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Old 7th September 2016, 07:53   #1
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Default Why do rear window sills slant upward?

Mods - I could not find any thread discussing this topic. Please merge if there is one.

Friends, visibility from rear window has become one of the important criteria for my spouse while evaluating a car. My kids are around 5 years old and she feels that kids at the back should have good visibility of outside and not feel claustrophobic. This might look like a silly criteria but I agree with her thoughts here.

I wanted to understand if there is any technical aspect apart from aesthetic one behind rear window being curved upwards - like safety related aspects.

I am attaching few snaps here with a straight line marking to show how much the rear window is curved. Let me know your thoughts so that I can see if I can convince my spouse not to reject on this criteria.

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Surprisingly Maruti Brezza and Ciaz don't have very steep curves

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Last edited by GTO : 7th September 2016 at 17:34. Reason: Typos
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Old 7th September 2016, 09:03   #2
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Default re: Why do rear window sills slant upward?

I also like to have nice big airy windows.
Globally there is major design "movement" (?) to make the cars more visually aerodynamic. If you have noticed the cars nowdays have more curved sloping roofs meeting the rear bumper. A decade or so back, cars used to be more boxy.
The window needs to be able to retract inside the door which has less height between the sloping roof and the wheel arch. Hence the curved windows which reduce the size and height of the glass.

The sub 4m rules also makes the manufacturers pull the rear wheels more forward reducing the size even more.

Last edited by timuseravan : 7th September 2016 at 09:05.
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Old 7th September 2016, 09:14   #3
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Default re: Why do rear window sills slant upward?

Possibly to allow the window to roll down further.

Notice that the wheel arch usually results in less vertical space near the back of the door (closer to the handle) compared to the front of the door (near the hinge). How far a window can roll down is limited by that space. The slope of the roof also has a bearing but usually, the roof has to remain reasonably flat to ensure rear headroom.
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Old 7th September 2016, 09:34   #4
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Default re: Why do rear window sills slant upward?

Quote:
Originally Posted by Simhi View Post
I wanted to understand if there is any technical aspect apart from aesthetic one behind rear window being curved upwards - like safety related aspects.
A bit of both actually, though more for the aesthetic reasons. Each car designer draws a car with a cohesiveness that cannot be negotiated with. For example if you sit in the Indica/Indicab of yesteryears you'll find that the window-line is too long, too wide, so much so that I feel awkward sitting beside it, the aspect ratio between the door and glass is 50:50.

Those days are gone now as cars are increasingly made to sit lower, reducing overall height of the vehicle helps in aerodynamics and also handling. If that is done the window line also has to be lower so as to give the proper aesthetics, it usually follows the line from the beginning of the shoulder crease all the way to the end with a slight curve to create a non-boxy illusion.. if the glass area is made taller upwards then the car will assume a bulbous, slightly non-cohesive design.. more of an aesthetics thing really.

When we speak of low window-lines and glass area one car comes to mind, the Elite i20.. it has all the visibility of a Lamborghini and it's nowhere close to being a sports car, this is despite its already large height of 1505 mm. My car in comparison is the Hyundai Getz, its big brother which has a height of 1495 mm (low slung) yet has much, much more glass area such that there is good all-round visibility and feel and it drives far better as well. Even the Polo with a lowest-slung body in class has better visibility than Elite i20. All this points to the fact that its a design choice, and its going to get worse in upcoming sedans. Also the recent cars are coming with a heavy kink in the side which flow out just as the window-line stops increasing the width by a few inches uselessly, while not resulting in any added shoulder-room or seating area.

In the end it may come down to personal preferences, some like the high window lines, some do not. One can also get adjusted to the new shape after driving around for a few months I guess.

Last edited by dark.knight : 7th September 2016 at 09:35.
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Old 7th September 2016, 09:51   #5
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Default re: Why do rear window sills slant upward?

Rear window glasses that don't roll all the way down are an eyesore. With cars having rear wheel arches cutting into the rear door significantly, it becomes tricky to accommodate the glass and still allow rolling down to maximum extent possible. As mentioned by others, this design constraint tends to dictate window-line sloping upwards.

Another aspect to look at is how the slope changes when the car is loaded. With 2-3 people in the rear seat and a boot full of weekend luggage, most cars would dip by a few inches at the rear and then the sloping line would not appear that much sloping.
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Old 7th September 2016, 10:20   #6
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Default re: Why do rear window sills slant upward?

Cars are mostly designed 'outside in', which means someone comes up with a nice exterior rendering, which looks sleek and dynamic and this serves as the basis for the interior design.

When you try to work the interior based on this exterior profile, you will have high set dashboard, high set rear windscreen, raising waistline etc.

I like the old school styling, just like my Forester which has very good all-round visibility but looks quite boxy from outside. I know that there is a issue of aerodynamics but it should be possible to strike a balance.
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Old 7th September 2016, 11:50   #7
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Default re: Why do rear window sills slant upward?

Quote:
Originally Posted by Simhi View Post
Friends, visibility from read window has become one of the important criteria for my spouse while evaluating a car. My kids are around 5 years old and she feels that kids at back should have good visibility of outside and should not feel claustrophobic.
Pick a MPV or a SUV if you want good visibility from the backseat. You sit higher - so you can see out better.
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Old 7th September 2016, 12:07   #8
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Default re: Why do rear window sills slant upward?

