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Discussion Starter · #1 ·
This has been niggling me for a while, in fact ever since I got the car.
It's got more noticeable in the cold(er) weather, so much so, that I am taking the car in for a cursory inspection.
Each morning, I get into the car, and make a sharp right turn from my drive onto the road.And each time I do that, I hear, and feel, something that I can only describe as "like the a wheel rim crunching on a flat tyre"
Obviously I have checked the tyre pressure (at rest), and it's at the prescribed pressure. I've checked the tyre. Seems fine. I've checked the wheel rim, it too is fine.
Once the tyre is warm, it does not do this. (And for the record, if I turn left from my drive, it doesn't make that sound either).
I've even increased the pressure by a bar (not this fancy Kpa thingie), and it still happens.
It's really weird, and I don't see how the garage is going to be able to identify this w/o keeping the car overnight... (Wot! and deprive me of my fun!)
Do any fellow G45ers have a similar experience?
 

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I would hazard a guess and say that it's the sound of the tyre compound scrubbing the road/drive surface as the wheel twists on its vertical axis during the sharp turn. The fact that it gets louder with cold tyres bares this out as the compound will be quite hard (assuming you are running summer tyres). The fact that you have wide, low profile tyres will also exasperate this effect. Alternatively, it could be something to do with the traction control sensing the twist/scrub of the tyre/wheel and trying to do something about it by - perhaps - attempting to momentarily apply the brake on that wheel or suchlike. Let me know what MB say, but I would invite them to call by at your house one morning. You could also ask your wife to pull the car out one morning, and then get down and see what is happening at close quarters.
 

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Discussion Starter · #3 ·
Yo!
You'll be glad to know that MB have heard from other GL45 owners about this.. however, its not deemed an issue yet.
I did a test this morning, and turned LEFT and not right.. and the same thing happened.
I think you might be on to something with your comment about the 4 wheel drive; MB intimated that this only happens on the cars that have 4 wheel drive AND low profile tyres.
Funny why it only happens from a cold start...
 

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Like I said, the summer tyre compound will be very hard when cold, so it will have different grip characteristics on your driveway, which will lead to a different sound when scrubbing (twisting on its own axis). Basic physics tells us that the wider the tyre, the more the scrub, and the lower the profile, the less flexibility against scrubbing. This is all assuming that your issue is one of tyre-scrub, of course. The 4WD issue might be because the tyre is likely to scrub much more aggressively under power. By that I mean that the traction control might be detecting a loss of traction from the tyre as it twists/scrubs, and then sending power to it to try and improve that traction. But then all that would happen is that the scrubbing effect would increase, and ergo so too would the sound of the scrubbing effect. Simples! I can't wait to find out if I'm right ...
or
?
 

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Discussion Starter · #5 ·
I wouldn't hold your breath; my impression is that it's logged with MB and added to the list of others that have noticed the effect.
It's not as if it's stopping me driving. It's just a tad disconcerting first thing in the morning.
 

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Question is - does it only do it when leaving your drive? What about after its been parked up in a works car park?
We have tarmac drive and pavement, the power steering does rip this up somewhat so you're left with small loose bits of gravel under your wheels.
 

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Discussion Starter · #7 ·
It's not my drive, its the road. It occurs whenever the car has been stationery for a few hours.
It would appear to be something to do with the 4x4 drive; it only occurs when you make a sharp turn (left or right) after being stationery. Once i have driven a few mins, subsequent turns do not generate the noise.
 

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It is to do with the setup of the car wheels camber I have had this also and thought it was a problem but once the tyres are warm the car is fine no bumping effect when starting off first thing in the car..
 
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