[YvesD]

What are your thoughts on the following.

Is there any reason why I cant fit a 'MO' (Mercedes Only) designated tyre to my OEM rims provided that they meet or exceed the required load index and speed rating?

Reason being I've ordered a set of Conti SC3's from Camskill 225/40 92Y MO front and 255/35 94Y MO rear. Thats all they listed in the Y rating tyre.

My BMW dealer wont fit them for me as they are not approved for the vehicle. I think this is more to do with the fact they are not runflats rather than the 'MO' designation.

What do you guys think?

Cheers

Yves


Interim update.


BMW were right to caution the use of these tyres on size grounds, the 255 rears ar MUCH wider than the OEM Flintstone Junkflats originally fitted. See picture! More apparent when looking straight down between the two in the second image.

The effect at the rear is that the arches are filled out to the extent I previously experiened when using 12mm spacers! No kidding. Its very tight on the Coupe, cant speak for the saloon versions.

Rolling diameter is about the same.

I also compared the CS3 MO 255's side by side against the SP5 265 wide tyres. In terms of actual tread contact patch, very little difference....

So, what are they like on the road? Excellent, the deeper sidewalls and much lower running pressures ( 32/35 ) give a silky smooth comfy ride whilst maintaining steering precision and tremendous grip. They feel right at these pressures, not heavy or stodgy at all.

The only gripe I have is I'm afraid they are quite noisy compared to the Flintstones. Oh well, cant have it all I suppose.

Have painted the inner lip of the rear arches with some gunge to see if it meets with the tyre sidewall at any point. Boy its close!

Cheers

Yves

[willhollin]

I would think your insurance company would be the people to ask, although I expect they are exactly the same tyre as the non-MO approved ones.

[kdiz]

I think BMW are only approved to fit the original type of tyre i.e. run flat. As for insurance, providing it meets the load index and speed raiting .

Not sure though

[YvesD]

Originally Posted by willhollin

I would think your insurance company would be the people to ask, although I expect they are exactly the same tyre as the non-MO approved ones.

Hi,

Insurerers arent concerned, the question is whether there is a technical reason not to use MO designation.

??

For example the Conti SC3 load and speed indexes are both far higher than the OEM tyres......

[kdiz]

Originally Posted by YvesD

Hi,

Insurerers arent concerned, the question is whether there is a technical reason not to use MO designation.

??

For example the Conti SC3 load and speed indexes are both far higher than the OEM tyres......

E92fan wrote in his review of conti SC5

"The 18" sizes are designated MO - Mercedes OEM fitment, but they are suitable for BMWs as well because the load rating is higher than that required for our own cars."

[YvesD]

Originally Posted by kdiz

E92fan wrote in his review of conti SC5

"The 18" sizes are designated MO - Mercedes OEM fitment, but they are suitable for BMWs as well because the load rating is higher than that required for our own cars."

kdiz, thats helpful, thanks for reminding me about that.

Yves

[willhollin]

Oh, you are going to SC3's and not the SC5's? You no like the new ones?

[225_AB]

Have you tried contacting anneka on this forum as she is an extremely knowledgeable sytner rep who would know or find out for you.

[doughboy]

Originally Posted by YvesD

What are your thoughts on the following.

Is there any reason why I cant fit a 'MO' (Mercedes Only) designated tyre to my OEM rims provided that they meet or exceed the required load index and speed rating?

MO doesn't mean Mercedes Only, its means Mercedes Original equipment. It means it has undergone some approval by Mercedes for OE fitment to their cars.

Just the same as Star approved means they are approved by BMW.

All that matters it the Load index and speed rating etc meet or exceed that required for your vehicle.

Any dealer that says otherwise is talking out of their arse.

[YvesD]

Originally Posted by doughboy

MO doesn't mean Mercedes Only, its means Mercedes Original equipment. It means it has undergone some approval by Mercedes for OE fitment to their cars.

Just the same as Star approved means they are approved by BMW.

All that matters it the Load index and speed rating etc meet or exceed that required for your vehicle.

Any dealer that says otherwise is talking out of their arse.

Doughboy, I'm with you 100%

My dealer WILL NOT fit these tyres for me for 'legal reasons'........They will only fit BMW 'star' rated tyres to me OEM rims.

Going to have to go elsewhere to get them mounted then.

Yves

[YvesD]

Originally Posted by willhollin

Oh, you are going to SC3's and not the SC5's? You no like the new ones?

No problem with the SP5's I just couldnt get them in the sizes I need and at the price point I wanted.

[m1bjr]

I will say the Falken 452s are better dry and wet grip than the oem flintstones.
And cheaper.

I respect that they are highly unlikely to be as good as a Conti-5, but for a winter hack tyre they will do nicely.

No point asking BMW is there... you know the answer

Remember a lot of this crap comes from the kraut metality of approving everything, and TÜV.

[YvesD]

Originally Posted by m1bjr

No point asking BMW is there... you know the answer

Remember a lot of this crap comes from the kraut metality of approving everything, and TÜV.

Its complete nonsense really.

They were happy to fit non approved tyres to non approved rims and let me drive around like that but....

Fitting 'non approved' tyres to 'approved' rims is treasonable

Makes no sense to me

[doughboy]

Its just that particular dealer I think, they vary so much, and each seem to have their own bullshit machines that turn out all sorts of random crap at the press of a button.

But agree wth m1bjr, why even go to Bmw for non warranty-keeping-essential items?

My BMW dealers don't even have a tyre machine (nor anyone to operate one), they just bring in local mobile fitter, and charge you for the priveledge.

