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      01-04-2013, 12:53 PM   #45
SPACEMANRICK
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Originally Posted by DerekS View Post
You obviously haven't lived here to witness past Vancouver winters when snow remained on the ground for a month or more. It was only two winters ago that our provincial insurance company, ICBC, stated that they would deny insurance coverage for drivers found at fault in a MV collision if their car was NOT equipped with snow-rated tires.

All season tires are next to useless on ice or packed snow. ICBC recognizes this obvious fact to limit their damage claims.
For Vancouver, all wheel drive is used much more for all the RAIN we get here 12 months a year than for any snow. That 2 day snow storm you referred to last month was 2 or 3 inches of snow for everyone except for you in your alpine chalet on the mountainside of Whistler. The last major accumulation of snow that you refer to was 4 years ago and before that what was it 15 or 20 years ago?......For all the snow that you talk about here in Vancouver do you also have a snowblower for all the major snowfall?

Today's week forecast for Vancouver (in the traditional coldest part of the winter) is yes for more rain and temperatures of about 7 degrees.
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      01-04-2013, 01:50 PM   #46
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Originally Posted by ynguldyn View Post
Exactly. As long as you can ignore extra weight, weight distribution, fuel consumption, and higher purchase and maintenance costs.
The weight diff. between AWD and RWD is less than 300 pounds, fuel consumption is the same in the city and 1 MPG diff on the highway. 0-60 MPH is 0.1 sec diff and the cost of the AWD is about the same as snow tires, rims and TPMS.

Small price to pay for the additional safety AWD provides.
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      01-04-2013, 02:19 PM   #47
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Originally Posted by elistan View Post
For what it's worth, everybody, the OP has Pirelli Sottozeros, which ARE winter/snow tires. They are not all-season or summer tires.
The Sottozeros (which are what I'm currently running) are performance snow tires. That means they lean more towards better driving dynamics in cold and dry conditions rather than optimizing for driving in actual deep snow. Studless snow tires offer better in-snow grip at the expense of dry performance.

So that's where the distinction comes in.
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      01-04-2013, 03:28 PM   #48
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Originally Posted by The X Men View Post
The weight diff. between AWD and RWD is less than 300 pounds, fuel consumption is the same in the city and 1 MPG diff on the highway. 0-60 MPH is 0.1 sec diff and the cost of the AWD is about the same as snow tires, rims and TPMS.

Small price to pay for the additional safety AWD provides.
You're missing the fact that the driving dynamics are also quite a bit different in the X drive cars. AWD is great for safety, but the reality is for many people 360 days of the year they won't drive the car in snow, so for the 5 days they might have to is it worth those tradeoffs?

Also - you can't say an Xdrive car pays for itself based on the cost of the tires. An AWD car with all seasons will be most price efficient, but won't handle as good as an RWD car with summer tires in the summer and dedicated winters - especially if you push your car towards the limits (which if you bought the 3 to be a sports sedan and not a luxury sedan, probably happens fairly oftne).

It all depends on your driving habits...Audi made a pretty successful business out of selling AWD cars. I just care that the car is safe enough to get me home in bad weather, the wife has a truck for blizzards (no AWD is going to get you over the fact that the car only has a few real inches of ground clearance)
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      01-04-2013, 04:57 PM   #49
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Originally Posted by Cyberdemon View Post
You're missing the fact that the driving dynamics are also quite a bit different in the X drive cars. AWD is great for safety, but the reality is for many people 360 days of the year they won't drive the car in snow, so for the 5 days they might have to is it worth those tradeoffs?

Also - you can't say an Xdrive car pays for itself based on the cost of the tires. An AWD car with all seasons will be most price efficient, but won't handle as good as an RWD car with summer tires in the summer and dedicated winters - especially if you push your car towards the limits (which if you bought the 3 to be a sports sedan and not a luxury sedan, probably happens fairly oftne).

