Getting Cold get ready for "Chatter or Hopping!"

[JerryU]

Yep the C7, especially the Z51, Grand Sport and Z06 will start having front wheel "Chatter or Hopping" as GM calls it. Starts at ~50F and at 40 F or below "hopping" is a more descriptive word! It's not Ackerman steering geometry (or lack of) although related. Proof? It goes away with winter and many all season tires with the extact same Ackerman steering geometry.

What's the casue that is much wore than my C6 Z51 with th same width tires as my 2014 Z51? - The Michelin OEM tire race car type very low "Slip Angles."

This is a PDF I developed with many pics and text defining the reason. It has many pics and defines why it's worse, as GM notes, when it's wet so it's not "sticky tires" : http://netwelding.com/Wheel_Chatter.pdf

Below is one of many pics in the PDF. It shows that full Akerman compensation is not built into rubber tires cars (since it has a negative effect in max attainable "g" force) since the rubber moving on a hard surface provides some of the different turning radius (outside and inside) compensation on slow steep turns. However a tire with low slip angles does not move much and causes chatter or hopping.

Easy workaround I have used for 5 years. When cold, I don't turn the wheel as much and make a "K" turn! Simple! When taking the extra time I think of the smile that 1.2 "g" lateral acceleration I get with my Grand Sport when warm around the fountain at the end of my street puts on my face! LOL

[MidEngine]

JerryU thanks for another very informative thread by you. My front tires chattered as I pulled out of its garage, wheels turned full lock, just a couple of days ago when, for the first time this fall, it was 40 degrees.

[John]

Thank you JerryU. Great reminder. Another one, relatedly, is that with colder temps, time for many of us to keep a closer eye on tire pressures. While mine were perfect just one month ago, when I drove it for the first time in a few weeks, at 44 degrees, noticed they were all down to 28 PSI. Put in 31 PSI on all four — because we know it will be getting even a little colder here soon.

Thanks again Jerry!

[meyerweb]

I'll probably put my A/S tires on this week. Temps were down in the 20s this morning, so getting a bit chilly for the summer skins.

[JerryU]

Thank you JerryU. Great reminder. Another one, relatedly, is that with colder temps, time for many of us to keep a closer eye on tire pressures. While mine were perfect just one month ago, when I drove it for the first time in a few weeks, at 44 degrees, noticed they were all down to 28 PSI. Put in 31 PSI on all four — because we know it will be getting even a little colder here soon.

Thanks again Jerry!

John, has gotten cold here a few times (although yesterday it was 81!) I do get some chatter at 40F, bit more at 35 BUT more like the C6, not that objectionable that I have to use a "K" turn after backing out of the garage to go down the driveway. Can still use full lock.

Does make me wonder if their will be a "better performance street tire" as there was with my two C4's and my C6! We'll see what folks find when I need new tires!

[John]

Jerry for sure better than the C7 was but when I backed out of my garage at full lock the other day, I did notice a little chatter — but not the “will the front end fall off” shuddering my C7 Z06 did at the same temp.

I agree with you that we will see a Cups 2 as standard on future models (C8 Z07/Z07?). I notice at TireRack we can get Cup 2’s and Pirelli Trofeo R’s for our C8’s now