Mixed advice from tyre suppliers

Gh3382

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I am replacing the two front tyres on my ML so I have been shopping around.

I am astounded by the mixed and what I believe to be bad advice from some of the suppliers. I wanted to upgrade from Continental Contact 2 to another brand in an effort to get a quieter tyre and I was considering Good Years or Michelin. I would do the fronts first then the backs when they needed changing.

Some suppliers say fine to change to another brand as long as both on the same axel others say no stay with the tyres I have and dont even upgrade to the Continental Contact 5.

Halfords have told me that I must change all 4 as uneven wear depth on front and back will cause damage to the transfer box due to it being permenant 4 wheel drive.

I normally change in pairs on the same axel with no problems mainly because of the cost and also the fronts wear more quickly than the rear. My manual also says put new tyres on the front but Costco said they would only fit on the back.

My Continental Contact 2's have been ok (20,000 miles mainly town driving) but not good on fuel consumption and are a bit noisy compared to ratings of many other tyres.

Think I might buy a pushbike.

Gh3382
 

Rorywquin

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Yea that misconception, he sells tryres so he knows about them. All they want to do is move stock or get a bonus from the tyre company.

Do your research at tyre manufacturer sites or reputable suppliers (Blackcircles etc).

The problem of replacement tyres is worse when front & rear are different sizes & directional.....o_O

We recently replaced tyres on my wife's car. Rears were fine & only replaced the front. No issues at the supplier (Kwik Fit).
 

tonysmb

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There might be a degree of truth in what Halfords have said, it's certainly worth researching further. It was the case that with the MK1 Land Rover Freelander differing tread depths front/rear could affect the transfer box and the advice was to change all four; I don't know whether it's a factor on the ML.
 

horatio

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One of those topics which quickly descends into 5 pages of arguments :)

Although if you just want a different type for quietness why not change all 4 and rotate for even wear. Put one of the good tyres on the spare if you have a full size. Not something you have to consider again. Until you get a puncture on a half worn tyre 🤣
 

grober

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Look up the purpose of differential gears- which every car has--4wd cars have an additional central one. unless travelling in a straight line all car wheels travel slightly different distances and thus rotate at different speeds relative to each other.
 

190

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Historically there have been some 4WD cars where it mattered that all 4 tyres had the same tread depth and that will be colouring the responses of the tyre outlets. I doubt it is so much of an issue today but either way, I wouldn't trust any of the tyre depots on this. If it's that important it will be found printed in the owners manual big and bold.
 

Bobby Dazzler

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A few questions if I may, the most important being: What is the measured tread depth on each of the four tyres?

If you already have a difference of say 3 mm between the axles, then if changing tyres on one axle means that you still have a difference of 3 mm between the axles then you’re in a similar position to today.

Are your tyres wearing equally across the full width of the tread, or are they wearing more on the inside, outside or centre?

If the front is wearing more on one side than the other then it would be worthwhile getting a four wheel alignment performed. Poor wheel alignment leads to lots of tyres being replaced prematurely.

I prefer to replace tyres in full matching sets. I’ve had three different generations of ML and all wear at very similar rates across both axles. I prefer to be sure that I have consistent performance on all four tyres.

99.99% of the time, there’s nothing to distinguish between excellent and poor tyres. Emergency situations and extreme conditions are where the difference is felt, and it’s the same with too.
 
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Gh3382

Gh3382

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A few questions if I may, the most important being: What is the measured tread depth on each of the four tyres?

If you already have a difference of say 3 mm between the axles, then if changing tyres on one axle means that you still have a difference of 3 mm between the axles then you’re in a similar position to today.

Are your tyres wearing equally across the full width of the tread, or are they wearing more on the inside, outside or centre?

If the front is wearing more on one side than the other then it would be worthwhile getting a four wheel alignment performed. Poor wheel alignment leads to lots of tyres being replaced prematurely.

I prefer to replace tyres in full matching sets. I’ve had three different generations of ML and all wear at very similar rates across both axles. I prefer to be sure that I have consistent performance on all four tyres.

99.99% of the time, there’s nothing to distinguish between excellent and poor tyres. Emergency situations and extreme conditions are where the difference is felt, and it’s the same with too.
Bobby Dazzler

The rears are at 5.5 mm and the fronts just under 3mm. They have even wear but I intend in getting a wheel alignment done anyway.

I bought this car second hand over 4 years ago and it had two new tyres on the front so obviously it had tyres replaced before in pairs not all 4.
If any damage is caused by a difference in front and rear wear to the transfer box I should imagine it has already been done

I think I have come to the conclusion I am just going with what is on the Continental contact 2's which have been ok at least I know how they will handle and they work ok on the car.

out of interest what did you put on your last ML ?

gh3382
 

Dryce

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Look up the purpose of differential gears- which every car has--4wd cars have an additional central one. unless travelling in a straight line all car wheels travel slightly different distances and thus rotate at different speeds relative to each other.

