Question C7 Tight Turns

[SockGuy]

Have a new 2018 Grand Sport (first vette for me) and have noticed that when making low speed tight turns, such as backing out of driveway onto street or pulling into parking spots that it feels as if front tires are binding. Anyone else notice anything like this?

 

[Rruuff Day]

Have a new 2018 Grand Sport (first vette for me) and have noticed that when making low speed tight turns, such as backing out of driveway onto street or pulling into parking spots that it feels as if front tires are binding. Anyone else notice anything like this?

Hey Sockguy... this is normal. we all get it... This is an explanation I posted a long time ago and will repost it here. Hope it answers your question...

Re-post
regarding your "hop hop" as it is a common occurrence (especially with the C6 and C7) and we have lots of new members coming on board that may be interested...

Temperature will only make very marginal differences in the wheel hop you refer to as what you are experiencing is explained in the Ackerman Steering geometry Principle.The quick and dirty explanation (at least I hope it will be) is:

The Corvette Stingray does not have perfect Ackerman (This is not a flaw. This is a happy medium for a combination track and street car. Perfect Ackerman would not handle as well on the track and about the only alternative to have perfect Ackerman and a vehicle that handles well on the track would be to have another differential installed between the front wheels.

In my feeble attempt at explanation, the front of the car and thus the front tires from one side of the car to the other both turn around the same radius point. During a turn each have a different length turning radius and angle; a shorter radius and tighter curve for the inside tire and a longer radius and flatter curve for the outside tire. This means the tire on the outside of the turn is travelling a longer arc distance than the inside tire. This results in the tires fighting with each other in their attempt to equalize themselves, and in a very sharp turn angle, this results in hop hop... crow hop...tire scrub..tire slip. there are lots of names for it. The wider stance, the lower profile tires, the sharpness of the steering angle, the camber and caster of the wheels, the width of the tires, the stickiness of the tires and the temperature all have some effect on the magnitude of slip which equates to how much you can actually feel the slip, but the tire fight is always there when the wheels are turned . It happens both in reverse and forward but we seem to turn the steering sharper much more often in reverse than when we are going forward. Except in parking lots... lol

 

[Jeremiad]

Eric's explanation is completely right.... just far too long and complicated.

Your tires are wide, and sticky. When turning, they will stick as long as they can until they just can't any more, and then they slip a few inches before they stick again. This is what you are feeling. It is normal.

 

[Rruuff Day]

lol .... Too funny Jordy.... Sticky tires have little to do with it.... Thus the explanation.... Whatdya expect out of an engineer... especially a retired one who still likes to practice.... Wait til Sockguy gets my invoice...

 

[Somebuddy]

And here I thought my vette was in four wheel drive!! ................... Good explanation guys.

 

[ddgermann]

I like the sticky tire one. But the over engineered one is good too.

 

[Black 03 Z06]

Eric, can you explain Ackerman steering effect on a locomotive?

Good explanation that even I could understand some of.

 

[Pep]

Hey Eric, can you explain the effect of Ackerman steering on the space shuttle in relation to the RPM of the hummingbirds wings please?

To the original poster it is very normal and it is indeed Ackerman steering and a compromise between a perfect setup for track and street.
Ackerman Wiki

 

[Black 03 Z06]

Eric has used his substantial engineering knowledge since he was a young lad. Here he shows show the local hottie, I mean student, the principals of Ackerman Steering.

 

[SockGuy]

Have a new 2018 Grand Sport (first vette for me) and have noticed that when making low speed tight turns, such as backing out of driveway onto street or pulling into parking spots that it feels as if front tires are binding. Anyone else notice anything like this?

Hey Sockguy... this is normal. we all get it... This is an explanation I posted a long time ago and will repost it here. Hope it answers your question...

Re-post
regarding your "hop hop" as it is a common occurrence (especially with the C6 and C7) and we have lots of new members coming on board that may be interested...

Temperature will only make very marginal differences in the wheel hop you refer to as what you are experiencing is explained in the Ackerman Steering geometry Principle.The quick and dirty explanation (at least I hope it will be) is:

The Corvette Stingray does not have perfect Ackerman (This is not a flaw. This is a happy medium for a combination track and street car. Perfect Ackerman would not handle as well on the track and about the only alternative to have perfect Ackerman and a vehicle that handles well on the track would be to have another differential installed between the front wheels.

In my feeble attempt at explanation, the front of the car and thus the front tires from one side of the car to the other both turn around the same radius point. During a turn each have a different length turning radius and angle; a shorter radius and tighter curve for the inside tire and a longer radius and flatter curve for the outside tire. This means the tire on the outside of the turn is travelling a longer arc distance than the inside tire. This results in the tires fighting with each other in their attempt to equalize themselves, and in a very sharp turn angle, this results in hop hop... crow hop...tire scrub..tire slip. there are lots of names for it. The wider stance, the lower profile tires, the sharpness of the steering angle, the camber and caster of the wheels, the width of the tires, the stickiness of the tires and the temperature all have some effect on the magnitude of slip which equates to how much you can actually feel the slip, but the tire fight is always there when the wheels are turned . It happens both in reverse and forward but we seem to turn the steering sharper much more often in reverse than when we are going forward. Except in parking lots... lol

That’s exactly what I thought it was, thanks for explaining so clearly. Seriously, thanks for taking the time to respond.

