"Bouncing" front wheels on RX450h

[Harry the spider]

When I am moving forward slowly on full lock there is a shuddering sound and feeling from the front wheels. It seems as though the wheels are being pushed sideways by the forward motion of the car.

Anyone have any ideas what is causing it?

[NemesisUK]

Only noticed in the colder weather?

[Barry14UK]

Some call this crabbing or side stepping and is experienced on hard lock to greater or lesser extent on all cars due to thrust and angle.  There is a long thread on a Mercedes Benz Club site on this as some of their models suffer particularly because of other factors which means a class action is brough against MB. The make and type of tyre and compound can make a difference.  I have pasted this from the thread :- 

"Car

His - Denim Blue A220 AMG Line Premium / Hers - Obsidian Black R172 SLK55

C250BLUE said:

How can I resolve this issue and what is Mercedes doing about this.

Answering your questions in order:

1. In the current colder conditions, you can eliminate the jumping on full lock by fitting winter tyres
2. Nothing

OK, I'll expand on the second answer. The sensation you're experiencing is commonplace on all cars running wide, low-profile, summer tyres in cold conditions. It's a function of the outer edge of the tyre needing to rotate at a different speed to the inner edge when on lock, and that's something that clearly can't happen. At low temperatures, summer tyres lose compliance and therefore have a noticeable "wind up then slip" characteristic that is felt as the tyre skipping or jumping. This is more prevalent when tyres are worn as the tread blocks have less "give", so even replacing the part worn tyres with new examples may reduce or stop the sensation, while swapping to winter tyres which have higher compliance in cold weather will almost certainly likely eliminate it completely.

Note that while this issue on a RWD car is similar to that experienced by owners of the current 4WD Mercedes cars, the latter experience the effect in a more extreme fashion and as a result of a litany of customer complaints Mercedes have made engineering changes to some models to reduce (but not completely eliminate) the sensation, and have also offered some owners replacement tyres that are more compliant. For RWD cars it's just the way it is and you will either have to learn to live with it or swap to winter tyres at your own cos.t"

Extract taken from https://forums.mbclub.co.uk/threads/car-crabbing-judder-when-in-full-lock.256286/

 

[Harry the spider]

Thanks for the 'crabbing' replies guys, they were very helpful and put my mind at ease. I notice from the Mercedes post you linked to, that a change of tyre manufacturer can get rid of the problem. Do you have any suggestions in this regard?

Thanks guys. Harry

[ColinBarber]

Michelin Cross Climate 2 would be a good option if available in your size. It's mainly summer tyres that crab when the temperature gets into single digits and they lose their grip.