ziggy1

I see a number of threads discussing the pros and cons of 18 vs 19 inch wheels on the RX, but I have a slightly different and admittedly naive question - in general, what is the supposed advantage of going to bigger wheels? All the manufacturers seem to be doing it, and it isn't clear to me why. I suspect it's more than just appearance, but what is it? Is it because with bigger wheels you can have lower profile tires and therefore increased grip? Is it because the larger wheels will require slighlty less rotations to go a given distance and therefore better tire wear? What is the reason?

Also, dealers offer the option of filling the tires with nitrogen which supposedly is better for them. How does the nitrogen protect the tires? Tires lose air with time, so what happens when you add air to nitrogen filled tires (I don't know of any stations with nitrogen, nor do I have a nitrogen tank at my house).

Joeb427

iTrader: (1)

19"
Pros
Nicer look
Better handling with the lower profile.
Cons
Rougher ride with the less sidewall height.
Tires more expensive in most cases.

Me,I prefer the 18" for the softer ride.

Nitrogen is said to hold air pressure longer.That's about the only advantage.
When you need air,you are pretty much screwed unless you pay a fee to a place that sells nitrogen.You can always buy a 12 gal airtank and fill with nitrogen to top off.
Not worth the hassle or cost,IMO.

Johnny

The outside diameter of the tire is virtually the same with either tire, so rotations are also the same. Only the rim diameter increases when going from 18" to 19". Therefore the profile, or thickness if you will, is reduced contributing to a marginally firmer ride (hardly noticeable), but improved handling when cornering or making sudden maneuvers, because the tires grip the pavement better. Whether they look better or not is subjective, as aesthetics or style is a matter of personal taste. I don't know why they would cost more, because you're in fact buying less rubber in most cases, but it may be due to manufacturing volumes.

Nitrogen is available with some installers, most notably Costco comes to mind, but they limit it to new installs and subsequent top-ups. Google nitrogen filled tires - there's tons of info on the benefits of using it (less leakage, corrosion and so forth).

MEP7557

My dealership automatically puts the nitrogen in the tires when they get the cars. They offer free top offs. I have noticed you don't get a pressure change between cold and hot weather.
I think the 19's are pure aesthetic, that's why I got them. They improve handling also but, I don't try to get the RX up on two wheels either.

Cruiter

Mep is right about the aesthetics angle. And also for profit. The tires are a wear out and replace commodity and sets of them matching the specs of the Auto manufacturer are generally provided in hopes you'll go back to the same tire for replacement. Our cars being a higher end car than say a standard Honda or Nissan w/o alloys will have a more performance specked tire with the knowledge that we will also be willing to cough up more bucks for replacement. I doubt you'll ever see another new Lexus where tires average $100 a piece. I miss being able to do that on my Gen 1 RX .

RE: Nitrogen, Consumer Reports recently did an article on that and could not find enough evidence to warrant the extra cost. They did say there may be some gain but it was too negligible to be worth extra money. It's a fad that started in NASCAR where they do use that and was picked up by a few enterprising dealers. I don't know of a single manufacture that recommends using nitrogen.

voerman

Another disadvantages of the lower profile tire associated with the larger wheels is that wheel is more likely to be damaged if you hit a pot hole. Also the lower profile tires are wider and do not do as well in the snow as the narrower higher profile tires do. I tend to avoid the larger wheels for both of these reasons.

Lou

euroja153

I think the larger wheels are purely for looks, I dont believe a RX with 19s would handle better than one with 18s. Living in Montreal (worlds worst roads) I actually prefer having the extra cushion with the 18s.

tfischer

I just saw a little piece on the telly about nitrogen: the difference between nitrogen and regular old free air is that there is no moisture in nitrogen and the molecules are larger. As a result, there is less rust and other degradation inside the tire, and leaks are fewer, as the exit route has to be larger. Whether these are advantages that offset the cost and inconvenience is a determination that is solely up to you, although you would have to be an idiot to think so.

krypttic

iTrader: (1)

Nitrogen (N2) is actually smaller than oxygen (O2), so the argument that the N2 escapes (diffuses) more slowly is inaccurate.

I have read about small improvements in pressure consistency at different temperatures and less degradation inside the tire (since oxygen is more reactive than nitrogen is) but, as a previous poster stated, I doubt anyone would notice the difference in a car (as opposed to aircraft and racing vehicles, which this was developed for originally).

Keep in mind that normal air (what you normally fill tires with) is already 78% nitrogen anyway. Only 22% is that "nasty" oxygen. Now, keep in mind that when you fill a tire with N2 at room pressure, there is still going to be some O2 in there (unless you fill and flush a number of times). Add this to the fact that you have to fill N2 at a special filing station (Costco is close, but the air compressor in my garage is closer) and the cost/convenience of nitrogen tires doesn't seem worth it.

Just my 2 cents

Joeb427

iTrader: (1)

Speaking of Costco and other places that fill with nitrogen with tire purchase....
Wouldn't the liquid lube used to mount the tire on the rim cause moisture in the nitrogen defeating it's so called advantages?

ziggy1

thanks for all the responses. My take on this is that larger wheels are popular because of looks and superior handling with downsides of a stiffer ride and increased risk of wheel damage.
Regarding N, virtually useless so forget it.