Lightweighting and aerodynamic optimization of a subcompact car.

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Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 23 2021 3:59pm

Hey all.

You might think it is weird to be talking about a gas car here. But actually there are no active forums for my car because it's a bit rare and has been produced under 4 different names. And i know a lot of you drive gas cars and we're all interested in lowering our footprint or just achieving efficiency or speed for the sake of it.

..and ecomodder is chuck full of ads and annoyances so screw 'em.

This thread is somewhat of a build thread and question/answer to inspire you to do the same, whether you car uses gas or electricity.

My story

I've been hypermiling since 2007.. and have achieved 10-30% boost in fuel economy on nearly everything i've driven, from SUVs to hybrids. I do not do extreme wayne geddes moves like shutting off the engine or do 50 in a 70.. i'm a daily driver hypermiler.. for my wallet and also the planet's health. It's a win win.

My car

Image

So i've got a Toyota IA from the late 2010's... Toyota's version of the Mazda 2.. The Mazda 2 weighs ~350lbs less in the Japanese/European version, yet has a nearly identical looking chassis and set of features.

Some of the weight difference is due to extensive use of high tensile steel in the original design. I think a lot of the weight difference came from Toyota's mistakes and cost cutting efforts.

You can immediately tell the car's engine is mismatched to it's weight. It lurches into first gear right off the lot. The 1.5L engine has a great torque curve but struggles to move the 2400lbs in low RPM.

I picked the car over a hybrid because i saw 50+mpg in hypermiling it and was incredibly impressed.. in sustained 65mph driving, i can see 58-70mpg highway, but average around 50mpg with a little city, mostly highway driving.

My all time record in this car averaging 45mph in city streets with no traffic and timing all the lights perfectly:
img (3).jpg
img (3).jpg (36.92 KiB) Viewed 662 times
Eye popping isn't it?!

The car has good aero overall, but no aerodynamic optimization in the underside. So it has tons of room for improvement to reach into 70mpg territory more regularly. It does coast extremely well... and i can make great use of pulse and glide type driving quite well already.

I went looking at the underside and engine bay of the car and found many brackets that were too long.. bolts that are generally 2-4x longer than needed.. about 20 studs hanging off the chassis with nothing bolted to them.. 1/4lbs steel plates used to hold wires when a zip tie would have worked. Some hooks in the center of the car which have no purpose.. probably a collective 50lbs of metal doing nothing to make the chassis more rigid and just creating unnecessary aero drag.

There's also a few lbs of unsprung weight that could be removed from the suspension in the form of brackets that nothing connects to.

The plan

I plan to cut a lot of these bolts.. repaint them.. build many brackets out of aluminum.. and add reinforcement to the suspension so it can take turns quicker, adding fun and more preservation of momentum to increase city fuel economy.
Mazda does this with their Miata to make it one of the most nimble track cars ever made.
This bastard child of a car deserves it just the same.

Very likely i'll be doing things like replacing heavy chassis parts such as bumpers with chromoly replicas... any weight at the ends of the car or up high will be subject to lightweighting so that the weight is more centralized for better cornering.

Reduction of mechanical friction is also high on the list.. exotic lubricants in everything that spins under power will be used. The gearbox itself will be using a teflon additive and the most expensive fluid money can buy, at the very least.

Underbody paneling will be made also.

Lightweight rims are absolutely on the table.. since there will be less weight on each corner to support.

I've been thinking of replacing the alternator with a large electric battery for years too. this seems to work well on some exteme Geo Metro mods..

End goal is 200lbs lost and 10mpg average gained.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Hillhater » Mar 23 2021 5:59pm

Nep,
Im sure you are aware that ar typical car speeds , <20mph, aero is FAR more important than any weight saving.
Things like those wing mirrors, wheel covers, front splitter, undertray, rear spoiler ,..etc would all be higher on my priority list than trimming weight.
..Or, just trade it for a PIP Prius !......which has all that and much more, already done. :wink:
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 23 2021 6:21pm

Aero gains you fuel economy on the highway.
Weight gains you efficiency in the city... improves acceleration times.. improves handling. And makes stopping quicker. And you also get better reliability since everything works less hard..

So why not both.. both are ideal in any vehicle :)
Ample room to improve upon that here.

I've driven all the hybrids on the market and hated how they handled, had sluggish power response, etc. They generally drive like crappy 90's econoboxes. The lack of a stick shift is a deal breaker too.
I even tried a Honda CRZ with a stick shift and found myself very disappointed.

