Yes we all do from time to time, it's nothing to worry about. Have a read of this thread Tyre "bumping" noise

 

Ah thanks for that @Forrester

 

Always get this query this time of year, when ambient temps drop below 7 degC approx!

 

Its that temp now? even in July?

 

Although I have to say I haven't noticed it yet on my current car. Probably needs to get a bit colder still.

 

It’s to do with the 4 wheel drive system and the rolling circumference of your tyres, nothing to worry about. My old a45 used to do it all the time (wet or dry), when I bought it the dealer put new tyres on the front, so I ended up with Michelin’s on the back and continental on the front and it would bang like mad when turning. I went to them and told them what was wrong but they wouldn’t listen. Ended up putting PS4’s on the front myself and it went away immediately, only ever did it when slippery and full lock. The old Vauxhall’s calibra’s where terrible for it, you could’nt just replace a tyre on them you would end up having to do all 4 regardless of needing them or not, the thing would be un-drivable.

 

The old Vauxhall’s calibra’s where terrible for it

That really takes me back. I could only manage a Cavalier as a company car.

 

It's less to do with 4 wheel drive, more to do with the anti-ackerman steering geometry setup, many 2WD drive cars also exhibit this characteristic, RWD Porsche's for example.

Anti-Ackerman gives you high speed steering characteristics by overcoming tyre slip angles at high speeds, but the trade off (no free lunch) is that at low speeds, at full lock steering, the front wheels are pointing in (slightly) different directions, so in effect both front wheels (at full lock) are trying to steer in different directions. Add in the low ambient temperatures, the tyre compound is harder, hence why the tyre blocks are "skipping" or "juddering" as they are being asked to go in different directions.

Hence why winter tyres (or different/softer compound tyres) mask this, the tread blocks are more compliant at low temperatures and just deform and squish/squidge to the direction they are being asked to take, as opposed to skip/judder with the harder compound of most UHP summer tyres.

All answered in the linked post in Post #2 above, it has numerous examples of other marques displaying this characteristic too.

 

Yes I’m familiar with the Ackerman principle, are you sure these cars run anti-Ackerman and not regular Ackerman?

Either way anti or standard Ackermanns the front wheels are always pointing at different angles when in full lock, they’re not so much trying to steer a different way they both need to be at different angles to go the same way.

 

Yes, anti-ackerman, in line with most high performance cars.
So the outside wheel has more steering angle than the inside wheel, as more lock is applied.

Standard Ackerman, the inside wheel has more steering angle than the outside wheel, as the inside wheel has a smaller radius to turn, so no tyre skip/judder in this situation.

 

I see, as I say I’m familiar with the principles and how they work I just wasn’t aware it was used on these cars. Good stuff learning everyday 👍👍

 

Been experiencing this recently and i'm not sure if its because it's getting colder or something to do with my car. When I start my engine in the morning, I usually do a 3 point turn to get out of my driveway. When locking my wheel or turning the steering wheel so its near locked, and I drive, there is a weird sound from the wheels like loud clunking or the wheels clipping against something? Anyone experience this or something similar?

It is not Ackerman, it happens to only when I turn left, and some people from the group said it might be a driveshaft issue.

 

Welcome to the forum. It is probably something mechanical if you are getting this only one side and during the summer. Did it just suddenly start and what sort mileage have you done.

 

Welcome to the forum. It is probably something mechanical if you are getting this only on side and during the summer. Did it just suddenly start and what sort mileage have you done.

lol it happens everyday since day 1, but it gets much louder than before. My car is around 21k km, the steering also becomes extremely loose once speed hits above 160km/h.

 

If you are still under warranty or even if you aren’t I would take it in. In terms of the steering lightness I used to think that of my car but I have now got used to it and am happy about it. I’ve done just over 21k miles.

 

Guys, just a word of warning.

While @veeeight 's outline is 100% spot on as always, I don't see anywhere in this thread any reference to wheel alignment.

1) Don't trust any MB Dealership Service Dept. when they tell you your vehicle's wheel alignment is " in spec".
2) Find a specialist wheel alignment facility, (preferably Motorsport focused) which has the unique Mercedes optional front suspension package for their alignment machine.
It IS unique to MB and it is absolutely required when correctly undertaking the work on our vehicles.
3) My vehicle was so far out of spec, as delivered, as to be ridiculous. a professional wheel alignment has seriously changed the way my vehicle drives, including the cold start "clunking".
Still there, of course, for the reasons @veeeight describes; however nowhere near as pronounced.

