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RE: Mercedes tyre 'skipping' - official statement

RE: Mercedes tyre 'skipping' - official statement

Friday 27th January

Mercedes tyre 'skipping' - official statement

That unpleasant front axle hop on full lock in Mercedes-AMG '43 models? It's just a 'comfort issue' apparently...



The new twin-turbo V6 powered Mercedes-AMG '43 models aim to plug a gap between 'civilian' Mercedes and the full-blown AMG flagships in the range, much as S-branded Audis and M Performance BMWs do in the line-ups of immediate German rivals. For those who feared this would dilute the power of the AMG brand comes the formidable riposte in the shape of the 612hp E63 - rather it gives the performance division extra headroom to make its V8 product even more mental. Bravo for that.


So far we've driven estate versions of the C43 and E43 and liked both for their understated looks, strong performance, all-weather all-wheel drive and 'all you'd ever need' mix of practicality and pace. Both, however, have displayed an unpleasant sensation of the front tyres juddering in low speed manoeuvres while on full lock. It's a problem seemingly apparent on equivalent GLC models too, including the non '43 models. And one that's got more than a few PHers reporting in with their own experiences on their cars.

As promised we have been chasing for an official response and a statement has been forthcoming and is reproduced in full below. The official version is that it's nothing to do with the 4Matic all-wheel drive system, despite the sensation being very much like a 'tight' centre diff reacting to different rotational speeds on the front and rear axles when making tight turns. Mercedes says it's tyres struggling for grip in low ambient temperatures.

To be fair to Mercedes we've also felt similar characteristics on the Porsche Panamera 4S diesel we had in on test last week, also in the low temperatures Mercedes says contributes to the problem. It was nothing like as obvious as it was in the C- or E43 though. Nor does it seem to occur in our PH Fleet Audi S4, the car the C43 in particular seems aimed directly at and one that has a comparable performance remit and power output, if a different mechanical layout for its four-wheel drive system. It also has comparably sized 18-inch wheels to the C43, though Audi fits 245/45 tyres all round while Mercedes uses 245/40s on the rear and 225/50s on the front.


Whether owners will be entirely delighted at being told (we paraphrase...) 'they all do that sir, your dealer will be delighted to sell you another set of wheels with winter tyres fitted' is something we can leave to the thread that will inevitably follow this story. The response to being told it's "a comfort issue" would, having experienced it ourselves, quite reasonably be "too bloody right, that's why I'm not happy."

There is, of course, a more PH solution to this problem. Whether it's indeed the 4Matic system or the tyres you could instead put some of that budget allocated to the extra set of wheels and upgrade to an E63. Simply engage the RWD, ESP off, Drift Mode, let the rear tyres dictate your direction of travel and make your low-speed parking manoeuvres considerably more spectacular and smoky. Maybe AMG could introduce it on the '43 models and rebrand it 'Comfort Mode' and be done with it. Surely it's a 4Matic control unit reflash away from being made a reality... We'd take that over a set of winter tyres for sure.


Mercedes-Benz UK statement issued 24/1/17 and reproduced verbatim:
We're sorry to hear that a small number of customers have experienced an issue with certain models, generally at cold ambient temperatures while manoeuvring at low speed with steering lock applied. The experience is of the front tyres apparently 'skipping'. This is a comfort issue, and does not affect the safety or performance of the vehicle.

This characteristic comes from flexibility within the tyre sidewall, the grip between the front tyres and the type of road surface being driven over. It is something which can be felt only at very low speeds, and when a certain percentage of wheel lock is engaged for turning. This is demonstratively more evident in colder temperatures due to the changes in the tyre rubber elasticity.

Winter tyres and all-season tyres on 18- or 19-inch wheels improve this characteristic and we would always recommend their use in temperatures which fall below approximately +7 degrees Celsius. The use of 18-inch wheels with summer tyres also improves the issue.

We do, however, appreciate that is not always possible or practical for customers to fit alternative tyres or wheels, and our technical experts in the UK are investigating alternative ways to help minimise this characteristic.


