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Cambered Tires Can Improve Fuel Economy
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.
If you ask me it IMPROVES ride quality. Some of us don't like driving a car that feels like an overstuffed sofa on wheels.
"Where quality is like a dead stinking rat - you just can't miss it."
How does this help fuel economy? More to the point, how is this story anything but an advertisement for some guy's new tire?
You do not have a moral or legal right to do absolutely anything you want.
Good for them. Have the government set up a rebate to have many, many people switch tires if it really does increase fuel economy without other negative effects.
If we ever do switch over to fully electric cars we can go back to the current tires.
The best part of this is that it's re-thinking the wheel!
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 ;)
-- Who is the bigger fool? The fool or the fool who follows him? --
TFA is light on details, and I fail to see how anything other than zero camber can be optimal for straight-line travel. I can see how it could reduce rolling resistance during cornering (in the same way it improves grip), but if you're looking to improve braking as the article claims, I'd be looking at caster (angling the wheel forward like the front wheel of a "chopped" motorbike) before camber.
camber wont help anything if the tires have the same contact patch. negative camber + regular tires = smaller contact patch so you get better fuel economy as less tire actually touches the ground.
Gee, less contact patch equals less friction and rolling resistance - and less traction with more treadwear on a narrower part of the tire if you get stupid about it. The car may also feel darty in a straight line but caster can also cause this. Auto manufacturers set alignments for more than just ride comfort and I'm pretty sure zero is NOT how many are set. Sheesh!
I know, lets put bicycle tires on cars and bump pressure to 120PSI. Bet it will get great MPG! Never mind the side effects...
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I don't really understand TFA. Could someone post a car analogy for me?
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This stuff has been messed with before, and we've stayed where we are for several reasons...
...also, the lower your rolling resistance, -it used to be- the lower your traction was--although supposedly they've fixed that some too.
Also, has anyone considered how spookily this will change steering response?
(I wonder why it seems like we're willing to exchange fuel economy for safety and aesthetics lately to such a degree. Huh.)
The summary and the article it was taken from are misleading and poorly written. They only use the term 'fuel efficiency' to describe one possible effect of mucking around with your tires in general, probably by increasing their pressure or using harder tires. However, the CamberTire appears to have nothing to do with tire rigidity - and hence fuel economy - whatsoever. What the article appears to describe is a tire which is optimized by shape for negative camber, in order to improve handling of the vehicle, without the faster tire wear that putting negative camber on regular symmetrical tires produces.
WIth negative camber, the tire will be able to withstand more lateral force since it is angled out at the bottom, 'into' the turns. Thus it will be able to corner harder without losing grip.
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It has to be a computer analogy. This is kinda like when you are uploading files, but need them to go faster. You do that by leaning the computer back so the bits flow out of the back of it faster. Same deal here.
XML is like violence. If it doesn't solve the problem, use more.
...when inflated with nitrogen.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Less rubber on the road, less friction, more fuel economy. How is this news?
I'm sure excessive camber can affect fuel economy to some degree as it increases the grip each tire has and that does create some rolling resistance.
But a much greater impact would come from excessive toe-in/toe-out. (The tires are always slightly turned in toward themselves or away from themselves). Too much toe and each tire is essentially trying to drag the car in opposite directions and this creates much more resistance than camber. It wears your tires out very quickly, too.
It's called dynamic camber. A car with 0 static camber at rest will gain some camber as it's suspension compresses because it pivots more or less around an axis. Those of us that do competitive driving will generally dial in static negative camber so that in a hard turn, the tire doing the work is near zero camber, and therefore has it's largest possible contact patch. Of course we drive around skating on the edge of our tires in a straight line, but that's OK, it just wears out the tires. Under acceleration weight shifts to the back of the car, compressing the rear, and getting you to zero while you need it (Assuming that you have a rear drive vehicle). Similarly, when you brake, weight shifts to the front of the car, bringing the camber on the front tires, and setting them us to work best when they are stopping the car. The fronts always do the majority of braking because of weight transfer.
