[empyrean]

Hi guys I switched stock rear 245/30/19 to 245/40/19, do you think anything bad might happen? It fits fine no rubbing so far, but read transmission might suffer/go bad. I live in pothole city that is why I did this.

Diameter goes up 7.7%, 630mm-678mm. I could fall back to 245/35/19.

ty.

[zachdog]

You should be fine going up a size like that, although I wonder if a small upsize will help much with potholes. Let us know. Have you calculated the difference in your speedometer and odometer readings?

[empyrean]

I kept 225/40/19 in the front. Feels much better than RunFlats. 3 days no issues lol.

No clue in how to check odo readings, I know it might change 5%, no real quantitative speed limit enforcement over here.

ty

[O Stater]

Originally Posted by empyrean

I kept 225/40/19 in the front. Feels much better than RunFlats. 3 days no issues lol.

No clue in how to check odo readings, I know it might change 5%, no real quantitative speed limit enforcement over here.

ty

Fire up the Waze app and compare your speedo to the GPS speedo at several speeds. I found that my speedo, in stock form is correct up until about 40mph then it starts going off by about 3%. if my speedo says 80, im actually doing about 77mph.

[marcthedark]

Originally Posted by empyrean

I kept 225/40/19 in the front. Feels much better than RunFlats. 3 days no issues lol.

No clue in how to check odo readings, I know it might change 5%, no real quantitative speed limit enforcement over here.

ty

So you went from 225/40-19F and 245/30R to a 245/40-19R
You now have 2.36% difference in circumference F <> R
But with 245/30 you had a 5.24% difference F<>R
That would probably sooner or later destroy the XDrive if you have that. Otherwise ....

[empyrean]

Originally Posted by marcthedark

So you went from 225/40-19F and 245/30R to a 245/40-19R
You now have 2.36% difference in circumference F <> R
But with 245/30 you had a 5.24% difference F<>R
That would probably sooner or later destroy the XDrive if you have that. Otherwise ....

It's RWD only.
Original OEM setup: Front: 225/35 R 19 Y Rear: 245/30 R 19 Y
My current setup: Front: 225/40 R 19 Y Rear: 245/40 R 19 Y
wdyt?

[aerobod]

Originally Posted by empyrean

It's RWD only.
Original OEM setup: Front: 225/35 R 19 Y Rear: 245/30 R 19 Y
My current setup: Front: 225/40 R 19 Y Rear: 245/40 R 19 Y
wdyt?

There is probably enough clearance to run those sizes, but there is a possibility of driveline malfunction codes and/or issues with DSC or ABS due to the large size difference (7.8% in the rear) from stock tyre size. Normally 3% variation shouldn’t cause any issues, but higher may.

A few people who have swapped differential ratios without recoding (with typically 10% change in rear ratio) have run into driveline malfunction issues in some cases as the DME calculated gear ratio has not matched the wheel sensor measured speed, leading to false detection of continuous wheel slip and consequent error conditions.

[empyrean]

Originally Posted by aerobod

There is probably enough clearance to run those sizes, but there is a possibility of driveline malfunction codes and/or issues with DSC or ABS due to the large size difference (7.8% in the rear) from stock tyre size. Normally 3% variation shouldn’t cause any issues, but higher may.

A few people who have swapped differential ratios without recoding (with typically 10% change in rear ratio) have run into driveline malfunction issues in some cases as the DME calculated gear ratio has not matched the wheel sensor measured speed, leading to false detection of continuous wheel slip and consequent error conditions.

Ty, very clear!