Wheel upgrades, need help

In NYC, I'm seeing tons of Gen 5 Prius' with bubbles & bent wheels. Wheels larger than 16inch on a Prius is a clever & unethical money grab from Toyota. #greed

 

Should probably work, but I'd be a little concerned about the width. I know some posters here have switched to a 7" or 7.5" wide wheel, but I don't know if anyone has switched to an 8" wheel. Hopefully someone with experience will chime in. Other than that it looks fine. Even the tire size is right between the two stock tire sizes(17" & 19").

Stock wheel:
19x6.5 (6.5" wide)
5x114.3 bolt pattern
60.1mm center hub
40mm offset
26.7" tire diameter (195/50-19)

TRD wheel:
19x8 (8" wide)
5x114.3 bolt pattern
60.1mm center hub
45mm offset
26.4" tire diameter (235/40-19)

Part number PT758-03200-02, BTW.
19" Wheel, Matte Black Alloy

 

Toyota isn't a tire manufacturer, its not really a greed move on their part. The only reason the wheels are bigger is consumer aesthetic taste.

 

Also having to deal with the problem of adding 60-80% more horsepower to the gen5 while also trying to keep the 195mm tire width for wind resistance reasons. They needed to increase the tread/road contact patch, and enlarging the tire circumference gave them that.

(Yes, I know the increased weight of the larger wheels/tires also negatively affects fuel efficiency, but we don't know the data on how a wider, shorter tire or a narrower, taller tire compare. A taller tire might actually be more efficient at moderate/high speeds, or it might have been a wash, and since looks are important for this generation in order to save the model with increased sales, so...)

 

The Prius isn't the only car to be experimenting with narrow but tall tyres for efficiency. The BMW i3 did earlier, to an even more extreme degree: 155/70R19.

BMW i3 Tires - Technical Details

The i3 wheels are both taller and narrower than the Prius, and on a smaller car:

i3 155/70R19: 700mm diameter, 155mm width = 4.5 aspect ratio

So that pushed the dimensions in both directions, and went to a totally custom size, limiting options far more than the Prius.

Compared to that the Prius's 195/50R19 is relatively restrained - you're still in the range of generally available other sizes:

Prius 195/50R19: 678mm diameter, 195mm width = 3.5 aspect ratio

They kept the same width and only pushed the height up, but you can justify it the same way.

It's a fairly universal comment from reviewers that the G5 Prius' handling performance is being held back by the tyres, so a wheel+tyre upgrade is the first thing to do. If the tyres had remained 195mm without the height increase, that would have been even more of an issue.

 

I'm new to this thread (only this page so far) and I'm with you in the post above up until this last line

unless you are referring to owners that would normally change wheel tire config anyway.
As an aside, since my tastes run more to the function as opposed to form/style, I was oddly amused the first time I saw a Corolla S in the showroom sporting low profile tires. Thinking to myself at the time (more than 5 years ago now) geez - now I'm thinking one step closer to TRD trim, like the newer Corolla trim.

@ArtVanDelay23 -industries - your handle give me a good chuckle - haha

@Hammersmith thanks for the TRD wheel link.
geez a grand for a set, must be nice for some bodies - haha

 

I'm no longer sure what they're thinking in the boardrooms (was it ever thus...), but I doubt terms/phrases like "simple", "practical", "cost effective, "fuel efficient", "readily available" see much use.

 

It's a clever move on their part; maintain reliability standards & low maintenance cost. Although make money from every bent wheel or tire bubble.

Someone at HQ will be receiving a hefty stock grant for every Prius bent wheel or tire bubble.

 

Not sure what you're saying.

I'm saying that the wheels+tyres are thought to be hindering the performance. If they were similarly sized to the previous generations, they'd be hindering it even more.

And I'm only attempting to justify the increased overall circumference, not taking the rim size all the way up to 19".

The clearest counter-argument I think would be "they shouldn't have increased the performance that much".

 

I've seen your posts on other "Gen5 Prius Tire/Wheel" discussions, and the one thing I keep asking myself is "at what point do we run into issues with the speedometer/other technical systems when changing wheel & tire sizes?" What's like, the range of different wheels & tire dimensions that can be swapped onto a Gen5 without worrying about any adjustments to the "brain" of the car?

I'm still waiting for my 2024 Limited to get through this Recall shit, but my plan is to just run out the stock wheels & tires and then change to something that's just a tad wider & "performance-y", without sacrificing a ton of mpg's. Not too well versed on all the specs, and I do want to maintain some aesthetics, but don't really understand the acceptable combinations of circumference/width/sidewall height/etc.

 

Seems the tire size is also more common in Japan.

You're forgetting the Prius is designed for Japan first. Prius sales were also dropping there before the gen5 arrived.

Toyota likely chose a tire for rolling resistance. A tire upgrade alone would probably work.

The gen4 had tires that were the same width, but smaller diameter. If the gen5 had the same size, the contact patch would be smaller than it has now, which means less surface for traction.

 

Yes they fit

 

As long as you stay within a few percentage points of the stock tire circumference or diameter, the car won't know the difference. A lot of us use http://www.tiresize.com/calculator to do the math for us(use the Tire Comparison tab). Good rule of thumb is to stay within 3% of stock.

I also use http://www.wheel-size.com/calc to see what tire widths work on different width wheels.

 

You're going to want to use a calculator tool - I like this one:

Rim & Tire Size Calculator. Custom Offsets - Wheel-Size.com

For the speedometer and other "brain" stuff, a commonly cited limit is not changing circumference/diameter by more than 3%. But you should aim for less than that. The standard 17" and 19" sizes are already 1.9% apart, giving you a spread to work in.

With the circumference as your target, you can then look to find acceptable rim diameter+width+aspect combos - you'll find quite a few reports from other users of sizes they've found. Acceptable rim widths depend on tyre width and aspect - the site above will indicate the permitted rim widths for a tyre - that's based on an official industry standard table.

What's left then is just clearance issues - the site gives guidance on that for whatever you select.

Unfortunately the Prius's size is too outlandish for the handy "plus size" visualiser chart to work - "Selected OE wheel/tire size is unfeasible" So you'll have to play with it manually.

I can't advise on wider tyre sizes myself - I've only researched sizes that would work on the standard narrow 6.5 rims.

 

Adding to say that I also agree with KMO that less is better when it comes to the % difference. I would do whatever possible to stay within 1%, but the odd stock tire size would cause me to accept up to 3% if there was anything out there even that close for a 19x6.5 wheel.

Or maybe a little more clearly: 3% is better than nothing if it's the only thing you can find. But if you can find something closer, that's very much more desired.

 

Yes. I ended up with 215/55R17 winter tyres, which are 1.5% smaller than the original 195/50R19, but they're still bigger than the standard 195/60R17, so I think that's fine. And there's very little choice.

Although it's not been established to what extent Toyota set up cars differently for factory 17" and 19" wheels. Most people believe that they don't bother trimming the speedo or other brain stuff differently for the 1.9% circumference difference, but there's no evidence either way. There was one suspension part number difference visible in the European parts database for the 17" and 19" fitted trims, but we don't know what the functional difference is. Could be related to differing sidewall width?

Edit: There is actually one place an ECU seems to know the tyre size - the default pressures listed in TPMS setup. That offers me the choice of 35/33 or 38/36, matching the manual's 19" values - presumably it would offer 36/35 for 17".