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18" wheel on model Y
- Thread starter Midnightsun
- Start date
That looks good! How's the ride and efficiency vs the stock 21's? I have a MYP and I was thinking about getting the same rims with the Michelin Pilot Sports on it.
The ride is great. It’s exactly what I was hoping for. No more rattling of the teeth over imperfect surfaces. No more worrying about curb rash on the wheels. The only downside, which is very slight but expected, is the larger sidewalls flex a bit more during hard cornering. Another plus is I can rotate the tires now. I can’t really comment on efficiency as I don’t really measure and track that. The car says 277wh/mi in the 568 miles I’ve driven it, mostly on the freeway.
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Don't know how you can make that claim. The Gemini 19" wheels are around 30 lbs each. You can easily find 19" wheels that are about 22 lbs each. That's 8lbs LESS UNSPRUNG WEIGHT. That's 32 lbs unsprung weight total for the car and that makes a huge difference in efficiency. If you think 15% gain going from 21" to 19" is marginal, well then I suppose it's all relative. The stop and go weight makes a difference. The aero of the wheels make more of a difference at highway speeds.
As for the cost, it may not make sense for most since lighter wheels tend to cost more. But that's up to the buyer and whether they want a softer ride if they are coming from 21" Ubers.
Here's the science.
I have both 18" Model 3 Aero Wheels running BFG Trail Terrain 255/55, and Model Y 19" with OEM Conti's. 2022 MYLR.
I ran test runs, same route, same speeds, same weather, same state of charge, 42 miles each run.
The difference in energy usage was not meaningful; a couple percent.
I spent $400 for the M3 wheelset and 1100 for sensors and the tires mounted and balanced. I have a need for minor off-road excursions.
If you're racing, unsprung weight can be meaningful for suspension management and handling. I did that for a decade with Porsche.
For the daily driving application, yes it can buy you a couple percent. Meh.
But the internet blogs, the car magazines, and the wheel marketers would have you believe it's all magic and worth the money.
YMMV.
EVer Hopeful
Active Member
I mean no offense intended. At the same time I wanted to point out some flaws in your testing that may (or may not) change your mind.
1) You compared an 18" wheel with BFG Trail Terrain tires (i.e. - this is as inefficient as can be) vs. your OEM 19" wheel with the Continentals. You didn't mention what the weight was with the 18" wheel. But even if it were the same weight as the 19", the BFG Trail Terrain tires will have reduced your efficiency by at least 10%. Going from the OEM tires to the Michelin Cross Climates documented around a 10% loss already. I can't even imagine what it would be for your tire that looks like below.
2) You underestimate the value of unsprung mass. I've been doing DE events for 28+ years and have instructed with PCA, BMWCCA and Audi CCA. While I can attest to faster laptimes with lighter wheels, more importantly, I was a licensed (i.e. - legally liable) mechanical engineer at a point in my career and the math/science that Engineering Explained in the video I pointed out is spot on.
Bottom line: tire cross section, wheel weight, and tire tread pattern significantly contributes to the overall efficiency given all other factors equal (overall car weight, speed, temperature, etc). If someone were to go from the MYP 21" wheel to a 22 lbs 18" wheel with the same tires, they can expect at least a 15% efficiency gain given all other factors equal.
Now... having said above, not including tires, is spending $1800 shipped for an 18" wheel set that weighs 22 lbs each worth it? Ummm.... ummm.... I think I'll suck it up with my OEM 21" wheel...
12kWh vs 14kWh for the 2 test runs, which included highway (HOV lane), toll road (smooth and traffic free), and surface streets (rough pavement and stoplights).
59.4 lbs vs 54.0 lbs.
yes, they couldn't be more different, the weight of the 19" was almost 10% lighter, and the difference in net energy usage was 2kWh over 42 miles.
now, the trip recording showed 290Wh/mi vs 320Wh/mi, call that 10% more for the knobbies.
this is an extreme difference in tire types but shows that even at this level, what are you gaining / losing ? Not too much.
It should be noted that the 18" knobbies have more sidewall and do provide a smoother ride quality, but it's subtle.
it boils down to how much do you want to spend?
Middle market Martian wheels are minimum $2500 plus sensors plus tires plus labor.
At the other end of the spectrum, TSportline are about $1000 cheaper but not lighter; you get what you pay for.
The math/science is true but for the daily driving application the value for money isn't that great. As you indicate.
Racing is another universe. Been there, done that.
Respect.
Been the PCA route from DE thru PCA Racing, Instructor, POC, etc. It was a great learning and life experience.
As Ferris Bueller once said, "if you have the means, I highly recommend it". What he didn't say: it requires both TIME and money. I never had a more time consuming hobby.
