The effect of wearing those 20' tires is multiple:


pro:

1) Much better braking..
2) Much more stable in curves..

cons:

3) Slight increase in gas consumption..
4) On rough roads, you really need to hold wheel tighter than customary.




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I like it

thks!

Looks good. For some reason it looks smaller than 22s to me.

Holy... Those are freaking huge! I like them! I didn't think we could fit anything that big on the rx400h...

While wearing higher-perfomance rubber can improve braking, all other things being equal, (like wheel weight) it is common knowledge that reducing unsprung mass, specifically from rotating parts, will not only improve acceleration, but it can greatly improve handling and braking too.

On the other hand, increasing wheel weight by even a few pounds will degrade acceleration and braking performance. Assuming your rubber on the larger wheels is sticker, braking may feel like it is better, but your rotors and calipers are now undersized and must work harder to stop all that extra rotating mass.

This is why you will see that vehicles having larger wheels as an option also have larger brakes.

Yes, I have to admit up to the last minute I thought they wouldn't fit... But they do even if the available space is millimetric...

Do you think, I should have larger brakes mounted ?

I'm awfully sorry, I just went to my garage, to check the tires size and you were right, they are 20s not 22s. I think the quid pro quo came from the fact the dealer told me I could mount up to 22s on those wheels (but they would not fit on the rx).
Congratulations on your eagle eye though.
Sorry again.

It is unlikely that a dealership would do this for you, but certainly, if you wanted to retain the original design's braking ability, that's what you would do. I have no doubt that acceleration will suffer with the hevier wheels and there's not much you can do about that. I would consider going to larger wheels ONLY if the combined weight of the new tires and wheels was equal to or less than the OEM weight. Even then, if we're talking about a Lexus, I'd still be a bit wary, due to the fact that the smooth ride would suffer because of the lower profile/stiffer sidewall tires.

Well, first of all, thank you.
I think weight must be pretty comparable since those wheels are aluminium wearing 20' tires while the heavier iron OEM I used were wearing 18'...
Also, I was fearing loss of acceleration but I can assure you, there was no change there.
Yes,the ride is a bit rougher but not much.

Hope this helps! rgds.

The OEM 18" wheels are aluminum not steel and since you are replacing rubber with metal by going from 18" to 20" the unspung mass would have to increase in your case. Physics dictates that a larger wheel will have exponentially higher inertia, but as long are you don't notice it, then I say just enjoy the look and feel of your new ride and don't worry about the physics.

The best way to improve handling on the 400h would be to add stiffer anti-sway bars... which are STILL not available .

As Skyfish stated, the OEM wheels are aluminum (Lexus doesn't have steel wheels on any of its vehicles.), so most likely, there is quite a large increase in unsprung weight in those 20-inch wheels.

Regarding handling, here are some springs that'll lower and stiffen the ride:

http://www.tirerack.com/suspension/Susptab...=&brand=all

.....but honestly, if you want a sedan-like-handling SUV, Porsche is the answer, although along with that handling comes horrible reliability and sky-high prices!

thks, even my wife did not notice any difference in the driving so I'm okay... ;-))

those are 20s or 22s? I have 20s on my car, love the better handling and better traction. what tires do u have on there? what have you noticed as far as a decrease in gas mileage?

Hi NeoN

They are 20s not 22s as initially erroneously thought and the tires are Nokian 275/40 R20 106 Y XL, much better traction and braking power but you got to pay attention when accelerating if road is rough the car will try to move on least resistance path and you need to hold wheel tight, don't you?
As far as gas mileage, I am not sure especially because I also changed the exhaust pipe as you can see on the picture and that double exhaustion might affect consumption as well.. But overall, imho, yes it probably makes a 15 %-20% difference on highways and 10-15% in town.

Best!

If anyone knows of a 4 OEM wheels buyer in Europe, please let me know...

Wow, that looks great! I love the dual-exhaust.