 

If you are still under warranty or even if you aren’t I would take it in. In terms of the steering lightness I used to think that of my car but I have now got used to it and am happy about it. I’ve done just over 21k miles.

Lol just sent my car in for the repair yesterday. They can duplicate the issue but can’t find the cause of it, and the service manager even wanted me to pay for the diagnostic fee (telling me dirt and small rocks were the reason, totally bs) Definitely I refused to pay for anything while my car is still under warranty. After I got home, noise is reduced but it’s still there. Similar situation happened on my bro’s CLA45 too while his car was also under warranty, shame on mb dealers in Vancouver area.

 

@DK666
Your issue is almost certainly a combination of the factors outlined previously in this thread by @veeeight and me.

No MB dealership anywhere in the world is going to be able to "fix" this issue for you.
So, no reason to single out the Vancouver area ones.

 

Probably the alignment from the factory is the reason 😂 I noticed the Ackerman effect when I picked up my car, and it’s pretty normal for performance car, but this metallic ticking noise isn’t caused by the Ackerman View attachment 11692

Sounds like plenty of possibilities!!
Good luck with your trouble shooting.

 

Hi All,

I've noticed when setting off with steering on mid to full lock there is what I can only describe as tyre scrubbing. It feels like the front tyres are fighting against the direction the car is trying to go in which results in grating/scrubbing/juddering feeling from the front of the car. Is this normal for the A45S or does it need adding to the list of Warranty issues that the car is booked in for later this month?

Tyre wear seems even, though I've only done around 2k miles. Tyres are relatively new looking Michelins PS4S.

Many thanks
James.

 

It's quite normal. Read this even though it's in the W176 section.

https://www.aclassclub.co.uk/threads/tyre-bumping-noise.4161/page-6

 

Thanks very much, apologies for not finding that thread, must just have been the search terms i used.

 

the car has suffered terrible crabbing

Do you mean tyre judder/skipping rather than crabbing?
(Crabbing is when your rear axle is not aligned with your front axle, so the car isn’t going in a straight line along a single axis)

If so, have a read of this thread and the links within it

https://www.aclassclub.co.uk/threads/tyre-skip-judder.19599/

 

Hi. I've just signed up to add my experience of this. Hope it helps.

I own a 2023 GLA 45 Amg. I took it for a service today and on collection was told it had also had the following done as part of a recall: Replace rear axle flex disk and install additional screening plate

I hadn't been made aware of this in advance.

On doing a quick search online I found this forum. Sorry for hijacking with a GLA!!

I also found the info in my attached image. Seems to be from America. I don't really understand it but those of you more technically minded may find it helpful.

Since purchasing second hand the car has suffered terrible crabbing. Mercedes told me this is standard for premium cars like Mercedes and that Audi and BMW do it too! I said if I wanted an Audi or BMW I'd have bought one of them instead! Mercedes advised me to replace the stock Continental run flats with seasonal tyres. So now I have Michelin summer and winter sets. Expensive. And no spare. Infuriating. I don't know if this recall will fix that. I doubt it.

View attachment 14670

The flex plate recall will not have any impact on your other driving issue.

Please can you clarify what your driving issue is? Our A45s drive straight and true year round on the same set of tyres, in most cases.

 

The flex plate recall will not have any impact on your other driving issue.

Please can you clarify what your driving issue is? Our A45s drive straight and true year round on the same set of tyres, in most cases.

Thanks for your input guys. My GLA sounds like it is going through a pothole when I turn. It can also skid a little and fail to grip properly. I have no technical knowledge I’m afraid. But I believe it to be some sort of problem with the design of the front suspension somehow. I spoke to another GLA owner with an older model than mine who gets the same thing to a lesser degree and has always just lived with it. Mercedes seem to be suggesting it’s down to the tyre wall in the Continental run flats rather than any problem with the car itself. They advised running winter and summer tyres. Due to the size and width of the rims (255/35 21) my options are minimal/zero when it comes to all season options. So I have to have two sets and change them seasonally. And not have a spare as there’s no room in the boot.

