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Discuss 18" vs 19" wheel/tire

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I am interested in the 18" wheels for 2 reasons:
  • Better ride quality
  • More cost effective
The slightly taller tire side wall offers more compliance and will result in softer ride. Now, let's not kid anyone, a 235/45R18 tire is still plenty stiff, but I think that the 19" might be too stiff and this is my daily driver. The second point is cost. I save $1,500 at purchase. The 18" tires are cheaper to replace and will get damaged less frequently.

Admittedly I think I like the appearance of the 19" wheels better. I also think that the 19" will perform better, but how much better than the standard 235/45R18?

Lastly, I will remove the aero covers. They just don't appeal to me. I will keep them for long trips, and may never put them back on.
 
I'm in the exact same boat. If is were just a matter of looks, I would go with the 19s. Add in the two points you bring up and my decision swings back to the 18s.

The really difficult question for me: what would I choose if Tesla offered the 19" rims as 18s, for a lower price point?

Edit - I do like the option of having the Aero covers for long trips, but 99% of my driving is <80 miles a day so I will probably store them most of the year.
 
As I have noted in a much earlier thread on the same topic, the 18 inch wheel is essential to those of us living in areas of heavy snow and most important large and small pot holes.

I have had 19 inch wheels that came on an Audi Quarto S-5 and the rims were regularly destroyed by pot holes due to the smaller inflated rubber gap (my word for distance from outer diameter of tire to outer diameter of wheel).

The rims were regularly deformed by potholes and after the cost of three wheel "straightening, I saw the light and went to 18 inch wheels.

I assume not an issue in sunny southern California and perhaps Runt8 in Colorado will not be using the Tesla in winter or in a "pot hole free zone".
 
C'mon!!! We know the real reason for the Aero covers is to hide the dirty rims when you haven't bothered to clean them.
Extends range - Ha!!!
Just so. Clean rims (and cars) don't happen anyway when you live on a dirt road in snow country, as I do:

Garage floor1854sf 1-8-17.jpg

^ 8 January 2017; there was a LOT more mud on the garage floor by the end of winter. As usual.

Might as well have dirty wheel covers too...
 
I want to know if my 17x8 5x114.3 aftermarket STI wheels (my winter tire/wheels) will fit over the calipers. They were carefully chosen to clear the STI brakes (stock are 18x8.5s).

I'd love to be able to pick up even more sidewall and cheaper tires than the 18s - sacrilege I know
If they had a 17" option, I would have taken it.
I'm another 17" wheel guy. The big factor is caliper fit. @DarthPierce keep us posted on your 17" STI fitment experiment. BUT, I do like the extended range the 18" aero covers provide on extended trips and the optional different rim look without them, so it's 18" for me.
 
Given the subject of this thread it is probably a good idea to review tire basics.

Diameter- 18", 19" etc is not inherently more or less durable, economical to operate although larger diameter tires do have more actual tread than to smaller diameter tires. The smaller the diameter, other things remaining equal the lighter will be the tire and the smaller the load capacity. Other things are not equal.

Cross section
- 235, 245 etc is distance of one side of tread to the other in mm. The wider the cross section the more tread reaches the road. In general wider cross sections are associated with "stickier" performance on dry smooth surfaces but less good performance on rough, wet surfaces. Very wide cross sections have less resilience torrid hazards than do smaller cross sections but also have increased load capacity.

Aspect ratio- 45, 40 etc. is the sidewall depth in mm. The lower the aspect ration the stiffer the tire and the better smooth road handling will be, but aspect ration is the primary size metric for tread wear, road hazard exposure and price. The lower the aspect ration the less flexibility the tire will have so the harder the tire must work. The price of better smooth road contact is lower durability and higher price. Thus the 35mm aspect ratio of the Model S 21" tires vs the 45mm aspect ratio of the 19" means that the 21" tires have higher exposure to road hazards and wear than do the 19".

Compounds/construction- these two factors are not directly disclosed, but there are hints in tire tread wear ratings, market positioning and type of vehicle for OEM cases. The typical case is that optional larger tires generally have lower aspect ratio and are built more for dry smooth surfaces than are the smaller diameter options that typically are standard equipment. So it is for Tesla S and X.

If the choice is for "looking cool" and better handling on smooth and dry, choose the optional sizes. If durability and resilience are the primary issues go with the base. Of course, always the "sportier"the choice the more expensive the tire and the shorter the tire life.

For energy efficiency the optimal choice is typically very thin cross section, large diameter with very hard compounds. That produces very low rolling resistance, thus consumes less energy, but the thin cross section also combine to increase road hazard risk, although the hard compounds typically have long life otherwise. the prototype for this combination is the BMW i3 with the base tire 155/70R19. The optional 155/60R20 is similar. The base tire has much less road hazards, while the optional one is even harder compounds and thus lasts longer if it does not fail with road hazards. Both are famously subjects to road hazards because of the tiny cross section and tire compounds, but the optional one is far worse.

