JDM cars having rear wipers compared to their USDM counterparts

[Grandea GTR]

So after suggesting a JP only Subaru Legacy in the suggestions section in the GT6 forums, I've noticed that compared to it's USDM counterpart, the JDM Legacy has a rear wiper.

I also noticed a bunch of other cars do this too: why is that?

 

[ImaRobot]

I'm going out on a limb here, but I'm going to guess that its used to wipe the rear window.

 

[Squach240]

 

[Grandea GTR]

I'm going out on a limb here, but I'm going to guess that its used to wipe the rear window.

Lol

I knew someone was going to come and say that

 

[motortrend]

Obviously so you can do this

 

[LMSCorvetteGT2]

Obviously so you can do this

wow that seems lame

 

[WrxScooby]

My wagon has a rear wiper and I love it. I dont know why its not at least a option on more vehicles. Thought about aiming it straight back to spray at tailgators. I read a mod for it on Nasioc a long time ago haha.

 

[Liquid]

Hang on, hang on, hang on.

Unless I am very much mistaken, can I conclude from this thread that USDM cars don't have rear wipers? That is absurd.

 

[Crash]

Certain USDM versions of Japanese wagons and certain hatchback/notchback have rear wipers. However USDM versions of Japanese sedans and coupes often didn't get the rear wipers.

 

[Tornado]

Boom.​

 

[homeforsummer]

Certain USDM versions of Japanese wagons and certain hatchback/notchback have rear wipers. However USDM versions of Japanese sedans and coupes often didn't get the rear wipers.

Rear wipers on sedans and "proper" coupes with trunks (as opposed to liftback-style coupes) are fairly rare anywhere, to my knowledge. Certainly appeared on 1990s stuff a lot in Japan and a lot of French sedans had rear wipers for a while too, but generally they're absent from most stuff.

Which is odd really, since sedans tend to have worse aerodynamics than hatchbacks and their rear screens get wet or mucky a heck of a lot easier. I'm not sure why the ability to see out the back is considered less important in such vehicles...

 

[R.S]

With more vertical back window the air is slower near the window and the dust from a dusty road can severely coat the rear window. On a sedan the dust blows away from the window more readily.
Also on a sedan the rear window is much further from the back of the car than it would be with a wagon, obviously the dust blowing from under the car will make its way to the wagon window very easily.

Wagon produce a low pressure area behind. Sedans have better aero. They produce less drag.

 

[Tornado]

Like for like, no they don't. Traditional 3 box sedans have plenty of rear turbulence because the air circles around the trunk and does the same thing behind the car. There's not too terribly much involved to make a wagon considerably more aerodynamic than a sedan equivalent, either.
The issue is that the design considerations required tend to be at odds with "reasons people buy wagons;" so manufacturers instead do things like raise ground clearance, make the roof slightly higher or completely flat, don't take precautions to keep the weight gain in check, give the glass portion of the hatch an extreme rake, etc.

 

[homeforsummer]

Like for like, no they don't. Traditional 3 box sedans have plenty of rear turbulence because the air circles around the trunk and does the same thing behind the car.

This. It's only very recently, with a handful of cars from companies like Mercedes-Benz, where they've become more aerodynamic.

What you try and minimize with aerodynamic drag is flow separation. On a three-box sedan of the sort being discussed here, airflow separates from the roof as the glass starts to fall away behind the car, and does so again off the trunk lid. Specifically, it's the separated flow (and therefore turbulence) that causes rain and muck to build up on the rear window. For a more extreme example, think of a pickup truck - even with a covered bed, that sharp cut-off after the roofline is pretty horrific for turbulence.

A regular hatchback (like a Mazda3 or Ford Focus) is slightly better, as while air becomes turbulent as it leaves the roof (and can muck up the rear screen) it's not then got a trunk to navigate and the resulting lip to create even more turbulence. Many now have small spoilers to allow the airflow to separate cleaner.

A liftback-style hatchback, with a smooth, curved roofline (see Prius, Insight, CRX, Mazda MX-3 etc) is even better as most conform to the right geometric angle for flow to remain laminar before it leaves the back of the car. The line is a slim one - cars like the Porsche 911 are pretty poor aerodynamically at the back, despite the curved roofline. Hence their need for retractable spoilers at higher speeds to reduce lift. Having not driven a 911 though, let alone in the wet, I've no idea whether it needs a rear wiper or not

My own Insight has a rear wiper on the top screen (the one I look out of - the bottom screen is too low) but above about 50 mph it doesn't actually need it, even in a thunderstorm - the attached flow of air keeps it perfectly clear.

TL;DR - You're more likely to get a dirty or waterlogged rear window in a sedan than a fastback. Which is odd, since sedans so rarely have wipers to correct it.

 

[Tornado]

For example of how even little changes can have a huge effect on it, look at the original Focus:

The coefficients of drag are (including the roof rack on the wagon), respectively:
.30, .31 and .35. Despite the cars being pretty much identical from the back of the rear doors and forward.



It's also why the followup Mk. II Focus hatchback looked so similar to the first car at first glance, but everything was given hard edges instead of the jellybean corners and wide ending the original car had on the rear (which is probably to blame for the aerodynamics being so poor compared to the wagon; with it's clear angles and tapered, narrow rear end).

 

[homeforsummer]

Incidentally, that post has reminded me how good the Focus used to look. And how good the new one doesn't.

 

[CyborgGT]

Thought about aiming it straight back to spray at tailgators. I read a mod for it on Nasioc a long time ago haha.

