Wheel sizes - some comparisons

Runestone

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I have been agonizing over which wheel size to pick, so I decided to do some calculations (and yes, I have read the other threads on this). Looks are important, but drivability even more son (at least to me). I have been a little worried about the larger tires on less than perfect roads. Things are complicated by the fact that the larger wheel not only has a lower rim but also is wider (which is positive on dry road and negative in rain). So if we start by looking at the wheel sizes we have:

FrontRear
19'225/55275/45
20'245/45285/40
21'265/35305/30

You can use that to calculate the height of the rim in mm.

FrontRear
19'124124
20'110114
21'9392

You can further use that to calculate the volume of the tire. This can give an indication of how much ”unevenness” the tire can swallow. The volume is given in dm^3 (= liter).

FrontRear
19'19.323.5
20'18.022.0
21'15.417.4

It seems that going from 20 to 21 is a bigger step than going from 19 to 20 (especially concerning volume). It is also interesting to compare this to other cars. If you for example compare 20’ on a Taycan and 20’ on a Tesla S you find that the rim height is a little lower on the Tesla. I also checked the tires on my daughter's new Audi A5 (default wheels) and they are 18’ with 245/40, which gives a 98 mm rim height and only 14.3 liter volume. It lighter car, but not an extreme sports car.

So my conclusion is that the Taycan wheels not are as aggressively configured as the rim diameter might suggest. Which I think is a good thing. I feel that 20' will be a good choice for me.

PS
I think that these two videos are good practical tests of rim height and tire width differences:


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GlasgowTaycanCT

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I am impressed with the detail of your calculations! :clap:
That is something I would spend hours on too! ?

I always tend to spec the largest wheel size possible for my cars as aesthetics is important to me, and I tend to feel larger wheels look nicer. But I understand your concerns for ride comfort and handling.

I was going to spec Cross Turismo with 20" wheels. I think that is the sweet spot for aesthetics and handling for the Taycan... especially on our really poor British roads!

But .... I went for 21" !! ?
 

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With the three-chamber air suspension of the Taycan (which is a next generation Panamera suspension) you won't notice the difference on such a heavy car like the Taycan.
The only thing that'll change is the responsiveness of the steering, less rubber is better but for comfort it really doesn't make that much difference.
I'm almost always in Sport mode and have the 21" but it's still comfortable.
It's just an amazing suspension. :)
 

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That's also the wheel size I went with. The 20" wheel I believe offers the best compromise between handling performance and range. Also, my decision was based upon replacement cost and frequency--the 21" wheels will wear substantially faster, probably 12000 to 15000 miles at best versus 25000 to 30000 miles for the 20" and cost significantly less than the 21" wheels when you do have to replace them.
 

atebit

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I was actually wondering if anyone would be interested in my 20” Turbo Aero wheels that are coming on my car so I can get the standard 19”‘wheels. I don’t think it changes the aesthetics for the worse, and I’d prefer the better ride and resiliency of the smaller wheels as well as the lower cost tires.
 


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I have a set of 20'' Taycan turbo aero wheels and wondering if I could put the same tires sizes on the front and rear? Is it possible to downsize the rear tires to 245/45/20?

It's for winter usage so having narrower tires on the rear could help.
 
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Runestone

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I have a set of 20'' Taycan turbo aero wheels and wondering if I could put the same tires sizes on the front and rear? Is it possible to downsize the rear tires to 245/45/20?

It's for winter usage so having narrower tires on the rear could help.
It had the same thought, but the workshop that change my tires strongly advised against it. The also checked with Porsche that said the same thing. The car is design to have different sizes front and back.
 

Oyinko

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It had the same thought, but the workshop that change my tires strongly advised against it. The also checked with Porsche that said the same thing. The car is design to have different sizes front and back.
They will of course don't say otherwise :) Just wondering if it's technically possible because the rear rim is wider.
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