Rainwater accumulation due to lack of a rear wiper in CSUVs

In models like the XM variant of the Tata Nexon, there is a rear spoiler, however, the car does not come with a rear wiper.

BHPian NovemberKing_91 recently shared this with other enthusiasts.

Problem Statement: Water accumulation on the rear windshield of CSUV like Tata Nexon during rain.

In the CSUV Tata Nexon and similar vehicles, in the absence of a rear windshield wiper, during rains, water accumulates on the rear windshield. While it is not critical to driving successfully, having a clear rear windshield is an advantage.

Explanation of the problem and possible solution

An example of a CSUV from Skoda, shows that the rear windshield has very little airflow to take away the water that may have accumulated there due to rain. The spoiler, while making the airflow smoother and providing downforce, also ensures a near-vacuum is created in the wake of the car.

Another image of a similar shaped car from Ford, shows the air velocity in different parts of the car. Our focus is on the blue area, immediately behind the car. Since there is minimum airflow over the car’s rear surface, water accumulation on the rear windshield is possible. For this reason, most of the hatchbacks come with a rear wiper.

In models such as the XM variant of Tata Nexon, the rear spoiler exists, but not the rear wiper. This ensures that there is neither airflow over the rear windshield, nor is there a means of effective removal of water accumulation during rains. This problem must be addressed.

The solution can be simple, to make the rear wiper standard across all models, or, to remove the spoiler, so that some air flows over the rear windshield. In the market, which is all but saturated with compact SUVs and visual appearance plays an important role in customer’s choice, removal of spoiler is not an option; while the addition of a rear wiper assembly, drives up the cost, which is not desirable too. So, a third option must be considered.

A spoiler, which is built in such a manner that, while maintaining the utility in terms of providing the necessary downforce, also allows for a stream of air to be pushed down the surface of the rear windshield. This should allow the water to be removed from the rear glass while ensuring that the cosmetics are maintained. An example may be as seen below in the case of the Porsche Cayenne.

In the absence of a wind tunnel or the skills to model the aerodynamic flow on my own, I request the learned designers to possibly give the idea a thought. The problem exists and the solution should be made available. Modification to the spoiler would not be a costly proposition but it will help the common man solve an inconvenience.

I hope the above article finds its way to the right people and this issue is solved. If someone explains to me why this cannot be done, guess that would satisfy the curiosity too, but then, there has to be a solution for sure.

Here's what BHPian VW2010 had to say about the matter:

Rear spoiler is not meant for deflecting wind back to the car and doing so can only cause poor efficiency and performance. Is it possible? Let me say yes for the sake of a non zero probability. Will it help with removing water at those speeds, I will take a calculated bet that it won't.

Nothing beats the rear wiper.

On such a rainy drive I have never once used the rear windshield, as my eyes are fixated on what is in front of me. The visibility at the front is already low in a moving car against the rain that side mirrors are the next best-used part of the car.

Here's what BHPian shancz had to say about the matter:

Just get the model with the wiper which sadly is nearing the top models since most of the car buyers don't use it or even know how to use it.

Don't think the Porsche example was using the spoiler to generate anything but downforce but I could be wrong.

As for your problem getting a rain repellant like Glaco before monsoons will help a bit but it cannot replace the utility of the wiper.

If it's just a matter of cost, get the wiper fitted. I would be more concerned about how much of the factory stuff will be opened to run the wiring, piping and attachments.

Here's what BHPian sushantk had to say about the matter:

I consider the rear wiper as a safety feature and totally endorse the view of making it mandatory on all cars. I use it regularly and find it very helpful especially in traffic.

I have seen people keeping banners and pillows and what not blocking the view of IRVM. I feel so much discomfort by looking at such cars being driven. A car without a rear wiper in rain is somewhat the same.

Check out BHPian comments for more insights and information.