I've done it on the RSX. My sprayer's mounted on the roof, since my window's at such an angle, so I've just aimed it to spray straight out. Jerks won't let me over when I have my signal on, so I let myself over and spray them! I should rig up something with brake fluid or aircraft remover...

Love having a rear wiper though.

 

[Parker]

I've done it on the RSX. My sprayer's mounted on the roof, since my window's at such an angle, so I've just aimed it to spray straight out. Jerks won't let me over when I have my signal on, so I let myself over and spray them! I should rig up something with brake fluid or aircraft remover...

Love having a rear wiper though.

You know that just because you have your signal on, that doesn't mean you have the right to move over, correct?

Your little modification is also illegal.

 

[CyborgGT]

I only had the sprayer aimed like that for a few days a couple years ago. But when someone puts their signal on, it's common sense that they need to get over and you should not be an inconsiderate prick. I had the signal on for quite a distance so I got annoyed, and when traffic finally slowed to a crawl I stuck my front end into the gap so they had no choice.

They even brought it up on Top Gear once, that Americans never let other drivers over. I see it all the time, a car ahead of me has their signal on when they're a bit in front of the car next to them, and that other car speeds up like they're more important. The same idiots pull into the empty lane at a red light only to not take off any faster than the person that was originally in front of them.

I always watch out for turn signals and, if it can be helped, I slow down and let them go. Most people aren't like me and don't drive just to drive; they need to be somewhere.

 

[homeforsummer]

They even brought it up on Top Gear once, that Americans never let other drivers over. I see it all the time, a car ahead of me has their signal on when they're a bit in front of the car next to them, and that other car speeds up like they're more important.

That happens everywhere really, not just the U.S. However, that doesn't stop what @peobryant said being correct. Since this:

Most people aren't like me and don't drive just to drive; they need to be somewhere.

...is a perfectly valid reason to let them do their thing.

Yes, if a constant line of traffic is going past while you're indicating to change lanes, then they're being a bit dickish. But they've no legal obligation to let you out, and if you're only "driving to drive" and they actually need to be somewhere, then why not let them get somewhere?

I see it all the time when I'm doing long distances. Invariably, the person indicating to change lanes doesn't really need to change lanes. But they'll join the busier, faster one anyway, and the very first thing that does - whether they've been let into the faster lane or simply pushed their way in - is slow down the hundreds of cars lined up behind. Everyone brakes a little more than the last car and traffic a mile back eventually comes to a total halt.

I accept this may not really happen as much in the U.S. outside of cities (every major interstate I traveled on tended to be pretty empty) but it's indicative of it just being better sometimes to let people do their own thing.

That, and it's still a bit of a dick move having your rear washer aimed at cars behind. Being petulant just makes you part of the problem of bad driving, not part of the solution.

 

[Moglet]

I've done it on the RSX. My sprayer's mounted on the roof, since my window's at such an angle, so I've just aimed it to spray straight out. Jerks won't let me over when I have my signal on, so I let myself over and spray them!

So you force your way in to traffic in a gap that's clearly not big enough or you wouldn't have to 'let yourself over', and then you decide to obscure their vision because you didn't like the fact that they didn't let you in when they weren't obligated to?

If everyone drove that way we'd all be dead.

 

[YSSMAN]

TL;DR - You're more likely to get a dirty or waterlogged rear window in a sedan than a fastback. Which is odd, since sedans so rarely have wipers to correct it.

My Celica has the window wiper and has decent enough aerodynamics to rarely need it. When I do use it, its mostly because the rear window is covered with pollen or dust, and the rain/mist that is on it has made it incredibly difficult to see out of. I don't know how I lived when I had my Jetta, who's rear window was always filthy.

I'm always surprised by how freaked out people are in my car when I used it. Instantly its a "what's that noise? what's on the rear window?" like they've never seen a wiper before.

If I ever move up to a newer car, I'm going to miss that little attachment.

 

[Harry6784]

They even brought it up on Top Gear once, that Americans never let other drivers over. I see it all the time, a car ahead of me has their signal on when they're a bit in front of the car next to them, and that other car speeds up like they're more important. The same idiots pull into the empty lane at a red light only to not take off any faster than the person that was originally in front of them.

The only time I actually try to not let people in are these guys:

 

[CyborgGT]

^ I can agree with that. It's fun to annoy ass**** drivers.

Misunderstood. In that instance, I wasn't 'out for a drive.' I was trying to get somewhere. I'm not that type that weaves through traffic trying to get ahead of everyone else. I actually very rarely do something like that said maneuver; I could probably count the instances on one hand in my seven years of driving. I like to get up to the speed limit quickly (still far from what a cop would probably call an "exhibition of speed"), but otherwise my friends say I drive like a grandpa when there's traffic; I hate cutting people off. My point was that if you see that someone is signaling to get over, it's not a matter of whether they have the "right" to get over (that sounds like a serious problem, if what's on your mind when you see a turn signal is deciding whether or not someone "has the right" to go somewhere), but it's a matter of assuming that maybe they need that lane because their turn is coming up soon. Why not be courteous and let them? All it takes is easing off the throttle.

Everyone, sorry for the off-topicness.

My only guess regarding American-market cars not having wipers while their Japanese counterparts do is an aesthetic thing. Like how pointlessly large, useless-for-offroading, gas-guzzling SUVs are so popular for doing the grocery run while station wagons are pretty much non-existent here.