[Ballzilla]

Hey Everyone

I have noticed my car feeling a bit unstable/floaty at highway speeds 100km plus. Tire pressure is set at 38psi

Tire pressure and alignment are fine. Tires are Michelin PS4s Non RFT

Any ideas? Thanks!

[bavarianride]

What tires are on your car? U may bring the car to a tire store to get road force balance esp. if u have non-Michelin tires.

[Ballzilla]

Originally Posted by bavarianride

What tires are on your car? U may bring the car to a tire store to get road force balance esp. if u have non-Michelin tires.

Michelin Ps4s Sport. They came with they M340 from factory

[bavarianride]

Originally Posted by Ballzilla

Michelin Ps4s Sport. They came with they M340 from factory

Yeah do check for tire balance first(road force is preferred), the tire shop can also check for road hazard damages and bent rims.

[Ballzilla]

Originally Posted by bavarianride

Yeah do check for tire balance first(road force is preferred), the tire shop can also check for road hazard damages and bent rims.

I have no vibration at all in steering wheel which is a sign tires are balanced 🤔

[G30M]

should be very stable upto 180km/h.
use sport suspension.
need 245 front tires 225 too narrow

[bavarianride]

Mine is 330i non-sport suspension and it is also stable way above 100km/h.

[Mtl128_25]

Yeah same here on my 430xi coupe. Same tires. Hope we get an answer soon. I just posted another thread earlier.

[madpistol]

Originally Posted by Ballzilla

Hey Everyone

I have noticed my car feeling a bit unstable/floaty at highway speeds 100km plus. Tire pressure is set at 38psi

Tire pressure and alignment are fine. Tires are Michelin PS4s Non RFT

Any ideas? Thanks!

Have you had your wheels aligned recently? How old are the tires? Have you checked around the car to see if all of the body panels and aero are intact? This includes under the car.

[Ballzilla]

Originally Posted by madpistol

Have you had your wheels aligned recently? How old are the tires? Have you checked around the car to see if all of the body panels and aero are intact? This includes under the car.

Car currently has 26000kms. Tires have about 15000kms on them since i only use them for Summer. Everything seems to be intact and no issues.

[madpistol]

Originally Posted by Ballzilla

Car currently has 26000kms. Tires have about 15000kms on them since i only use them for Summer. Everything seems to be intact and no issues.

OK. Have you had the wheels aligned recently?

[Shaneartistry]

I have a 2024 M340i with the AS 19” square set up. I’ve felt the car feels floaty at interstate speeds as well.

[cyam]

I have a 2020 M340ix with staggered PS4S*, mine seems perfectly stable and I've sat on 250kmh no issue. Solid as a rock.

[G30M]

i think the car is very sensitive to ride height, which produces lift at high speeds (that's why people put a wing at the back for rear downforce, and splitter at the front to reduce front lift -technically not for front downforce)

when was on stock RFT tires the car felt floaty above 130kph

then i put slightly smaller and much softer sidewall tires, i noticed the car had ride height reduced by around an inch. i also put spacers so the wheels were flush with the car to reduce air turbulence around the wheel area. it was very stable at 180kph. i did not try to go higher speed because you have to change gear at 180kph and there is a lot less power with the next gear but i believe it will be stable above 200kph

[Assassin]

You don't don't say what driving mode you are in. In Sport or Sport+ it should be nice and tight at almost any speed. Comfort or Eco are much softer. No way should it be floaty at those speeds. Worth considering the road you are on when feeling that sensation. Many highways are heavily worn by trucks etc and in / just after heavy rain you will notice two lines of surface water where the wheels run and little water in the middle or at either side of the lane. Its not noticeable when the road is dry. These depressions are typically wider than a car and can cause a wandering sensation as the car tries to settle into the depression at one side or the other and the driver corrects it without really noticing. It often referred to as tramlining (as it used to be when a wheel got caught in the tramtracks in the city). Make sure your test run is on good quality, flat road surfaces. Some tyres are much more prone to this than others.

If its floaty in all modes it needs checked out in case of alignment or suspension issue.

[Redditor9000]

Is this a recent feeling or are you saying this car in general is floaty? What car are you coming from or are comparing it to?

[Ballzilla]

Originally Posted by Assassin

You don't don't say what driving mode you are in. In Sport or Sport+ it should be nice and tight at almost any speed. Comfort or Eco are much softer. No way should it be floaty at those speeds. Worth considering the road you are on when feeling that sensation. Many highways are heavily worn by trucks etc and in / just after heavy rain you will notice two lines of surface water where the wheels run and little water in the middle or at either side of the lane. Its not noticeable when the road is dry. These depressions are typically wider than a car and can cause a wandering sensation as the car tries to settle into the depression at one side or the other and the driver corrects it without really noticing. It often referred to as tramlining (as it used to be when a wheel got caught in the tramtracks in the city). Make sure your test run is on good quality, flat road surfaces. Some tyres are much more prone to this than others.

If its floaty in all modes it needs checked out in case of alignment or suspension issue.

Went to work this morning on a different stretch of highway. Did over 130kph and all felt fine and stable. No issues.


So far all 👍

[AlexC2er]

My car feels pretty stable even at 170km/h. Probably the tires

[kaps_89]

Hi Ballzilla

had the exact same issue with my m340i above 120 kmph

A quick check at the wheel alignment revealed bent rims (3/4 in my case). Although very minimal, it tends to amplify at high speeds

[arjun_3421]

Had the same kind of unstable feeling on my m340. I took it in and they found that the front two rims were bent.

[BingoTheClown]

Just wanted to add something that was not mentioned.

I had an issue with a different car. I had a big old Cadillac Escalade. Suddenly, one day it felt very floaty on one highway. Every time. It felt scary at times. Like the car was almost floating and out of my control.

My issue was suspension.

Probably not your issue - but wanted to put it out there.

[Motorwerke_man]

Originally Posted by arjun_3421

Had the same kind of unstable feeling on my m340. I took it in and they found that the front two rims were bent.

I would agree it's probably a bent wheel or several.

BMW OEM wheel quality is not what it should be. Heavy and very susceptible to bends. 1/4 wheels is bent on mine and I only have 35,000kms. 3/4 were bent on my old F30 when I got it with 17,000km.