OE marked tyres - why?

[Grumpyjohn1957]

Had the Winters refitted at the Pirelli Performance Centre in Burton a few weeks back.
Whilst waiting I enquired about the difference between marked tyres, E.G Merc, BMW, Jag etc. They explained at some length and produced examples of how OE tyres vary. To begin with its down to manufacturing tolerances. Apparently standard tyres can vary up 10 mm in width and or diameter from the previous “standard” tyre off the production line! Bigger the tyre, bigger the variation can be.

Marked tyres are tightly controlled during manufacture conforming to a specification laid down by the car manufacturer. E.G., a maximum +/- 3mm tolerance and consistent weights.

Construction: The salami sliced tyres I was shown came from the same size of P Zero fitted to the following cars. Audi R8, Ferrari 458, Porsche 911 and a Lamborghini something. – (They are numbered – Alas I forget to note the details, I think they were sized at 305/30/20 and which fits what I don’t remember). The treads appear identical when next to each other however that’s where the similarity ends. If you study the photo, you can clearly see differences. Some beads are square, some round Samples 1 & 2 have rim protection 3 & 4 not.
The number of elements within the beads is not the same nor apparently is the diameter and grade of the steel used.
The distribution and the number of cords below the treads differs greatly as does the proportions of Kevlar/Nylon/Steel/Polyester/Rayon used in the makeup of the individual cord layers.
Layout of the cords within the carcasses is different in each case.
The rubber compounds used to surround the cords is different between tyres.
Finally, the tread strips themselves are made from different rubber compounds laid around the tyre to further provide the desired combination of grip, wear, temperature rating or whatever other characteristics the car maker wishes to impart.

Having never given it much thought, I was amazed how much engineering goes into a humble tyre. (But maybe not in the case of Mr Wu’s finest ditch finders). They get frozen, baked, soaked, smacked down potholes, twisted around in corners, compressed under braking and stretched by centrifugal forces at high rotational speeds. Speaking of which, according to TIreSize.com, my 285/30/20 do 755 revs per mile. By my dodgy maths that’s 755rpm at 60mph, 1510rpm at 120mph, or a dizzying 2265rpm at 180mph. Frightening considering the weight of a wheel & tyre.

It isn’t all marketing BS after all – I was intrigued, seems there’s as much engineering in a humble tyre as goes into the rest of car.

[ali]

I met with a Michelin tyre engineer at my local Costco as he happened to be in town adn I was having issues with the 265 / 30 / 19 rears rubbing on my E46 B3
The porevious Falken FK 452 that were exactly the same size on the side wall turned out to actually be narrower than the 265 Michelin.
As you say the tolerances are what the reason is. Lesser tyres give you 265 less 3 or 4mm and Pirelli give you more rubber hence why the 265 pirelli rubbed and the 265 Falkens didn't
I've now switched the rears to 255 michelin PS4 but yet to try them as currently have the winters fitted

[JohnW]

I’m aware those that have rim protection are listed with that? Some distributors may not differentiate.

[Cygnet]

Very interesting, Grumpyjohn. Thanks for posting.

[shaziman]

I can concur what is said here, i am working with a colleague whom jut left Contintntal tyres in germany. He has said much the same.

The best thing here is, you fit a sticker on your car in the UK and the insurance classes it as a modification and the insurance wont pay out...

But lets fit downgraded tyres to OEM tested and verified, and its all good!

After buying my first B3 and having Bridgestone tyres fitted and a plethora of issues that i spent hundreds trying to fix, and only thanks to the tyres being changed due to wear that fixed the issues, i will only buy Michelin tyres but not OE spec as the quality is so much higher that even a poor quality Michelin is better than some OEM spec other brands!

Thats said, i have only ever had one blow out and it was with a micheln tyre...

Also, Michelin own 90% of the rubber plantations around the world, so they are the raw material provider to all tyres manufacturers