So anyway, this guy as come up with a way to get a tire that is skinning when you need it (straight line friction reduction), and wide when you need it for cornering, acceleration and braking. It's conical rather than cylindrical. It's hard to say if the tire actually holds together for long straight trips, but I think the idea is sound and rather clever. I'm interested to see how the car would feel in transition. Grip would always start rather light and build as weight transfer brought more of the tire to bear.
Wouldn't they do the same thing. Decrease friction = better gas mileage?
But who cares I love my unpractical 35" Pro Comp Xtremes and my 16 mpg truck which I drive 100km to and from work 6 days per week.
by TheSpoom (715771) Uncaring Linux user here. I have nothing to add to this but please continue. *munches popcorn*
Just what I need; tires that wear quicker. I couldn't give two shits about my mileage. Where are the inexpensive tires that don't deflate? Isn't there a honey-combed tire that I can afford, or will it put firestone-death-wheels out of business? Yeah, yeah, I know. They changed their name to bridgstone because they've had so many recalls over the past 80 years that people started getting a clue. I'd invent the wheels myself but I know I'd probably get hit with a piano on the way to the patent office. I'd call them Lux-O-Glides or maybe X-Flats-O-Matix.
It's like dragging a car sideways to the tires for many miles. In what universe does this make sense?
The game.
Sorry if that goes against the short attention span mentality we generally have these days, but that's life. Sometimes there isn't a good or reliable reference for something online, you have to go get a book.
"either way I win"
No not really. You may "win" in your own mind but that is meaningless. If you mean "win" as in convince others you are right, you have failed. Sorry.
These tires are a terrible idea in terms of handling and performance.
Tires produce the most grip when they are at zero camber, the problem is that when you are using all of that grip your car is rolling quite a bit, which adds positive camber to the outside wheel (where all of the load is being carried). Therefore, to produce a performance car you want your camber such that at full load the static negative camber from your alignment balances out the positive camber gained through body roll. A conical tire simply adds positive static camber, which just makes things worse at full cornering load.
I could see a small market using these tires backwards to gain negative camber on McStrut cars, which have terrible camber curves and can almost never get enough static negative camber.
Oh yeah, and a conical tire doesn't roll in a straight line, so be prepared to play endlessly with your toe-in to get it handling correctly again.
Performance cars and race cars don't care much about tire wear, and it's well known that negative camber improves cornering. However if you look at the article they show a tire of "continually decreasing diameter", allowing a negative cambered tire to maintain a flat contact patch with the road. This means different parts of the tire have a different lateral speed when moving in a straight line. Even though it may be microscopic amounts, the tire would be creating continuous additional drag and tread wear.
As for performance, my real world experience is limited to 1/10 RC cars, but part of the benefit was that in cornering as the car rolls the contact patch of the outside tire is increased, which this tire would also negate. My pan (on road cars) always had hard suspension and practically no camber, while my off road cars with soft suspension benefited from more negative camber. If someone has more expertise to offer, I'd love to be educated.
have to take it to the logical extreme:
http://www.youtube.com/watch?v=_r6ltUgtFWI
Pretty soon, all stock Toyotas and Hondas will look like this! XD
Comment removed based on user account deletion
Everyone should camber their tires. I did this myself on my subaru rally car. It is very easy, just a couple of button presses on the old PS2 remote, and you have cambered tires. And your car looks way cooler.
But I think you need to buy the racing body first.
This seems to be yet another one of those "look at my new patent (on an old idea)!" type of PRs.
BFG race tires featured asymmetric sidewall construction in the 90's specifically to increase effective negative camber in situations where it was limited by race rules and the chassis.
Mechanics of the Aysmmetric Construction
Pinewood derby physics anyone? Boyscouts have known this for years. Pinewood Derby is mostly a matter of reducing friction rolling down the track. The camber of the tires reduces the contact with the track and thus friction. For that matter, angling one of your axles so that one tire doesn't quite make contact with the track is another. So, just replace all your tires with roadbike tires and watch the blow outs and gas mileage savings pile up.