 

[ddgermann]

That’s exactly what I thought it was, thanks for explaining so clearly. Seriously, thanks for taking the time to respond.

This Question comes up a few times a year and it’s always great to give the answer as there is nothing wrong with the car.
The next one to consider is your alignment. Your car is set more for the track from the factory and many have reported low KM tire scrub on the inside edges of the front tires. Lots of members have adjusted the alignment to more neutral settings.
There are a few threads on this as well with good information.
I’ve never had a Corvette with 10k KMs so not something I’ve experienced yet. Maybe the one I have now will hit the 10K mark...
Eric @Rruuff Day will likely set his fishing rod or beer down for 5 minutes and send you a link.
Enjoy that new GS.

Derek.

 

[Tony Gull]

My earlier Stingray did this until the negative camber was made closer to zero. My current z06 hops as well which will result in front tire inside tread wear but I think the rears will be worn 1st anyway with all the power. The big long answer talked about another differential, as if, the front tires are not connected to the drive train so they’ll do what they do because of the width and alignment settings.

 

[DavidWG]

I also find it is more noticeable in my C7 Grand Sport than in my C7 Stingray, not sure if that can be attributed to factory set up or the difference in tire size. I also notice it more as the temperature drops. Enjoy that new GS.

 

[2015c7]

Normal with Michelin PSS run flats.
As I don't track my C7 I replaced the OEM run flats with Michelin AS 3+ all season tires. No more wheel hop, no degraded braking in cold temperatures, do not throw stones/debris, quieter, and I think a bit softer ride. Mine are non run flats with the softer side wall. I carry the GM compressor/slime kit and for me the benefits outweigh the risk of a flat.

 

[Rashwan]

If you take the all-new Stingray for a drive, you may notice something before you even leave the parking lot. This little something may seem like a defect, but it’s not.
It’s called the “Ackermann Effect”, and although the issue was resolved 200 years ago, Chevy left it alone on the Corvette.
The reason? It’s the same reason the Corvette has a 50/50 weight distribution and electric power steering: performance.
Explaining the Ackermann Effect:

Without getting into too much geometry and mathematics, the Ackermann Effect is a skipping or lurching of the wheels when the vehicle is turning sharply. The effect is created by the inside and outside wheels traveling at different speeds and distances.
Essentially the outside wheels are traveling further, creating a skipping or jumping effect.
A system, which was patented by Rudolph Ackermann in the 1818, turned the wheels at different angles and created a smooth turn for four-wheeled wagons.
Most cars use a system to mitigate the Ackermann Effect, the Corvette Stingray, however, goes without.

 

[Riley P]

Eric, can you explain Ackerman steering effect on a locomotive?

Good explanation that even I could understand some of.

It's actually really fascinating how locomotives go around corners with their wheels being tapered so as the train enters a corner, the outside wheel actually "grows" in diameter, and the inner wheel decreases in diameter to allow the two wheels to covered different distances even though they're locked together on the same axle.

 

[Rruuff Day]

This Question comes up a few times a year and it’s always great to give the answer as there is nothing wrong with the car.
The next one to consider is your alignment. Your car is set more for the track from the factory and many have reported low KM tire scrub on the inside edges of the front tires. Lots of members have adjusted the alignment to more neutral settings.
There are a few threads on this as well with good information.
I’ve never had a Corvette with 10k KMs so not something I’ve experienced yet. Maybe the one I have now will hit the 10K mark...
Eric @Rruuff Day will likely set his fishing rod or beer down for 5 minutes and send you a link.
Enjoy that new GS.

Derek.

Derek.....How could I set my fishing rod down when my past 5 days were full of this....

 

[Rruuff Day]

If you take the all-new Stingray for a drive, you may notice something before you even leave the parking lot. This little something may seem like a defect, but it’s not.
It’s called the “Ackermann Effect”, and although the issue was resolved 200 years ago, Chevy left it alone on the Corvette.
The reason? It’s the same reason the Corvette has a 50/50 weight distribution and electric power steering: performance.
Explaining the Ackermann Effect:

Without getting into too much geometry and mathematics, the Ackermann Effect is a skipping or lurching of the wheels when the vehicle is turning sharply. The effect is created by the inside and outside wheels traveling at different speeds and distances.
Essentially the outside wheels are traveling further, creating a skipping or jumping effect.
A system, which was patented by Rudolph Ackermann in the 1818, turned the wheels at different angles and created a smooth turn for four-wheeled wagons.
Most cars use a system to mitigate the Ackermann Effect, the Corvette Stingray, however, goes without.

hmmmmm.... appears to be an accurate explanation to me.....

 

[Rashwan]

Also I suggest to read GM Service Letter 14-03-10-001C: (Google it)
14-03-10-001C: Tire Hop / Tire Chatter During Tight Turns At Parking Lot Speeds – 2014-2017 Chevrolet Corvette

 

[ddgermann]

Derek.....How could I set my fishing rod down when my past 5 days were full of this....

View attachment 17642

Wow Eric! Completely see why you’ve been EMCOM the last few days.
Well done. I can smell the butter and pepper in the pan from here man.
Well done