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Discussion Starter #1
Hi everyone, SLK 250 cdi blue efficiency AMG Sport (2012)

Had a front tyre - 225/40 R18 92Y XL replaced 28th August (matching make and model, continental conti sport contact 5's) and got tracking done at same time, steering wheel was straight prior and post wheel change. Replaced 2 warn rear tyres - 245/35 R18 92 Y XL with Avon ZV7's on Tuesday and steering wheel is now off by approximately 1 cm. Been back and all tyre alignments are spot on so no one was able to give me an explanation or sort out the issue.

I'm booked in to my garage next week who have said they will sort out the issue for me... but my question to you is, has anyone come across this before and can you give me a definitive answer as to why rear tyre change should/could cause such an issue?

Thanks
 

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Super Moderator UK SLK 55 AMG 2007
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Discussion Starter #3
Thanks for the quick reply.

I've had a read through of all the post titles and although it seems I'm not the first to have the issue, I couldn't find a definitive answer. I await the opinion of "experts" with interest!!!!
 

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Registered 2012 SLK350
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So a complex question, in short a rear tire change (of both tires) will not affect alignment.

In detail going through you post I can make the following notes but not a determination.
1. A front tire change of just one side can affect the alignment depending on level of wear of the tire on the other side.
2. A rear tire change will not affect the alignment as long as they don't touch the rear alignment (which they typically wouldn't).
3. New tires can be defective, especially lower tier tires. If one of the tires has a significant enough variation in circumference the alignment will be affected.
4. Check tire pressure, high difference of pressure will affect alignment.
5. It might be perception, you might simply had the alignment going of because of suspension wear but did not consciously check it until tires were changed.
 

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Super Moderator UK SLK 55 AMG 2007
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So a complex question, in short a rear tire change (of both tires) will not affect alignment.

In detail going through you post I can make the following notes but not a determination.
1. A front tire change of just one side can affect the alignment depending on level of wear of the tire on the other side.
2. A rear tire change will not affect the alignment as long as they don't touch the rear alignment (which they typically wouldn't).
3. New tires can be defective, especially lower tier tires. If one of the tires has a significant enough variation in circumference the alignment will be affected.
4. Check tire pressure, high difference of pressure will affect alignment.
5. It might be perception, you might simply had the alignment going of because of suspension wear but did not consciously check it until tires were changed.
OP has rechecked alignment after the tyre change.

Wonder if he's hit a kerb/pothole and loosened something in the steering.
 

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Discussion Starter #7
No, definitely haven't hit curb or pothole.
Drove in for rear tyres and noticed a difference in steering wheel position during 9 mile drive home.
 

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Long Time Member 2005 SLK350
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Change the other front tyre as it is already worn to the way the car sits on the road.

The inner of the tyres wear off quicker than the outer edge due the the way the suspension is set up

So you will have one tyre with equal tread wear across it , lets say

6 mm inner 6 mm middle 6mm outer tread depths

The older tyre lets say

3mm inner 4mm middle 5mm outer tread depths.

This means untill the new tyre wears off a bit its is kind of trying to sit flat on the road while the other is worn to the way the suspension has been set up.

This will cause your pulling over and move wheel out slightly , live with it for a while and get some miles on it to bed the new tyre in or get another to even them out

Hope that kind of makes sense for you

Pete

P.s I did this to mine after fitting one new front after hitting pot hole.
Car then had service and tracking , still pulling so I fitted another new and it was fixed
 

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Discussion Starter #10
So a complex question, in short a rear tire change (of both tires) will not affect alignment.

In detail going through you post I can make the following notes but not a determination.
1. A front tire change of just one side can affect the alignment depending on level of wear of the tire on the other side.
2. A rear tire change will not affect the alignment as long as they don't touch the rear alignment (which they typically wouldn't).
3. New tires can be defective, especially lower tier tires. If one of the tires has a significant enough variation in circumference the alignment will be affected.
4. Check tire pressure, high difference of pressure will affect alignment.
5. It might be perception, you might simply had the alignment going of because of suspension wear but did not consciously check it until tires were changed.
Thanks VII7 for taking the trouble to respond.

I agree, fitting rear tyres won't affect steering wheel alignment, however it has!

1) There was no issue after fitting single front tyre (I drove over 1,000 miles before getting rears replaced)
2) It was a straightforward job of replacing rears, also they don't do rear wheel tracking as they don't have the correct machine for four wheel tracking, when I returned they sent me to another organisation to get it checked, so again, I agree with your sentiment, but steering wheel doesn't lie.
3) £100 a tyre, so not exactly budget.
4) I'll revisit tyre pressure.... thanks.
5) Definitely not correct in this case, I've driven over 17,000 miles since I bought the car, so I'd know if it had been out for a while, it's one of the things I love about driving the SLK, how true and straight the drive is/was.

Cars, don't you just love em!!!!
 

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Discussion Starter #11
So a complex question, in short a rear tire change (of both tires) will not affect alignment.

In detail going through you post I can make the following notes but not a determination.
1. A front tire change of just one side can affect the alignment depending on level of wear of the tire on the other side.
2. A rear tire change will not affect the alignment as long as they don't touch the rear alignment (which they typically wouldn't).
3. New tires can be defective, especially lower tier tires. If one of the tires has a significant enough variation in circumference the alignment will be affected.
4. Check tire pressure, high difference of pressure will affect alignment.
5. It might be perception, you might simply had the alignment going of because of suspension wear but did not consciously check it until tires were changed.
Was your previous set evenly wore?
Does the car pull to either side?
A sort of "yes" to the first question: both tyres were over worn in the centre, so I reduced them to 35psi from the recommended 38psi for the final 1000 miles

Car runs true with perhaps a slight tendency to pull left, but I've put that down to road camber?
 

