Different tyres a problem ?

[nickyboy1]

Hi to all !
Can anyone help with a query about my tyres ?
I have a 98 SLK 230, and have just noticed my tyres have been replaced incorrectly when I had a bump !
The rear 2 are 225/50/16, and I should have 205/55/16 on the front 2.
One of the front 2 is however a 225/50/16...the same as the rear.

Woul this pose a problem, handling, etc ?

Thanks for any help !!

Nick

PS How many other SLKs have been "grounded" this last week ? (snow)

 

[mlc]

I think you have a problem. You need to check with your tyre dealer but I think the legals are that you must have the same tyres across an axle. Clearly get you home spares break these rule but I think thats a legal exception.

Hope this helps.

Mark.

 

[jberks]

Im not sure in reality it would make a drastic effect, especially given the fact that ESP and ABS will look after you if one tyre grips differently to the other, but the fact remains that you will have different handling characteristics across the axle, which is fundamentally wrong. Also, as one tyre will have greater grip than the other I imagine it will stuff up your tracking too.

I'd get them to put a 205 back on . In fact I'd also insist they replace both front tyres so you have 2 tyres worn to the same level - its the least they can do given their incompetence!

 

[Myros]

The diferent rolling diameters may fool the abs/esp into reacting incorrectly if they trip in. Definitely get the same all round, or at least across an axle (and carry two spares?)
Space savers are ok but don't go faster than the stated max speed, usually 50 mph. Better to get the real mccoys fitted as soon as poss.

 

[SLinKyjoe]

They need to be the same. the 50 are lower than the 55 so one wheel will be rotating slightly faster than the other...you should check to make sure which type you should have on. the fuel filler cap will have the wheel size and pressure fitted to your car at the point of sale. take it back

 

[nickyboy1]

Thanks to all replies....will be chasing the company for a refit !
Many thanks !

 

[pascal]

205/55 x 16in = 55% of 205 = 113mm(112.75) + 203mm(1/2 16in)
So overall radius = 316mm

225/50 x 16in = 50% of 225 = 113mm(112.50) + 203mm(1/2 16in)
So overall radius = 316mm

They both have the same radius, so the circumference is the same on both.

So they will not fool the ABS

Having said that the 225 will have more thread on the road than the 205 (20mm)
and more grip and I would find this unacceptable.

If MB designed the car around these parameters, they did so for a reason.
They wanted the same rolling circumferance f/r but more rubber on the back.
Trust the designers on that and insist that the garage change it.

PS; no coments on the 1/4mm difference

Pascal

 

[SLinKyjoe]

205/55 x 16in = 55% of 205 = 113mm(112.75) + 203mm(1/2 16in)
So overall radius = 316mm

225/50 x 16in = 50% of 225 = 113mm(112.50) + 203mm(1/2 16in)
So overall radius = 316mm

They both have the same radius, so the circumference is the same on both.

So they will not fool the ABS

Having said that the 225 will have more thread on the road than the 205 (20mm)
and more grip and I would find this unacceptable.

If MB designed the car around these parameters, they did so for a reason.
They wanted the same rolling circumferance f/r but more rubber on the back.
Trust the designers on that and insist that the garage change it.

PS; no coments on the 1/4mm difference

Pascal

that is of course what i meant to say in mine.....ahem!!!!

well i would have had i known. At least he should have them changed.

 

[pascal]

Thanks Joe,

Tyre manufacturers make a lot of different sizes of tyres
But you'll find that they all cumulate in only a fraction of different rolling circumferences.
This is so people can upgrade their car without affecting their gearing, abs etc.

A lot of people think that 35..40..45..50..55..60..65 refers directly to the width
of the sidewall. It doesn't directly; but indirectly as a percentage of the overall tyre width,
205..215..225..235..245..etc

Pascal

 

[mlc]

I think we are missing the point here. I suspect that for most people the difference in tyre our friend has would be hard to spot in terms of driving, indeed his post infers that he has driven for some time without noticing.

