nooo RIP the aero Insight 😭

I've actually just started planning a video about this, specifically looking at the tires effect as the latest models from the tire manufactures show huge savings due very small changes in the sidewall profile or smoothness. Maybe we ought to have a chat sometime

So, I tried it out. 80% front wheel covers only, plus 50% upper and lower grille blocks, and fog light tape over. My usual to work trip, 26kms highway/4kms city… I used 22kms of fuel instead of my usual 28-30kms depending on amount of stop lights. This is in a 2015 Mazda cx-5. Thank-you!

30%, I would have never thought that. Every day is a school day. Great info as usual Julian.

So many don't realise the impact of larger wheels and tires. So many choices are aesthetics driven, especially in this age of every econo-hatchback being lifted into a pseudo-SUV. Even with the same section width and diameter, as mentioned, lower profile often has a more squared shoulder shape, but more importantly the bigger wheel would exponentially pump more air with the same spoke design. When C+D did their wheel size comparison on a 2010 Golf, many blamed the increased moment of inertia for the worsened performance, but I think much of it came down to the aero for the ~10% worse total consumption. As even on an efficient vehicle with energy recovery like the new Prius Prime, going from 17" to 19" rims loses 10-15% on rated range (battery only or total). Looking back, I'm sure a big part of the higher rated fuel consumption on the "bigger engine" option of a vehicle is actually due to them default coming with and therefore being certified with larger wheel and tire packages (and other body aero tweaks). E.g. you bought the 4cyl based on advertised consumption which was rated on 16" wheels, but you ordered it with the "performance package" incl 19" wheels/tires, so you get close to the same consumption as the V6 model that came with that bodywork and wheel/tire package as standard.

Just found your youtube channel. I remember the name and dug out my very old copy of 21st Century Performance to confirm. Good to see you're still at it. Still remember your R32 GTR with centre diff potentiometers.

I remember once you made a video about a porsche patent that redirected hot air from the cooling system to the front of the wheel. that improved both cooling but also decreased drag. I just cant find the video but i do remember you talking about that.

I’ve always thought the bmw i3 had very skinny tires. Now it makes sense! Great video!

Wow super underrated channel. This was great stuff man.

I finally bought your book! Both this and the history of aerodynamic work on car designs. I've been watching your videos for some time, studying to apply relevant principles to electric motorcycle streamlining for range increase. It has been very tricky to apply lessons, as a lot of the constraints, proportions, and circumstances are different, but I definitely want to say I appreciate what you do, and that videos like this are very good exposure for people to what factors use up power in their cars.

As I thought, the factory wheels that Honda fitted to their cars, thinking of your Insight, and my 4WS Accord. Good to know, and thanks. Excellent video, mate.

Hi Julian ! I learned tonnes of technical info and aerodynamics from your articles in AUTOSPEED mag some years back. Thank you Sir for that education🎉🎉❤

Amazing as always, legend!

I just found your channel and am looking forward to going through it! This is important content: no frills just good explanation and interesting topics.

So what your telling me is gm salad shooter wheels not only look good but are the best aerodynamically

Im lucky with my car, that I still have steel rims. With that I was able to mount Mooncaps. This alone helped reduced drag and also reduced Fuel usage (only by 0,1-0,2L/100km, but its something!). Same I am going to try with narrow tires, since I need new tires anyway. Just bought two of your books and very love the detailed Information in there! Hats off and Thank you!

I have all you books and absolutely love them. I have enacted a lot of little bits on my own dirt speedway race car with great results. How about a focus video on what us dirt racers can do to reduce lift from air getting under the roof of the car (no windows)?

Amazing!

Yiss! Been looking for this

It's crazy how basically no company addresses this but Tesla with their drag reducing covers Thank you so much Julian I'm so glad there's someone out there who is honest and actually knows what they are talking about.

Good show. Would love to hear in a future video by how much these contraptions were measured to reduce the drag on the cars you've modified

intersting insights! i am especcialy curious about how the mclaren at 6:13 seems to have stationary covers in the front, i wonder how much the not spinning of the covers affects drag.

Huge!

I put some fender skirts on my car. Now I'm contemplating putting a moon disc cover on the rim behind the fender skirts.

Who knew pizza dishes had such a cyberpunk vibe.

