Left and right wheels plus directional tires

RealOEM.com confirms that there are right- and left-side versions of the 428 and 429 wheels (i.e., if they're mounted on the opposite sides, they would look different). The first photo below is the way my and almost all 429 wheels are mounted judging by the photos I've seen. The second photo shows the 429 wheels mounted on the opposite sides which I think looks much more dynamic. This is also the way that almost all 428 wheels are mounted judging by the photos I've seen. Mounted this way, the spoke ends near the wheel rim trail the spoke ends near the centers as if the wheel speed when the car is rolling forward is causing the outer ends of the spokes to lag behind the center ends. I plan to swap my wheels from side to side to get this more dynamic look. I wonder why BMW chose the more dynamic rotation direction for the 428 wheels but not the 429 wheels.

Also, the tread pattern of the 19" Bridgestone Ecopia tires isn't symmetric. When I view the tread area from the front of the car, the concave side of the horizontal tread cuts in the area closest to the outside edge of the right tire points down whereas it points up on the left tire. I could not find any directional arrows on the tires, so I guess Bridgestone doesn't consider them to be directional, but the tread meets the road in different ways on the right and left tires which I find odd.

Just a couple of observations from someone who must have too much time on his hands…


Standard - rotation direction looks backward to me


Better - rotation direction looks forward to me

At a wild guess: less resistance????

alohart said:

Just a couple of observations from someone who must have too much time on his hands…

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and £560 !

alohart said:

Also, the tread pattern of the 19" Bridgestone Ecopia tires isn't symmetric. When I view the tread area from the front of the car, the concave side of the horizontal tread cuts in the area closest to the outside edge of the right tire points down whereas it points up on the left tire. I could not find any directional arrows on the tires, so I guess Bridgestone doesn't consider them to be directional, but the tread meets the road in different ways on the right and left tires which I find odd.

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There are directional tires and there are asymmetrical tires.

Directional tires are meant to rotate in particular direction going forward. When you have those you can only rotate wheels from front to back on the same side, swapping them around requires remounting them on rims.

Asymmetrical tires are designed to have one side always facing out, the other always facing in. They can be rotated around at your wish, and you won't see arrow marks on them. The only time it matters is when they are mounted on the rim, after that they will always be correct.

Tomasz said:

Asymmetrical tires are designed to have one side always facing out, the other always facing in. They can be rotated around at your wish, and you won't see arrow marks on them. The only time it matters is when they are mounted on the rim, after that they will always be correct.

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I would agree with you if the tread pattern were such that the contact patch of the tires mounted on the left and right sides were mirror images of each other, but that's not the case for our tires. The image below shows the contact patch of a tire mounted on the left side (i.e., the right side of the image is the side facing out). The image of the contact patch of this tire when mounted on the right side would be this image rotated 180º which is not the mirror image. The wavy pattern of the tread when the tire is on the right side would be upside down from this image, so the tread's interaction with the road surface, water on the road surface, etc., would differ from this same tire mounted on the left side.

Maybe the difference in behavior of this tread design when rotating in opposite directions isn't significant, but I have to believe that Bridgestone's tire designers made the tread wavy for some reason other than just looks.

alohart said:

but I have to believe that Bridgestone's tire designers made the tread wavy for some reason other than just looks.

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Probably, but those same designers also made the decision that the tires need not be directional.

Given the situation with the unavailability of 20" winter tires, I would have to question the wisdom of any decision made by the folks at BMW regarding tires

WoodlandHills said:

Given the situation with the unavailability of 20" winter tires, I would have to question the wisdom of any decision made by the folks at BMW regarding tires

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Talk to anyone in the industry that has dealt with winter tires for a long time and you'll get the recommendation that a taller, narrower tire is better in the winter. There's a reason the tire is only available in 19" size (and narrower/taller) than the performance/summer tire on the 20" wheels.

alohart said:

The image below shows the contact patch of a tire mounted on the left side (i.e., the right side of the image is the side facing out). The image of the contact patch of this tire when mounted on the right side would be this image rotated 180º which is not the mirror image. The wavy pattern of the tread when the tire is on the right side would be upside down from this image, so the tread's interaction with the road surface, water on the road surface, etc., would differ from this same tire mounted on the left side.