It all depends on your driving habits...Audi made a pretty successful business out of selling AWD cars. I just care that the car is safe enough to get me home in bad weather, the wife has a truck for blizzards (no AWD is going to get you over the fact that the car only has a few real inches of ground clearance)
I bet you a spark plug that 90% of the 3 series owners have never push their car to the limit. I echo others in saying that, unless you are on a close track, you will not notice the performance difference between a AWD and RWD.
AWD is not just for snow, it can help power a car thru a turn, it can help with traction in heavy rain and driving over large puddles. If you loss traction for whatever reason, it can recover faster than a RWD car.
Where I am, it snows a lot more than 5 days a years. I guess if I live in an area where it only snow 5 days a year, I would not need a AWD car.
In the Northeast, there is almost no RWD stock around, its actually cheaper to buy a AWD car off the lot than to order one from Germany. If one consider the cost of snow tires, rims, TPMS and labor, the AWD is actually a couple of thousand cheaper than the RWD
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      01-04-2013, 09:06 PM   #50
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In the Northeast, there is almost no RWD stock around, its actually cheaper to buy a AWD car off the lot than to order one from Germany.
That's just bad negotiation skills.
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If one consider the cost of snow tires, rims, TPMS and labor, the AWD is actually a couple of thousand cheaper than the RWD
A winter set with Blizzaks and cheapo wheels will run under $1K, and if you know how to work craigslist it'll be more like $500. Besides, you can ignore the cost of the tires, since while you putting wear on them, you're not putting wear on your summer set.

And if I ever have to choose between AWD with all-seasons and RWD with winters, I'll always choose the latter. Because being able to stop without the help of the trunk of a car in front of you is a million times more important than being able to drive up a hill.
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      01-05-2013, 03:26 AM   #51
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Originally Posted by The X Men View Post
I bet you a spark plug that 90% of the 3 series owners have never push their car to the limit. I echo others in saying that, unless you are on a close track, you will not notice the performance difference between a AWD and RWD.
There are a lot of RWD vs AWD threads going on in this forum right now, and it seems you are trying to argue your point in all of them. Are you an Haldex rep?
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      01-05-2013, 11:26 AM   #52
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There are a lot of RWD vs AWD threads going on in this forum right now, and it seems you are trying to argue your point in all of them. Are you an Haldex rep?
arguing is the wrong word, I am debating

Let em ask you this, are you a snow tire salesman ?
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      01-05-2013, 11:50 AM   #53
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I echo others in saying that, unless you are on a close track, you will not notice the performance difference between a AWD and RWD.
I continue to be surprised with this statement. I can easily feel if any car is carrying an extra 300 pounds and has increased understeer as does the XDrive. The difference in handling between RWD and XDrive is pronounced, easily noticeable in day to day driving.


Keep in mind the BMW AWD system is fairly unsophisticated, defaults to 40% front/50% rear (read, increase understeer at all times) and has open differentials front and rear. The system does not integrate torque vector steering or even an LSD. Thus, it simply cannot improve handling - contrary to claims here. (Unless you are one of the few who actually believes front wheel drive improves handling over RWD, asserting the nonsense that FWD "pulls" the car through turns. )

XDrive is great for straightline movement/acceleration on slippery surfaces and should be purchased by those more comfortable with such a system in the winter. It is otherwise extra weight, lesser handling, increased cost.

Your choice.
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      01-05-2013, 04:52 PM   #54
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Quote:
Originally Posted by The X Men

The weight diff. between AWD and RWD is less than 300 pounds, fuel consumption is the same in the city and 1 MPG diff on the highway. 0-60 MPH is 0.1 sec diff and the cost of the AWD is about the same as snow tires, rims and TPMS.

Small price to pay for the additional safety AWD provides.
But what about the fact that when the weather is ok 9 months of the year, you won't have RWD?
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      01-05-2013, 05:38 PM   #55
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That's right this is all about choice and acceptable risk. RWD is not a no brainer and AWD is not a no brainer either. Its all about your usage, climate, and acceptable risk level.

In MTL, OTT, TOR, what did we do before AWD was common?

I don't ever remember getting stuck in my father's old cutlass when I was growning up.

I'm not saying AWD doesn't help. Of course it does. But do "I" need it? Nope.
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      01-05-2013, 05:48 PM   #56
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For a Canadian-equipped vehicle, it's 60 kg (130 lbs) heavier. Not 300 lbs. And that's very low-slung weight as well.

