Colorado Guy AF Ret.

Some people like me do not like the 20's on the A-Spec. Looking "cool" is not cool when you hit a hole in the road or bump a curb...it's costly. The ride is not as good, and those Goodyear Eagle RS-A's are crap.
Damaging those 20's can be expensive to replace.

This is what I'm doing with my RDX A-Spec. Putting on the TLX, Black Diamond Cut wheels, 19"...yes they fit fine....and mounting 255/50/19" Michelins of my choice. Yes, the tire diameter is exactly the same, 29.2"
So, all is well with the drive/monitoring systems. The TPMS sensors that come with the new TLX wheels are the same part # that are on the 20" wheels.

I'll have the same contact patch...255....gain a little aspect ratio...50 over the 45's....and, I sold my 20's back to the dealer for a "4 figure amount." And, I get 25% off of Accessories I buy. That makes the wheels
costing me $1395....then subtract the $$ for my 20's. Just about pays for the wheels. I would have replaced the tires anyway...no big deal there.

So, now I'll have a better ride...better tires...and not worry so much about the lower profile tires on those super expensive wheels...that I don't like, also 'cause they are totally dark. The TLX wheel has some polished spokes,
and the outer facing rim is polished to give some contrast....the rest of the wheel is black. Center cap has the chrome "A" on a black disc. It will look great.. To me and many other's I'm sure.

Each to their own...some like/love all black wheels. Takes away lots of the "cool looks" of the new RDX to have a totally "black hole area" with black wheels with black tires in a black fender well. Bring some "life" back to
the side view. IMHO....of course.

Just a thought and suggestion. Would you get the same "deal" at your dealership? Perhaps not...then sell those 20's on your own. Probably get even more. They'll fit Gen 2 RDX's
and...the tire diam. is the same as the 235/60/18's that come on the Gen 2's!! So, somebody will want these new "hot" 20's.

horseshoez

iTrader: (2)

Not only will you end up with improved impact compliance and a better ride, you will also end up with better acceleration, braking, and handling. Good call on dropping from the 20" wheels to the 19" wheels.

catbert430

My dealer had a decent deal ($1,400) on the Glint Black Diamond Cut 19" wheel and I was interested for my TLX until I found out that the TPMS sensors were for 2018-9 and wouldn't work on my 2016. I wanted to keep the 18s for snow.

Then I was distracted by the new shiny object (2019 RDX).

I think they will look great on your white A-Spec; better than the charcoal gray OEMs. The dealer will have zero trouble selling those to a Base, Tech, or Advance buyer.

Post Pix!

Dizzyg12

jcardona1

Don't the TLX wheels have a different offset than the 20" ASpec wheel?

Colorado Guy AF Ret.

Nope. The reason is Acura and most all company's make it simple for themselves, since the same brake, suspension set up is the same or similar so they can fit the 19's of some models and 20's also.
One thing I did find out is that IF someone wanted an MDX 20"....won't work. The center mount hub is different diam. and the bolt pattern is also different.

Colorado Guy AF Ret.

What work?? I pick out the wheel I want, I order the tires in, which I would have changed anyway....THEY mount and balance and when I pick it up, it's sitting there with my choice of wheels and tires ready to drive off.
Where's the work??? None...Shark grey, whatever....it's DARK...and yes, each to their own. I've read where many like me don't like darker wheels. Ya like what you like.
And the tiny chrome A is not enough to put any kind of contrast or "lightening up" those dark holes. This isn't my first rodeo. I like what I like and know how to make it happen. No work...just sign the check.

Colorado Guy AF Ret.

TPMS sensors are easy to change. They are mounted to the back side of the valve stem. Yes, you have to pay the $$ for them, but, it's no big deal to swap out to match your needs of your car's system.
I would have done that with the '19 RDX...if the sensors that come on the TLX wheels were not the same part #. But, luckily they are, and saved a few bucks there.

jajji

Is this pretty much universally known?

If so, it's made me reconsider the aspec.

horseshoez

iTrader: (2)

Yup, if you look into the physics of larger wheels you'll learn how much of a performance hit they can make on cars. For a little light reading, look up things like "Rotational energy", "Rotational Mass", and "Angular Kinetic energy".