Maybe the difference in behavior of this tread design when rotating in opposite directions isn't significant, but I have to believe that Bridgestone's tire designers made the tread wavy for some reason other than just looks.

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Like this:



You are suggesting that both BMW and Bridgestone have no idea what they are doing?

I think you will find that there is next to zero difference in the performance of these tyres side to side. If there were, there would be a direction of rotation arrow on the tyre and mirrored tread designs left to right. I can understand that having slight differences in tread symmetry between left and right might offend your sense of exactitude but I somehow doubt your assertion that it would make any practical difference at all.

alohart said:

I would agree with you if the tread pattern were such that the contact patch of the tires mounted on the left and right sides were mirror images of each other, but that's not the case for our tires. The image below shows the contact patch of a tire mounted on the left side (i.e., the right side of the image is the side facing out). The image of the contact patch of this tire when mounted on the right side would be this image rotated 180º which is not the mirror image. The wavy pattern of the tread when the tire is on the right side would be upside down from this image, so the tread's interaction with the road surface, water on the road surface, etc., would differ from this same tire mounted on the left side.

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I've looked more into that about 15 years ago when I first encountered asymmetrical tires and from back then I remember that my findings were that the most important decision factor was the placement of big water channels. The reason for that is mainly to direct water in certain direction (did you notice that water channels are bigger on the outside half of the thread?), provide solid grip on straights by the inside part of the tire and enhanced grip in turns by more knobby outside part of the thread.

Also if you look at the waves they are kind of symmetrical (kind of S shaped) so they will behave pretty much the same no matter in which direction they are rotating.

jadnashuanh said:

WoodlandHills said:

Given the situation with the unavailability of 20" winter tires, I would have to question the wisdom of any decision made by the folks at BMW regarding tires

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Talk to anyone in the industry that has dealt with winter tires for a long time and you'll get the recommendation that a taller, narrower tire is better in the winter. There's a reason the tire is only available in 19" size (and narrower/taller) than the performance/summer tire on the 20" wheels.

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Jim, now you have really confused me...... Would not your comment above indicate that a 20" snow tire would be better than a 19" one? Or is there some absolute limit to rim size above which snow tires won't work? What is to prevent a 20" snow tire from functioning on an i3? It might not be of ideal width, but wouldn't it be a marked improvement over 20" summer tires? I bet BMW and their tire OEM have the technological ability to do so if they chose, they could even make it a bit narrower than the summer version. BMW can design the wheel arch and other areas with enough clearance if they want......

Talk to anyone that sells snow tires (well, someone that actually cares more than just selling a tire to you) and they'll tell you a higher profile, narrower tire always will work better slicing through snow and slush. A wider tire tends to float over the stuff, not cut in down to the pavement. Read about it on TireRack (http://www.tirerack.com/winter/tech/techpage.jsp?techid=126) or most any informed site that sells them, often, they'll recommend going minus 1 on wheel sizing because it works. You need to maintain the OD of the assembly, but what you do not want if you want real winter traction at its best through the crud is a lower profile, wider tire. If you are only going to deal with just the cold and never see any ice, snow, or slush, I suppose you could stay at the larger rim size, but most people, if they go to the trouble of swapping, do it for the safety of being able to go better when the weather gets lousy. Given the small quantity of i3's that need a tire like was designed for it, there isn't a great market, and it may be awhile (or never) where you see other options; at least those that have low rolling resistance characteristics to optimize the range on the EV.

The other big thing in the winter is that the snow can often cover road hazards, and having a low-profile tire/wheel is much more prone to failure...having a bit more height in the sidewall does make a difference.

jadnashuanh said:

...You need to maintain the OD of the assembly, but what you do not want if you want real winter traction at its best through the crud is a lower profile, wider tire...