The comments about increased understeer are being bandished without any qualification. Increased understeer is possible in a very limited set of circumstances, but most times not. Such as if you're plowing the front end through a steep corner on full throttle, and the outside wheel has already lost traction.

Here's some marketing speak for the bored:

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The BMW xDrive system detects any oversteering or understeering before they even start. Within a tenth of a second it distributes up to 100% of the engine power to the front or rear axle via the transmission and an electronically controlled multiple-plate clutch before returning to the normal 40:60 distribution ratio.

With the BMW xDrive system each axle uses its traction to the maximum. Whether in tight corners, during hill starts, on slippery surfaces through rain and leaves or on snow-covered carriageways, the optimum amount of power reaches the road. Your BMW provides stable acceleration in every situation – even out of bends. With BMW xDrive your vehicle exploits the benefits of rear-wheel drive to the full: precise handling, optimum cornering and a clear separation between the engine and steering.
and from the international site:

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xDrive is the permanent all-wheel drive system from BMW: under normal circumstances, it distributes driver power between the front and rear axles in a 40:60 ratio, and changes this figure variably when the road surface or overall driving conditions change.
Acting virtually instantaneously and a manner so subtle as to be go virtually unnoticed by the vehicle's occupants, xDrive can direct up to 100% of drive forces to one axle. Enabling the driver to start up effortlessly even on slippery surfaces or steep hills, xDrive routes all power to the axles with the greatest traction. When parking, the system reacts to the need for high manoeuvrability at low speed by opening the clutch completely so the powertrain functions optimally.
At the first sign of understeering, drive power to the front axle is reduced. If oversteering is detected, xDrive directs more power to the front axle. Thanks to this dynamic redistribution of power, vehicle stability returns to normal even before the driver notices anything amiss.
Driving on a winding road or taking a fast bend in dynamic style is particularly enjoyable with xDrive: you feel as if your BMW is being guided along the curve. xDrive ensures that none of drive power is wasted on a loss of traction: every kilowatt of power is effectively brought to bear on the road.
xDrive is regulated by Dynamic Stability Control (DSC) and uses information from the latter system’s sensors to monitor road conditions. In addition, brake force courtesy of DSC is used when there is traction difference between the two sides of the vehicle and wheel spin is likely.
So basically as soon as it detects understeer, it diverts power (up to 100%) to the rear axle, and the resultant behaviour is thus quite similar to the RWD.
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      01-05-2013, 08:27 PM   #57
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So basically as soon as it detects understeer, it diverts power (up to 100%) to the rear axle, and the resultant behaviour is thus quite similar to the RWD.
Not really.

The marketing sources you cite are describing what the car does when the tires are actually slipping on the pavement from too much power. This has nothing to do with the fundamental handling balance of the car; any car will exhibit understeer or oversteer if the limits if adhesion are exceeded on that end of the car.

Front wheel drive cars exhibit tremendous understeer as a fundamental handling characteristic, as well as torque steer upon throttle application. This does not mean the front wheels are spinning. AWD cars exhibit precisely the same characteristics of a FWD car to the extent the front wheels are powering the car.

Also, keep in mind the front wheel slipping under power understeer being addressed by xDrive is directly caused by the xDrive system itself! This form of understeer will never occur with RWD so there is nothing to "fix.". This is yet another example of xDrive understeer.

Last edited by Elk; 01-05-2013 at 09:19 PM.
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      01-05-2013, 10:03 PM   #58
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Not really.

The marketing sources you cite are describing what the car does when the tires are actually slipping on the pavement from too much power. This has nothing to do with the fundamental handling balance of the car; any car will exhibit understeer or oversteer if the limits if adhesion are exceeded on that end of the car.
That's what understeer is - the tires slipping on the pavement. If they're not slipping, it's not understeering; it's just steering. When traction is lost, the system detects the difference in the rotational speed of the wheels and redirects power accordingly.

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Front wheel drive cars exhibit tremendous understeer as a fundamental handling characteristic, as well as torque steer upon throttle application. This does not mean the front wheels are spinning. AWD cars exhibit precisely the same characteristics of a FWD car to the extent the front wheels are powering the car.
By your logic, an AWD vehicle would thus exhibit a percentage of understeer based on the proportion of their front wheel drive power, and a percentage of understeer resistance based on their rear-wheel drive power? And the net effect of this is what? A hole in the space-time continuum?

