Not long ago, Dongfeng Citroen officially launched an epoch-making new car - Versailles C5 X, we have also pushed articles before to talk about this car. But what we're going to talk about today is not the car itself, but one of the points of contention on it – the width of the tires.
How many width tires should a car use to fit? What dimensions do manufacturers consider when matching tire widths to vehicles? What performance does tire width affect on the vehicle? Let's dissect these problems this time.
First of all, the discussion of this article is aimed at the impact of tire width on the vehicle, according to the principle of a single variable, it will set the tire for the same brand of the same series or even the same diameter, the same tire pressure, the same tire wall thickness (although the tire wall thickness is based on the tire width by flat ratio, objectively can not be completely unified, but this is a theoretical analysis, we can assume its unity), and the impact effect on the same model as a prerequisite.
What does tire width serve?
The question is simple, 99% of people can answer it with their eyes closed: the wider the tire, the better the grip. On some rear-drive models with large horsepower, manufacturers will match the front narrow rear wide tire combination, which is commonly known as "front and rear matching", in order to give the drive shaft better traction.
I wondered about this myself, because my Alfa Romeo Giulia had 280 horsepower, but the standard tires were only 225 widths on the front and rear, which was the same width as my last car, the Artez, but the Artez only had 192 horsepower. This also resulted in my inability to accelerate at full force in gear 1 when the ground adhesion was poor (the electronic system would limit the output when it detected slippage), and to increase to 2 gear to get stronger acceleration.
I've also been wondering if changing to a set of tyres of the same width but with better grip can significantly improve this problem, such as the Michelin PS4, or change it to a front-and-rear combination, because the Giulia car officially has a front-and-rear option of the front-and-rear 255. But then I had to buy a new set of rims, which was a lot of trouble for me, who advocated the original factory (the point is that this car is difficult to match with a style that is both good-looking and applicable and reliable except for Alfa Romeo's iconic petal rims).
▲ After the Giulia 280 was equipped with an optional 19-inch rim, the tires were replaced by "front and rear matching", and the rear wheel width was 255
In the manufacturer's original tire width program, there is a "famous scene" like existence - Audi RS 3 provides a front wide and rear narrow tire collocation, the previous generation of models sold in China is the front 255 after 235, and the new generation of overseas models is the front 265 and the back 245.
This inevitably reminds us of the title of Audi's "push head king", although most of them are from some "folk masters", but Audi officials probably hope to increase the grip of the front end of the RS 3 in such a simple and rough way to the RS 3, a high-horsepower performance car based on the front-drive platform, and also allow the rear of the vehicle to show relatively active characteristics.
These examples all illustrate the positive correlation between tire width and grip, but if you've seen some rally footage, you might be confused again. When running a rally in the snow, why did the car change to a tire that was as narrow as noodles?
This tire is not another tire, the snow tire used in rally racing is specially made, and there are many nails on the tread, which is commonly known as the nail tire. Nail tyres cannot be driven on a conventional road surface, and the staple tires are completely different from the conventional tires in the way they provide grip, which is already out of the premise we just talked about, so it is not within the scope of what we are discussing today.
We will also find that some SUVs or models with larger curb weight will use wider tires, which is also because heavier cars need more grip when accelerating, steering or braking. It can be explained with junior high school physics knowledge, F=ma.
So the wider the tire, the better?
The wider the tire, the more grip it does provide, but it definitely does not mean that the wider the tire, the better, because when the tire is widened, it will also bring some negative effects.
The first is energy consumption, the tire provides grip at the same time, but also will produce rolling resistance, the wider the tire, the greater the rolling resistance, obviously, the extra resistance will bring additional fuel consumption. Nowadays, the world attaches great importance to the energy consumption level of automobiles, whether it is fuel vehicles or electric vehicles, all of which must be compared to energy consumption. Gasoline cars rack their brains in order to reduce emissions, and if electric vehicles can reduce drag from the source, they can get more mileage and reduce endurance anxiety.