So, for Model 3 the 18" and 19" on the surface are not too much different. The major issue is whether the two are compounded differently. Personally, I would never choose the larger wheel sizes for S or X, but I might on the Model 3 because there is no obvious major difference to suggest one will be less economical or efficient than the other. My guess is that they're quite similar. When the Performance version finally comes I am sure that the optional tires will have a 'stickier' tread, maybe even a smaller aspect ratio so probably will have characteristics to the optional sizes on S and X. Right now there is not enough data to reach similar conclusions about Model 3 choices, although apparent different supplier for the two tire give clues and with the precise tire specifications we can know.

For my Model 3 I'd really like to have the wheel design of the 19" in the 18" size. Who knows, that might be a choice by the time production grows.
 
Diameter- 18", 19" etc is not inherently more or less durable, economical to operate although larger diameter tires do have more actual tread than to smaller diameter tires.
I disagree with this part of your post. With regards to the model 3, the tire diameter is the same whether it is the 18" or 19" rim. Car manufacturers do this to keep suspension, electronics, and handling constant and consistent. The amount of tread is the same unless you go to a wider tire, but again that is not recommended due to the reasons listed. It is recommended that you keep tire diameter and tread within 3% of OEM.

In the case of the model 3 19" rim, you are getting the same diameter tire but with 1/2" less sidewall which translates to a rougher ride under some conditions and potential for greater damage to the larger 19" rim. Generally speaking, rubber tire weighs less than cast aluminum rim. So generally speaking a 19" wheel (rim + tire, with more aluminum and less rubber) will weigh more than a 18" wheel of the same diameter which will have a negative impact on range under some conditions.

Go with the model 3 19" wheel if you wish, but just realize the trade offs you make. In the case of the model 3, 19" gives you a bigger rim, not a bigger wheel with more tire tread (within 3%).
 
I disagree with this part of your post. With regards to the model 3, the tire diameter is the same whether it is the 18" or 19" rim. Car manufacturers do this to keep suspension, electronics, and handling constant and consistent. The amount of tread is the same unless you go to a wider tire, but again that is not recommended due to the reasons listed. It is recommended that you keep tire diameter and tread within 3% of OEM.

In the case of the model 3 19" rim, you are getting the same diameter tire but with 1/2" less sidewall which translates to a rougher ride under some conditions and potential for greater damage to the larger 19" rim. Generally speaking, rubber tire weighs less than cast aluminum rim. So generally speaking a 19" wheel (rim + tire, with more aluminum and less rubber) will weigh more than a 18" wheel of the same diameter which will have a negative impact on range under some conditions.

Go with the model 3 19" wheel if you wish, but just realize the trade offs you make. In the case of the model 3, 19" gives you a bigger rim, not a bigger wheel with more tire tread (within 3%).
I agree with everything you said. I was wrong in my statement, assuming that the aspect ratio in the larger tire is reduced sufficiently to make the circumference identical between the two wheel sizes. Most OEM's do that. Some have enough design clearances that they do have net tire circumference different between sizes. I have no idea about Tesla.

As for your last point, most OEMs who offer larger wheel sizes tend to also have lighter wheel construction, often not the traditional cheap castings used for base choices. I do not know whether Tesla base wheels are in fact lighter than the optional larger ones. Do you? The price increments would suggest that there is more than just tire cost involved.

We are a bit constrained by "generally speaking". I wish we had the actual data, especially about Model 3, where we have no real world experience thus far.
 
I do not know whether Tesla base wheels are in fact lighter than the optional larger ones. Do you? The price increments would suggest that there is more than just tire cost involved.
No, I don't have the weights of the model 3 rims, I am going on the basis of precedent. The MS/X guys have weighed their 19" and 21/22" rims and they are significantly heavier (several pounds each) in the larger diameters. I see no suggestion why TESLA would change their marketing model now. 19" rims that weighed the same as their 18" rims would be significantly more expensive to produce. The reason for the $1,500 premium for the model 3 19" wheels is: higher cost of the tires + higher cost of more aluminum in the larger rims + increased profit margin.
 
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Just to clarify:
235/45R18 = 4.16" sidewall depth
235/40R19 = 3.70" sidewall depth
So half inch could very well make a difference in performance, comfort, etc.

Tire Rack price on Michelin Primacy MXM4 (Telsa's OEM tire on the 18")
18" $211
19" $226
Of course this varies by the tire you select but at least in this case using equivalent name brand tires, it's only $60 additional for the set of 19s. I'd say that price difference is small enough to be a non-factor in the overall cost of ownership.

And to add my own anecdotal evidence, my last car had a 3.66" sidewall depth and I drove it for 2 years in WI (where roads get destroyed by constant freeze/thaw cycles) and didn't have any problems with bent rims or blown tires.. Maybe I'm just lucky? :D
 
Forgetting about all the specs, the ride, and even the price, the problem I'm having is that basically 18" = dark. 19" = silver

If you like the way the darker wheel looks, you have to get 18" and if you don't, or you like the silver, you have to get the 19"

And if you want 19", but want aero's for range increase, you can't.
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