No way i'd consider one when i am already returning hybrid like fuel economy numbers with 46.5mpg average over 30k miles. :mrgreen:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Hillhater » Mar 23 2021 6:50pm

So why not both.. both are ideal in any vehicle
Priorities.... where do you spend most time <20mph or above ?
I've driven all the hybrids on the market and hated how they handled, had sluggish power response, etc
Really ? Even the Volt ?... i dont think it can be called sluggish .. (0-60 in under 7 secs ? !

Ps 46.5 mpg.. i get better than that , 5.2ltr/100km.(47mpg) With normal driving in a 2 litre , Turbo mid size family wagon ( Blutec Diesel). No hypermiling techniques, 110 kmh hyway
Its computer logs the best at 3.0ltr/100km (80+mpg) over a 50 km hyway run.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 23 2021 8:02pm

Hillhater wrote:
Mar 23 2021 6:50pm
Priorities.... where do you spend most time <20mph or above ?
I do a mixture of city and highway driving and want better acceleration and better fuel economy. Why chose just one?
Hillhater wrote:
Mar 23 2021 6:50pm
Really ? Even the Volt ?... i dont think it can be called sluggish .. (0-60 in under 7 secs ? !
Especially the Volt.. worst handling hybrid i've ever driven, and tons of torque steer when pushed. I could have bought one for $5k less than my Yaris.. and was actually on the lot looking for a 2019 Honda Insight.. but couldn't stomach how it drove.
I briefly considered a 2019 Prius but it was a snoozer to drive.. both options cost around $7k more and drove way worse.
Hillhater wrote:
Mar 23 2021 6:50pm
Ps 46.5 mpg.. i get better than that , 5.2ltr/100km.(47mpg) With normal driving in a 2 litre , Turbo mid size family wagon ( Blutec Diesel). No hypermiling techniques, 110 kmh hyway
I'm not sure what standard you're on, but my 46.5mpg lifetime average converts to UK 55.8mpg and my highway average ( 55mpg ) converts to UK 66mpg. My all time 30 minute highway record would be 82mpg in UK gallons too, for comparison.


But the point of this thread doesn't have anything to do with your selection of car. It has everything to do with with improving the efficiency of the car you drive today. :wink:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Hillhater » Mar 24 2021 12:44am

The consumption standard i use is Litres per 100kms.....so.no confusion there.
Sure you could make a lot of improvements, but if the goal is to reduce fuel usage etc , then a switch to a more efficient base vehicle should be an option... but i get your angle. OK.
There are many other cars i could have bought, maybe even “wanted” to buy..if a Volt was available here it would be high on the list ).. but this Diesel Bluetec Wagon had them all liked on fuel economy..and the Turbo diesel is a Torque monster, which is part of the reason it is so economical.. 1500rpm @ 70mph ! ... and diesel is 20% cheaper than Petrol here .
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 24 2021 1:57pm

I get you. I'm not going for the world's best fuel economy over all considerations.

Here in the states, diesel is more expensive than gasoline and diesel vehicles come with a premium matching that of hybrid cars.
But few hybrids pay for their additional costs.. the prius, insight, and ioniq do make sense though.

I don't drive very much since i work from home and bike whenever possible. The car is also useful for long roadtrips, since 50-60mpg is easy to achieve on those. So a small gas car made sense for me when i purchased it, and into the future.

I have parts on the way, so there should be progress on my car fairly soon.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Mar 24 2021 4:23pm

Image

When they prep a car for GT racing, I think the average is 200 pounds they take off, but that's going to be your carpet, radio, AC, etc. Not sure there's much you can do there.

Aero at the speeds you mostly drive is negligible, right? Late 1960's Chrysler had their missile division aerodynamists tell them that the open grill was so bad for aero that they were losing races in NASCAR because of it. So they came up with the wedge nose for the Charger/Daytona and Roadrunner/Superbird and bang, instant advantage. Until it was banned.

For racing people go to the trouble of closing the entire gap between the edge of the tire and the fender. Rubber, perhaps silicone, it can start off dragging on the tire, etc. The same material can create a 1/2" airdam under the front, my Mustang used to drag so bad in and out of the driveway until I removed the solid airdam, didn't see the point of creating a malleable one but it might help.

But the main place the passenger car suffers in aero is the wheel well. I might also think of some barge board arrangement to get air out of the wheel well. Large effort, small gain though. Venting, at least, can help. Bruce McLaren made 'Whiskers' a staple on his cars, this was said to help mpg more than speed.