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I'm going off the tangent, but I have experience with Cross Climate 2 for more than 35,000km now so I think I have a reasonable data.
CC2 did not hit 10% efficiency for me. Both when I switched to, and from the original Conti. I recently switched back to Conti about 3 weeks ago, and I saw no noticeable increase in range, as per TeslaFi. That was a surprise, since I was expecting a big bump up. My driving pattern is relatively constant week to week.
I also have to drive almost 400km route every weekend. Just long enough to force me to get to a supercharger during the winter, but arrive back less than 15% during the summer. I think this is a good test to find out how my overall range is doing, especially with respect to battery degradation and tires.
I'll check again in about a month or so, but so far, at least for me, CC2 hit me with less than 3%, if that.
If I can gain another 5% by switching to 18", it's worth $$.
CC2 did not hit 10% efficiency for me. Both when I switched to, and from the original Conti. I recently switched back to Conti about 3 weeks ago, and I saw no noticeable increase in range, as per TeslaFi. That was a surprise, since I was expecting a big bump up. My driving pattern is relatively constant week to week.
I also have to drive almost 400km route every weekend. Just long enough to force me to get to a supercharger during the winter, but arrive back less than 15% during the summer. I think this is a good test to find out how my overall range is doing, especially with respect to battery degradation and tires.
I'll check again in about a month or so, but so far, at least for me, CC2 hit me with less than 3%, if that.
If I can gain another 5% by switching to 18", it's worth $$.
That's really good info to know. CC2s are the BEST all season (they are "all weather" tires, actually) tires we've ever driven. We have it on our family SUV. Prior to that, we had the Michelin Pilot AS4s. They were good, but the CC2 puts them to shame especially on snow. We had a chance to drive the CC2s on hard packed snow and we were super impressed. So with reports that CC2s dragged the efficiency down 10%, I would have been weary of putting them on the Tesla. The CC2's tread pattern compared to the AS4s would hint at that. But maybe for city driving it wouldn't make much of a difference.
you might want to arrange a 'borrow' from a buddy before you dive in.
assuming you have the tools, find a friend with an 18" M3 Aero wheelset and swap wheel/tires for a weekend.
as you discovered with the CC2 tires, most of internet efficiency calculations need better verification.
Is there a consensus best value forged 18 wheel (or wheels) ? V-FORGED VF10 are $550 at Discount Tire or perhaps Martian MW03. Granted Flow Forged may be sufficient for our driving. I was a little bummed the Gemini's are cast.
Do any of the after-market forged wheels offer aero options ? Even if it's with an insert ? We take the occasional long trip over mountain passes where we care about range.
Are the foam insulated tires worth it ? My 3 a few years back had a few issues with foam separation. Hopefully the newer ones are better. I appreciate low noise.
Do any of the after-market forged wheels offer aero options ? Even if it's with an insert ? We take the occasional long trip over mountain passes where we care about range.
Are the foam insulated tires worth it ? My 3 a few years back had a few issues with foam separation. Hopefully the newer ones are better. I appreciate low noise.
Only if your commute never has any potholes.... The strength of the wheels is not just for track use. Tracks don't have potholes. Forged wheels are for track use since they are LIGHT. But the strength of the wheels is best to combat against potholes... and in the case of EV's lighter = better mileage.
I believe the testing I documented earlier in this thread shows that while the calculations may indicate lighter can equal better range / mileage, in practice it's marginal at best.
The car weight and aerodynamics dictate the majority of the calculation; the rest is marginal gains.
And Tesla is selling cast wheels, which they've determined to provide a good balance of cost/weight/strength/range/safety etc.
It's always your money and your choice. Realize that the car mags and advertisers are trying to sell you on something.
The personal testing you documented is flawed as I stated previously. I don't know why you keep bringing it up. You have ALL TERRAIN TIRES (which have the rolling resistance of square blocks) on one set of wheels and road wheels on another. That alone destroys any credibility on your testing.
I guess it also depends on 3 other things: 1) your definition of marginal, 2) in practice, you have a much heavier foot which negates any gains, and 3) your comparisons from your own wheels are comparing going from 19" to 18"... the gains there will not be as large as going from 21" to 18". Did I mention the difference in tires???????
Here's yet another video where it compares going from 20" to 18". He goes from 335 Wh/mile to 263 Wh/mile. But I suppose a million different videos and other owner's own practical experience will not suade you.
I don't know why you think it 'flawed'
it's an excellent example of how little difference in energy use results, even from greatly different tire types, from tire diameters, wheel sizes and weights.
this is much ado about minutiae.
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