[walkday]

Originally Posted by AGONXF30

How is the speedometer with the larger set up!

No setup is needed. It's a small difference. BMW Genius told me it's Okay.

[AGONXF30]

Originally Posted by walkday

No setup is needed. It's a small difference. BMW Genius told me it's Okay.

By set up I meant the set of larger diameter tires. I find the speedometer in the X5 to be spot on and I would not like to risk a different speed readout.
How is your new speed compared to Waze?

[walkday]

Originally Posted by AGONXF30

By set up I meant the set of larger diameter tires. I find the speedometer in the X5 to be spot on and I would not like to risk a different speed readout.
How is your new speed compared to Waze?

I didn't measure.

After all, the GPS speed isn't as accurate due to elevation and numerical errors.

I use https://tiresize.com/comparison/ to calc the differences.

Factory front 21": 275/40R21
New front 21": 275/45R21, sidewall +14%, circumference +3.4%

Factory rear 21": 315/35R21
New rear 21" 315/40R21, sidewall +16.3%, circumference +4%

I inflated all new tires according to the factory psi (despite the size difference). Theoretically, the travel distance is 103.4% of the odometer distance. The new tires have softer sidewalls, though.

[AGONXF30]

Originally Posted by walkday

I didn't measure.

After all, the GPS speed isn't as accurate due to elevation and numerical errors.

GPS is pretty accurate. More so than an uncalibrated speedometer. Now, you could say that a GPS sensor in a phone could be more inaccurate than a purpose mutliband GPS, but GPS as a whole is pretty darn accurate as a system and why its used in aviation and many other industries.

My other BMWs have inaccurate speedometers, are RWD, so tire size often times is not as relevant. In the X5, I found the speedometer to be pretty accurate so I wanted to know what differences these bigger tires had not he speedometer.

[walkday]

Originally Posted by AGONXF30

GPS is pretty accurate. More so than an uncalibrated speedometer. Now, you could say that a GPS sensor in a phone could be more inaccurate than a purpose mutliband GPS, but GPS as a whole is pretty darn accurate as a system and why its used in aviation and many other industries.

My other BMWs have inaccurate speedometers, are RWD, so tire size often times is not as relevant. In the X5, I found the speedometer to be pretty accurate so I wanted to know what differences these bigger tires had not he speedometer.

I agree GPS speed measures can be more accurate than a speedometer. But in general, it is not an accurate instant speed measure.

I was talking to a colleague who wrote an algorithm that uses ground stations to improve the accuracy of some special GPS receivers. In short, GPS positioning accuracy is about 3 meters. The instant speed of the receiver is calculated from positions. If driving on a flat road, instant GPS speed readings can be off by about 20% at worst. Signal reflections and interference can make matters worse. But if you're driving on an open field, like a runway at a constant speed, he says the readings are within 2-3%. Under normal driving conditions, he said he wouldn't trust the GPU's instant speed readings.

[yoandry]

Originally Posted by chicken1

They will not

How are all these tires size so far? Are these the MICHELIN PILOT SPORT 4 SUV?
More pic at normal height? Thanks
I want to get rid off my Pzero RF and go 45/40 on the MICHELIN PILOT SPORT 4 SUV.

[chicken1]

Originally Posted by yoandry

How are all these tires size so far? Are these the MICHELIN PILOT SPORT 4 SUV?
More pic at normal height? Thanks
I want to get rid off my Pzero RF and go 45/40 on the MICHELIN PILOT SPORT 4 SUV.

Tires have been great no complaints work as they should.. these are the Michelin primacy your a/s

[SLOWER]

I would like to go this route, but do not have air suspension. Any issue there? Do I still have the option to update the sizes in the computer to the 275/45 and 315/40?

[SLOWER]

Also noticing that these Michelins are not XL rated. Any concerns there?

[IS350]

Originally Posted by Big_CG

I have two front 21" pirelli all season run flats- someone please take them off my hands as Im moving. Only $100 for both! Like new.

Can you please confirm size and age?
275/40/21?

[eelnoraa]

Originally Posted by walkday

Thank you @chicken1

I had Discount Tire put Michelin all season 275/45 on the front and 315/40 on the rear, on the 740m rims. On my 45e, the ride and tire noise are both noticeably improved.

I can confirm with the stock air suspension, there is no rubbing even at the lowest height for loading.

Needless to say, I bought a tire repair kit and a mobile inflator for emergencies

Wait. Stock 740 wheel is 9” wide, how did you manage to mount 315mm tire on them? Even 275mm is in the widest end of the fitment ?

[IS350]

Originally Posted by eelnoraa

Wait. Stock 740 wheel is 9” wide, how did you manage to mount 315mm tire on them? Even 275mm is in the widest end of the fitment ?

Agree, is he referring g to the 20in rim?

[eelnoraa]

Originally Posted by IS350

Agree, is he referring g to the 20in rim?

The post said 740m. I assume it was the stock M sport 20” wheel.

[mojoJJ]

I’m also interested in making the switch to taller 21” tires. Waiting to hear long term reviews.

I have a 24 X6 40i with ID8. There’s a setting for automatic detection of tires, I wonder whether it can pick up non standard tires and compensate the spedo accordingly.

[mojoJJ]

What’s the difference between Primacy Tour AS and Pilot Sport AS 4 ? Why did the tire shop agree to put non-standard PT AS but refused PS AS?

[Keithwand]

Does this affect the future mileage shown on the odometer?

[mojoJJ]

Originally Posted by Keithwand

Does this affect the future mileage shown on the odometer?

Yes, it’ll add 30 miles every 1000 miles (+3%).

[Keithwand]

Bummer. Nicer the other way around

[915M]

Wouldn't it be opposite?
Since larger diameter will rotate less rev per a miles?
(If odo shows 60miles, then it actually traveled 62miles)

[mojoJJ]

Originally Posted by 915M

Wouldn't it be opposite?
Since larger diameter will rotate less rev per a miles?
(If odo shows 60miles, then it actually traveled 62miles)

Sorry, yes opposite. So 1000 miles actual travelled would show up 970 miles on the odo.

[rochoa21]

Just got these tires two weeks ago and put about 1500 miles round trip, they are great, lower noise than my fun flats.

[Keithwand]

Originally Posted by mojoJJ

Sorry, yes opposite. So 1000 miles actual travelled would show up 970 miles on the odo.

Aha. Much better.