Enclosing the rear wheels altogether is good, but that's if you have enough tuck (inset) for the cover to be flush.

One good bet would be vortex generators. But you'll need persuading rather than just my say so, so I'll let this guy explain. Just to make sure you understand, flow attachment good, flow separation bad. Indycars used to use turbulator tape as used on aviation control surfaces to prevent separation and put air behind the car to reduce the vacuum/wake, but what was good for the car in front was bad for the car behind it trying to pass in the higher air pressure, so in the name of racing and not parading they took them off.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by spinningmagnets » Mar 24 2021 4:24pm

This website covered every possible improvement, and its a good primer on adding aero to a car...

https://aerocivic.com/

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Mar 24 2021 8:20pm

that one right after mine was perfect. It's got the nose cone us like they had in NASCAR and the deadly long tail from the then made deadly long tail Porsche 917. But the vortex generators from the video makes that unnecessary. When they took the long tail off and it got much faster, Brian Redman famously remarked "That's it--now it's a racing car!"
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by markz » Mar 24 2021 10:32pm

Shaving grams can get expensive, just like in the bicycle industry.

How much you willing to spend for optimal fuel mileage?

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Chalo » Mar 25 2021 1:27am

neptronix wrote:
Mar 23 2021 3:59pm
i'm a daily driver hypermiler.. for my wallet and also the planet's health. It's a win win.
Win-win is no car. Just sayin'.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by The fingers » Mar 25 2021 10:12am

Tip: For sustained 65mph driving or doing 50 in a 70, :mrgreen: simply relocate the horn to the rear of the car 🚗 to honk at tailgaters. Saves having to give ‘em the California Salute. :wink:
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 25 2021 12:56pm

markz wrote:
Mar 24 2021 10:32pm
How much you willing to spend for optimal fuel mileage?
$3000, but i doubt i'll spend that.

spinningmagnets, i swear i've seen that site before but it was a good refresher, thanks for the link.

dauntless, that video was a good lead and i'd like to buy that guy's book.


Immediately i was thinking of a wheel cover. He convinced me that a partial wheel cover would be better.

Image

The wheels on the original Honda Insight seem to be the most optimal design even today.

There's lots of full wheel covers designed for 15 inch wheels.

Image

Adding one of these and having a 1/2 inch gap for air intake and exit would get my stock wheels rather close to the Insight's wheel design. My rims have a slight outwards curve, so a completely flat disc wouldn't work well.

Shame that the Insight wheels can't be used here. They were designed for a car that weighs about 600lbs less than mine and are 14's instead of 16's. My car uses bicycle like wheels, ie narrow and tall. Rims of an appropriate size are nearly impossible to come by. So i'll have to make my own aero wheels, for sure.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by JackFlorey » Mar 25 2021 1:02pm

neptronix wrote:
Mar 23 2021 8:02pm
I briefly considered a 2019 Prius but it was a snoozer to drive.. both options cost around $7k more and drove way worse.
I have a 2019 Prius Prime and I find it definitely not a snoozer in EV mode. My average MPG is . . unknown, but it's more than the 199.9MPG the gauge can display. I fill up about once a year and I drive about 10K a year, so it's probably around 1000mpg. My next gas station visit will probably be this summer.

The problem I am facing now is that Toyota recommends not letting gas sit in the tank for more than six months, so I may have to start driving less efficiently.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 25 2021 1:56pm

JackFlorey wrote:
Mar 25 2021 1:02pm
neptronix wrote:
Mar 23 2021 8:02pm
I briefly considered a 2019 Prius but it was a snoozer to drive.. both options cost around $7k more and drove way worse.
I have a 2019 Prius Prime and I find it definitely not a snoozer in EV mode. My average MPG is . . unknown, but it's more than the 199.9MPG the gauge can display. I fill up about once a year and I drive about 10K a year, so it's probably around 1000mpg. My next gas station visit will probably be this summer.
I looked up some 0-60 runs in pure EV mode and saw 11-12 second 0-60's pretty consistently. You have a very different idea of what's snoozy compared to me. But that's fine. Car tastes are subjective.

This thread isn't really for comparing cars though, it's about ways to improve what you have.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by marty » Mar 25 2021 2:43pm

If you fill car with helium balloons. Would car weigh less? Less weight > better gas mileage.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Mar 25 2021 3:12pm

Image

Simon McBeath is considered the standard, I have his book, but I suspect I went into it as a lifelong racing fan and way ahead on aerodynamics and maybe this other guy brings it to life better for the less knowledgable.

https://www.amazon.com/Competition-Car- ... 1787111024

Image
marty wrote:
Mar 25 2021 2:43pm
If you fill car with helium balloons. Would car weigh less? Less weight > better gas mileage.
Car no, boat YES.