Author
Discussion

Kenny Powers

Original Poster:

492 posts

48 months

Friday 27th January
quotequote all
This isn't that unusual, perhaps surprisingly to some. It comes about through imperfect Ackerman geometry and will indeed be felt more at low speeds on low grip surfaces. It isn't anything to be concerned about in terms of mechanical integrity.

urquattroGus

577 posts

111 months

Friday 27th January
quotequote all
C7 RS6 does this...

dxg

4,781 posts

181 months

Friday 27th January
quotequote all
Kenny Powers said:
imperfect Ackerman geometry
This is the point i was going to make, but the other way round. How can a can manufacturer get the design of something as fundamental as the steering rack and arms wrong? Could this be a case of part-sharing gone too far?

swisstoni

5,478 posts

200 months

Friday 27th January
quotequote all
How often does any car spend on full lock? Seems a fair bit of fuss about not much unless I'm missing something, which isn't out of the question.

kambites

51,752 posts

142 months

Friday 27th January
quotequote all
dxg said:
Kenny Powers said:
imperfect Ackerman geometry
This is the point i was going to make, but the other way round. How can a can manufacturer get the design of something as fundamental as the steering rack and arms wrong? Could this be a case of part-sharing gone too far?
I don't think it is "wrong" as such. Modern cars generally don't run pure Ackerman geometry for handling reasons so pretty much all modern cars will have a certain degree of "scrub" on the front axle at high steering inputs. Mercedes have clearly taken this a bit further than other manufacturers and/or have fitted tyres which are particularly sensitive to it but I suspect it was intentional - presumably they consider whatever handling benefit they're aiming for to be worth the trade-off of a slight NVH type issue in low-speed manoeuvring at low temperatures.

I think one could argue it's just another disadvantage of the current fashion for enormous wheels and rubber-band type tyres.

Edited by kambites on Friday 27th January 09:00

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Kenny Powers

Original Poster:

492 posts

48 months

Friday 27th January
quotequote all
dxg said:
This is the point i was going to make, but the other way round. How can a can manufacturer get the design of something as fundamental as the steering rack and arms wrong? Could this be a case of part-sharing gone too far?
I think it's more that all design is a compromise. There will likely be all sorts of considerations, especially with large rims. Probably particularly more so when drive shafts are involved. Most likely the lock geometry is optimised for normal driving, with a compromise to low speed turning lock manoeuvres. One thing I am certain of, is that Mercedes will have been very aware of this during the design stages. It isn't a mistake, and it's not the only car to exhibit such traits.

Whether or not this is acceptable is down to the individual smile

big_rob_sydney

1,881 posts

115 months

Friday 27th January
quotequote all
It does beg the question though; when other manufacturers of cheap-arsed cars can get it right, why should people spend big money on a "premium" brand, to get it so wrong?

MB can go fk themselves.

Kenny Powers

Original Poster:

492 posts

48 months

Friday 27th January
quotequote all
kambites said:
I don't think it is "wrong" as such. Modern cars generally don't run pure Ackerman geometry for handling reasons so pretty much all modern cars will have a certain degree of "scrub" on the front axle at high steering inputs. Mercedes have clearly taken this a bit further than other manufacturers and/or have fitted tyres which are particularly sensitive to it but I suspect it was intentional - presumably they consider whatever handling benefit they're aiming for to be worth the trade-off of a slight NVH type issue in low-speed manoeuvring at low temperatures.

I think one could argue it's just another disadvantage of the current fashion for enormous wheels and rubber-band type tyres.

Edited by kambites on Friday 27th January 09:00
Agree completely smile

Nezquick

1,021 posts

47 months

Friday 27th January
quotequote all
My M235i does this too. Full lock turns create a very unpleasant juddering - a friend's does exactly the same too.

Very odd.

GranCab

979 posts

67 months

Friday 27th January
quotequote all
I had a 4WD "head count" yesterday and I have owned 21 since 1990.