AWD cars still have the rear wheels pushing the back of the car, which is fundamentally different from a FWD vehicle. So no, an AWD car does not understeer in proportion to the power delivered to the front wheels as your argument suggests. This is fundamentally and physically false.

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Originally Posted by Elk View Post
Also, keep in mind the front wheel slipping under power understeer being addressed by xDrive is directly caused by the xDrive system itself! This form of understeer will never occur with RWD so there is nothing to "fix.". This is yet another example of xDrive understeer.
The "form" of understeer is irrelevant. If the RWD vehicles when pushed exhibit an understeer of say 1x, and the AWD vehicles under the same conditions exhibit an understeer of say 1.2x, the "form" of understeer is of no consequence. Understeer is understeer, and the RWD vehicles are certainly not immune. The AWD, under certain conditions (and when pressed very hard), can have slightly more understeer. That's it.

That's why I stated that the xDrive system could produce results that were "quite similar", not identical. I clearly stated that under a limited number of circumstances, the AWD had a higher propensity towards understeer. However, the BMW system does a very good job of managing this phenomenon when the vehicle is pushed hard, and compensates well.

And when the vehicle is not being driven past 99%, it's entirely a non-issue.

So what's the end result? Maybe a tick higher lap times with the RWD, but in every-day usage, you'd be picking nits.
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      01-06-2013, 06:48 PM   #59
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That's what understeer is - the tires slipping on the pavement. If they're not slipping, it's not understeering; it's just steering. When traction is lost, the system detects the difference in the rotational speed of the wheels and redirects power accordingly.
This is only true for a spherical car in a vacuum. If it applied to real cars just like you're describing, all AWD cars would have perfect neutral handling. For some reason, however, throughout many generations, a 3 series could always turn better than an A4. Do you have a good explanation for this?
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      01-06-2013, 07:22 PM   #60
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I'm not saying AWD doesn't help. Of course it does. But do "I" need it? Nope.
exactly
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      01-06-2013, 08:24 PM   #61
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Originally Posted by The X Men View Post
In the Northeast, there is almost no RWD stock around, its actually cheaper to buy a AWD car off the lot than to order one from Germany. If one consider the cost of snow tires, rims, TPMS and labor, the AWD is actually a couple of thousand cheaper than the RWD
I bought my RWD 335i in NY from Germany and paid only a few hundred over invoice, the AWD cars are still more expensive, but for an average person who doesn't know how to negotiate a car deal I can see dealers being more willing to move an XI off the lot. But unless dealers are throwing XI's off the lot under invoice (which no one on this forum seems to support if you read the deals) then that doesn't make much sense.

Either way, the invoice price of an XI is $1800 more - so assuming you can negotiate the same deal on either vehicle, you can get winter tires, TPMS, fancy rims from Tirerack for around $1100.

So I don't get how you can do the math and say that AWD is in any way shape or form a couple thousand cheaper. At very best it's several hundred more expensive and you still don't get the added benefit of snow tires.

AWD helps with handling, but when you have to stop short because it's snowing your AWD means nothing, and you're left to the will of your all seasons. A RWD car with real snow tires might save you from crashing into the rear of that truck - so winter tires even on AWD are still worth the investment.
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      01-06-2013, 08:33 PM   #62
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Originally Posted by ynguldyn View Post
This is only true for a spherical car in a vacuum. If it applied to real cars just like you're describing, all AWD cars would have perfect neutral handling. For some reason, however, throughout many generations, a 3 series could always turn better than an A4. Do you have a good explanation for this?
Love the reference!

I've stated that there are situations where the AWD 3 will still produce increased oversteer. If it produces increased oversteer before reverting to RWD in those circumstances, it will be marginally worse in performance in those circumstances. The system takes a bit of time to transfer the power (up to a tenth of a second after it's registered), so one would still be subject to both the increase in initial understeer plus this delay.

Further, the AWD will have different handling and more notably different steering feel (heavier and prone to torque-steer). They're not the same, and you can't drive them like they're the same.

So, no, I don't think AWD better, nor neutral. It's different, with some disadvantages in some circumstances, and some advantages in others.