Definitely getting moon discs on my next car, even if they were to inadvertently increase drag - the cool factor would more than make up for it! Also love cars with enclosed rear wheel fairings - that should come back. Love the air suspension that lowers with speed as well.

@JulianEdgar at 4:48 in the video you discuss a technical paper on the design of the Tesla Model S wheels which I also have on my Tesla Model X. The problem with them that has been discussed since the wheels were released is that if they are designed to be extremely aerodynamic they forgot to reverse the pattern for one side of the car because on the passenger side the flat edge of the blades faces forward which should be creating far more drag on that side than the drivers side. Wouldn't you agree? I will test with tufts of yarn on both sides to see the difference.

Julian, as a fellow Aussie I would like you to contact Carbon Revolutions. They make Carbon fibre wheels but none are aerodynamic and therefore few people with EV's would consider their wheels (and many stock wheels on EV's are either ugly or not very aero). If they made aero carbon wheels I believe they would sell like hotcakes.

Would you consider having a digital version of the book? I agree the turbo wheel covers look cool, I made myself some on a 3d printer. Doubt that they help with aero much, since I made them stand out by about 30mm, maybe someday I'll try to make real aero ones.

Just purchased your book on Amazon, should arrive on Saturday. What % of vehicles would you anticipate full smooth wheel covers would not being beneficial? I have a quite slippery vehicle, the ioniq 6-and the base model wheels are much more efficient than the spoked 20” wheels on my trim level. Thanks for the video!

I'd love to build an aero CR-Z

Would be active ventilation for the brakes a solution to better cover the wheels? With temperature controlled fans blowing a the brakes, it also would have the advantage, that cooling can continue at stop or low speed driving, while self ventilated brake disc only cool at higher rotation speed.

Excellent video, I am particular interested in the subject trying to produce stability and reduced drag with aero modifications to an underpowered car. Your nismo custom wheels look like the turbo fan wheels of eras past. Do turbo fan wheels provide similar benefits?

Very interesting. I am curious if you tested a smooth wheel cover that covers the edge of the wheel inward but leaves the center open vs the design with pizza dish covers that cover the center of the wheel outward but leaves the outer edge of the wheel open? Is there a difference in cooling or drag with different designs? I am also interested in the inflatable front air dam as used by Porsche a few years ago and how it would benefit reducing tire drag but also increasing total frontal area when inflated. I assume it would help keep the air flow smooth around the front and into the sides of the vehicle more than any added frontal area increase for a net benefit. Great channel and I look forward to getting your book.

I'd like to know what you think of the "Solar powered" aptera, that thing was designed to be aero and efficient!

Ive often wondered if fitting wheels spacers noticeably increases drag by plasing your spinning turbine blades (wheels) more in the path of the air?

To reduce drag, remove the nismo package 👍

Recently retired and building a camper to go on the back of my truck. I'm trying to find information about aero and sharp/curved edges with an eye to rounding all edges to allow for better aero. From another of your videos, you mentioned rear spoilers with sharp edges for clean seperation, but I cant seem to find info on how rounded frontal/side edges should be. Any suggestions on publicly available info? thank you.

What's your take on wheel spat attached to the bodywork rather than covers on the rear wheels? I have a theory that turbofan style covers on the front wheels only to actively evacuate air from the front paired with bodywork mounted rear spats and an undertray would generate overall improved performance.

Does the exhaust outlet have a lot of influence on aerodynamics? Does its position influence the gas output? Old nascars use the barrel at 45 degrees, modern ones are straighter in relation to the body.

For an enthusiast, would there be a setup possible with a spinning wheel and measuring wind speed in certain positions ? Would such a setup be viable/useful to come to some conclusions and see what design of wheel causes least drag ? Or can it only be measured on the car itself ?

Sr i have a question i found your books on amazon usa but id like to get them signed for my collection, is there away we can get that done??

What about removable covers that cover the entire rear wheel wells? Slightly less convenient to change the wheel but would retain the body shape throughout the rear quarter.

Julian, how would attaching stiff rubber seals down the side of a car by the pitch welds (similar to PSNI Riot Land Rovers) affect drag?

