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18 vs 19 inch tires

18 vs 19 inch tires

Is there any advantage or efficiency with the 18 vs 19 inch tires? I realize it may be small but I am all about efficiency. Also wondering what braking setting is most efficient.

Lonestar10_1999 | June 10, 2017

The smaller wheels should be more efficient as they have less mass. It should take less energy to accelerate or decelerate the wheels with the smaller inertia.

Rutrow | June 10, 2017

A larger wheel is more efficient at higher speeds due to angular momentum. A larger wheel allows for a larger brake disc allowing for more stopping power, but only if the manufacturer takes advantage of the larger wheel to increase the disc size. I've seen many cars with after market large rims with stock brakes.

nelscharli1970 | June 10, 2017

Smaller wheels = better everything. Outside diameter of wheel/tire combo will be very close to maintain design parameters for stock suspension. Smaller wheels are lighter, more efficient.

eeb9 | June 10, 2017

I'm hoping that a brKe upgrade is part of any performance package, and that the "performance" rims are lighter than the stock counterparts as well as being larger.

Larger,lighter rims, better brakes and the stiffer sidewall provided by a lower aspect ratio makes for a nice combo!

cessna182 | June 10, 2017

part of my "life" right now involves driving many types of cars and trucks with wildly varying options. One significant factor in ride is wheel size. I have noticed, on most autos I've driven (most greater than 500 miles) is same model, one with 17" wheels vs 20" wheels; ride is much better on the 17. Even asked to have tires checked on a 21" due to the bad ride. If the 3 comes with different wheel sizes, I'll be choosing more "sidewall"!

eeb9 | June 10, 2017

Yup - that's part of the tradeoff.

Huey52 | June 11, 2017

Definitely the 18". Taller sidewall for a smoother ride, especially on uneven roadways.

HockeyEV | June 11, 2017

i hear smoother ride i actually hear softer ride. i am in the minority but i love to feel the road and the responsiveness of stiff sidewall tires. Now is the Model 3 meant to be a car like that? I am not sure

Efontana | June 11, 2017

Run flats make sidewalls stiffer.

sem3p | June 11, 2017

19" will probably look better, 18" will almost certainly be lighter (although depending on forged vs. cast and other design specifics it may not be as big a difference as you would expect, need the actual weighed mass for each). 18" will have better accel/decel because less rotational inertia. 19" will likely handle better. BUT if you live in an area with significant potholes and other road hazards I'd recommend the 18" wheels because they allow thicker tire sidewalls and a significantly reduced chance of a flat tire or bent rim after hitting a big pothole or road hazard. Also, everything else being equal, tires on 18" rims will last longer than those on 19" rims.

eeb9 | June 11, 2017

@sem - the accel/decal depends much more on the weight than the size of the rims. A lightweight 19" rim will have less inertia than a heavier 18" rim, for the same tire diameter.

Now a combo of smaller rim with smaller tires *does* make a difference. Looks strange, but it works

Bluesday Afternoon | June 11, 2017

..

Bluesday Afternoon | June 11, 2017

Will 20's fit? Another push

eeb9 | June 11, 2017

I'm willing to bet that someone makes 20"rims and a matching-spec tire that would work.

You'd have almost zero sidewall though, meaning harsh ride and higher risk of damage to the rims from road hazards...

Pkalhan | June 11, 2017

I know the 18s are the smart play, but I am really leaning towards the 19s. The 3 looks to be a decently sized car and the 18s look a little small.

eeb9 | June 11, 2017

i'm with ya - but hoping that the larger rims are just one component of a decent performance package

gar1116 | June 11, 2017

Don't go with larger wheels if you live in an area with potholes, or you will be replacing tires alot. One bad winter my wife had to replace three different low profile tires on her car (all different potholes). 18" for me!

Pkalhan | June 11, 2017

gar1116, I totally hear what you are saying, but fortunately, we also have an SUV for that so in bad weather we would be set for that. I mean, I get everyone wanting the most range they can get, but I think appearance is somewhat important too.

A few weeks ago, I test drove the Model S P90D with 21' wheels, I was expecting it to be very harsh and bumpy, but it wasn't. My wife who def likes a very Lexus soft ride admitted that there were bumps, but it was not very bad at all. So my thinking is, if the 21s were not bad for her, the 19s would be even better.

