Highway Speed Swerve

[i7iceguy]

Just got my 2014 i3 Rex over the weekend and loving the car. There is however an issue I want to see if it's common to these cars and if it warrants taking the car in to look at.

At high way speeds, I feel the car swerves a lot. I naturally assume because the wheel is thin and car is light but wonder how others feel.

Your input is appreciated. Thanks!

Albert

 

[Sparky]

Make sure your tire pressures are correct. Dealers are notoriously bad at setting them correctly.

 

[SSi3]

Along with tire pressures, be light on the steering inputs, small corrections, its very sensitive and was never really meant for highway driving. Would be nice if it had speed sensitive steering to dial down the assist at higher speeds.

 

[Boatguy]

Along with tire pressures, be light on the steering inputs, small corrections, its very sensitive and was never really meant for highway driving. Would be nice if it had speed sensitive steering to dial down the assist at higher speeds.

+1

 

[jadnashuanh]

The i3 begs for a light hand on the steering wheel. Because it is fairly tall, a sidewind does cause it to lean. The natural tendency is to try to make a steering correction, but in reality, the car is still going straight and you caused it to turn! Way back when learning to drive, the instructor I had placed a glass milk bottle on the floorboard and every time you knocked it over, either from jerky acceleration, stopping, or turning too rapidly, you lost points for the day. This instilled learning to be smooth just like a pilot needs to be to provide a decent ride in an airplane. You'd be amazed how much longer brake pads and tires last, and your average trip time stays the same or improves along with efficiency. Correct tire pressure does, though, change the i3's handling characteristics for the worse when it is not set properly.

 

[peteinlongbeach]

Along with tire pressures, be light on the steering inputs, small corrections, its very sensitive and was never really meant for highway driving. Would be nice if it had speed sensitive steering to dial down the assist at higher speeds.

Sorry to say, that's just ridiculous. It's a 93 mph car.
And, the steering IS speed sensitive - it reduces assist with speed, and is quite noticeable if you're paying attention.

In my opinion, the steering is a bit quickly geared for the average driver. I also believe the front end geometry could benefit from more caster, which would induce more self-centering and stability (this is unfortunately not adjustable on the i3). Also, the rear mounted motor / rear drive contributes to the dynamics somewhat. Finally I think the LRR tire design contributes to road contour and groove sensitivity. All of these elements add up...

I do not believe the dynamics are related to "light weight" (the car is of similar weight to other similar-sized sedans). I also don't believe the dynamics are related to what is generally described as "skinny tires". I drove French cars for many years and hundreds of thousands of miles, most of them with 125 or 135 width tires (the i3 is 155 in front). These old cars were very directionally stable with no twitchiness, and were much lighter than the i3. So, it's not tire "size".

All that said, I have lowered the front tire pressure to 29 psi, and it is noticeably less sensitive at speed, and is actually acceptable at the governed maximum. I plan to do some more experimenting with lower front pressures, but this will not completely eliminate the inherent effects of the front geometry, steering ratio, tire design, and overall layout of the car.

 

[i7iceguy]

Seems like the consensus is telling me that this is normal for this vehicle. I will try some of the tips you guys suggested.

 

[justanotherdrunk]

not tire pressure related for me

my car was delivered with wildly varied pressures

correcting made no difference

F 33psi R 41psi

its also not related to surface rough/ smooth/ grooved


yep shes a wanderer on the freeway and its normal

 

[MikeS]

I don’t find my i3 to be a wanderer at all. For the first few days I found the steering to be a little more responsive than my previous cars but I soon got used to it and no longer notice anything unusual.

 

[BrianStanier]

Same here.. Maybe a difference between UK/EU and USA specs?

 

[PhilH]

I've concluded that it's more sensitive to road camber than previous cars I've driven. If the road banks slightly, I find I need to make a conscious correction to get it back on the straight and narrow. Perhaps road changes like this are more common in the USA?

 

[WoodlandHills]

Certainly American highways are of lower quality construction than in developed countries like in Europe. I am not surprised that the car rides a bit rough and has other quirks since it was developed in Germany where the pavement is the best on the planet. The same with the complaints of rattles from the interior: I don't think the German engineers really were aware how rough an American road can be!

