[TheCoolX3]

Swapped my wheels back to my factory 20" wheels with new non RFT ps4s. I had the 18s on for about 10k miles.

Since I've swapped them I've noticed while regularly accelerating in first gear a subtle popping that almost feels like wheel spin. After I get past ~5-10mph it stops popping and will only do 3 or 4 pops. I figure it's the transfer case.

I have swapped wheel sizes many time previously and never had any issues with it because it seemed the car learned the new wheels and adjusted the speedo too. I never had an issue with this popping before.

Now my question is, can I some how tell the car it has 20s now or engage some learning process? I am worried that the XHP transmission flash is not allowing the car to learn the new size.

Thank you!

[TheCoolX3]

Also a noticeable thud when I let of the gas and the car is in first gear

[one 35i]

Simple first--check lug bolts torque.

[pungo]

Are you saying the diameter of the tire is much different now? Generally, no matter what diameter rim you run, 17,18,19,20 you should try to keep the tire diameter as close as possible. I'd be concerned with a popping sound. I'd remove each wheel and double check the fitment of the rim to the hub, then retorque the lug nuts.

[n55ke]

Had a similar issue after tyre change from square to staggered with 0.4% difference front to back. Advice online was to replace transfer case fluid and reset adaptation using ISTA.Issue was resolved and all good so far over past 1000km

[TheCoolX3]

Originally Posted by one 35i

Simple first--check lug bolts torque.

Lugs are tight I torque to 94lbs.

[TheCoolX3]

Originally Posted by pungo

Are you saying the diameter of the tire is much different now? Generally, no matter what diameter rim you run, 17,18,19,20 you should try to keep the tire diameter as close as possible. I'd be concerned with a popping sound. I'd remove each wheel and double check the fitment of the rim to the hub, then retorque the lug nuts.

I had my 18 inch wheels on the car (squared set up). I put on my factory 310Ms on which are staggered 255/275 and are 20in. New tires front and rear.

[TheCoolX3]

My tire sizes are:
Front: 255/40/zr20
Rear:275/35/zr20

I matched the factory spec besides going from 245 to 255 in the name of grip. Would the side wall being slightly thicker in the front cause the issue I'm having?

I took off all four wheels and put them back on ensuring torque spec and proper mating.

[pungo]

Originally Posted by pungo

Are you saying the diameter of the tire is much different now? Generally, no matter what diameter rim you run, 17,18,19,20 you should try to keep the tire diameter as close as possible. I'd be concerned with a popping sound. I'd remove each wheel and double check the fitment of the rim to the hub, then retorque the lug nuts.

Originally Posted by TheCoolX3

My tire sizes are:
Front: 255/40/zr20
Rear:275/35/zr20

I matched the factory spec besides going from 245 to 255 in the name of grip. Would the side wall being slightly thicker in the front cause the issue I'm having?

I took off all four wheels and put them back on ensuring torque spec and proper mating.

You should have stuck with the factory recommended tire sizes or at least matched the diameter front to rear. The front to rear diameter are too different and now you are straining the transfer case and will probably end up damaging it. Didn't the tire shop tell you you need to keep the same diameter tires front and rear?

[TheCoolX3]

Originally Posted by pungo

You should have stuck with the factory recommended tire sizes or at least matched the diameter front to rear. The front to rear diameter are too different and now you are straining the transfer case and will probably end up damaging it. Didn't the tire shop tell you you need to keep the same diameter tires front and rear?

The size that came from the factory was
Front: 245/40/r20
Rear:275/35/r20

When I bought new tires I just matched that number. My factory PZeros were those sizes and the car had no issues with it. The only thing I changed from factory sizes was the 245 to 255 on the front. Everything else is the same.

[pungo]

Originally Posted by TheCoolX3

The size that came from the factory was
Front: 245/40/r20
Rear:275/35/r20

When I bought new tires I just matched that number. My factory PZeros were those sizes and the car had no issues with it. The only thing I changed from factory sizes was the 245 to 255 on the front. Everything else is the same.

You did not keep the same diameter by going from a 245 to a 255, the 255 is taller, that's where you went wrong. Just sayin... The tire shop should not have even put them on with different diameters.

[atrueb]

Originally Posted by pungo

You did not keep the same diameter by going from a 245 to a 255, the 255 is taller, that's where you went wrong. Just sayin... The tire shop should not have even put them on with different diameters.

Completely agree. The tire shop should have informed you that the overall wheel diameter and circumference changes. FYI the "40" is not a measurement unit, it refers to the sidewall being 40% of what the width (i.e. 245mm or 255mm) is. The sidewalls are higher on 255/40 than on 245/40, so now your front wheels and rear wheels have different circumference which will interfere with the xdrive, as front and rear are moving at different speeds.

[TheCoolX3]

Originally Posted by atrueb

Completely agree. The tire shop should have informed you that the overall wheel diameter and circumference changes. FYI the "40" is not a measurement unit, it refers to the sidewall being 40% of what the width (i.e. 245mm or 255mm) is. The sidewalls are higher on 255/40 than on 245/40, so now your front wheels and rear wheels have different circumference which will interfere with the xdrive, as front and rear are moving at different speeds.

Ohhhh okay I see now. I thought the 40 was a measurement opposed to a percentage.

I guess I have to size down my tires!

[rcsup1]

Here is a really helpful calc. Honestly I would replace the transfer case fluid if you've never done that. Your front tire is 11mm taller than the rear it shows as a 1.7% difference. You can also try putting the 18's back on and see if the problem goeas away.

https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm

[TheCoolX3]

Im going to service all drive line fluids. I just bought new tires from tire rack for the fronts.

Originally Posted by rcsup1

Here is a really helpful calc. Honestly I would replace the transfer case fluid if you've never done that. Your front tire is 11mm taller than the rear it shows as a 1.7% difference. You can also try putting the 18's back on and see if the problem goeas away.

https://www.wheel-size.com/calc/?whe...cl=50mm&sr=0mm