For a long time, many consumers who pursue the need for passability on bad roads have paid great attention to the "chassis height" of the car, or in professional terms, "ground clearance". It seems that the chassis is high, That is to say, the high ground clearance means that the passability is good enough.

On this point, whether from the perspective of subjective perception or objective actual evidence, there are many things that can explain the problem. For example, the Honda Fit, which has been criticized for its poor performance, has the official minimum distance. The ground clearance is only 105mm, which is a little more than 10 centimeters. For hardcore off-road vehicles, even the Mitsubishi Pajero without a frame has a minimum ground clearance of 235mm, or 23.5 centimeters, which is more than twice that of the Fit. Naturally, there is no need to worry about backing up...

However, judging from the "rural cross-country" trip that Calabash Man took during the Spring Festival, ground clearance is really not the only absolute guarantee of passing ability. After all, in After driving my own urban SUV with low ground clearance and my drunken relative's car with high ground clearance on the same unpaved road with potholes and mud, the final outcome was that the former was safe and sound throughout the entire journey, while the latter kept hitting bottom all the way." Bang bang bang”.

The picture above is the chassis of Huluxia's own model. The picture is from the Internet, but it is enough to see the lowest point of the chassis. The position of the lower swing arm of the front suspension is the lowest point of the chassis. The official data is the lowest 149.5 mm, less than 15 centimeters; and the picture below is of a relative’s car with a high ground clearance. The official data is a minimum of 165mm, which is 16.5 centimeters, which is more than 1 centimeter higher than Huluxia’s own urban SUV, and to the naked eye Look, it's really not low to the ground.

It’s very interesting that the car with a higher minimum ground clearance was undermining, but the SUV with a lower ground clearance was unscathed.

In fact, friends who know cars must already know what Calabash Man is going to say, which is nothing more than three parameters: "approach angle, departure angle and longitudinal breakover angle".

The most important series of indicators for passability

In fact, it is indeed the combination of these three parameters and the ground clearance that forms the basis of the physical indicators of vehicle chassis passing.

The approach angle is mainly affected by the length of the vehicle's front overhang. The longer the front overhang, the smaller the approach angle. When approaching an obstacle, the front bumper is more likely to bottom out and collide; of course, the front overhang is On the basis of the same length, a high ground clearance will increase the approach angle, and the two complement each other.

Same principle, the departure angle on the butt of the car is affected by the length of the rear overhang. The longer the rear overhang, the smaller the departure angle. At the end of a downhill slope or at the beginning of a steep slope, the rear bumper becomes wider. It is easy to hit the bottom; and the ground clearance is also related to this.

As for the longitudinal passing angle, it is directly linked to the wheelbase. On the basis of the same ground clearance, a car with a longer wheelbase has poorer longitudinal passing ability and is easier to support the mid-chassis; so when driving off-road There has always been a famous saying in the industry, "It is better to have less wheelbase than to have more locks." For example, the two-door Wrangler is more powerful than the four-door Wrangler, and the Jimny with a short axle to the extreme is even invincible, etc. It is enough to show the impact of angle on passability. Influence.

To illustrate with intuitive data, comparing the two cars mentioned above, Huluxia’s urban SUV has very short front and rear overhangs, which has significant advantages over sedans. At the same time, this SUV? The 2460mm wheelbase is also shorter than the 2580mm wheelbase of that sedan. Although the chassis ground clearance is more than 1 centimeter behind, it has overall better chassis passability parameters, and naturally it is less likely to bottom out.

Of course, if you think this article is over, then Calabash Man himself feels sorry for the audience. In fact, after driving the car at that time, Calabash Man spent time studying this problem and found the problem In fact, it is more than just "three angles".

The lowest point of the chassis does not represent the overall chassis height

In fact, when we were discussing the passing ability of the chassis alone, there was another detail that was almost forgotten by everyone, "the official minimum Ground clearance ≠ average height of the chassis from the ground."

It seems a bit convoluted, right? Let’s go back to the picture just now. For an SUV with a height of 149.5mm from the ground, the lowest point visible to the naked eye is the lower swing arm of the front suspension, but this position is movable. And the lowest point will move with the movement of the front wheel in the vertical direction. For example, when the front wheel presses on a relatively high place, the lowest point will actually be raised. Moreover, this lowest point is very close to the tire position, as long as the front wheel presses on a relatively high place. The tires can be pressed to a high position, and the lowest point will naturally not touch the ground;

In addition, from the naked eye, the lowest height of other parts of this SUV chassis is far away It is 149.5mm higher than the lowest point of the lower swing arm. Visual inspection is basically upwards from 180mm. In other words, although the official data is 149.5mm, other parts of the chassis, including the oil pan, three-way catalytic converter, bottom side beam, etc. The average minimum ground clearance is definitely much higher than 149.5mm.

The car chassis is another matter. Although the official data is a minimum of 165mm, judging from the picture, this minimum ground clearance is basically equal to the average ground clearance of the chassis, and its chassis is flat. The height is higher than that of an SUV, that is, including three-way catalysis and other components, it is basically the same height. Indeed, the official minimum is 165mm, but overall it is not higher. In other words, if the ground obstacle really reaches 165mm, then the support of this car will be inevitable.

Of course, the two cars may not be convincing enough. In fact, you can search for chassis pictures of more models on the Internet to compare. Although the official ground clearance of many urban SUVs is not ideal, Basically consistent with this conclusion, the average ground height of its chassis components is higher than the minimum ground clearance. In actual driving, as long as you avoid the risk of bottoming out at the lowest point, the other parts are basically safe; as for cars, It is said that the chassis is smoother and the minimum ground clearance has greater guiding significance. The advantages of driving on paved roads are low wind resistance and low fuel consumption, but the disadvantage is that the risk of bottoming out on non-paved roads is greater, and bottoming out is The subsequent losses were even greater.

So in conclusion, the minimum ground clearance is indeed not everything about passability. When actually driving, car owners are asked to know the significance of approach angle, departure angle and longitudinal breakover angle; at the same time, for car owners For example, even if your chassis has a high ground clearance, you still have to be careful. After all, your car is not an SUV, nor is it a hard-core off-road vehicle. If the potholes on the ground exceed the minimum ground clearance, don't try too hard.

This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.