The reason it would work for a boat is because you want to lift as much of the hull out of the water and reduce the sheer resistance created by moving the water out of the way.

The reason it would not work on a car is because you're only lightening the car in relation to going upward. Going forward the full weight of the car is still pushing back on you.

Image
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Hillhater » Mar 25 2021 5:06pm

The reason it would not work on a car is because you're only lightening the car in relation to going upward. Going forward the full weight of the car is still pushing back on you
Yes, exactly,..... it is the difference between “weight”. (Due to gravity),.. and Mass ( due to Density )
Toyota recommends not letting gas sit in the tank for more than six months,
Jack, you probably know that is mainly due to condensation in a partly full tank ..leading to corrosion ,.. ( plus some minor evaporation of volatiles).. but these can be dealt with using additives......or just ignored !
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 29 2021 2:53pm

So far i have approximately 100lbs removed from the car.
I attacked the weight that's up high first since that would give me a handling benefit immediately. Completely pulled apart the trunk and top of the engine bay.

The haul thus far:
bagofparts1.jpg
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bagofparts2.jpg
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A lot of the bolts of excessive length were unbolted, hit with an angle grinder, and then hand filed so that the initial threads were smooth. The hood bolts were really thick and 2x longer than they needed to be. The motor mount bolts were insanely long and cut to half the pictured size.
bolts1.jpg
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bolts2.jpg
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There was a 2lbs weight in front of the transmission and i have no idea why. It was removed thinking that i'd rather feel any vibrations in the suspension/transmission that it eliminated.
weights1.jpg
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Here's some pictures of brackets that were replaced with high temperature rated zip ties, since there was always a wire nearby hooked to a bracket which could support the original wire.

There are lots of grounding cables that are excessively long ( we're talking about an extra few feet of wire ) which will eventually get cut and re-terminated to both reduce their weight and increase their electrical efficiency in one shot.
ziptie1.jpg
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ziptie3.jpg
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There are a couple brackets left which will be replaced with aluminum equivalents once the front bumper is torn off to see what weight could shed from the front of the car.. a more juicy place to find weight losses and help create a better weight distribution.


Overall i'm happy with the better handling and acceleration. The car notably rolls uphill in neutral for longer and doesn't gain as much speed downhill. There's less front end dive when hitting the brakes too. I'm seriously impressed with the difference 100lbs makes and can't wait to get at that other 100.

There's been no compromise to structural integrity or interior comfort.. other than the hole created by removing the backseat adding some noise. But the car is chock full of noise padding so with one backseat missing, i'm not really suffering! do plan to replace the backseat with a lightweight panel which latches to the car body using some tiny neodymium magnets.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 29 2021 5:12pm

I'm giddy. I found out that the Mazda 2 had a conservative little spoiler in Japan.
rXU6bk4o.jpg
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Just ordered one off ebay. It looks like the type that would function as an aerodynamic aid, knowing mazda and the shape. Worth doing some tests on. :)

The most recent generation of Honda Insight has a spoiler with a VERY similar shape:
2021-03-29 16_13_29-Window.jpg
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Mazda is also selling a hybrid version of the mazda 2 soon, and it seems to have the same chassis.
There may be things like underbody panels and such i could order and install. Pretty exciting.
Dropping in a hybrid drivetrain would be even more exciting.
Mazda also made an electric 2 for a while. So.. there's like.. an electric motor hiding out there for my car.
technology_env_ev_en_3rd-row_img.ts.1602150248480130.jpg
technology_env_ev_en_3rd-row_img.ts.1602150248480130.jpg (69.89 KiB) Viewed 472 times
...actually, this is turning out to be a good platform. :shock:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 30 2021 12:58pm

Apparently nobody makes rims that fit this car... 16 x 5.5"'s are a super odd size..
..so an aerodynamic rim is totally out of the question.

..however, looking at the Japanese market again, i see that i could import some steel wheels used on the original Mazda Demio/2... which would allow me to use moon discs or some other aerodynamic hubcap design, such as the ones on the Nissan Leaf:
2021-03-30 11_43_32-Window.jpg
2021-03-30 11_43_32-Window.jpg (21.55 KiB) Viewed 438 times
..awaiting a weight differential from a seller before making a decision.