WAIT hold on guys, I just took a land vehicle dynamics class last semester and if I find my notes.....
Oh here they are one sec let me find the section on Camber caster, and kingpin inclination angles
alright first off rolling resistances
influenced by:
applied load
inflation pressure
tread design
compound
The primary cause of rolling resistance is hysteresis (or internal friction) of the tire material, which occurs as the tire flexes
it increases with
higher load
higher tread design agressiveness (net to gross footprint ratio)
higher tread depth
and decreases with
increasing tire pressure (i.e. less contact patch)
it can be calculated at the contact patch as
F_r= [(s+1)(t_in/R_l)-F_x]cos(a)-F_y*sin(a)
where
F_r is the rolling resistance
s is the slip ratio= (Omega*R_l/V_0)-1
F_x is the longitudinal force (+ driven - braking)
F_y is lateral force
Omega is the angluar velocity of the wheel in rads/second
V is the forward velocity (in ft/s)
a is the slip angle
R_t is the tire radius
and T_in is the driving torque
so on to camber angle
camber angles is the tilt of the center of the tire patch axis from vertical
camber is positive (if viewing from the front of the car) if the tops of the tires are further away from each other than the bottoms
Trucks run positive camber to account for different loads
a small camber is used to account for road crown
some trucks have different camber settings to account for the huge torque their engine can output (this counteracts the torque of the engine's affect on the suspension
mechanics used to bend axels to give cars positive camber ( they shouldnt be doing this anymore >)
so some reasons why camber angle would increase gas efficency
well for one, it makes the effective tire radius larger (by a tiny bit) which should decrease rolling resistance, also, it makes the contact patch smaller, however, depending on the sidewall strength of your tires, this could merely cause more internal hysteresis friction and decrease your effective gas milage
one of the big reasons you probably should not do this is... most consumer tires are manufactured assuming no camber angle, so you'd probably run into some issues with tires wearing out quickly. Also, if you, like most people, forget to check tire pressure before every ride, it would probably be fairly easy to blow out your sidewall in a tight corner, especially if you were running with a heavy load
and if you're especially stupid, and put too much negative camber, you could probably screw up your suspension geometry enough to make your tires move further than the designed rattle space in you car (the open area where the suspension can move) and perhaps your tires would rub on the inside of the wheel wells before the suspension bottomed out.
but it really depends on the type of suspension your car has (and there's wayyyyy to many to list) to get a definite answer as to whether this is doable or advisable. I would go with the factory recommended settings personally and just firkin keep your tire pressure high enough (the recommended amount) and you'll save a TON on gas
oh and a warning, ALWAYS REPLACE REAR TIRES if you're only gettin 2 tires, if you replace the front tires (regardless of a front or wheel rear drive car) only, you could potentially put your car in an oversteer condition, and that is what causes people to lose control, and spin out, unless you're a formula 1 driver and you know WTF you're doing, always keep your car in an under steer condition (i.e. more traction in the back dawg)
This is what i got for taking a land vehicle dynamics class, i hope you find some of it useful
In fact, one of the main problems is friction. Perhaps the most economic solution would be Teflon Tyres; this would also increase road safety over time, as it will tend to remove the more aggressive drivers from traffic.
I was a mech for many years and grew up in Detroit. Just about ewveryone I knew worked in the auto industry, and I myself worked in the auto industry as an engineer.
And just about every car I have ever worked on or known about specifies some amount of negative camber right from the factory. You can call this anedote if you like, but the fact is I've worked on LOTS of cars and seen a LOT of specs and have seen zero or positive camber specified on a car so few times I could probably count them all on one hand.