The points I made were both to correct some inaccuracies as well as calm down the exaggerated rhetoric. It's a slight difference overall, and only in circumstances where the vehicles are pushed to the limits do these differences really come to light.

Comparing to a different make of vehicle is apples to oranges, so doesn't really provide a useful metric. I could compare the RWD 3-series to our decade-old Porsche Turbo or the GT-R, and the AWD platforms would steer circles around the RWD 3'er, therefore AWD must be better? Not valid. Drive the Turbo next to the GT2, and again the RWD feels sharper.
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      01-06-2013, 08:35 PM   #63
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Originally Posted by Cyberdemon View Post
...AWD helps with handling, but when you have to stop short because it's snowing your AWD means nothing, and you're left to the will of your all seasons. A RWD car with real snow tires might save you from crashing into the rear of that truck - so winter tires even on AWD are still worth the investment.
+1 to that! Too many seem to think the AWD will really help them stop or turn in adverse conditions.

Then they're in the ditch scratching their heads...
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      01-06-2013, 10:22 PM   #64
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Originally Posted by S-Dot View Post
That's what understeer is - the tires slipping on the pavement. If they're not slipping, it's not understeering; it's just steering. When traction is lost, the system detects the difference in the rotational speed of the wheels and redirects power accordingly.
Assuming for purposes of discussion your concept of understeer is both accurate and complete, xDrive does not, and cannot, do anything to the front wheels other than to decrease the amount of power transferred to them.

That is, xDrive can only address the loss of traction induced by xDrive transferring too much power to the front wheels in the first place. Ironic, at best. It is not coincidental that the best handling is achieved by not transferring power to the front wheels in the first place.

Quote:
By your logic, an AWD vehicle would thus exhibit a percentage of understeer based on the proportion of their front wheel drive power, and a percentage of understeer resistance based on their rear-wheel drive power? And the net effect of this is what? A hole in the space-time continuum?
No, but very cute. "Understeer resistance?"

The problem with AWD and turning: any front tire traction used to propel the car forward cannot be used to turn the car. This inherently decreases the ability of the car to turn. With RWD, all of the front wheel traction is available to turn, one of the reasons RWD handles better (there is also AWD torque steer, weight differences, etc.)

This relative unwillingness of an xDrive car to turn is easily felt in day to day driving. A car using only 50% of its capability to turn feels very different than a car using 85% of its ability in the exact same turn. This is why a sports car feels much more comfortable than a sedan in a corner; it is working much less hard. This is one significant difference between RWD and xDrive.

xDrive is great for increased traction in snow and on ice while going in a straight line. This ability has its costs. Only the individual buyer can determine whether the compromise is worth it. This is a perfectly valid choice.
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      01-07-2013, 12:13 AM   #65
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I'm trying, from a physics point of view, to follow this strange discussion.

Do people who buy BMWs not have enough funds to get both xDrive AND snow tires? And I'd think xDrive and snow tires both help handling is slippery conditions, either alone or doubly together. Why the extended discussion of either/or? I bought the xDrive, and if I need snow tires, I'll get them too.

And I don't get the claim that xDrive only helps while traveling in a straight line and accelerating. Whenever a wheel starts to lose grip, its traction diminishes, dynamic friction is less than static friction. Unless one is just coasting, with no breaking nor accelerating on any of the wheels, xDrive can reapportion the force on all wheels to reduce the number of wheels slipping and the differential rate of slip. Wheels can slip (or have traction) accelerating, breaking, or from centripetal force while turning.

The statements "A car using only 50% of its capability to turn feels very different than a car using 85% of its ability in the exact same turn" and "a sports car feels much more comfortable than a sedan in a corner; it is working much less hard" are also mysterious to me.
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      01-07-2013, 09:37 AM   #66
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I bought my RWD 335i in NY from Germany and paid only a few hundred over invoice, the AWD cars are still more expensive, but for an average person who doesn't know how to negotiate a car deal I can see dealers being more willing to move an XI off the lot. But unless dealers are throwing XI's off the lot under invoice (which no one on this forum seems to support if you read the deals) then that doesn't make much sense.
My guess is that you could have gotten an Xi off the lot for under invoice.
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