Quote:
Originally Posted by smartcat View Post
Pick a MPV or a SUV if you want good visibility from the backseat. You sit higher - so you can see out better.
Might have no relation to MPV or SUVs but the WagonR that I have been using since a decade now has its rear seats placed higher than the front that the passengers seated behind always have a very good visibility from the backseat.

Thankfully, the tradition continued with the Ertiga as well.

Lower roofline & smaller windows have their share of stories from my side too when it comes to motion sickness. I have a friend in Mumbai who owns a Ford Fiesta 1.6 and in last 7 years of its ownership, he has only driven to Ganapatipule from Mumbai with his 2 daughters and both threw up. So bad that he doesn't take his kids out in his car in and around Mumbai also.

And then he also mentioned how they were happy in the back seat of an Innova when they hired it once in Rajasthan. Earlier this year when I drove to Mumbai, all of us did city rounds in my Ertiga and his daughters never had any trouble.

Take the case with my daughter - I cant say that she's just used to the Taller seating but she did complain of tummy pain (her way of telling she will throw up) when we drove less than 10 kms inside city in a Friend's Linea.

For me, larger windows, Taller seating and good head and shoulder room is very very important.

The other day when my relative almost booked the Celerio AMT which was a better choice to WagonR AMT In terms of equipment and the car itself, the moment he sat in the WagonR and drove, he didn't have to think twice. His decision was mainly because he already drove a WagonR before (He is at 68 Years). so at times one is too pampered with such a roomy set-up that everything else seems "Small"

Last edited by paragsachania : 7th September 2016 at 12:09.
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Old 7th September 2016, 12:18   #9
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Default re: Why do rear window sills slant upward?

Quote:
Originally Posted by paragsachania View Post
Might have no relation to MPV or SUVs but the WagonR that I have been using since a decade now has its rear seats placed higher than the front that the passengers seated behind always have a very good visibility from the backseat.

Thankfully, the tradition continued with the Ertiga as well. For me, larger windows, Taller seating and good head and shoulder room is very very important.
aah, yes. The Wagon R is one of the cars that gives you the "sitting-in-a-Volvo-city-bus" feeling. This one comes pretty close -

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One of the rare cases where window line curves downwards!
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Old 7th September 2016, 14:34   #10
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Default re: Why do rear window sills slant upward?

No nit picking but I think that's a slant than a curve. I got a little confused when I read the thread title and had to actually go through the OP's post twice to get the context since I was looking for a curve. I actually thought about the glass having a curve.
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Old 7th September 2016, 16:24   #11
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Default re: Why do rear window sills slant upward?

IMHO

The issue is possibly related to the wind noise element on the rear seat.
An upward curving window would reduce the pressure difference and inturn reduce the wind noise
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Old 7th September 2016, 17:32   #12
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Default re: Why do rear window sills slant upward?

There's not one reason - there are at least four!

Design: A rising window line looks 'sporty' & sexy.

Cost: Metal is cheaper than glass.

Weight: Glass is very, very heavy.

Safety: Metal protects, glass doesn't. More metal means easier packaging of the side airbags.

Compare the Esteem to the Ciaz and you'll see how the belt line is climbing up:




Or the big daddy:




Frankly, any car with a low belt line just looks awfully outdated today.
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Old 7th September 2016, 18:41   #13
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Default re: Why do rear window sills slant upward?

Quote:
Originally Posted by timuseravan View Post
I also like to have nice big airy windows.
Globally there is major design "movement" (?) to make the cars more visually aerodynamic. If you have noticed the cars nowdays have more curved sloping roofs meeting the rear bumper. A decade or so back, cars used to be more boxy.
The window needs to be able to retract inside the door which has less height between the sloping roof and the wheel arch. Hence the curved windows which reduce the size and height of the glass.

The sub 4m rules also makes the manufacturers pull the rear wheels more forward reducing the size even more.
Yes, i too like airy windows. Those steep window lines are the most irritating design lines to see. I guess, if the wheel arch is the problem, they can always have a fixed quarter glass and a straight window line, with a fully retracting glass like in a Ford Ikon.
http://www.team-bhp.com/forum/attach...e-p2140144.jpg
Could never understand why "designers" put unnecessary curves / lines when there are ways to avoid it.
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Old 7th September 2016, 20:01   #14
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Default re: Why do rear window sills slant upward?

As GTO said, lower belt line and bigger Windows would surely look outdated in today's times. Agree that bigger windows have their share of benefits but today if such a car is launched, most of the buyers would reject it and call it outdated.

I guess, apart from window glass space inside the door and aesthetic points, the rising window line gives a sense that the car is in motion and moving forward and manufacturers term these elements as kinetic/liquid flow/dynamic etc. As the result, most of the cars on sale which are considered as sporty/modern have this design element.
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Old 7th September 2016, 22:15   #15
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Default re: Why do rear window sills slant upward?

It just seems to be an effort to keep up with the trend (currently trendy being sleek rather than boxy), with no apparent technical constraint. The latest Discovery seems to have given up its trademark low window line, so characteristic of its profile.
Why do rear window sills slant upward?-2015landroverlr4sideprofile.jpg
Why do rear window sills slant upward?-2015landroverdiscoverysporthse.jpg

This trend seems go along with the rearward sloping roof line as well, with the Evoque taking this to an altogether new level!
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