Because it's NOT just about how the car grips in the corners, but how it handles in a straight line; Too much negative camber will make the car twitchy as it bump steers over every wave or truck rut, but NO negative camber also makes the steering feel lighter, which is also not a good thing when it means the car has absolutely no "return to center" correction. Any rear wheel drive car will try (to some degree) to straighten itself out, but half a degree to two degrees (depends on car) negative camber is pretty much standard. Part of this is also because cars tend to get knocked out of alignment because of neglect, and POSITIVE camber is really no fun - it tends to make the car even more vague in steering. So a little negative camber is built in just to help make certain things don't go positive.Of course too much is also no fun, since it will make the car try to steer away from the crown in the road and heavily crowned roads will make you feel like the front end is badly out of alignment (because it is).
The same holds true for caster: toe the front wheels out a bit and the thing will wander all over the place; toe them in and the car will tend to center itself. Both of these also will tend to increase friction as well, which also it seems would negatively affect mileage. Given many cars nowdays run on low profile tires inflated to 40psi or more I have a hard time believing it's going to make much difference on a properly tuned and aligned vehicle, however.
actually most cars come factory with about -0.1 to -0.3 camber so that when you are on the highway, the downforce produced on the vehicle pushes down and cuases the camber to become 0 and flattens the tires out for best grip.
Nobody's thought of this, yet? My google-fu might be weak but in three pages of searching I didn't find anything quite what i had in mind.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
is to get American car companies to produce more fuel-efficient cars, either with diesels or a petrol. Whatever works, otherwise, it's all gimmicks.
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In theory *and* practice these tyres have conical threads, which means the inner side rolls at a slightly different speed than the outer side of the thread.
The consequence is that at least part of the thread is slipping while the car is on a straight, with higher rolling resistance, higher tyre wear, and possibly less *lateral* resistance, making it less safe to drive.
Yes, I know, race cars usually have cambered tyres, but race cars are optimized for turning faster curves, which is where races are usually lost or won. It's amazing how much faster the car can turn into a curve if you accept the fact that the tyres must be replaced every 200 km.
I don't know why cars don't come with a line that automatically keeps tires inflated to optimal pressure. Or at least show the pressure (vs optimal) on the dashboard, a warning to reinflate them. It's been over 100 years living with these machines, and the amount of gasoline we've just wasted on flat tires is criminal.
I also don't know why batteries don't come with two partitions, with enough juice in #2 to start the car even when we've left the lights on and killed partition #1.
Why don't cars all have a slot for a mobile phone with a charger and Bluetooth speakerphone/callerID over the stereo?
How much waste have we endured leaving out those two basic features we've all needed? Meanwhile, cars come with ass warmers and rainforest woods. No wonder all the carmakers collapsed towards bankruptcy when the loan money ran out.
--
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In a pure theory aspect, less tire on the road, less rolling resistance.
Now I am completely new to this whole area, so please don't flame me too hard if what I ask is something stupid and obvious.
It is logical that less friction, less power is needed to keep the wheel spinning. But in poor, wet or icy conditions I need every unit of friction possible for safety (Aside: What is the unit of measure for friction?). Therefore, isn't this new tire design makes it more difficult for me to brake and thus more hazardous?
Saving me money in fuel is good, but if some child runs out in front of my car on local road and I can't stop in time with these tires...
friction force =mu * normal force
mu is the coefficient of friction and normal force is the force in the direction orthogonal to the surface. so the contact patch area has nothing to do with it.
but why do race cars have bigger tires you ask? bigger tires spread the heat generated over a larger area, so they wear slower. this is only important in a race car.
Just some random thinking, camber can be induced when a wheel is raised or lowered by forces during maneuvering. What if they designed the suspension such that under normal conditions there was mild negative camber but when the car drops during breaking or turning the camber levels out. The sway bar could be used to prevent uneven roll and could even be applied from front to rear as well (or automatically adjusting suspension lengths...).
(Sorry if this is double posted, having trouble with submission)
Just a random $0.02...
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.
