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Question regarding low profile 21" rims

beatle

Active Member
Aug 31, 2019
1,025
493
Springfield, VA
Exactly. The best choice of tires & wheels is a direct ruction of :
  • the environment you're driving in (snow, rain, potholes, etc.)
  • you style of driving: aggressive, casual, hyper-miler
  • budget
IMHO the 21" Arachnids are great for sunny SoCal... but your 19" Arachnid TS Sportlines are better for all-weather Colorado.

Low profile 21" tires & wheels will ALWAYS outperform 19" tires & wheels. Look at ANY high performance sports car or road course race cars... they're ALL low profile tires & wheels. Think Formula 1 where budgets are non-existent and performance is KING.

But Tesla Model S is NOT a sports car... but 21" staggered Arachnids with super stick Michelin Pilot Super Sport tires definitely make it handle better... and hook up better in stop light races too.

I agreed with the first part of your post, but the second part is not always true. It is always risky using superlatives (see what I did there? :)) All other things being equal, a smaller wheel+tire combo will weigh less than a larger one, and that's a good thing. Sidewall height is only one part to the handling equation.

I think it's fair to say the S with the plus or raven suspension is at least "sporty", though I also wouldn't classify it as a "sports car." I think it does benefit from tires with more grip, however, but some people would prioritize range and tire noise above that.

Also, F1 used 13" wheels up until 2021... Revolutionary wheels: Why F1 going 18-inch will change everything · RaceFans
 
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BrokerDon

Active Member
Aug 23, 2014
1,399
1,289
Newport Coast, CA
I agreed with the first part of your post, but the second part is not always true. It is always risky using superlatives (see what I did there? :)) All other things being equal, a smaller wheel+tire combo will weigh less than a larger one, and that's a good thing. Sidewall height is only one part to the handling equation.

Smaller wheel+tire combo allows the tread to squirm / deflect more than a larger wheel+tire combo because the smaller wheel+tire creates a taller sidewall which deflects more when cornering (especially) and accelerating (less so). That's why most sports cars have low profile tires on larger rims than smaller wheel+tire combos. They handle better. If it wasn't true, you'd see all the sports cars at a road course track running smaller wheel+tire combos... which obviously you don't.


Yes F1 did USE 13" wheels until 2021... but as the article stated F1's primary reason for running 13" wheels with "taller" tires was so the tire manufacturers could have LARGER brand names stamped on the sidewalls. The reason F1 went with an 18" rim instead of a 20" or larger rim wasn't handling... it was the tire manufacturers demanded 18" rims were the smallest they could go and still get readable advertising on the sidewalls. The article further stated moving to 18" wheels could drop 3 seconds PER LAP vs. 13" wheels. That's HUGE.

The one place where smaller wheel+tire combo that weigh less than a larger one being a good thing is in drag racing where spinning up the wheel+tire rapidly is critical. However drag racing is in a perfectly straight line... not cornering or braking like everyday driving and road racing.

YMMV

Closed course... Professional driver. :D
 

beatle

Active Member
Aug 31, 2019
1,025
493
Springfield, VA
Not every track prepped car runs the largest wheels possible. (Slightly) larger wheels on a Miata, for example, are desirable because you can run larger brakes. Many track prepped Miatas run 15" wheels with brakes that barely clear the spokes, even though there are plenty of larger wheel options available.

Acceleration is important in all kinds of racing, not just drag racing, and a smaller, lighter combo will help that. Unsprung weight reduction also improves ride quality and allows the suspension to do its job better over bumps as it has less inertia to damp. If the combo is too heavy/stiff, or the bumps are too severe, the tire will lose contact with the pavement and traction will be reduced or even lost. Depending on the circumstances, this shortcoming can be of less consequence on a perfectly smooth racetrack, but it's very desirable on a street-only car like the S.
 
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BrokerDon

Active Member
Aug 23, 2014
1,399
1,289
Newport Coast, CA
Not every track prepped car runs the largest wheels possible. (Slightly) larger wheels on a Miata, for example, are desirable because you can run larger brakes. Many track prepped Miatas run 15" wheels with brakes that barely clear the spokes, even though there are plenty of larger wheel options available.

Interesting... but track prepped Spec Miata's weigh less than HALF what our P85D's weigh... so clearly you can run significantly smaller tires & wheels (Spec Miata 2,275 to 2,4025 lbs. vs, 4,962 lbs for P85D). Spec Miata - Wikipedia Physics matter.

Acceleration is important in all kinds of racing, not just drag racing, and a smaller, lighter combo will help that. Unsprung weight reduction also improves ride quality and allows the suspension to do its job better over bumps as it has less inertia to damp. If the combo is too heavy/stiff, or the bumps are too severe, the tire will lose contact with the pavement and traction will be reduced or even lost. Depending on the circumstances, this shortcoming can be of less consequence on a perfectly smooth racetrack, but it's very desirable on a street-only car like the S.

Exactly why forged Arachnids are the best Tesla made wheel for handling since they're significantly lighter than cast Turbines... and even most (if not all) Tesla's 19" wheels. The staggered Turbine rear wheels also provide more traction for Performance Teslas like our P85D's which have more powerful and heavier rear motors.

If smaller wheels & taller sidewalls handled better, you'd see them on all the street legal cars running the Nürburgring... including Tesla's Plaid prototype. Clearly Tesla didn't run wider lower profile tires on the Plaid to make it SLOWER around the Nürburgring.
 

beatle

Active Member
Aug 31, 2019
1,025
493
Springfield, VA
Well you can't go by weight. An F1 car only weighs like 1600 pounds.

A lot of modern cars have large brakes and need large wheels to fit over them. The Porsche 918 has enormous brakes that barely clear the 20 inch wheel. The diameter of the Porsche's 265/35/20 front tire is within half an inch of the 245/40 I have on my car. Porsche clearly could have put larger wheels on that car, but they did not. See how the brakes barely clear the wheel barrel here:

http://sportscarbible.com/_images/p...spyder-lg/porsche-918-spyder-ldsc03142scb.jpg

Also, if bigger is always better, why didn't Tesla stuff 22" wheels under the S? Some people on this forum run them with rubber band tires. Manufacturers and enthusiasts often use what's aesthetically pleasing, and bigger wheels (almost) always look better. However, I'd probably stick to hard parking and not hard driving if I had 22" wheels, forged or not.

It is clear you enjoy having 21" wheels, as do a lot of people, but they are not the end-all-be-all-no-downside choice.
 

BrokerDon

Active Member
Aug 23, 2014
1,399
1,289
Newport Coast, CA
It is clear you enjoy having 21" wheels, as do a lot of people, but they are not the end-all-be-all-no-downside choice.

EXACTLY. I never said Arachnids were "the end-all-be-all-no-downside choice". In fact I said I run a set of 19" Cyclones on road trips where there's snow and potholes... both virtually non-existent in sunny dry SoCal where most of my P85D miles happen.

Many Model S owners including me are definitely enjoying our 21" Arachnids for their looks... and better traction, handling and acceleration from their lighter weight and stronger forged construction.

Other people, especially in areas where there's snow and potholes... 19" wheels & tires are probably a better choice.

This debate is no longer productive. Life is short.

Moving on...
 
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