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Ackerman Steering

 
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Old Nov 14, 2020 | 10:59 PM
  #1  
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Default Ackerman Steering

Hello Tadge,

What did your engineers do to the C8 steering geometry to reduce the front tire bumping/dragging related to Ackerman steering. This tire drag was very prominent on the C6 and C7 Z51s. It is not noticeable at all with my C8.

Thank you,
Ed K

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Nov 22, 2020, 07:28 AM
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Originally Posted by KOMCZYK
Hello Tadge,

What did your engineers do to the C8 steering geometry to reduce the front tire bumping/dragging related to Ackerman steering. This tire drag was very prominent on the C6 and C7 Z51s. It is not noticeable at all with my C8.

Thank you,
Ed K
Hello Ed,

I think I can help out with this one.

Ackerman correction is kinematics in the top view. It is the position of the steering rack relative to the steer arm on the spindle. Actually, that will affect the angle of the tie rods which increases or reduces Ackerman correction.

The fifth generation Corvette did not have the tired chucking that the sixth generation did because the Ackerman correction was reduced for the C6. The reason the six generation had reduced Ackerman was because if you recall, we also did the XLR in conjunction with the C6. In order to accommodate the NorthStar engine, the steering rack had to move forward in the top view.

At that point, we did not realize the car would have a tire chucking in the parking lot problem, however, we knew that reduced Ackerman would be significantly make the car better on the racetrack, and for handling in general. The theory behind this is reduce slip angle on the inside tire while cornering.

So, when we went to the seventh generation Corvette, we realized we would like to reduce the chucking and increased Ackerman correction to the same values as the fifth generation. From my standpoint, it was a delicate balance of increasing the Ackerman just enough to get through the parking lot without taking a major hit and handling. But what we did not realize with the increased grip of the tires over 10 years from the fifth to the seventh generation, we would still have the chucking issue.

Even though I was not part of the eighth generation Corvette, I suspect there was a dramatic increase in Ackerman correction to reduce or eliminate the parking lot corner chucking. I suspect they used data accumulated from all of the reference cars they use during the development of the C8.

Hope that helps, Jim
Old Nov 14, 2020 | 11:05 PM
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I haven’t looked but I’m guessing the wheel base is shorter and the tires are a bit smaller width? Either of these would help.
Old Nov 17, 2020 | 12:59 AM
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^^^^
Neither
Old Nov 21, 2020 | 11:02 AM
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Changed to standard all seasons tires. Different rubber compound.
Old Nov 22, 2020 | 07:28 AM
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Originally Posted by KOMCZYK
Hello Tadge,

What did your engineers do to the C8 steering geometry to reduce the front tire bumping/dragging related to Ackerman steering. This tire drag was very prominent on the C6 and C7 Z51s. It is not noticeable at all with my C8.

Thank you,
Ed K
Hello Ed,

I think I can help out with this one.

Ackerman correction is kinematics in the top view. It is the position of the steering rack relative to the steer arm on the spindle. Actually, that will affect the angle of the tie rods which increases or reduces Ackerman correction.

The fifth generation Corvette did not have the tired chucking that the sixth generation did because the Ackerman correction was reduced for the C6. The reason the six generation had reduced Ackerman was because if you recall, we also did the XLR in conjunction with the C6. In order to accommodate the NorthStar engine, the steering rack had to move forward in the top view.

At that point, we did not realize the car would have a tire chucking in the parking lot problem, however, we knew that reduced Ackerman would be significantly make the car better on the racetrack, and for handling in general. The theory behind this is reduce slip angle on the inside tire while cornering.

So, when we went to the seventh generation Corvette, we realized we would like to reduce the chucking and increased Ackerman correction to the same values as the fifth generation. From my standpoint, it was a delicate balance of increasing the Ackerman just enough to get through the parking lot without taking a major hit and handling. But what we did not realize with the increased grip of the tires over 10 years from the fifth to the seventh generation, we would still have the chucking issue.

Even though I was not part of the eighth generation Corvette, I suspect there was a dramatic increase in Ackerman correction to reduce or eliminate the parking lot corner chucking. I suspect they used data accumulated from all of the reference cars they use during the development of the C8.

Hope that helps, Jim
Old Nov 22, 2020 | 06:49 PM
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Jim -

Originally Posted by Jim Mero
I think I can help out with this one.
Thanks for picking this one up. I appreciate it.
Old Nov 23, 2020 | 07:03 AM
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Originally Posted by jvp
Jim -



Thanks for picking this one up. I appreciate it.

Last edited by Jim Mero; Nov 23, 2020 at 07:05 AM.
Old Nov 23, 2020 | 07:39 AM
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Default Still notice on z51 c8

I still experience this effect in parking lots in a tight steering situation at very low speeds. Better than C7 but not gone.
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Old Dec 18, 2020 | 10:01 PM
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At full lock my Z51 C8 has a pretty bad turning scrub/skip/chuck.
Old Dec 22, 2020 | 08:44 PM
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Originally Posted by Jim Mero
Hello Ed,

I think I can help out with this one.

Ackerman correction is kinematics in the top view. It is the position of the steering rack relative to the steer arm on the spindle. Actually, that will affect the angle of the tie rods which increases or reduces Ackerman correction.

The fifth generation Corvette did not have the tired chucking that the sixth generation did because the Ackerman correction was reduced for the C6. The reason the six generation had reduced Ackerman was because if you recall, we also did the XLR in conjunction with the C6. In order to accommodate the NorthStar engine, the steering rack had to move forward in the top view.

At that point, we did not realize the car would have a tire chucking in the parking lot problem, however, we knew that reduced Ackerman would be significantly make the car better on the racetrack, and for handling in general. The theory behind this is reduce slip angle on the inside tire while cornering.

So, when we went to the seventh generation Corvette, we realized we would like to reduce the chucking and increased Ackerman correction to the same values as the fifth generation. From my standpoint, it was a delicate balance of increasing the Ackerman just enough to get through the parking lot without taking a major hit and handling. But what we did not realize with the increased grip of the tires over 10 years from the fifth to the seventh generation, we would still have the chucking issue.

Even though I was not part of the eighth generation Corvette, I suspect there was a dramatic increase in Ackerman correction to reduce or eliminate the parking lot corner chucking. I suspect they used data accumulated from all of the reference cars they use during the development of the C8.

Hope that helps, Jim

Hi Jim,

Yes, your explanation helps. Thanks for your effort and time. It is appreciated.

Ed K
Old Jan 5, 2021 | 06:04 PM
  #11  
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My C8 does this when backing out of my driveway and turning, the outside tire feels like it drags but its a very minimal thing. If you want a good handling car with wide tires, its a small price to pay overall
Old Mar 23, 2021 | 03:58 AM
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Hmm, I've got a book "Automotive Engineering Fundamentals" by Richard Stone and Jeffrey Ball, but it doesn't have too much on steering design. It does go into some detail on design as far as understeer/oversteer, and the caster/camber/toe/etc..., but it's more of a general overlook. Wish I could be of more help.

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