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Wheels, Tyres, Brakes & Suspension Discuss all wheel related matters

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Old 05-12-2016, 09:07 AM   #1
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Tyres not as owners manual - confused!

The 1 year old E Class 220 Bluetec SE (W212) that I bought 3 weeks ago has 17" wheels. The owner's manual says they should have 245/45 R17 95W tyres all round.

However, the tyres on the car are 225/50 R17. Is this different size a problem? Does this mean they are non-standard rims? Or can both size tyres fit on the same size rim?

Incidently, I can't see this size tyre (225/50) anywhere in the manual for any variant of the car - but it is listed on the sticker inside the petrol flap.

Also, looking at the tyres, the rears are both speed rated 98Y (both Hankook), but the fronts are 94W (one Continental, one Nankang).

I'm concerned about the mix between front and back, but more so between the two front tyres. Should I be?

When I was buying the car the dealer said they don't let cars out with less than 4mm tread on the tyres so I suspect that's why there's a mix. However, the car had only 9,500 miles on it so I'm surprised the tyres have been changed at all.

On the other hand, the tyre pressures were all around the 235 - 250 kpa mark whereas the petrol flap sticker said they should be 280 kpa. I wonder if the dealer actually checked them at all?

Before I ask the dealer, what are your thoughts?

Thanks in anticipation!
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Old 05-12-2016, 09:53 AM   #2
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Originally Posted by Gaggsy View Post
Incidently, I can't see this size tyre (225/50) anywhere in the manual for any variant of the car - but it is listed on the sticker inside the petrol flap.
According to the January 2016 edition of the E-Class price list, 17-inch 5-twin-spoke wheels with 225/50 tyres are standard on the E 220 BlueTEC SE Saloon and Estate, with 245/45 tyres on other models, so it looks like they're the right size for your car.
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Originally Posted by Gaggsy View Post
Also, looking at the tyres, the rears are both speed rated 98Y (both Hankook), but the fronts are 94W (one Continental, one Nankang).

I'm concerned about the mix between front and back, but more so between the two front tyres. Should I be?
The speed ratings (Y and W) are both higher than the top speed of the car so are also OK, and the load ratings (98 and 94) are also OK.

While I (and many others) prefer not to mix tyre brand/model front to rear it's rarely an issue. What I would not do (and it is considered to be bad practice) is mix tyre brand/model on the same axle. Personally I'd ask them to either put a pair of matching tyres on the front.
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Old 05-12-2016, 09:56 AM   #3
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They're a bit narrower than what you say the standard fit should be...but the bigger profile number means they are about the correct diameter.

Unless you are ragging it on a regular basis I wouldn't worry too much about the mix. But...next time you need new tyre you could put the new ones of the wider variety on the rear and eventually you will have what you want all round.
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Old 05-12-2016, 10:24 AM   #4
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...the bigger profile number means they are about the correct diameter.

...next time you need new tyre you could put the new ones of the wider variety on the rear and eventually you will have what you want all round.
Will they fit? Can 245 be a replacement for a 225 tyre?
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Old 05-12-2016, 10:41 AM   #5
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The 245/45/17 will be slightly smaller diameter wise, but nothing to worry about.

225/50/15 245/45/17
Diameter 656.8mm 652.3mm
Circumference 2063.4mm 2049.3mm
Speedo error 0% 0.69%
Reading at 30mph 30mph 30.21mph
Reading at 60mph 60mph 60.41mph
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Old 05-12-2016, 11:07 AM   #6
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Will they fit? Can 245 be a replacement for a 225 tyre?
The tyre will be 1 cm closer to the suspension upright...so check the existing distance. And 1 cm closer to the arch...so check that too.
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Old 05-12-2016, 11:20 AM   #7
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Originally Posted by Gaggsy View Post
On the other hand, the tyre pressures were all around the 235 - 250 kpa mark whereas the petrol flap sticker said they should be 280 kpa. I wonder if the dealer actually checked them at all?
I think on Bluetec cars the pressure is listed higher for economy reasons.
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Old 05-12-2016, 12:50 PM   #8
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I think on Bluetec cars the pressure is listed higher for economy reasons.
^ This.

It's also the reason the E220 BlueTEC SE was supplied from the factory on 225/50 tyres rather than 245/45's: it improves fuel economy which means lower emissions which means cheaper VED. The manual makes mention that you can run lower tyre pressures to improve ride comfort if you wish, but that in doing so it will increase fuel consumption.

The OP's car is on the size of tyre it was "meant" to be, i.e. 225/50. Assuming that the wheel size (both width and offset) is the same on the E220 BlueTEC SE as it is on other variants fitted with 17-inch wheels, then there will be no problem swapping to 245/45 tyres if that's what he wants to do, other than a marginal increase in fuel consumption.
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Old 05-12-2016, 01:08 PM   #9
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^ This.

It's also the reason the E220 BlueTEC SE was supplied from the factory on 225/50 tyres rather than 245/45's: it improves fuel economy which means lower emissions which means cheaper VED. The manual makes mention that you can run lower tyre pressures to improve ride comfort if you wish, but that in doing so it will increase fuel consumption.
My C180K Blue Efficiency is the same with the tyre size reduced from 205/55 to 195/60 in order for it to scrape into a lower VED band. You wouldn't think 10 mm narrower would make much difference but apparently it reduces aerodynamic drag as as well as rolling resistance.

I do run 5% lower pressures to improve the ride after finding some data which suggested a 5% reduction in pressure would only drop economy by 0.4%

With a book pressure of 280 kPa (40 Psi) I had to convert it to something I understand, I would be wanting to reduce the pressure by 10% to 36 Psi.
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Old 05-12-2016, 01:26 PM   #10
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Thank you all so much for your replies. Exactly the sort of information I was looking for.

What a wonderful resource this forum is!
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Old 20-12-2016, 11:07 AM   #11
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Following up my original post, I've since been to another MB indy service centre for a separate issue (faulty NOX sensor causing engine diagnosis warning lamp to come on) and back to my original dealer. I've now gleaned this information:

* The original factory fitted tyres were 225/50/R17 with a W rating.
* Original tyres were Continental MO.
* The car had a puncture after about 750km and one front tyre was replaced with a Hankook.
* The rear tyres were replaced with Nankang Y rated tyres by the dealer before selling the car to me because the originals did have not have sufficient tread left on them.

At he indy dealer I asked their opinion about the tyre mix. The guy I spoke to said it would all pass an MOT and was legal, the front tyre mix wouldn't concern him but he would prefer the same tyre on the axle. He thought the rear Nankangs were a budget tyre and in his view he would ask the dealer to put decent tyres on - after all I'd spent 22k on the car. (He also said "but don't say I said so!")

Back at the original dealer, they were only concerned about the speed ratings. The Y's on the rear were OK because they exceeded the specified W's. They said the Nankangs were intermediate rather than budget tyres. Changing them to something more 'premium' was not offered.

Ah well, the tyres will eventually resolve themselves when I replace them as they wear out. The car is running really nicely and I'm just going to relax and enjoy the drive!
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Old 12-04-2017, 09:40 AM   #12
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i would not run at low pressure, i have hankook mo 225 50 r17 94w that have been run at a minimum of 2.75 bar, they have warn as if under inflated, with 4.5 mmm of tread left in the center 80% (probably another 20,oookM) Both Hankook and mercedes are 'surprised' by this. To me they are dangerous as breaking and water clearance will have been severly compromised by this contact pressure. I am now running a new set at 2.9 bar at the front and 3.1 at the rear. ( In France you can not have different tyres on the same axle)
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