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01-25-2020, 04:13 PM | #1 |
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Tire pressure PSI
Hi guys,
During delivery of my 7 series the PSI was 32-33 goes up to 35 when it warms up today out of curiosity I decided to take a look at the side of the driver's door to see what PSI should the tires have and it shows 44 psi when cold. I have 21" M-performance wheels Wheel part # 36116867341 Not sure why the PSI was inflated this low during delivery but should I top inflate it to 44psi? This is the first time owning 21" wheels usually other cars I've owned was 35psi. Thanks for the feedback |
01-25-2020, 04:23 PM | #2 |
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I inflate to 45psi cold on 20" M-B wheels. M-B recommends mid-30s which causes uneven tire (shoulder) wear. I air up my wife's G01 X3 tires 5 psi higher than BMW recommends. I don't recall the specific value in psi at the moment.
Carmakers are wishy-washy about tire pressure. Lower pressure generally gives better ride quality and avoids complaints, especially with harsh 20" and 21" wheels these days. There is no escaping the harshness with larger wheels, even more so when the tires are runflats. The downside of low inflation pressure is poor tread life. M-B calls for excessive, in my opinion, rear camber and toe settings, and this also plays into tire wear, in concert with inflation pressure. Airing up well beyond manufacturer specification, as I do, maximizes tread life with an unnoticeable change in ride quality. 20" and 21" wheels are harsh, no matter what inflation pressure is chosen. On your 7 series, if you want maximum tire life, air up to at least 45 psi, or 50 psi. If you want maximum comfort, keep the pressure in the mid-upper 30s and watch the shoulder wear appear after about 10k-15k miles. |
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01-25-2020, 06:04 PM | #4 | |
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01-26-2020, 09:43 PM | #5 |
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It is interesting to note that in Europe a range of tire pressures is listed based on load and speed. The USA pressures listed for my 7 series is for a full load of 5 passengers and full luggage, no alternative. I found that with my usual light loads, the car rode harshly on 20" wheels with those pressures, so started using the European suggestions for the similar model which are 34psi for 2 persons up to 160kph. The ride improved a lot and I did not notice any degradation of handling in normal driving (I don't track my car). So far, after 10k miles I'm not seeing abnormal tire wear, however, every BMW I've owned with staggered wheels has worn the outside edges of the front tires and center of the rear tires first, regardless of pressures. In a non staggered configuration, you can rotate front to rear to mitigate that situation. My advice: try the 44psi, if you don't like the harshness, don't be afraid to use 34psi for light loads and pump up if you run heavy.
Interestingly, my S-Class Mercedes had two tire pressure placards, one on the drivers side B pillar which had USA pressures, the other, inside the gas cap cover, for the rest of the world. The differences were substantial. Once I started using the RoW pressures, my enjoyment of the car increased. |
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01-27-2020, 11:40 AM | #6 |
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I have the 21" - always 44psi. Warmup it goes up to 48-50. Perfect ride.
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05-09-2020, 08:26 PM | #7 |
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05-10-2020, 09:20 AM | #8 |
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On my 750, I keep the cold pressures at about 38psi, which I find is a good compromise. But I have 19" wheels. Here in Metro NY, having 20's or 21's would mean frequent wheel repairs.
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05-10-2020, 12:57 PM | #9 |
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05-10-2020, 03:29 PM | #10 |
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Insurance is smart with larger wheels. But there is also a PITA factor. Those bent wheels can produce vibrations, and getting them fixed means a trip to the dealer. I'm fine with the 19's. So far no issues. But then I haven't driven much.
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