I am hearing a loud thump-thump-thump coming from the front wheel areas.

I've read SO MANY opinions about what causes this noise in cars during initial slow, hard turns after a cold start (seems like in colder weather also). I am a new 07 XKR owner so this is a little creepy. This happens, for example, when pulling out of a parking space. By the way my XKR has only 37k miles, tire are a little worn (Pirelli p-zero in front).

I have yet to read an opinion from XK/XKR owners who may have experienced this. Even newer Porsche 911 owners complain about this exact issue and are told by the dealer that this is normal. Other folks on other cars state that this is definitely a suspension/bushing/bearing issue. Some state that it's related to the Ackerman effect and harmless to the car. Some state that it's definitely a tire/grip issue when turning, and still other state that it's the tires rubbing something during turns.

Why would the problem disappear after it's warm or during normal driving?? This is the mystery.

I'm about to put it in a shop that specialized in European cars to check things out, but I want to know what to ask them so I don't get another "guess" about what it is.

This newbie would value XK/XKR owner opinions very highly!

Thank you in advance!

 

This is probably due to the summer tires not having enough traction as you are making a tight turn. The car is RWD as well so the drivewheels aren't helping turn the car as a FWD car's drivewheels would.

Your issue is completely normal and expected--summer tires are not meant for cold weather use! I have the same noises, by the way.

 

amcdonal86, Could you explain this concept of "summer tires"?
What you are saying makes perfect sense, but I not conecting the dots...why wouldn't every single RWD car experience the same issue? I've never experienced it before the XKR. thanks

 

It probably also has to do with suspension geometry (Ackerman effect, as you said), but cold weather amplifies the issue as it makes the tires (especially summer tires) much harder and reduces the amount of grip/friction. The tire slips sideways, then regains traction, then slips again. This is the thumping.

I have experienced it on my beater Mustang (RWD) when we had temps near zero degrees. It has all-season tires, though, so it's not as dramatic as when the XKR does it.

I'm not a tire expert, but generally summer tires are designed so that they have optimum grip in temperatures above 60 degrees. Below those temperatures, the rubber compound gets very hard and does not provide much grip. Compare that to winter tires, which above 60 degrees are overly soft (providing poor friction), but achieve their optimum grip at cold temperatures (below 40 degrees). All season tires are a compromise between the two.

 

Here's a previous thread on the subject. Lots of interesting comments.

https://www.jaguarforums.com/forum/x...en-cold-90633/

 

I think you may have linked the wrong thread!