Help! Bumping vibration/sound when wheels turned to lock either way and moving slowly forward or reverse

[dhewett]

I have a 2015 coupe which makes a bumping noise and vibration when the car is moving slowly either forward or reverse and when turning either left or right. It seems like it is bumping at a rate of about 2 times in one wheel revaluation. A friend has a 2014 doing the same thing.

I talked to the service manager and he says it is just the nature of the beast and it is being caused because the tires are so wide and causing them to slide sideways when turned sharply. I told him that I would have to sleep on that and think about it. I have and I don't!

Did I hear that this car has variable speed steering? Could this be the culprit when turning lock to lock? I don't really understand how VSS works.

Thanks for your thoughts,
Don

 

[67vet]

The Service Manager is correct. I had the same thing happen on my 2014 Convertible and now on my 2015.

 

[Hib Halverson]

What you feel is the front tires "chattering" when at a sharp turn angle. Pilot Super Sports do it. The Pilot Sport Cups on my '12 do it and the F1 Supercars on my C5Z do it sometimes.

In fact, any wide tire, with a soft tread compound and a tread design with very large, stiff tread blocks will chatter at slow speed in sharp turns. Temperature has an impact, too. The colder the weather is the more likely they'll chatter.

It chatters because in a turn like that the actual distance traveled by the inside and the outside of the tread is different. Something has to give in that situation so part of the tread suddenly breaks loose and sort of "jumps ahead or behind" and that's the chatter you feel and hear.

It is normal with wide tires.

 

[4 the ride]

Hib is right

I recently purchased a 2015 Z51 Coupe. Took delivery in Michigan and drove it down to Florida. When the weather is below the specified range for "summer only" tires, they chatter even worse. As sticky as these tires are in warm conditions, they are like hockey pucks when cold. Add rain and it's even worse.

 

[korvettekarl]

My ZL1 Camaro does it as well as my 14 Stingray. It scares the heck out of my wife, so it has some value.:L

 

[RTurnConn]

Chatter

"Normal" for 14-15 corvette. My CTS Coupe did the same thing only worse. It is frightening the first time you hear it.

 

[kpic]

I thought I posted this.. Anyhow, it isn't the tires; It is called the Ackermann Effect. To design a car which handles as superbly as the C7; GM's engineers made the decision to ignore it. A little aggravation in a parking lot or at low speed means superb handling at speed.

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.
Explaining the "Ackermann Effect" in the 2014 Corvette Stingray

What is amazing is Ackermann figured it out in 1818. Actually a man named Lankensperger figured it out and Ackermann got the credit.

Although the tires accentuate the effect; however, they aren't the reason for it.

This sensation is called the Ackermann Effect, named for Rudolph Ackermann, who patented Lankensperger's steering system in Great Britain in 1818.

As stated it was Georg Lankensperger who figured it out; Ackermann patented it.

The question is do you want superb handling or low speed agility? Do some searching, some guy in the early 1800s figured it out so his wooden wheeled wagons wouldn't chatter, it is interesting reading

Edit:
For those interested in a bit more of a technical discourse:
https://sweetmfg.biz/uploads/files/tech-04understandingsteering-4.pdf

 

[korvettekarl]

kpc, cool stuff. Thanks for posting. KorvetteKarl

 

[JR 427/60th]

I thought I posted this.. Anyhow, it isn't the tires; It is called the Ackermann Effect. To design a car which handles as superbly as the C7; GM's engineers made the decision to ignore it. A little aggravation in a parking lot or at low speed means superb handling at speed.


What is amazing is Ackermann figured it out in 1818. Actually a man named Lankensperger figured it out and Ackermann got the credit.

Although the tires accentuate the effect; however, they aren't the reason for it.


As stated it was Georg Lankensperger who figured it out; Ackermann patented it.

The question is do you want superb handling or low speed agility? Do some searching, some guy in the early 1800s figured it out so his wooden wheeled wagons wouldn't chatter, it is interesting reading

Edit:
For those interested in a bit more of a technical discourse:
https://sweetmfg.biz/uploads/files/tech-04understandingsteering-4.pdf

Kinda neat reading, Thanks. Just learned it had an name last week at NCCC Governor's meeting.

I had this on my 427 vert and now also on my 2015 z51. It's mentioned in the operators manual in 2013 a bit on the obscure side but it's a pretty prominently mentioned int he 2015 manual.

My experience is this happens mostly in lower temp weather and much less to hardly at all during summer time high temps. There's also a Tech Bulletin about the tread actually cracking when using these summertime only tires. Basically it says don't operate under 40 degrees and don't even move it at all at 20 degrees or less. I think there's a bunch of 'cush factor' in those temp ranges as I've driven both of mine in 30 - 40 degree weather but avoid below 30 if at all possible. That's reserved for Z-71...

 

[kpic]

Kinda neat reading, Thanks. Just learned it had an name last week at NCCC Governor's meeting.

I had this on my 427 vert and now also on my 2015 z51. It's mentioned in the operators manual in 2013 a bit on the obscure side but it's a pretty prominently mentioned int he 2015 manual.

My experience is this happens mostly in lower temp weather and much less to hardly at all during summer time high temps. There's also a Tech Bulletin about the tread actually cracking when using these summertime only tires. Basically it says don't operate under 40 degrees and don't even move it at all at 20 degrees or less. I think there's a bunch of 'cush factor' in those temp ranges as I've driven both of mine in 30 - 40 degree weather but avoid below 30 if at all possible. That's reserved for Z-71...

Whose name did they use?

There was a decision made and folks wanted to be competitive with foreign machinery. The C7 does and quite well.

I tested mine for heat in the mid-20s. As it is a blower motor with a 160F; I was relieved to see she made good heat.

Due to the way the front end geometry is set up, it is unavoidable. It was a choice made by the suspension designers. Blaming the tires was a bit over the top as the handling you enjoy is the root cause.

The cold to hot difference you notice is probably rubber compound, that is just a guess. Suspensions are not my forte. That being said, I played with the alignment on a Z-28, a family car; very harsh on tire life, but wicked handling.

Understood, we had snow and my Z-71 gloats at the garage queen.

 

[Tom Martin]

Cold weather and tire noises

I had that problem on my '12 GS. I took it back to the dealer and told them what was happeming. They tried it the next day and called me in to talk to me. They showed me a GM bulletin that explained that under about 40 degrees the tires will do that. Later on I was told about Vettes being delivered in really cold weather actually destroying their tires in relatively short drives. The tires cracked then started "chunking" and falling apart. My GS never came out of the garage under 50 degrees. Now I've got a '14 Stingray. I'll have to see what it does this next winter but I'll bet it's the same.

 

[Fitz]

I had that problem on my '12 GS. I took it back to the dealer and told them what was happeming. They tried it the next day and called me in to talk to me. They showed me a GM bulletin that explained that under about 40 degrees the tires will do that. Later on I was told about Vettes being delivered in really cold weather actually destroying their tires in relatively short drives. The tires cracked then started "chunking" and falling apart. My GS never came out of the garage under 50 degrees. Now I've got a '14 Stingray. I'll have to see what it does this next winter but I'll bet it's the same.

All cars with really wide front tires do this. The tires scrub, catch, and scrub when the wheel is turned near the lock on either side. Easing off on the wheel stops it.