Cambered Tires Can Improve Fuel Economy 317
thecarchik writes with an excerpt from Green Car Reports: "We already know that it's possible to curb your fuel consumption just by having your tires properly inflated, or better yet, installing a set of low rolling-resistance tires, however, soon there may be an additional avenue to look at when picking the most fuel efficient rubber for your ride. The answer is the camber of your tires, more specifically, the negative camber. This is when the tops of your car's tires are angled inwards towards the chassis. Of course, there are negative effects too — namely increased tire wear and impaired ride quality — which is why production cars almost always have zero camber." The linked article, as well as the New York Times article from which it draws, describe a new tire which is designed to minimize those negative effects.
BMWs, Minis (Score:3, Interesting)
Apparently, BMWs and Minis (and probably other sport-ish cars) are negative cambered because it helps with handling. I found this out replacing the tires on my mini... the ones that I burned through in 1.5 years because I drive it like a sport-ish car ;)
Re:How? (Score:2, Interesting)
I suspect this is pure stupidity along the lines of the contact area, hence friction would be lower.
Of course just using a narrower tire does the same thing, but since everyone wants to see
nice wide tires under their cars....
On a poorly designed suspension setup you could get more grip in corners thana narrower tire
like this, but that is in effect a design fault.
And ihave a strong doubt there is anything they can do to mitigate the wear problems except
make tires with thicker tread on one side, which is double stupid - wear will still be higher. I
suspect the additional costs would be higher for the tires than any saving.
The fact is, if you care, just run narrower and harder tires.. Thus giving lower friction and
more economy, duh!
So many other links (Score:2, Interesting)
Why do you people keep pushing one that requires registration?? Here, Watch some Leno [autoblog.com]
Re:"Negative Effects" (Score:4, Interesting)
That's exactly what it is - the outer edge of the tyre has a lot less loading than the inner edge. Not only does this make the ride unpleasant but it drastically reduces grip and makes the car handle like a greasy weasel. If you want to know how to get the best out of your suspension, look at how tarmac rally cars are set up. That's going to be about the closest in "performance" suspension to what will be suitable for a daily driver. You'll find it has little camber, very soft springs with a lot of travel, and very stiff damping. On the road, this would give you a soft, comfortable ride with excellent grip on uneven road surfaces. Having really hard suspension means you have no grip at all, on anything but a perfectly glass-smooth racing track.
Re:"Negative Effects" (Score:1, Interesting)
Erm, an angled tyre tread makes the contact patch larger for a given width of wheel. Any changes to rolling resistance are nothing whatsoever to do with the cambering design of this tyre. (I second the statement that this is a poorly written marketing piece rather than a genuinely insightful documentary piece..)
This design is all about performance, and alleviating the wear problems of driving a car with heavy camber under normal straight-line circumstances. Or at least, to some extent. The assertion that "almost all production cars have zero camber" is also nonsense. Almost all cars made in the last 15-20 years have at least 0.5 degrees of negative camber. My 1995 VW has -1.2 degrees..
Re:"Negative Effects" (Score:2, Interesting)
This is exactly what is happening - reduced contact surface with the road reduces friction. As others have noted, this results in longer stopping distances and less ability to control the vehicle. Camber is heavily utilized in NASCAR stock car racing. Since most NASCAR races are run on ovals, adjusting camber allows the cars to have more surface area of the tire in contact with the track surface in turns at the cost of contact in the straights. I'd suggest watching more than a few NASCAR races and reading The Physics of NASCAR to anyone with an interest in engineering and automobiles. Great place to learn about this stuff, and you learn why you don't want to do stuff like this on your road car.
Re:"Negative Effects" (Score:3, Interesting)
I agree. I had higher-pressure tires that came with my Civic Hybrid. This past year, they finally were to the point of needing replacement. Having moved to Minnesota (from Colorado) in the meantime, I went with regular tires for the somewhat better traction. My mileage has dropped maybe 1 MPG as a result and traction seems noticeably better in rough weather. (It's a bit of apples and oranges to compare, of course.)
On the other hand, in Colorado I seldom had any traction problems with the high-pressure tires. But we hardly had any snow on the ground, ever, so that's not so surprising. If you live in a low-snow state, I would happily recommend that type of tire.
Re:BMWs, Minis (Score:3, Interesting)
Agreed, I have $110.00 Eagle GT II's on my pontiac fiero and I am certain I can eat his big heavy saloon BMW hard in the corners (and the straights with it's 528hp V8 I swapped in and added a turbo to bring me to 5lbs per HP makes it nearly twice as fast than his 9lbs per HP..) When I do track days I will swap to MT's simply for the grip, but they have a problem that 90% of drivers never understand. they grip hard until they cant anymore, then they let go completely. It's like you fell off a cliff. Granted my racing suspension that does not allow any body roll really exacerbates this. I actually prefer the warning I get from low cost tires like the Eagle GT-II tires.
Tires and wheels only help if the car is set up for performance cornering. $800.00 each MT's on a stock civic will not help it corner in any way.
There are few production cars set up for performance. Even the Corvette z06 is a utter dog in the corners compared to a car that is set up properly. I typically have corvette owners pissed that I destroy their track ET's and they cant figure out why I have zero body roll in the corners. It's the difference between a wrench turning racer and a checkbook racer.
If you want a fast cornering car, set up the car first, then get tires AND wheels. most stock wheels are garbage and flex way too much, and are too heavy. losing even 3 pounds per rim makes a huge difference.