 

Thanks for your input guys. My GLA sounds like it is going through a pothole when I turn. It can also skid a little and fail to grip properly. I have no technical knowledge I’m afraid. But I believe it to be some sort of problem with the design of the front suspension somehow. I spoke to another GLA owner with an older model than mine who gets the same thing to a lesser degree and has always just lived with it. Mercedes seem to be suggesting it’s down to the tyre wall in the Continental run flats rather than any problem with the car itself. They advised running winter and summer tyres. Due to the size and width of the rims (255/35 21) my options are minimal/zero when it comes to all season options. So I have to have two sets and change them seasonally. And not have a spare as there’s no room in the boot.

1. Is it at low speeds

2. is it at full steering lock or nearly full steering lock?

 

1. Is it at low speeds

2. is it at full steering lock or nearly full steering lock?

1. Yes

2. Near enough

Typically turning into and out of driveway or turning in a cul-de-sac. Tyre temperature doesn’t seem to make much difference.

 

1. Is it at low speeds

2. is it at full steering lock or nearly full steering lock?

FYI this is what the dealership I bought from said:

Having liaised with one of our master technicians, the "crunching sound" you are referring to sounds like something called tyre skip. This is created by turning the vehicle in full lock in low temperatures with cold tyres. Effectively, the vehicle is struggling for grip due to the nature of the size or the tyres and the tight turning circle. This is a common thing found in most high performance vehicles such as Audi RS, Porsche and obviously Mercedes Benz AMG.

And in a later email from Mercedes Customer Services:

[The dealership] have informed us that Tire skip is a known problem on AMG, referred to as a characteristic of the vehicle.

And further from Mercedes AMG UK:

We would like to apologise that you are unhappy with the tyre skipping on your vehicle, as advised by your Retailer, this is something that is considered a characteristic and not a fault and our recommendation is to fit season appropriate tyres.

We would like to provide our official statement on the matter;

''The distribution of weight on the front axle differential is different for all cars and manufacturers from left to right hand drive. In line with the Ackerman Principle this means there is a dependency on the tyre wall flexibility to help absorb the angles of steering when on a firm lock. When the rubber on the tyre is cold in certain temperatures the elasticity and flexibility of the tyre side wall results in a lack of absorption and essentially the tyre skips whilst trying to grip. It is something which can be felt only at very low speeds and when a certain percentage of wheel lock is engaged for turning. As per the Mercedes-Benz Digital Handbook for any car, we would always recommend the use of correct and approved tyres including winter tyres for temperatures which fall below approximately +7 degrees. This isn’t a safety issue.''

We have worked with the Driver and Vehicle Standards Agency (DVSA) and The Motor Ombudsman with regards to the tyre skipping characteristic. We are therefore able to confirm that there are no safety concerns, and this doesn’t affect the performance of your car.

 

Thanks for your input guys. My GLA sounds like it is going through a pothole when I turn. It can also skid a little and fail to grip properly. I have no technical knowledge I’m afraid. But I believe it to be some sort of problem with the design of the front suspension somehow. I spoke to another GLA owner with an older model than mine who gets the same thing to a lesser degree and has always just lived with it. Mercedes seem to be suggesting it’s down to the tyre wall in the Continental run flats rather than any problem with the car itself. They advised running winter and summer tyres. Due to the size and width of the rims (255/35 21) my options are minimal/zero when it comes to all season options. So I have to have two sets and change them seasonally. And not have a spare as there’s no room in the boot.

If it's this its normal:

(26) Tyre jumping thumping scrubbing noise on full lock? | Mercedes A-Class Forum

 

If it's this its normal:

(26) Tyre jumping thumping scrubbing noise on full lock? | Mercedes A-Class Forum

That seems to be it. The chap that uploaded the two Porsche videos to YouTube made me chuckle because I couldn’t hear a noise at all!!

I understand that it’s commonplace. I’m not sure that we as consumers should be describing it as ’normal’ though. Not if it’s something that can be engineered out with the right part.

I don’t really feel that it’s acceptable to be paying over £60k for a car only for it to sound like it’s going through a pothole every time you turn at slow speeds. Worse than that even. My car seems to lose grip and slide a little. Doesn’t give me a huge amount of confidence.

I also don’t like the Mercedes argument that other cars do it. If I wanted a car that was like an Audi, BMW or Porsche I’d have bought one of them!! The fact that they do it should be a reason for Mercedes NOT to!

 

We don't have run flats on the A45s. My experience of RFs from my daughter's mini are not very good. But you have different tyres now anyway. The bumping only starts when cold and damp, for most of us but at least you now have an answer.