My understanding from hacknig cars for a couple of decades is that auto manufacturers tend to specify slightly negative camber, and even progressive negative camber that increases with tire deflection (when the steering wheel is turned) in order to IMPROVE handling. Without negative camber, cars tend to feel squirrley and difficult to control. With negative camber, the car tends to feel more stable, and, importantly, the steering wheel returns to center on its own.
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They require registration to read the link.
Either post a link from a reputable news organization not behind the paywall, or don't post at all.
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Some folks appear to be confused by this article, as the headline makes it sound as though if you switch to cambered, you'll get better mileage. Bzzt. This only applies to cars whose tires -happen to be- mounted with negative camber. The tires only reduce the negative camber friction penalty in higher performance cars whose tires were already mounted with negative camber. They do NOTHING for production cars already in existence whose tires are mounted zero camber. This isn't something they're going to do to regular stock automobiles. Negative camber, even with the negative camber wheels, will always have -some- extra friction as compared to zero camber wheels. Zero camber will always get better mileage than wheels with negative camber.
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... if you end up paying for a new set of tires, anyways?
You will spend the money you saved on gas, and then some, on a new set of tires - be it a new tire technology, or just a new set of tires at improper camber.
Personally, I would prefer the nicer ride, handing, and tire life - to dealing with this whole pseudo-environmentally-friendly "tech tip".
Please leave out the lame rationalizations about safety. There is always someone who whips out the safety issue whenever they doubt an idea. Do you know whether this suggestion about tires significanty affects safety? No? If you have something, great. Please share it. But for all you know, this idea may be a tiny bit safer. Better handling, perhaps.
If you were really committed to safety, you wouldn't drive at all. You'd live in an urban setting where a car isn't a necessity. Failing that, you'd drive slower. Just 5 mph slower would give you much more time to stop than any but the grossest differences in tires. Save gas too. Of course you never ever use the cell phone or fiddle with the radio or eat while driving, right? Never exceeded the speed limit either. Speeding is unsafe!
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Summary is wrong. Production cars don't ship with zero camber. Most ship with a degree or two of negative camber. It improves the handling.
I'm hoping you just mis-spoke here, or that you're not a suspension engineer. Caster and toe are completely different entities. Toe is whether your tires are pointed inward (toe-in) or outward (toe-out) when viewed from the top. Caster is a measurement of how far the center of the contact patch is behind the steering axis. Caster is what makes the wheel want to straighten out. Both toe and caster are much more important for straight line stability than camber is.
I'm hoping you pull that ivory tower out of your ass and listen to what the man is saying. While caster is responsible for the centering force, it's absolutely true that toe-out makes a vehicle wander (sometimes toe is turned out on the rear of a car that needs to turn easier) and that toe-in is what helps you hold it steady, by producing a dead zone. Too much camber makes the car wander in a straight line due to reduced/uneven road contact, ESPECIALLY on low-profile tires, so I'm not sure what this guy is trying to say about THAT.
Maybe you're the one with the ivory tower stuck somewhere. What you are saying is correct, however you missed the important point mungtor made which is that caster and toe are not the same thing. poptones probably just mis-stated it by accident, but his post appears to state that caster and toe are the same thing. They are not.
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When I remember to drain it.
We used to have a large Kodak copier/duplicator in our office which used compressed air to run a number of systems in the document finisher. One particularly humid summer the finished sets started coming out wet. You could see water in the clear plastic pneumatic lines pretty much all the time.
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First of all, most sports cars already have camber set between 0 and maybe -2 degrees. Any much more than this will wear out the inside edge of the tire and require much more frequent tire changes. Correct me if I am wrong, but I'm pretty sure that tires are a petroleum product. So it might be that the only parties to gain anything from this effort would be tire manufacturers.
grandparent is referring to Toe-in. You need some to keep the car stable, but excessive toe-in will create tire wear.
Some cars that are going to be constantly side-loaded (Nascar, for example) will run negative camber to improve tire contact in turns.
