineers will fix it this time around since there's more in the steering area to deal with the issue. (I presumed that it wasn't fixed in the C7 because of the complexity and space required in the FE).

            You'd imagine a flagship car wouldn't have such an issue (an issue that's been already been solved over a hundred years ago).
            Yes, the "issue" was solved over a hundred years ago.Actually, 200 years ago. At the expense of cornering performance. Ackerman steering geometry, as designed into most street cars, optimizes low speed turning at the expense of ultimate cornering performance. The Corvette, as befits a high performance sports car, is optimized for performance driving, not driveway turns. Neither have anything to do with the lack of space in the C7 wheel well. I certainly hope a flagship sports car doesn't compromise performance to satisfy a few people who get upset turning into their driveway.

            As just as a BTW, the "issue" (I don't consider it to really be one) shouldn't be called the "Ackerman effect." It's really the lack of Ackerman steering geometry, combined with the sticky summer tires, that causes it. Ackerman steering is designed to prevent the low speed wheel hop, not the cause of it. So the real "Ackerman effect" is the lack of wheel hop, and a loss of high speed cornering performance.

            For those who don't know what we're talking about: https://en.wikipedia.org/wiki/Ackerm...ering_geometry

            TL;DR summary: When making a tight turn, the inside wheels track a tighter radius than the outside wheel. If both front wheels are turned the same about, the inside wheel isn't turned far enough to match the radius in which it's turning (or you can look at it as the opposite: the outside wheel is turned too far). Ackerman geometry solve this "issue" by turning the inside wheel more than the outside wheel.

            Click image for larger version  Name:	330px-Ackermann_turning.svg.png Views:	1 Size:	24.3 KB ID:	38604

            But what works at parking lot speeds and tight radius doesn't work so well at high speeds and wider radius.
            Last edited by meyerweb; 05-31-2019, 01:47 PM.
            SunKissed, my 2015 2LT, 7MT, Black over Daytona Sunrise Orange Metallic, Stingray convertible (One of about 40)

            Purchased 5/2/2015,
            >35,000+ miles

            Proud member of the Old Dominion Corvette Club. Check us out http://www.olddominioncorvetteclub.org

            Never grow up - It's a trap.

            Comment


            • #7
              Meyerweb, good post about ackerman. Suspension geometry is a science and art form at the same time. It all can be optimized for each intended use. I do believe the corvette tire problem is caused by
              1. The width of the tire at the tread
              2. Low profile tires with very stiff sidewalls.
              3. Tires with low traction at low temperatures
              4. The twisting and resultant torque loading across the tread when turning a wide tire at low speed. When the distorted tire patch load gets to critical, the tread unloads this distortion, and that unloading it what you hear. It’s snapping back to shape.
              I believe that the scrub radius across the tire is the cause of the problem., and has little to do with the Ackerman designed into the suspension. Ackerman is used to control toe in, toe out, across both front tires when turning. One basic trick of Ackerman is used to add more toe out to the inside tire to create drag and that causes the car to rotate into the corner . Simple description of a very complex dynamic
              I would say a Corvette is a high performance car and has settings in the suspension that work well for high speed driving, and do not work well for parking lot driving.
              News flash,,,,,,, can’t have it both ways.

              Comment


              • #8
                Good to know Mr Ackerman is a trade off to assure I get good cornering at speed. I take u-turns very slow. Always try to time them so oncoming vehicles don't have to slow or wait for me to complete the u-turn. Of course those on-coming cars are just specks in my rear view mirror after I complete my u-turn.

                Comment


                • #9
                  Thanks everyone for the discussion responses.

                  Overall, it looks like the consensus is that most likely we'll get the hops and noise still, but will have to wait and see for the actual behavior of the car for a definitive answer.


                  Mark

                  - Brave men run in my family -

                  3LT - Accelerate Yellow - Performance Exhaust - High Wing - Torch Red Seat Belts - Yellow Stitching - Bright Red Calipers - Black Side Rockers - Splash Guards - Carbon Flash Mirrors & Spoiler - Front End Lift - Carbon Flash Open Spoke Wheels

                  Comment


                  • #10
                    Originally posted by khanmark View Post
                    Thanks everyone for the discussion responses.

                    Overall, it looks like the consensusYou**** Pornhub Tubegalore is that most likely we'll get the hops and noise still, but will have to wait and see for the actual behavior of the car for a definitive answer.

                    Ackerman can easily be changed in the current space available. Simple geometry, steering arm length and angle to the tie rods. My opinion of the hopping noise is due to the width and cold temp hardness of the tire.
                    Last edited by karim7800; 06-06-2019, 03:31 PM.

                    Comment


                    • #11
                      >But what works at parking lot speeds and tight radius doesn't work so well at high speeds and wider radius.

                      Would love to hear a full explanation from you of that... (slip angles, CofG, weight xfer)

                      Comment


                      • #12
                        Originally posted by BlueMoon View Post
                        >But what works at parking lot speeds and tight radius doesn't work so well at high speeds and wider radius.

                        Would love to hear a full explanation from you of that... (slip angles, CofG, weight xfer)
                        Google is your friend. There are quite a few articles about it, although I don't know if any go into the detail you're looking for. But it's really pretty simple. The inside tire turns a tighter radius than the outside tire. If both tires are turned an equal amount, one of them is going to scrub.
                        SunKissed, my 2015 2LT, 7MT, Black over Daytona Sunrise Orange Metallic, Stingray convertible (One of about 40)

                        Purchased 5/2/2015,
                        >35,000+ miles

                        Proud member of the Old Dominion Corvette Club. Check us out http://www.olddominioncorvetteclub.org

                        Never grow up - It's a trap.

                        Comment


                        • #13
                          Read an article in one of the car rags (sorry, can't remember which one and left it on an airplane yesterday) that explained that despite a 1 inch+ longer wheelbase than the C7, the C8 will have a tighter turning radius (36 feet versus the C7 37.7 feet), and that the steering vector will be variable at slower speeds. While the article did not address the Ackerman effect, the mid engine placement will have a definite positive effect on turning radius and low speed steering.

                          Comment


                          • #14
                            At the reveal, Tadge said the wheel hop is no longer an issue. I'm sure that would be the case for the All Season tire, but it was unclear to me if that was true for both types of tires.
                            It never bothered me. In fact I,considered it a reminder of how special the car was!

                            Pete

                            2014 Premiere vert
                            Last edited by Gearhead2014; 08-12-2019, 03:04 PM.
                            Now - 2014 Premier convertible #236
                            Next - C8 Shadow Gray, Morello, Z051, Mag ride
                            or C8 Premier Launch Edition

                            Comment


                            • #15
                              Welcome Gearhead2014. Thanks for your first post. You ask a good question. I volunteer to test out the Z51 in cold weather at full lock.
                              GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5ZZ high wing; 5VM vis CF ground effects pkg; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards. Separately getting from my dealer RCC Edge Red engine cover and 5JR vis CF mirror caps.

                              Lifetime, annual contributors, and 20+ year members of National Corvette Museum.

                              Comment

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