Long story short, beyond the sweet spot in the 16" to 17" wheel size range, pushing the bulk of the weight of a wheel (i.e. the rim) further out from the axis of rotation increases rotational mass, said another way, if say a 17" wheel and a 19" wheel are of the same weight, the 17" wheel will take less energy to start, turn, and stop. The greater the rotational mass, the more energy it takes to spin them up, turn them, and stop them. To play with the concept, pick up the wheel of a small child's bicycle (which is typically fairly heavy) by the axles and spin it, try changing the axis of rotation, and then stop it from spinning. Now pick up a light weight bicycle wheel from an adult's racing bike and perform the same experiment. The wheel from the child's bike, even though it is as heavy, and probably heavier, will be easier to start, stop, and move around while spinning.

Wander

Well, since you brought up the bicycle wheel analogy, this has been debated and debunked and debated again ad nauseam, and when it has been studied in the lab and wind-tunnel it turns out that differences in rotational mass are usually insignificant compared to the translational mass of the entire bicycle/rider system. This is why heavier, more aerodynamic rims are usually preferred for all-around sport riding and competition. The perception of the rider is a whole different story, and flyweight rims "feel" fast, even when they test slow.

Back to cars, the mass of the rim is still tiny compared to the mass of the car. And lest we forget, the tires weigh something as well. This isn't to say there isn't a flywheel/gyroscope effect; of course there is. But at real-world velocities it's probably not very noticeable.

A narrow, lightweight wheel/tire combo may feel "nimble" but test poorly compared to a wider, heavier wheel/tire that has more grip and less tendency for the tire sidewall to "fold under". If you could manage to find an old British "open air" sports car ( with maybe 13" or 14" wheels and 70 or 80 series tires? ), you would probably be floored by how agile and fun it felt. But don't challenge a wide-tired 'Vette at the skid pad ( lateral acceleration ) or you would leave with your exhaust tucked between your wheels.

All of which is to say, I don't think the difference between 19 and 20 inch RDX wheels will be noticeable ( or maybe even measurable ) in terms of acceleration or braking. As for handling, that may have more to do with the width of the A-Spec wheel and rubber. And the wider wheel/tire probably hurts aerodynamics ( fuel economy ).

But the potential for wheel damage certainly increases as the tire wrapped around it morphs into a rubber band. And without modern multi-stage shock absorbers, it would take true grit to drive on real-world streets with some of these setups. Tire compliance is an important contributor to comfort, but engineers have other tools to tame the beast.

Just $0.02 ( slightly overspent )

TacoBello

horseshoez

iTrader: (2)

The concepts of rotational mass are what they are and the size of the vehicle doesn't change the laws of physics relative to said rotational mass. There have been numerous studies performed in controlled track conditions which prove without qualification that the sweet spot for wheel size is in the 16" to 17" range. Folks can choose to disbelieve this, personally I don't care.

Dizzyg12

horseshoez

iTrader: (2)

Sorry, gotta call you on that post; nothing with RS-A tires will handle well, regardless of speed. The RS-As are without a doubt one of the crappiest "performance" tires on the market.

reddogTL

In response to the Op:

I partially agree with you. I do like darker colored wheels however whereas I know you don't but thats just a personal preference. Where I agree is the 20" wheels with only 40mm of meat on them to protect the RIM. I wouldn't even think about running that low here in NJ. Potholes were absolutely abysmal this year. If I were to go the A-Spec route for the RDX(I'm waiting for now since pricing is at MSRP) then I'd bake a swap into the negotiation to get the Advance 19" wheels or one of the accessory wheels instead of the 20".

HotRodW

A common misconception. The aspect ratio is not the height of the sidewall. It's the ratio of sidewall to the tread width. A 255/45/20 indicates that the sidewall height is equivalent to 45% of the 255mm width, or 114.75mm. That's a full 4.5" of sidewall to protect the rim, which is still more than many passenger car tires. Switching to 255/50/20's increases the sidewall height to 5".

Dizzyg12

horseshoez

iTrader: (2)

What point are you trying to make regarding the 235 section width of a NASCAR tire? Certainly nothing to do with comparing wheels of different sizes.

TacoBello

Dizzyg12

Madd Dog

cruiserchuck

Not if they have to take the 19" off an unsold Tech. However, if a prior buyer has upgraded to the Diamond cut wheels, and the dealer still has the 19" in stock, then I suspect they might. It probably depends on how good a negotiator you are.

Wander

300hp accelerates a mass, rotationally or translationally, far more effectively than my 0.3hp bicycle motor. Context does matter.