So cut out the middle man and go direct!

[HighlandPete]

Interesting comments from the industry.

The British Tyre Manufacturers’ Association

Vehicle Specific Tyres
Vehicles homologated on specific tyres should have the equivalent replacements fitted when they require changing.
Specific tyres for a specific vehicle (and marked accordingly) are possible. It is recommended to follow the vehicle handbook guidelines closely (or seek assistance from vehicle or tyre manufacturers) when changing these.
Examples are possible where one could deviate from those marked and others where that is not recommended –
e.g.

1) MO marking for Mercedes. It is possible to fit non-MO marked (and could use MO marked for another vehicle)

2) N-marked tyres for Porsche. Due to the particular characteristics of their vehicles, Porsches must take the correct N-marked fitments. It is also recommended that N-marked tyres are not used on any other vehicles.

Others versions exist in the main for performance/prestigious vehicles such as Porsche, Chrysler, Ferrari, Mercedes AMG, Audi, Bentley, BMW and others.

NB: Other countries may have different laws regarding the replacement of Original Fitment tyres.
If in doubt, always contact your vehicle or tyre manufacturer for advice.

I translate example 1, as meaning not necessarily recommended, but acceptable, 2, as a 'no no'.

Agree?

HighlandPete

[swanny71]

Originally Posted by YvesD

My BMW dealer wont fit them for me as they are not approved for the vehicle. I think this is more to do with the fact they are not runflats rather than the 'MO' designation.

Think your dealer is talking out of his arse.
Bought my M3 as an approved used car and as part of the deal it came with 4 brand new Conti SC3's.
The fronts are marked MO, the rears have the * - I spoke to the service manager about this - "no problems" he said.

[doughboy]

Highland Pete -

Agree, N tyres are manufactured specifically for porsche to have their required characteristics.

But, for example, an MO tyre is not different to a non MO tyre of the same rating etc, it just has MO stamped on it to show that Merceds has approved that tyre as it stands, not had it altered or made specially to suit their cars.

Call me cynical, but in Star/MO etc i'm sure it's all to do with commercial tie ins and providing an 'approved' link to certain products.

Just like BMW reccommend 'Castrol' oil etc.

[milesr3]

Originally Posted by swanny71

Think your dealer is talking out of his arse.
Bought my M3 as an approved used car and as part of the deal it came with 4 brand new Conti SC3's.
The fronts are marked MO, the rears have the * - I spoke to the service manager about this - "no problems" he said.

And therein lies the crux of the issue: The dealer will tell you whatever it takes to sell you the most expensive option, be it an M3 or a * marked tyre.

[Em135eye]

Conti have easily won yet another Evo tyre test with the 5P - this time it had "proper" competition too.

[YvesD]

Originally Posted by 335diesel

Conti have easily won yet another Evo tyre test with the 5P - this time it had "proper" competition too.

All interesting stuff guys, thanks for ypur input.

Now heres a bit more hard science for you.

I have now got both my different style Conti tyres loose and side by side to compare visually and with a ruler.

1st thing I can report is that the 255 18 inch MO SC3 is visually identical in rolling diameter to the larger 265 19 inch SP5. Put a ruler accross the two treads, middle to middle and its dead level. Wasnt expecting that.

Now to width. 18 inch 255 MO SC3 is 265mm wide overall, whereas the 19 inch 265 SP5 is only slightly wider at 270mm overall....

Close call. I can now see where the Dealer was coming from in saying the MO tyres are actually bigger than the markings suggest which might cause rubbing.

Fortunately, I know that the 235/265 tyre combo doesnt rub so these should be OK too.

The only other thing to consider is Im going back to a 37 offset wheel at the rear from 35 on the Alufelgens. Dont think that should be a problem either.

Finally, I have been in contact with Continental Tyres technical deaprtment about the suitabilty of MO tyres in the stock sizes for my exact vehicle. No problem came the reply, they will fit just fine.


Cheers

Yves

[doughboy]

You want all sizes to be same rolling diameter regardless of rim size, so your 265/30/19 should be the same diameter as a 255/35/18.

A calculated 620mm diameter (+ or - a couple of mm) is what all our OE tyre are.

265/30/19 or 255/35/18 or 225/40/18 or 225/45/17 etc etc.

There are other tyre markings too, like ones that indicate a rim protector, this means the wall is a little wider to overlap the rim edge more.

Maybe the MO tyres have rim protectors?

Anyway, my 18" CS3's which are all MO, are if anything narrower than the PS2 OE runflats of the same size...

[YvesD]

Originally Posted by doughboy

You want all sizes to be same rolling diameter regardless of rim size, so your 265/30/19 should be the same diameter as a 255/35/18.

620mm diameter (+ or - a couple of mm) is what all our OE tyre are.

265/30/19 or 255/35/18 or 225/40/18 or 225/45/17 etc etc.

There are other tyre markings too, like ones that indicate a rim protector, this means the wall is a little wider to overlap the rim edge more.

Maybe the MO tyres have rim protectors?

Anyway, my 18" CS3's which are all MO, are if anything narrower than the PS2 OE runflats of the same size...

The MO's do have rim protectors, yes.

Just slung the tape over the tyres, yes they are 620mm give or take. I mentioned it as the Forum wheel and tyre size calculator says that the 19 inch 265/30 has a larger rolling diameter. Clearly thats not always true.

I'm now comfortable that theres no issue fitting these tyres, especially as you are running the exact same things!

Cheers

Yves