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Registered 2012 SLK350
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Ok, to check the tires simply switch them to the other side and see if there is a change (if they are directional you have to switch them back after testing).
 

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Discussion Starter #13
Change the other front tyre as it is already worn to the way the car sits on the road.

The inner of the tyres wear off quicker than the outer edge due the the way the suspension is set up

So you will have one tyre with equal tread wear across it , lets say

6 mm inner 6 mm middle 6mm outer tread depths

The older tyre lets say

3mm inner 4mm middle 5mm outer tread depths.

This means untill the new tyre wears off a bit its is kind of trying to sit flat on the road while the other is worn to the way the suspension has been set up.

This will cause your pulling over and move wheel out slightly , live with it for a while and get some miles on it to bed the new tyre in or get another to even them out

Hope that kind of makes sense for you

Pete

P.s I did this to mine after fitting one new front after hitting pot hole.
Car then had service and tracking , still pulling so I fitted another new and it was fixed
Thanks for the response Pete, it does make sense, however I'm going to disregard it as an explanation, firstly I'm not buying another tyre!!! and secondly, I drove a 1000 miles after having the new front tyre fitted with no ill effects before getting the rears changed.

I hate these problems that can't happen... as I said in my original post, my mechanical garage have told me they can sort it out for me.... I'm more keen here to get that definitive reason why the thing that can't happen, has happened!!
 

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Discussion Starter #14
Ok, to check the tires simply switch them to the other side and see if there is a change (if they are directional you have to switch them back after testing).
Thanks, that's a top tip, I'll let you know
 

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Registered 2005 SLK55 AMG
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There is nothing complex about this, it is simple user/equipment error.

The alignment has been carried out but the wheel is now off centre, it won't be anybody's fault per say - other than the equipment giving you off readings unknowingly.

I've done 100's of alignments on Merc's over the years, most successful, but other's that I've genuinely pulled my hair out and done 3-4 times. Ultimately you're at the mercy of the equipment you use. Even the latest and greatest Beissbarth/Hunter equipment isn't immune. You will lock the steering wheel with the chock as tight as you can lift it, align the car so that everything is spot on and all in spec, drive it down the road and the steering wheel will be miles out!

As the increments of degrees are so fractional, it's very easy for reading to be skewed somewhat. You will never put the same car on an alignment ramp twice and get the same readings/measurements and there are many variables that can alter the readings.

Ultimately, it just needs re-aligning again until it's correct. I don't think I've ever had an alignment at a tyre place that has resulted in a perfectly straight steering wheel after unless they did it by sheer luck. They need to keep going at it until it's right, or sacrifice the £25 quid and go to a different place that specialises in suspension setup/main dealer. (that you can have a moan at because you spent £120 and it's still not right)!
 

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Premium Member 2014 SLK55 AMG
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was going to suggest that you take it elsewhere for alignment but Topaz has hit the nail on the head I think.
 

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Discussion Starter #17
There is nothing complex about this, it is simple user/equipment error.

The alignment has been carried out but the wheel is now off centre, it won't be anybody's fault per say - other than the equipment giving you off readings unknowingly.

I've done 100's of alignments on Merc's over the years, most successful, but other's that I've genuinely pulled my hair out and done 3-4 times. Ultimately you're at the mercy of the equipment you use. Even the latest and greatest Beissbarth/Hunter equipment isn't immune. You will lock the steering wheel with the chock as tight as you can lift it, align the car so that everything is spot on and all in spec, drive it down the road and the steering wheel will be miles out!

As the increments of degrees are so fractional, it's very easy for reading to be skewed somewhat. You will never put the same car on an alignment ramp twice and get the same readings/measurements and there are many variables that can alter the readings.

Ultimately, it just needs re-aligning again until it's correct. I don't think I've ever had an alignment at a tyre place that has resulted in a perfectly straight steering wheel after unless they did it by sheer luck. They need to keep going at it until it's right, or sacrifice the £25 quid and go to a different place that specialises in suspension setup/main dealer. (that you can have a moan at because you spent £120 and it's still not right)!
Interesting read Topaz, the bit that I'm unsure about, I'd already done over a 1000 miles with the new single front tyre with no ill effects, so have to presume the alignment at that time was 100%, it was only on getting the 2 rear tyres 3 weeks later that the problem occurred. The next day I went back and they suspected rear alignment needed doing, as they didn't have correct equipment, they sent me to a competitor with the 4 wheel alignment equipment. It was here that they confirmed all figures were within acceptable tolerances.
 

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Premium Member 2014 SLK200
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It was here that they confirmed all figures were within acceptable tolerances.
So they also thought is was acceptable for the steering wheel alignment to be out despite having checked everything?

Something doesn't add up.

Have you driven on a dead flat surface to check or just on roads with a camber?
 

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Discussion Starter #19
So they also thought is was acceptable for the steering wheel alignment to be out despite having checked everything?

Something doesn't add up.

Have you driven on a dead flat surface to check or just on roads with a camber?
Can confirm that the miles I driven since the issue includes roads both with camber and without, so it's the car rather than the effect of the road..... sadly!
 

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Registered 2012 SLK350
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Well I had a new set of tires install and it was the Rear that cause the front end problem that cause the front end issues. Tires were switch from side to side and the issue follow the change. In the end it was a new front and a new rear that cause the car steering wheel to change and my vehicle would also go left or right depending on tire positions. My alignment guy new what was causing but not which tire until after the position change. New tires fixed the issue. Straight and true now for a few years.



Not keeping the tires match can also cause this issue.
 
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