The best part about this though is that there is no wrong answer really, you get what you want and like. I am just hoping they offer 19' gloss black turbines...I will be all over them lol.

ReD eXiLe ms us | June 11, 2017

Pkalhan: It is so weird to see someone referring to 18" wheels as being 'a little small'. I first saw them on the Dodge Intrepid and Eagle Vision a bit over twenty years ago at the Los Angles Auto Show. That was a rather HUGE car and the wheels basically filled the entire wheel well. I think the production cars only had 16" or 17" wheels instead. To my eye, anything over 17" seems to be ridiculously huge on a Midsize car. The Model S can just barely pull off the 21" wheels, but it looks like it's rolling on wagon wheels when someone moves up to 22" in size.

Huey52 | June 12, 2017

Always an aesthetics/performance vs. road suitability consideration. My area roads have too much feel [read potholes, etc.] so again will opt for the 18". Albeit the 19" are sure to look a bit better and I too have made that compromise/sacrifice in the past.

Iwantmy3 | June 12, 2017

I expect that the tires on the 18" wheel will be cheaper to replace. If the decision is this difficult, cost over-rules.

Sandy’s 3 | June 12, 2017

I really like the 19" on the 3. Guessing a minimum of $1500. Most likely higher. To upgrade after means wheels and tires. $1000 minimum for performance summer 235/40/19 (TireRack) and $2400 for the BBS wheels I like. I realize I can do other wheels for $1000. I will most likely pay the Tesla upgrade price.

Pkalhan | June 12, 2017

@FLHX13 I'm with you. I am thinking the upgrade will be cheaper than aftermark from Tire Rack. I looked on their site last night and for the wheels I liked plus tires would run over $3k. Not sure if I want to pay that much. We will see in a few weeks.

IHaveArrived | June 27, 2017

@eeb9 writes: "@sem - the accel/decal depends much more on the weight than the size of the rims. A lightweight 19" rim will have less inertia than a heavier 18" rim, for the same tire diameter."

Not so. The moment of inertia is more complicated than that. Imaging two bicycle wheels of the same size and weight. One has plexiglass spokes and a cast iron rim. The other has a cast iron hub, and plexiglass spokes and rim. While both would absolutely suck for actual bicycling, the one with the cast iron rim would take considerably more energy to move, because the weight is biased outward.

For two automobile wheels of different sizes but the same weight, the smaller one requires less energy to turn, because the larger one has weight further from the axis. Simplifying a bit, the energy required to move a certain amount of weight around an axis varies proportionally to the square of the distance from the axis.

Frank99 | June 27, 2017

eeb9 is right in that it's possible to have a lightweight 19" wheel with a lower rotational inertia than an 18" wheel - imagine, if you will, a standard steel 18" wheel vs. an aluminum 19" wheel. The steel rim at a 9" radius is likely to have a much higher inertia than the aluminum rim at a 9.5" radius. Even among aluminum alloy wheels, it's possible to have a 2:1 weight differential between identical sized, but differently styled wheels.
The conclusion has to be that the 19" wheel will start off with an inertial penalty, but may still come out ahead with proper design and attention to weight.

johnse | June 27, 2017

If there is an appreciable difference in angular inertia, I would believe that will be on the 19" wheels. Both sizes will feature the same outside diameter, the 19" will have shorter sidewalls and thus the tire itelf will be lighter. The rim will be further from the hub, and have more material, so if same material, thickness, etc, would weigh more and have a longer lever arm. Usually such rims are made from more exotic (lighter, stronger, but often more brittle) materials to counter this.

The noticeable effect is going to be cornering as the shorter sidewall will flex less and keep more of the tire surface in contact with the road. Also a stffer, more noisy ride, and the tires will wear more quickly.

Choose wisely depending on your preferences.

Sandy’s 3 | June 27, 2017

For any given 18" to 19" wheel size eg. 19 x 8.5 the weight can VARY by more than 10 pounds. Low 20 lb to low 30 lb. Massive difference in both unsprung weight and rotation mass. Tesla factory alloy wheels are at the higher end of the weight range. Most likely reflecting the stenght needed do to the cars weight. As well forged wheels compared to low pressure cast are stronger but much more expensive.

eeb9 | June 27, 2017

This is why we need the weight of the wheels, along with their sizes, to make good decisions.