If the weight difference is more than 1lb then forget it.. i'll make my current rims more aero one way or another..
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Mar 30 2021 5:21pm

neptronix wrote:
Mar 30 2021 12:58pm
Apparently nobody makes rims that fit this car... 16 x 5.5"'s are a super odd size..
..so an aerodynamic rim is totally out of the question.
I assume that measurement is the diameter and width. (If so,it's not unusual.) If a car takes a 16" you might have your tires saying something like, oh, let's just go with P185/60/R16. That is a measurement of the width of the tread face (Just over 7"), height of the sidewall in millimeters, 25.4 per inch so a little over 2", and the wheels size in inches. Keep in mind the width doesn't have to exactly match for the wheel and the tread.

Now, might you be saying that your 5.5 is a hubcap size? My understanding is that ALL wheels of a size take the same hubcap. I would think you just want a flat cap with no openings, that should be the best aerodynamics. https://www.amazon.com/Grand-General-10 ... B00FS66TLA

What seems uncommon to me is that 4x100 bolt pattern on a 16" wheel. But I'm seeing those are out there. There are a lot of old rims available to you, and that has been one of my favorite little games over the years, finding neat unique rims for a car. My Mustang just HAD to have Bullitts, I mean did you ever see Steve McQueen in 'Bullitt?' I picked up two sets from older Mustangs that all fit, but mine is just a V6 and they only come on the V8 packages. So people are so confused, 'You can do that?'

But I have interchanged Ford and Mazda 4x100 before, seemed fine at the time.

If you want to go with a 15" wheel, the P185/60/R15 tire will have some speedometer error, though not big. If you put a P185/70/R15 you get most of it back.

How much like the Mazda 2 IS your Yaris?

Yaris iA Bolt Pattern (Lug Pattern) PCD 4x100 See Adapters
Stock wheel offset 35 to 45 mm Wheel Spacers
Center bore (hub bore) 54.1 mm Use Hub Centric Rings
Thread size (Lug Nut Size) M12 x 1.5 Lug Nuts
Stock Rim Sizes Range 14x5.0 – 18x7.5 Hubcaps

Mazda2 Bolt Pattern (Lug Pattern) PCD 4x100 See Adapters
Stock wheel offset 38 to 45 mm Wheel Spacers
Custom Offset Range 19 to 42 mm
Center bore (hub bore) 54.1 mm Use Hub Centric Rings
Thread size (Lug Nut Size) M12 x 1.5 Lug Nuts
Stock Rim Sizes Range 15x6.0 – 17x7.0

Dang, I'd say there's an excellent chance of interchangeability here. The only Mazda wheel I've ever known to be a different bolt pattern is the RX7, but I suggest checking whatever car the wheel comes off individually. The picture is from a set of 4 available for $60 not far from me, if you're in a less crowded area there might be a little more looking. Mazda's, 5.5" wide according to the ad. found another ad where the guy is claiming his MINI Cooper 4x100 wheels will fit "Civic Yaris Fit Accent Rio."

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Mar 30 2021 6:15pm

P185/60R16 is right on the money. It's such an odd size that until now, only one tire manufacturer made it.
I would guess that the car is about 90% Mazda2 ( 2014+ )

Closest thing is a P185/65/R15 which would have a 0.8% smaller diameter. The 2006ish prius uses this size, so there's a decent amount of fuel economy oriented tires in that size. However, the question is can i make up for the tiny penalty..

P175/65/R15 would have a much smaller diameter.. and P175/70/R15 doesn't really exist.

I'd actually prefer a taller tire.. but tires get wider as they get taller.

Perhaps i should wait and see what happens with the next gen Mazda 2 ( ~2022 ) and see what the wheel choices are.
In the meantime i could add some aids to make my current rims more aerodynamic and see some improvement that way.
My tires have a lot of meat left on them, so i'd like to use them up.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Mar 30 2021 9:50pm

Of course I had the right tire, I looked it up. I do this for people regularly. It's fun.

Are you looking for a narrower tread for less rolling resistance?

175/70/R15 https://www.tirerack.com/tires/tires.js ... um=77HR5SC The 185 and 195 do offer choices in 70-75, most of which are N spec for Porsche, etc., meaning $150-300 each. WalMart does have some under $100 195/70/15. And yes, the diameter jumps more than the width as you step up from say a 185 to a 195. Not sure I've understood why.

Oh, what's this? Why it's a calculator to compare tire sizes. Now THAT is fun, when you're considering all this.

https://www.tacomaworld.com/tirecalc?ti ... -195-70r15
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