 

[peteinlongbeach]

not tire pressure related for me
my car was delivered with wildly varied pressures
correcting made no difference
F 33psi R 41psi
yep shes a wanderer on the freeway and its normal

The 19" tires are more forgiving than the 20" tires, due to differences in the aspect ratio. Try lowering your front pressure to about 29 psi and see how you like it. Works better for me.

 

[i3Alan]

In my opinion, the steering is a bit quickly geared for the average driver. I also believe the front end geometry could benefit from more caster, which would induce more self-centering and stability (this is unfortunately not adjustable on the i3). Also, the rear mounted motor / rear drive contributes to the dynamics somewhat. Finally I think the LRR tire design contributes to road contour and groove sensitivity. All of these elements add up...

I could be wrong, but here is what I perceive on the i3 steering. First, it is quick, with small steering inputs yielding large yaw changes. However, I believe it has a large hysteresis that shows up at center/straight mostly. When the wheel is under the slightest tension, it is excellently responsive, as a fine sports car should be. However, there is nearly half an inch of free play when the wheel is not under tension, and that makes the car feel skittish.

Most of my previous cars have have much slower steering, but nearly zero hysteresis. When tooling down a straight road, most precision cars will stay centered in the lane with barely a thought, much less any noticeable wheel movement. With the i3, I can purposely move the wheel left or right within that "center zone" and see absolutely no car response. So, for example, every time I do need to adjust within a lane on a straight road, the first 1/8" to 1/4" of wheel turn does nothing, and the next 1/16" gives me the full steering input I want. On my Lexus ES with much slower steering, the first 1/32" wheel turn noticeably starts the correction, but I may need a ½" to get the full correction I want.

The transition from dead zone to actual steering input is hard to feel, unless you try, and then it is quite noticeable. You can feel it with the car turned off just wiggling the wheel slightly without getting any tire movement on the pavement.

I took the car to the dealer to complain about this. The service tech drove the car with me, and within a mile stretch on the freeway, he said he could clearly feel what I was talking about, but had never noticed that on any other BMW. He said he would contact HQ and let me know what could be done. The answer was the steering was responding as expected.

I am pretty used to this now, and it does not bother me much, but it drove me crazy for the first few hundred miles with the car.

 

[PhilH]

Obviously, the power steering is electric rather than hydraulic. I know there are some other cars on the road that use electric power steering because it's more efficient. I have read reviews that criticise this steering as worse than hyraulic, although the reviewers didn't say in what way. But perhaps what you're describing is just how electric steering feels in comparison with hydraulic?

 

[peteinlongbeach]

The perceived "hysteresis" is likely due to the electronic steering sensor at the rack, which can impart a negligible amount of "springy" lost motion from the steering wheel to the rack pinion, but this should be imperceptible in normal driving. This sensor responds to torque input from the steering wheel linkage to energize the electric assist. That said, I have never noticed this perceived dead zone in my i3 nor my previous RX8 (which also had electric steering) in normal driving mode. It might be interesting to disable the electric assist and see if that reduces the sensitivity at speed.

Although the sensor and calibration of the system may contribute to the sensitive dynamics, I still believe much of it lies in the basic steering / suspension geometry and general layout of the car. My RX8 was a bit like this until I had an alignment shop dial in a bit more caster into the front geometry, and then any twitchy behavior was completely eliminated and the steering feel was as perfect as anything I've driven. I would do this on the i3, but with McPherson strut suspension this is not normally possible.

 

[Sparky]

After reading this thread I checked out my car. It has no dead zone at all. Any inputs to the wheel causes motion left or right.

 

[PluviaPlumbum]

Certainly American highways are of lower quality construction than in developed countries like in Europe.

That made me smile a bit. - Can I refer you to the Beatles 'A day in the Life' "Four thousand holes in Blackburn Lancashire", the next town over from me, but that was 1967 and the local authorities assure us they are working hard on the problem :lol:

 

[i34me]

FWIW, Both of us experienced what we thought to be no dead zone when the car was new, but now at over 8k miles I can feel about a 1/4in or maybe a little more "dead zone".

This is all I can think of that is different:
1. We have more experience at driving the car.
2. 8k miles break-in on the tires and steering components.
3. We use different tire pressures now, the front was 30-31 when new but now we use 33-34.