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I have hard time understanding why would 155 wide tire mounted on 19" wheel be any better from 155 wide tire mounted on 20" wheel if the outside diameter is the same. the width, height and contact patch size will be identical.

I get your point about a narrower tire being better in snow than a wider tire all other things being equal. But the i3 already has some of the narrowest tires sold on any car in 2014 and the difference in width between 19" and 20" snow tires won't change that. Compared to snow tires on any other car sold by BMW any 20" i3 snow tires would be inches narrower and thus far better in snow. So why not 20" snows for the i3? Does that tiny bit of width increase make the 20" snow tire so much less effective that it would be unsafe?

It's both the sidewall height and the width...but, given the slight differences, in reality, it's probably not a big difference. FWIW, even on the 19" wheels, they come in two widths, so on many, the tires are not the same front/back. They only make the winter tires in one size/width right now, on the 5" rims/19" OD). Then, you have to consider, how many of them will be sold and could the company making them make any money (in this case Bridgestone). If there were a business case for also making 20" versions for the i3 (i.e., enough volume), I think that they'd make them. As to 20" on other cars...the likelihood is that same tire could be used by more than one car model and brand, so the potential volume would be high enough to justify making the molds and maintaining some inventory. I do not think the market for the i3 is big enough for them, at least in the first year or two, and in reality, the 19" version does have better performance in bad weather.

BMW says not to use snow chains on the 20" X5 wheels/tires as well, due to clearance issues.

This may be the case for the i3 as well, although as noted above, given how similar the widths are it's hard to see why appropriately sized chains would work on the 19" but not the 20" combo. I did check the clearance between my front i3 20" wheel and the strut, and there is very, very little space. One would expect the 19" to be similar though, at least at the front, since the offset and wheel width are the same.

Apologies for reviving an old topic but it's the closest I have been able to find to what I am about to say.

I've just ordered an 94ah i3 Rex with the same wheels as the OP's car. On closer inspection the web configuration shows the car would come without "handed" wheels I.e. One side would have the spokes swept forwards whilst the other would have the spokes swept back.

Suspecting this might be a web site oversight, I checked with the dealer who then checked with the BMW UK head office for i brand; long story short it's not an oversight and cars ordered from now on will come with wheels which look different on each side of the car.

There's not much I can do about it, although its disappointing that BMW have made the decision to sacrifice looks for the sake of stocking fewer varieties of wheels. I just wanted others who may be about to order a car to be aware that there will be a different look to each side of the car. Now I have to figure out which 19" wheels look the best and disguise the cost-cutting approach.

MTF said:

I've just ordered an 94ah i3 Rex with the same wheels as the OP's car. On closer inspection the web configuration shows the car would come without "handed" wheels I.e. One side would have the spokes swept forwards whilst the other would have the spokes swept back.

Suspecting this might be a web site oversight, I checked with the dealer who then checked with the BMW UK head office for i brand; long story short it's not an oversight and cars ordered from now on will come with wheels which look different on each side of the car.

There's not much I can do about it, although its disappointing that BMW have made the decision to sacrifice looks for the sake of stocking fewer varieties of wheels.

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BMW installed "handed" wheels on only 2014 and maybe some early 2015 i3's. Many people don't notice the "handedness", but I do. I'm happy that our i3 has the proper wheels although if in the future I need to replace one of the discontinued "handednesses" and learn that it is no longer available, I won't be as happy.

Art, I'm slightly jealous of your "handed" wheels!

The local dealer hadn't noticed the change, he now curses me for pointing it out because every time he sees one of the newer demonstrators the wheels jump out at him. Guess it's one of those things you can't un-see.

A year ago, my car was in for repairs and when I picked it up I noticed the spoke directions were different on both sides. Took it back and it was easily corrected. Took me a while to notice though.