Very good lecture, also the one about longitudinal centerline air pressure. You have an interesting collection of books available, i will consider some. Regarding this lecture, when you say 30% of aerodynamic drag is a consequence of wheels and tires, do you really mean a third of the *aerodynamic* drag? That is, as opposed to the second major source of drag at high speed, that of rolling resistance (on a flat surface). Second, did the pizza tins on the rear wheels of your Nismo actually make a difference? Id have thought not, since they're close enough to the rear of the vehicle to be aft of the laminar separation anyway... I ask because i often see semi tractors with such covers on the drive (rear) tandems, which seems like a waste of money. Thanks for the lectures!

could you make a video on how to deal with old car shapes with sharp windshield leading edges causing unattached flow and lift on the roof?

Hello, Which paper did you reference about the Tesla Model S wheel dsign aerodynamics? best regards

I have read that if the bottom of a vehicle was smooth, increasing ground clearance helps lower drag. But if the surface is uneven, then lowering the vehicle is better? It seems counter-intuitive to me that difference a small difference in the frontal area of tires, in proportion to the rest of the vehicle, would make any meaningful difference?

My old pre-facelift benz w124 had aero style flat hubcap and some say it helping cooling the brakes, but my question is can this cooling effect and hubcap fin design ruined aerodynamic?

If rear wheel covers don’t do much to help keep flow attached to the body behind the wheel, why did you put them on your Nismo? There’s not much body after the rear wheels on it.

Hello sir , i have a hatchback car and planning to install a batman spoiler will it be good ? As i drive at very high speed around 130km/h ?

How does one attach the “tufts” to a vehicle? What are they made of?

8:16 I'd like to know how you did this one in greater detail, because I am doing everything that I can to increase the range of my Toyota. Factory says Highway is supposed to be 29mpg, but I am currently getting 52mpg with the modifications that I have made, and am aiming for 65mpg Highway (or better) by the end of 2025. I hope to bring the City Mileage from 19mpg to 30mpg as well.

Any role of Thread pattern of the wheel .

Have you seen those panels on large 18 wheeler trucks? They put them behind the wheels to push the wheel wake outboard. When you do that to a wheel, the wheels turbulence turns into a coherent vortex, which has less drag, and makes the wake easier to manage, keeps it from getting under the body, which increases downforce, as there's less turbulent mixing from the tire wake with the fast moving flow under the body of the trailer. This also works in cars, you can achieve this two ways, by outwashing airflow behind the tire, or adding static toe out to your alignment. Of course the former is preferable because using toe out makes a car harder to drive and affects tire wear and rolling resistance.

How does a fat lip effect the aero of a wheel?

All I'm hearing is "Turbofan rims work", so... Maybe I should get some

Has anyone actually done the opposite, and to deliberately send airflow into the wheelwell, and thus cool the brakes? I've had a mild idea that the wheel itself could be designed to work like a fan, with blades, to suck cool air into and over the brakes.

I read "The Aerodynamics Development of the Tesla Model S - Part 2: Wheel Design Optimization" paper and got a few points from it: 1. Reducing the rotational moment is part of overall efficiency and contrary to a fully covered wheel 2. A covered wheel increases pressure inside the wheel, which adds a lot of lift 3. A more exposed wheel can energize air flow, which can reduce the functioning of diffusers (like in kzfaq.info/get/bejne/ns2IocyQsbvLp5c.html ), but might be desirable (e.g. at the front of the car?) Is this right? Makes it seem like a covered front and open back is better on a car without a good diffusers (Speedtail), since it gives rear downforce; but otherwise front and back each have good reasons to be covered or not...

Thought you might get a kick out of the moving front wheel spats on my RX7. It's primarily aesthetic, but also intended to reduce drag. kzfaq.info/get/bejne/eJN9npiFqLyUhoU.html kzfaq.info/get/bejne/p8iDd6yI3JPeqIU.html Anyway, was just going through some of your videos thinking about making some type of front air dam to help increase pressure for the bottom feed radiator, and considering the trade off for increased drag. I intend to do a flat bottom and rear diffuser next, would hate to disrupt the under car flow too much. Better buy your book before that 😁

So sad about the Insight.

Would be nice to see car where whells give +30% drag. Actually, it is unbelevable. I expected to see prove.

😂 People are rediscovering hubcaps. Hilarious.

Yea but aero wheels are just way too ugly😢