Under normal driving conditions, loading one sidewall more than another could lead to premature failure of the tires.
Arguing with an engineer is like wrestling a pig in the mud. After a while, you realize the engineer enjoys it.
I don't see how this tire design has any effect on _actual_ camber. It is asymmetric and requires setting the car up for a few degrees of negative camber to _get it flat on the road_. The reason negative camber drives quick on tarmac is because it puts more rubber on the road in hard cornering. So this tire + negative camber is just going to lower your car by about an inch or so. If this design worked it would have been done ages ago in many classes of racing. As far as I know, the only asymmetry in high performance tires is with the tread and internal belting.
old volkswagen beetles and karmann ghias had a camber to the rear tires. nowadays it looks a bit odd when you see an old one on the road with it's tires akimbo but it's perfectly normal.
Direct link to relevant RB comic.
With the constant whining about copyright-infringment (aka - thievery) on this fucking site, it really surprises me that none of the loud-mouthed, little bitches around here doesn't just post the article text.
This POS tire is cone shaped. Roll a cone and what happens? It turns. The outside edge of this tire has a larger circumference that the inside edge. One edge of the tire wants to go further than the other edge per revolution. Tire wear will be horrible. This is a solution to a "problem" no one is interested in solving.
If he really thinks we're the Devil, then let's send him to Hell.
Camber something controlled by the suspension. A proper double-wishbone suspension controls camber during cornering so that even as the suspension is compressed, the tire maintains contact with the road.
A cambered tire is completely moronic because it is basically a section of a cone! A cone does not roll in a straight line, okay?
How can cambered tires possibly reduce the wear associated with cambering, if, whenever the car is travelling straight, the wheels are actually trying to roll in a circle?
It's like having severe misalignment.
Use the tires that your car was designed for. End of story.
Cambered tires are for the same crowd that believes you can run an engine without oil if you just add some magic additive. Or that magnets clamped to a fuel line can improve fuel economy.
As a tire engineer already knows, the AREA of the contact patch does not
change when tires are wider.
It is the SHAPE of the contact patch which changes.
More important than the width of the tire or the shape of the contact patch is the
rubber compound.
And yes, I have been involved in the tire business, at both the sales and design levels.
You people who imagine that a wider tire = a larger contact patch are misinformed. Of course,
this IS Slashdot, where any idiot can be an expert, even if he / she doesn't know anything about
the subject.
Even directional tires grip in both directions. The directional part comes in when they have to expel water, dirt, sand etc while maintaining traction.
but it costs me new tires per year. i dont see how this is saving anything. if you look at people that don't rotate tires you see front tires wear down and the rear tires good. now this is from just normal driving and left/right turns. so if not rotation tires can kill them in 10-15k miles. just from making turns. how far can i go with them constantly on an edge...... so per year 2 tires... right of if the car has independent suspension 4 tires that can have the camber adjusted.... i'll take the ride quality and the price of gas over 4 or 2 new tires per year. call me a troll or what ever.
The advantages are the differences between a low profile tire and a conventional tire, the camber is just inefficiency.
Now IF the wheel camber was greater then the tire camber, THEN you might have something because the tire give greater contact when cornering and breaking.
But, of course, when the tires wears then you are back to conventional tires, SUCH A STUPID IDEA !!!
Like everything, negative camber (i.e., "tilting" the tire slightly) means you're riding on the edge of the tire. Duh, of course you'll have less resistance. You have less rubber in contact with the road. Why doesn't everyone just use bicycle tires then?
Because contact with the road means more efficient acceleration (less slippage) and deceleration (the all important braking!!) Bicycle tires are most efficient when the vehicle is at constant velocity (speed AND direction!) but changing velocities require a bit more rubber, and thus friction is a good thing.
So this seems kinda silly, like the AquaTred tires of the 90's, but maybe it'll be cool in the end. In the interim, my bicycle tube has a flat so I'm going to go swap it out on my hummer.
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