Problem is that there are different 4WD systems.

This tyre depth thing seems to have become a sort of myth applicable to all cars. I've tried explaining the concept of a 4x4 with a differential to acquaintances adamant that all tyres must be replaced if they get a puncture - because that is what they are rep[eatedkly and assertively told by tyre suppliers.

My understanding is that the problem setups are those with viscous couplngs instead of differentials (eg. Suzuki). And there may be a case for some clutched non-permanent systems getting caught out in some circumstances.

For those with real differentials - then I haven't had a viable explanation as to why in the modern day and age those differentials can't do their job. I guess it's a convenient truth to the tyre suppliers that all 4 tyres need replacement - just like the concept that runflats are not repairable.
 

Bobby Dazzler

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Bobby Dazzler

The rears are at 5.5 mm and the fronts just under 3mm. They have even wear but I intend in getting a wheel alignment done anyway.

I bought this car second hand over 4 years ago and it had two new tyres on the front so obviously it had tyres replaced before in pairs not all 4.
If any damage is caused by a difference in front and rear wear to the transfer box I should imagine it has already been done

I think I have come to the conclusion I am just going with what is on the Continental contact 2's which have been ok at least I know how they will handle and they work ok on the car.

out of interest what did you put on your last ML ?

gh3382
So at the moment you have around 2.5 mm difference in tread depth between front and rear axles. New summer tyres typically have around 8 mm so the difference will be similar, and so the risk of it causing problems will be similar too.

At 3 mm you’re still some way away from the legal minimum tread depth, so you could go further without replacing them if you can put up with the noise for longer. Just be mindful that they’ll be less able to clear water in wet conditions.

If you do buy a quieter tyre, then you may not notice the difference until the rears are changed to a quieter tyre too.

In summer I have run both on Pirelli PZero, replacing like with like, but I have just switched one to Michelin Pilot Sport 4 S. The Michelin seemed louder at first but seemed to have quietened down, although I’ve not known that with new tyres before.

In winter I run Continental CrossContact on both cars, and I’ve been very pleased with them. Apart from the Michelin being noisy at first, I have never really noticed any significant difference in noise or performance between brands or season.
 
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Gh3382

Gh3382

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UPDATE

I have booked it in for two new tyres and staying with the Contact 2's.

I have spoken to both Continental and Mercedes who both tell me they do not advise changing from the original Contact 2's because they are in still in demand that is why Continental are still making them and there is updated Continetal tyre for the car.

As for fitting, both the handbook and Mercedes say to put the new ones on the front. As for replacing all four tyres at the same time to avoid transfer box damage Mercedes tell me this was an issue with early permenant 4 wheel drive but not my ML unless the front and rear have extremes of wear such as newish on one axle and nearly bald on the other.

So despite me trying to be a smart **** and better things I am staying with the same set up.

Thanks for all your input.

GH3382
 

markjay

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Personally, I would change all 4 tyres. Nothing to do with 4WD, I just would, even the 5.5mm ones (and yes I am aware that this attitude isn't eco-friendly). Changing just 2 tyres at a time is a cycle that's difficult to break, so you swallow the pill once and you are then sorted. If the wheels aren't staggered, I would also rotate the wheels front-to-back at every service (or every other service - depending on annual mileage). And don't forget to take the car to someone with a Hunter machine for full geometry adjustment as soon as the 4 new tyres are on the car. This is what I would do, anyway - 4WD or not.
 

MercedesDriver

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Personally, I would change all 4 tyres. Nothing to do with 4WD, I just would, even the 5.5mm ones (and yes I am aware that this attitude isn't eco-friendly). Changing just 2 tyres at a time is a cycle that's difficult to break, so you swallow the pill once and you are then sorted. If the wheels aren't staggered, I would also rotate the wheels front-to-back at every service (or every other service - depending on annual mileage). And don't forget to take the car to someone with a Hunter machine for full geometry adjustment as soon as the 4 new tyres are on the car. This is what I would do, anyway - 4WD or not.
But the OP bought a car with new front tyres 4 years ago and those went from 8mm to 3mm while the rears lost 0mm-2.5mm in the same period. Unless he doesn’t resolve the the thread wear at the front he’ll probably go through this front set before having to change tyres at the rear.
 

markjay

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....Unless he doesn’t resolve the the thread wear at the front he’ll probably go through this front set before having to change tyres at the rear.

Agreed:

....And don't forget to take the car to someone with a Hunter machine for full geometry adjustment as soon as the 4 new tyres are on the car...
 

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