My hope is that the designers take this into account when the do the performance package - shorter/stiffer sidewalls for better cornering *and* lighter wheels for lower inertia on stops/starts

Along with tighter suspension and *really* good brakes...

Bluesday Afternoon | June 27, 2017

I have no doubt the brakes will be "really" good. My Model S brakes are excellent and with regenerative braking, which is so cool, you'll find they last at least twice as long. I usually apply my brakes just before the stop sign/light/car due to the regen system when not using TACC. Pretty close to one pedal driving. With TACC engaged it is no pedal driving!

Sandy’s 3 | June 27, 2017

From what I have seen in the photos the RC's have quality Brembo (branded Tesla) front brake calipers. The rear calipers appear more generic and are sliders with both brake and parking brake functionality.
Tha MS and MX use Brembo calipers front and rear. Apparently Brembo is opening a Mexico plant to produce the calipers.

eeb9 | June 27, 2017

Brembo front and rear works a treat... :-)

95dawg | June 28, 2017

35/19s looks nice but it will be mostly for visual value. One could argue better corning but how much better vs 18s with 45 sidewall? 17 and 18 seem to be the popular choices for track cars, sweet spot for performance/cost/fuel efficiency.

Interestingly, during cornering, lower profile grip better on the outside wheels but sometimes break traction sooner on the inside tires. Car mags have done comparo of diff wheel/tire combinations and larger wheel + low profile tires don’t always do better.

As for weight and inertia, cast aluminum weighs more than twice as much as tire rubber. If you are upgrading to a 19” wheel+tire option at purchase, I wouldn’t expect significant improvement performance wise.

nadurse | June 29, 2017

I will most likely get the 18" rims, cheaper and more tire options and less likelihood of a bent rim living in pothole ridden ohio. But depends on if they are the same design or not

LA-Fohlen | June 29, 2017

With the decision of going with the factory upgrade 19" or something like TireRack is partially the costs but I would think if you hate the rims that Tesla offers it might be better to go with the TireRack option.

For myself, I stay with the 18s. With my 2 years of experience now Texas appears to be one big pothole although I had that feeling in SoCal as well. 10 years ago the 710 was just a mess.

Ehninger1212 | June 29, 2017

I'm probably going with the base wheels and getting some wheels I really like after market. Of course they will be 18's, black, staggered, lightweight with a slight lip :D

@LA-fohlen
Yes TEXAS is one big pothole haha

hmgolds | July 1, 2017

@Pkalhan

Around here, potholes are created in winter, but last all year long. So it's 18s for me.

stevebpage | July 3, 2017

I live in sunny southern california. From this thread I am guessing it's a money thing versus performance. At first I wanted the 19" since that was the base for Sedan "S" but now I am thinking more toward the 18". It's my first Tesla. And I want the best I can get. I love to drive fast though I don't I will find many places in LA to speed. Therefore, the car is basic to my driving habits with few trips so far. So what is the opinion on my sticking with 18" wheels? Cheaper less to replace, I have checked. Cheaper by 50% per tire.

eeb9 | July 3, 2017

We don't yet know the particulars, and whether the 19" setup will be for performance or just looks. Same could be said for the 18s, for that matter...

They have lots of variables and widely divergent sets of expectations to balance - it will be interesting to see which way they jump.

It will also be interesting to find out if there are any software or suspension geometry issues to deal with if one changes rims (while keeping the overall diameter the same).

Ditto tires - the traction-control systems have a ton of built-in assumptions and specs for tings like cornering ability and traction - what happens to those if you install tire with traction specs substantially different than the factory settings.

These things could make things tricky

Or not.

We don't know yet....

msmith55 | July 4, 2017

I remember seeing a table which showed the smallest tires got the best range! Tessa could improve this by eliminating the spokes, as the spokes act like air blowers and provide excellent cooling of the brakes, which is not needed. Instead the wheels should be perfectly flat, inside and outside. That should give 2 percent more range!

eeb9 | July 5, 2017

Actually, brake cooling still matters, even in a BEV

At least for some people some of the time... :-)

Now if they could make those aerodynamic wheels look good and still provide efficient airflow (including to the brakes) I'd be happy.

dd.micsol | July 5, 2017

18 Better range.

noleaf4me | July 5, 2017

My bet is the 19's will look a lot better thus almost pushing people into the upgrade. I'd frankly would like to stick with the 18's but not sure if i'll like what they have to offer there.