Back to the realm of cars, if we were talking about a Lotus Esprit or an F1 car I would be more inclined to believe that lightweight wheels would make a noticeable difference. On a two ton SUV, not so much.

Is this to say that I think the trend toward ludicrously large wheels is rational? Not at all. But who ever said people are rational?

FWIW I usually run 17" or 18" wheels for winter on my two ton SUVs. But not for performance benefits.

nuke

19RDX

"Yes, the tire diameter is exactly the same, 29.2""

Acceleration would not change due to having the same diameter and handling would be theoretically worse due to more sidewall, but otherwise I agree.

horseshoez

iTrader: (2)

Incorrect, the tire diameter being the the same is irrelevant. The issue here is the location of the bulk of the mass of the rim; it is the rotational mass which is significantly higher for a 20" wheel (even if the weights are the same which, all else being equal, is unlikely) which will negatively impact the acceleration and braking of the vehicle compared to the same vehicle running on 19" wheels. Please don't take my word for it though, research Angular Kinetic Energy from whichever source you choose, and come to your own conclusion.

Dizzyg12

Wander

Tires also have mass. And the actual "rim" weight is probably pretty constant, within a given wheel width. ( The rim is that portion of the wheel to which the tire mounts ). What changes is the amount of aluminum between the rim and the center of rotation. And that will change the angular momentum of the wheel, and thus the amount of energy required to accelerate it. The question I am debating is whether this difference is likely to be noticeable within the context of a crossover such as RDX, with such a minor change as 19 inch to 20 inch wheels. ( Although, we shouldn't neglect the increased tire and wheel width of the A-spec ).

If you want an example where this effect is certainly noticeable, jack up an old Bronco or Jeep CJ and put some big meaty off-road tires on it. The thing will roll over anything, but it won't accelerate for $hit.

Dizzyg12

HotRodW

^ Yes, largely splitting hairs. I've done more than my share of hair-splitting, so far be it from me to criticize. But the difference between 19's and 20's will be more attributable to tire model than wheel diameter. In this particular case, the OP is doing what I would do, which is using a wider 19" tire. (I'd use a wider wheel with a more aggressive fitment, however.) All else equal (same wheel design and same tire model in the same width), I'd wager that very few people could distinguish between a 255/45/20 and a 255/50/19 from behind the wheel. That said, the standard RDX's 19" tire is 20mm narrower than the A-Specs, and a completely different tire design. Distinguishing between them would be possible for sure, although I contend your average driver would never feel a difference in daily driving.

horseshoez

iTrader: (2)

The point is, the higher energy demands of the larger wheels (and in this specific case a wider/heavier tire) will not improve performance. Granted, the reduction in performance may be relatively minor, but it will be a reduction no matter how you slice it.

HotRodW

But it's not a wider tire in this example. If you check manufacturer specs, you'll find that it's not unusual for a 255/45/20 tire to weigh the same or less than the same model in a 255/50/19 size. (Makes sense - the width is the same, but there's less side wall.) If you go smaller in diameter and narrower on the tire, as you would going from the A-Spec wheel to the Advance or Tech wheel, then you're obviously going to see a more noticeable weight difference. But you're also decreasing the tire's contact patch, and consequently, reducing grip.

But again, we're splitting hairs. People should buy what they want as long as they understand there are minor tradeoffs. Having said that, anybody looking to maximize fuel efficiency should definitely choose a model with the 235/19's.

reddogTL

Shiver me timbers. This entire time I've been looking at tire/rim sizes wrong. Thank you for that explanation. Completely changes my thinking now when selecting vehicle/tire/rim packages.

hondu

Yes, since the overall diameter will be the same on the A-spec wheels and Advance/Tech/Base wheel, the main difference is the overall mass/weight of the wheel.

Looking at the tire models and similar wheels on Tirerack, I estimate the A-spec wheel package weighs about 6 LB/wheel more than the others, or about 10% difference in MOI.

The tires on the A-spec are wider and supposedly stickier (sportier tire class), so while they should be slightly slower off the line (in equivalent grip situations), I think they will still corner better through the twisties (less flex/better grip) even though they weigh more.

But as some have mentioned, I would go drive the different trims and buy the one you like best.

horseshoez

iTrader: (2)

The flaw in this thought is the Goodyear Eagle RS-A tires which come on the A-Spec are some of the absolutely crappiest "high performance" tires made by any manufacturer over the last ten or so years; regardless of manufacturer.