10-16-2018, 10:05 AM | #1 |
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M135i xDrive LCI winter tire vibrations?
I recently purchased a second hand 2015 F20 M135i xDrive (LCI) with 25000 km (15500 miles) from a BMW dealer ship with 2 years of BMW premium warranty. The car still had the factory summer tires on from 2015 with 6-7mm of thread.
Since I need winter tires in here (Germany), I immediately ordered winter tires. I want to keep the original 436 style rims for the winter, so I ordered same size tires as the original summer tires. This is exactly what I bought: - Front tires: Pirelli W Sottozero 3 XL 225/40 R18 V92 - Rear tires: Pirelli W 240 Sottozero XL 245/35 R18 V92 My tire shop told me during the installation of these winter tires on the stock rims that they actually should have a star on them (which means that they are certified by BMW). These star signs can be found on the original stock tires from the factory. However, they told me that I should have no vibrations whatsoever. If I do have some, these tires won't work. This made me very suspicious about some vibrations... On the highway, I feel some very minor vibration through my seat (not through the steering) around 120 km/h (75 miles/h) on some highways. But I don't know if this was the same with the summer tires on... I already got the winter tires/rims rebalanced, but they were perfect. I also got the car aligned to BMW specifications. I did some research and found that if you have an xDrive (and thus transfer box to distribute the power between front and rear axle), the tires should have the same circumference in the front and rear, although there is a tolerance allowed up to 1% in difference. Therefore, I calculated the sizes with this tool. The front tires have a circumference of 2002 mm (78.8") while the rear tires are 1974 mm (77.7"). So there is a difference of 28 mm (1.1") or thus 1.2% . I don't know if I am hypersensitive to vibrations since this story of not having the star signs on the winter tires, or if there is actually a problem. I don't want to damage my transfer box, although I have warranty. I'm pretty sure my dealership won't put a new transfer box in under warranty if I have tires without the star sign... (as other people on the internet). I read that it is possible to unplug some fuses to deactivate the transfer box. This would actually make the car RWD. However, I don't know which fuses? Does somebody have any idea to test if these vibrations are normal or not? Could I do something else to test if this tire combination is good for xDrive?
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10-16-2018, 11:24 AM | #2 |
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Don't worry about star marks: BMW does sell their OEM winter wheels with non-starred tires. I have a set. No permanent vibrations (I recall a noticeable vibration once: I did not stop and it gave up ), no xDrive, no LCI, no shit. No M135i either. This mustn't matter, of course. It's all right with factory sizes as well. People played with non-standard and even no proper match between rim and tire here on the forum but kept their complaints, if any.
Check the tire pressure. |
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10-16-2018, 01:13 PM | #3 |
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The tyre circumference is actually rather important on AWD cars. It should get better with time, as the front tyres usually wear faster than the rears. You can also compensate with higher tyre pressure in the rears than the fronts.
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10-16-2018, 02:11 PM | #4 | |
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Factory sizes can't be wrong.
The first 300 km, 200 miles according to the handbook (page 240). I have an unusual case then. Or do you mean those regular "AWD" (We know there are 4 mounted and no factory spare. This should make 4WD, precisely. I hate the "AWD" term - it looks so stupid.) that are FWD with RWD added? xDrive is (isn't it?) unusual here as well. Quote:
And by the way, once the car hasn't been tested on other tires it can be really the transmission (not the tires) issue. Last edited by No one; 10-16-2018 at 02:18 PM.. |
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10-16-2018, 03:32 PM | #5 | |
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Yes, they can. Two different tyre models with the same size can vary a lot in size.
Quote:
That is of course possible, but in case that happens, it would be very easy to fix. |
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10-16-2018, 04:30 PM | #6 | |
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Quote:
My impression is "AWD" popped to clarify previous "4WD" flattering those who didn't know how many that was. When you sweat your ABS on a racetrack, I suppose. Last edited by No one; 10-16-2018 at 08:20 PM.. |
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10-16-2018, 04:59 PM | #7 | |
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Quote:
So I went out to find a petrol station with a handy air station. I gradually played with the tire pressures and went for a test drive each time. Eventually, 2.3 bar in the front and 2.7 bar in the back makes the car less cluncky on slow accelerations. Vibration is also less, I guess... Either way, the difference in circumference is too much. Therefore, I will try a new set of tires and rims officially from BMW (square setup with 225/40 R18 on 385 style rims). Now I will have to quit driving the car until the official ones arrive. Fingers crossed
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10-29-2018, 09:32 AM | #9 |
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Indeed. After some hassle with the new rims (one was delivered damaged ), I could finally test the square setup.
And yes, the car drives without vibrations and without hesitation on slow accelerations... Problem solved
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