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-   -   Cold starts and wheels jumping (https://mbworld.org/forums/c63-c63s-amg/734721-cold-starts-wheels-jumping.html)

slowc 02-01-2019 11:07 PM

Cold starts and wheels jumping
 
whenever I do a cold start and let it warm up and go to turn the wheels for the first time it jumps so bad and sounds horrible turning. ( while driving forward not stationary turning)

benzbell 02-02-2019 12:20 AM

If you are running wider than stock tires in the front and when it's colder it could be the "Ackermann Effect." It's basically Tire Chatter/Hop. Common in the C7 Vette, AMG GTR and others.


Ackermann Effect

slowc 02-02-2019 12:36 AM


Originally Posted by benzbell (Post 7670664)
If you are running wider than stock tires in the front and when it's colder it could be the "Ackermann Effect." It's basically Tire Chatter/Hop. Common in the C7 Vette, AMG GTR and others.


Ackermann Effect

thank for the info! It’s stock.. it has the summer performance tires. Maybe that’s a factor? It’s stock tire from mb

benzbell 02-02-2019 06:19 AM


Originally Posted by slowc (Post 7670678)

thank for the info! It’s stock.. it has the summer performance tires. Maybe that’s a factor? It’s stock tire from mb

A car can still be prone/prevalent with stock tires as well. My GTR comes to mind. Actually, that is where I learned about this - on the GTR forum. Since I haven't heard of anyone mentioning this before on a C63 or another vehicle for that matter. Is why I brought up wider than stock. Doesn't mean you can't be experiencing it slightly with stock tires.

KJ 02-02-2019 02:09 PM


Originally Posted by benzbell (Post 7670740)
A car can still be prone/prevalent with stock tires as well. My GTR comes to mind. Actually, that is where I learned about this - on the GTR forum. Since I haven't heard of anyone mentioning this before on a C63 or another vehicle for that matter. Is why I brought up wider than stock. Doesn't mean you can't be experiencing it slightly with stock tires.

I had this happen on my 911 Turbo before and was always wondering why. Always figured my wider tires were rubbing on the fender liner with full lock.

Thanks for sharing!

ShakyTom 02-02-2019 04:20 PM

Isn't that only a thing that occurs on AWD vehicles?

benzbell 02-02-2019 06:13 PM


Originally Posted by ShakyTom (Post 7671108)
Isn't that only a thing that occurs on AWD vehicles?

Nope - happens a lot in Porsches and the Z06 as well.

ems23 02-02-2019 06:34 PM

Hi, I have the same issue when the wheels would jump when turning during cold weather! I thought this is to do the with fact that the car has a limited slip diff?

benzbell 02-02-2019 07:21 PM


Originally Posted by ems23 (Post 7671184)
Hi, I have the same issue when the wheels would jump when turning during cold weather! I thought this is to do the with fact that the car has a limited slip diff?

Diff is in the rear - hop is in the front.

ems23 02-03-2019 01:14 AM


Originally Posted by benzbell (Post 7671212)
Diff is in the rear - hop is in the front.


I have no ideas about this, my rationale was the LSD opposes the turn in (becaus wheel 4&2 are locked) creating a YAW opposite direction to the turn in, this would cause the wheel with least traction to skip, in this case it could be wheel number 3 and you get your hop in the front caused by the diff in the back?

i have no idea about the setup of the suspension of the car just a guess... as I don’t see how Ackerman geometry causes it? Just interested in how it works?

Woodr85 02-05-2019 10:33 AM

I had this is my s5, and have it in my c63s now too, when very cold outside. Audi said it was hop, and it’s the same on the Merc with a sharp turn in the driveway or parking lot in the morning

msd3075 02-05-2019 12:25 PM

I feel this all the time when making full lock turns, mostly when parking.

I always assumed it was due to the pronounced camber in the front wheels when at full lock (the edge of the tire rolling over, then not, then rolling over, then not).

I also assumed it was the main culprit for those of us that have issues with the inside edge of the front tires wearing prematurely.

Woodr85 02-05-2019 12:44 PM

I only have it when <~45F


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