However having done a little bit of checking I am sure that mixing tyre sizes on an axle breaks the construction and usage rules. The car would fail an MOT and could easily cause you trouble if you had and accident or insurance claim. Worst case could be that the insurers that paid for the replacement tyre could refuse to cover your lose - which would be ironic if nothing else!

I think that you should push for a replacement tyre of the correct size ASAP, however I dont think you have any chance of getting them swapped as a pair. Assuming that you are insured with a reputable company I would expect them to assist you if you dont get immediate satisfaction from the repairer.

I also spotted the rule on space saver tyres. They can only be used as advised by the car maker, must be of a different colour and must have a sticker stating their speed restrictions - you learn somethig every day.

Mark.

 

[pascal]

I don't feel we are missing the point.

Everyone bar one advised replacement.

Also I think that ones safety is of vital importance as is staying within the law.

But in that order

In this case changing the tyre will satisfy both.
So again:

Trust the designers on that and insist that the garage change it.

 

[jberks]

I don't feel we are missing the point.

Everyone bar one advised replacement.

Also I think that ones safety is of vital importance as is staying within the law.

But in that order

In this case changing the tyre will satisfy both.
So again:

Who was the "bar one" - just been back through and as far as I can tell, everyone says the same thing - get it fixed. - There are differences of opinion as to the severity of the issue from a pure safety point of view, but no one I have read considers it acceptable.
My point was that the key difference would be traction, given that they have the same rolling diameter (The abs/esp warning light would be on otherwise) and this is precisely what ESP and ABS is designed to handle (traction differences between wheels) so I believe the car is "safe" from an "is it going to kill me" view point - but legally and sensibly its clearly not an acceptable situation and I would have it changed immediately.

 

[mlc]

Gentlemen - I didnt mean to start an row. Every one seems to agree that the tyre should be changed at the cost of the repairer. My point was simply that its easier to go back to them and say you have made the car illegal by fitting an inappropriate tyre, the replacment should then be automatic.

Mark.

 

[johnmc]

Driving with one full size wheel slightly different to the rest is not a big
issue, just don't go mad when driving. Moderate your speed and slow down
more in corners. I have a Seat Ahlhambra where the spare is full size but 16inch instead of 17inch that are on the road wheels, and it is one size down in width. Seat recomends not exceeding 50mph when it's on the car as in EXTREME cases like high speed cornering the car's handling will be less good than with all wheels the same size. When driving normally, within road speed limits etc it will be just fine.

It's now worse than adding winter tyres to your car, as many folks do with the rear wheels on Mercs. When something is non-standard be careful.

John

 

[pascal]

Driving with one full size wheel slightly different to the rest is not a big
issue, just don't go mad when driving

Using one for a spare is a different proposition altogether, just like with spacesaver
wheels. But should only be used to get you home or to a garage.

To drive a car that is 1% less than perfect on purpose on a regular basis, when
the remedy is as simple as going back to the garage to get it put right for free,
in my opinion is totally irresponsable.
Also

When driving normally, within road speed limits etc it will be just fine.

does not wear with me at all unless its just to 'get you home' or to the garage

 

[jberks]

Pascal,
I think there is a subtle difference between unsafe and undesireable. hence the apparent 'disagreement'. I can see no technical reason to declare such a situation as unsafe as discussed above, but agree wholeheartedy that if its not spec, its not acceptable and I would happily drive it 100 miles to the garage to have it changed! (insurance rules depending). Clearly if the insurance co said no, then its a low loader job.

 

[Geoff_Slade]

If the car would fail an MoT then there's no question that the tyre needs replacing. The MoT only checks safety related items hence if it's a fail it must be unsafe. That's not to say that you will immediately go off the road but you need to get it changed (for free) ASAP.

 

[pascal]

This is no fun...... we're all agreed

Got that NickyBoy?

Well if you didn't, Get them to change that tyre immediatly.

Tell them all us 'experts' at MB club said so. (joking)
(but WE did).

Pascal

 

[SLinKyjoe]

yes tell them.

and tell them our dads are bigger than theirs too and we are not frightend to use them!

is this the first thread where we have all agreed?

 

[Myros]

I'd say it was, but remind me what it was we agreed on. Good thread chaps, keep it up.