1985 Ford Sierra XR4x4
1989 Ranger Rover Vogue
1991 Land Rover Discovery
1991 Isuzu Trooper LWB
1994 Isuzu Trooper LWB
1995 Subaru Impreza Turbo
1997 Subaru Legacy Turbo
2001 BMW X5
2003 Range Rover Vogue SE
2005 Ranger Rover Supercharged Sport
2006 Mercedes Benz R320
2008 Mitsubishi Outlander Diamond
2008 Range Rover Vogue SE
2009 Land Rover Discovery HSE
2009 Nissan R35 GT-R
2010 Audi S5 Cabriolet
2012 Audi Q7
2014 Audi RS4 Avant
2016 Mercedes Benz A45 AMG
2016 Land Rover Discovery Sport HSE
2016 Mercedes Benz C43 AMG Cabriolet

The Mercedes Benz C43 AMG is the only one that has shown this odd phenomenon of skipping front tyres on tight low speed turns ...

N.B. the C43 is on 18" rims ....

Edit ... I missed off the XR4x4 smile





Edited by GranCab on Friday 27th January 15:49

glm1977

169 posts

82 months

Friday 27th January
quotequote all
isn't this just super cold tyres...? happens a lot on my cars in the winter when pulling out of the drive. come warmer times it disappears.

kambites

51,752 posts

142 months

Friday 27th January
quotequote all
I don't think it's related to 4wd; it's just a steering geometry issue combined with very stiff tyre sidewalls.

markoc

1,057 posts

117 months

Friday 27th January
quotequote all
My Boxster does this - and having looked at ackerman in the past (doubting the dealer's "they all do that sir...") I'd have thought that bigger wheels won't help. Mine's on factory 19's so perhaps more pronounced than in previous Boxtsers which have been on 17's and 18's.

I guess the compromise of absolute full lock slow speed manouevre (low frequency event) versus handling at speed (high frequency event) is the payoff...

... but I'm no engineer.

beerexpressman

62 posts

58 months

Friday 27th January
quotequote all
Maserati Ghibli does it too - mainly on very smooth surfaces in car-parks...

GranCab

979 posts

67 months

Friday 27th January
quotequote all
I must add that I have also had 33 2WD cars (starting with a Mk1 Ford Cortina in 1973 ...) and have never experienced it in any of them !

loose cannon

4,343 posts

162 months

Friday 27th January
quotequote all
My Megane rs 250 does it when the weather is very cold

ikarl

3,491 posts

120 months

Friday 27th January
quotequote all
GranCab said:
I had a 4WD "head count" yesterday and I have owned 20 since 1990.

1989 Ranger Rover Vogue
1991 Land Rover Discovery
1991 Isuzu Trooper LWB
1994 Isuzu Trooper LWB
1995 Subaru Impreza Turbo
1997 Subaru Legacy Turbo
2001 BMW X5
2003 Range Rover Vogue SE
2005 Ranger Rover Supercharged Sport
2006 Mercedes Benz R320
2008 Mitsubishi Outlander Diamond
2008 Range Rover Vogue SE
2009 Land Rover Discovery HSE
2009 Nissan R35 GT-R
2010 Audi S5 Cabriolet
2012 Audi Q7
2014 Audi RS4 Avant
2016 Mercedes Benz A45 AMG
2016 Land Rover Discovery Sport HSE
2016 Mercedes Benz C43 AMG Cabriolet

The Mercedes Benz C43 AMG is the only one that has shown this odd phenomenon of skipping front tyres on tight low speed turns ...

N.B. the C43 is on 18" rims ....
Surprised you have a 95 Impreza on your list, as my v2 STi skipped quite noticeably during tight turning

Cyder

6,170 posts

141 months

Friday 27th January
quotequote all
I'm sure I've felt this in the wife's A4 as well.

Kenny Powers

Original Poster:

492 posts

48 months

Friday 27th January
quotequote all
GranCab said:
I must add that I have also had 33 2WD cars (starting with a Mk1 Ford Cortina in 1973 ...) and have never experienced it in any of them !
Congratulations biggrin

Some cars do, however, exhibit this phenomenon. As I say, whether or not it's acceptable is an individual's opinion, but you can rest assured that with all considerations, and with everything Mercedes needed to achieve with this vehicle and combination of tyres, performance etc. that it was a necessary compromise. Most people think they can do everything better than everyone else, but that doesn't make it so wink

Neural

78 posts

164 months

Friday 27th January
quotequote all
Lotus Evora does it too.