Aftermarket 20" 9.5J / 10.5J tire advice

[samhatoum]

I'm considering getting the Forgestar F14's for my Plaid MX in this color combo (my MX also has been wrapped with XPel Stealth)

As much as I like the look of the 22" wheels however, I don't like the discomfort and vibrations so I'm looking at the 20" versions. After a query to Forgestar, it seems the options are: 9J, 9.5J, 10.5J. The stock Cyberstreams I currently have on there are a 9J / 10J configuration, so I would have to go for a 9J/10.5J or a 9.5J/10.5J combo.

Now the stock 9J / 10J configuration uses 265/45/20 and 275/45/20 tires. How do I adjust for the extra .5" width? My semi-mathematical brain is looking at the problem like this:

265mm = 10.4331" (9J front)
275mm = 10.8268" (10J rear)

Going up 1" in rim width means going up 0.3937" in tire width which is basically 10mm. So going up 1/2" means sizing up by 5mm.

So question # 1: does this mean the "correct" tire sizes for 9J/10.5J would be 265/45/20 and 280/45/20, and for the 9.5J/10.5J it would be 270/45/20 and 280/45/20?

And question #2: Any thoughts on 9J vs 9.5J on the front? I assume 9.5J would give more traction but also less range due to friction.

 

[Richbot]

If it were me I'd stick with the OEM sizes in whatever tire you choose - reason being, it probably helps efficiency to have a bit of "stretch" on (This is how the Model Y is set up, 255/45-19 on a 19x9.5" wheel)

I don't think the wider wheel under the same tire will make range worse - the opposite in fact, all things being equal, because a lot of the energy lost to "rolling resistance" manifests in the form of heat due to internal friction due to sidewall flex. Wider rim under the same tire = less sidewall flex. Less flex = less battery energy dissipating in your tire sidewalls

Plaid and Long Range Model S use the same setup for the 19's - 255 on a 9.5 in front, 285 on a 10.5 in the rear. The Long Range gets really impressive efficiency, so, they've figured something out there. A 255 on a 9.5 is a "stretched" tire in that it's at the upper end of the rim width range for the tire. This all makes engineering sense when you sit and think about it for a minute. And it also makes sense that they didn't have the option to change the widths and tire sizes for X's because they didn't do any body mods to fit a bigger package - it's the same exact sizes as the old model, with slightly different widths/offsets depending on spec

And, 270 and 280 width is not a thing. It'd be 275 and 285 front and rear, if you went up a size.

Also, read all of the fitment guides on here.

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Then go to tirerack.com and look for tires you might want

 

[samhatoum]

Hey thanks for this. So if I go for the 22x9.5, 22x10.5 I can just put the stock tires on both. It would actually make my upgrade easier since I can take the tires off my Cyberstream rims.

Do you happen to know if I can also swap the TPMS the old wheels to the new ones easily enough?

 

[ngng]

A 22" wheel is going to ride sig worse for both ride quality and efficiency. The TPMS is held in with a nut, I forget what size. Easy to swap. I try to avoid a staggered setup if possible so I can rotate my wheels. Especially when our cars have uncorrectable rear toe.

 

[samhatoum]

Oops, my bad I meant to say 20x9.5, 20x10.5 - I really don't like the 22" ride quality.

The Plaid already has a staggered setup stock, it comes as 9J and 10J

 

[ngng]

Oops, my bad I meant to say 20x9.5, 20x10.5 - I really don't like the 22" ride quality.

The Plaid already has a staggered setup stock, it comes as 9J and 10J

Yes, all of the X are staggered from the factory. I'm just suggesting if you're buying the wheels already consider buying ones you can rotate.