High speed wobble 130+MPH???

[BMWadrenaline]

Ok so today I experienced a strange wobble when accelerating, started at about 130 MPH and got worse the faster I went, let out of it at 145 MPH because it felt very unstable. I've had it up to the limiter several times before and it has felt stable every time. It was a little windy so I thought maybe that was the issue. I had the wheel torque and balance checked, all good. I also had an alignment performed and it was all in specs. The suspension was checked and nothing abnormal was found. Has anyone else experienced this?.


THIS WAS ON A CLOSED RUNWAY - NOT ON PUBLIC ROADS BEFORE EVERYONE STARTS FREAKING OUT!!

[P1]

May I ask where you were going 130/145mph?

[secretariat]

I purchased this vehicle so I could drive it, not sit in jail.

[BMWadrenaline]

Private event on a closed runway, I've been to several, but never had it do this before. NOT ON PUBLIC ROADS!!!!

[gizmo958]

never experienced this my self , try again now its been retracked. on your closed run way ;-)

[BMWadrenaline]

Originally Posted by gizmo958

never experienced this my self , try again now its been retracked. on your closed run way ;-)

Yes a closed runway, no joke, used to go to a public event in North Georgia, "Heavens Landing"

[Louv]

How old are your tires?
When were they balanced?
Are all of the wheel weights still attached?
Tires all at the 100+ mph suggested pressures?
Pressures all equal (left to right) ?
When was the alignment last done?

[raym3cs]

i hit 147 in my F86 on the nj turnpike at 3 in the morning going to the airport...
the road was empty and i just had my dinan stage 1 installed so i wanted to see what it can do ....

the f85 / f86 are very heavy... i also felt it wobble a little at that speed ...

[BMWadrenaline]

Originally Posted by Louv

How old are your tires?
When were they balanced?
Are all of the wheel weights still attached?
Tires all at the 100+ mph suggested pressures?
Pressures all equal (left to right) ?
When was the alignment last done?

Balanced and aligned about 200 miles ago, yes all wheel weights are still attached, tires have about 4mm tread remaining in rear, 6mm front, all pressures are set to 35psi. I also just had the car on a lift and had the axles checked to see if any were bent/warped. I already ordered rear tires so I'll just have to wait and see if it happens again at the next meet. Thanks for you help.

[BMWadrenaline]

Originally Posted by v8twinturbo

i hit 147 in my F86 on the nj turnpike at 3 in the morning going to the airport...
the road was empty and i just had my dinan stage 1 installed so i wanted to see what it can do ....

the f85 / f86 are very heavy... i also felt it wobble a little at that speed ...

I just find it strange I've had it at limiter probably 20 times and have never felt it, felt very stable, want to have it flashed for top speed limiter removal and see how high I can take it

[elm3]

Do you have spacers in your hubs? (Wheel spacers). Or is it completely stock.

[GladiatorOwner]

Tires

[Manoloiv]

Ive been at the aforementioned speeds (135-145mph) and have not experienced this.
There is slightly more movement but this is expected at those speeds. I dont feel unstable nor does the x5m wobble.

[Alan l.]

At those speeds the slightest thing could cause massive vibrations. I would take it to a good tire shop that offers Road Force balancing. Also check for a slightly bent wheel as well.

[ajob]

Originally Posted by BMWadrenaline

Ok so today I experienced a strange wobble when accelerating, started at about 130 MPH and got worse the faster I went, let out of it at 145 MPH because it felt very unstable. I've had it up to the limiter several times before and it has felt stable every time. It was a little windy so I thought maybe that was the issue. I had the wheel torque and balance checked, all good. I also had an alignment performed and it was all in specs. The suspension was checked and nothing abnormal was found. Has anyone else experienced this?.


THIS WAS ON A CLOSED RUNWAY - NOT ON PUBLIC ROADS BEFORE EVERYONE STARTS FREAKING OUT!!

You could also check each wheel on a balancing rig and look for runout (eccentricity) at the tire surface - should be not more than 1 mm (~1/32").

Wheel runout is a geometric problem, different from wheel unbalance which is a weight distribution problem; unfortunately you sometimes may have both together, which then makes wheel balancing such a tough, imperfect act.

Runout may be very bad for shock absorbers, wearing them down inexplicably fast. New, perfectly round tires may gradually deform and develop some runout after fast driving, moreso if it's very hot.

Balancing may well compensate runout's caused forces up to a speed, but beyond it they reappear strongly and if the suspension starts resonating, a vibration may appear suddendly and will stop only by slowing down quite a bit.

In my case I tried a couple of times to reach max speed (no limiter, option 7ME) on a smooth German autobahn with no traffic (rare!) and the car was stable - little or no wind, 20" Pirellis Zero at 2.6 bar (~38 psi).

[jlawphoto]

Originally Posted by P1et

May I ask where you were going 130/145mph?

.....

[P1]

Originally Posted by jlawphoto

.....

Did you mean to post this three days ago?

[BMWadrenaline]

Determined it was the left rear tire run-out was higher than the other three, replaced rear tires and problem is fixed. Thanks for the help!!

[Louv]

Go fast. Take risks.
...safely.

[Alextacy]

I was impressed how stable the car was at speed, I was frequently over 200-210kmh on the track recently.
Braking from that speed after a few laps was another story, and stability control intervention in the different modes..

[BMWadrenaline]

Originally Posted by Alextacy

I was impressed how stable the car was at speed, I was frequently over 200-210kmh on the track recently.
Braking from that speed after a few laps was another story, and stability control intervention in the different modes..

I dont think the brakes on the X5M are good enough for the weight and speed it can achieve. Wish carbon ceramic were an option.