You see the BMW i3, as BMW's extremely inferior work in the field of electric vehicles, madly used a tire with a width of only 155, so narrow that it was almost as narrow as a bicycle.
The underlying reason why rolling resistance affects energy consumption is that it "eats" some traction, which is called offsetting. Since it will counteract the traction, it means that the overall "power" of the vehicle will also be eaten, just like a plant that breathes all the time and consumes oxygen. When the traction force is much greater than the rolling resistance, we may not feel the presence of rolling resistance, but at higher speeds, the traction will be more obviously offset.
Secondly, the NVH of the vehicle will also change with the width of the tire, and the width of the tire is also not conducive to NVH.
Just like rolling resistance, the wider the tire, the larger the area of contact between the tire and the ground, and the larger the contact area, the more vibration and noise will naturally occur. Even when we stand on the side of the road and watch vehicles pass by at about the same speed, we will find that the road noise is especially those with fairly wide tires, such as luxury large SUVs such as the Land Rover Range Rover.
Let's go a little deeper and talk about it from the perspective of driving control. As the tire widens, the undersprung mass increases, and if the width increases to a certain value, the matching hub also needs to be widened accordingly.
The increase in the under-spring mass will also have an impact on the handling characteristics of the vehicle and the dynamics of the chassis. On the other hand, after the tire width is increased, the feel of the steering will also become slightly heavier, and for individual models, it may also destroy the excellent road sense feedback set by the original engineer.
Therefore, changing to wider tires may have an immediate effect on extreme performance, but it may also bring some potential "adverse reactions". We don't recommend blindly changing the tires of their vehicles wider in order to improve the grip, in contrast, we think it is better to replace the tires that provide better grip with the same size.
Although tires with better grip may also have subjects that they are not good at, such as noise, etc., but... Mainly considering that most car owners may be close to the time when it is time to change the tire, the vehicle needs to go online for annual inspection, and it is possible to be embarrassed if the tire size is inconsistent with the certificate of conformity.
So what's wrong with the tires of the Versailles C5 X?
After a brief analysis of the impact of tire width on the vehicle, let's go back and look at why the tires of the Versailles C5 X are controversial.
At present, the tire specifications of all Versailles models are the same, for 205/55 R19, from the perspective of 19-inch rim diameter, it is a very generous approach to such a car priced at 143,700 yuan ~ 186,700 yuan, which is a change from the style of Dongfeng PSA in the past. Looking at the width of the 205, the flat ratio of 55, and the diameter of the 19-inch rim, each of them also meets the positioning of the Versailles C5 X. But the problem is that combining these data is more awkward.
My last car, the Artez 2.5L, had a 225/45 R19 tire specification that was already an awkward presence that year, and the combination of 225 width and 19-inch inner diameter was very rare, and before the Artez, it basically only appeared on the front wheels of the high-end BMW 3 Series GT or Infiniti G37 Coupe. Although there are a little more models of this size than a few years ago, they are still not very friendly when it comes to changing tires. For example, the Michelin PS4S I changed, the price is as high as 2000 pieces, which is hundreds of times more expensive than the size of 245/40 R19.
Since the width of the 225 matches the inner diameter of 19 inches is already considered "strange", then the Versailles C5 X's 205 width with 19 inches is even more incredible, and even once on a tiger APP, such specifications could not be found at all. It is expected that in a short period of time, it is difficult for other tire brands to launch this specification of tires for the owners of versailles C5 X to replace, fortunately, the Versailles C5 X original matching tire brand series is Goodyear Royal Ride, the comprehensive quality is not bad. However, even if it is the original tire, it may not be easy to buy in the tire shop outside, and the cost of tire replacement in the 4S store may be relatively high.
▲The owner of the BYD Tang high-end version calls the insider directly!
Of course, we do not advocate that everyone deny the Versailles C5 X car because of this tire specification problem, after all, the product force of a car is composed of many aspects. What's more, as we just said, the benefits of tire width and width, narrow and narrow considerations, after all, is a matter of choice and trade-off.
What car are you driving in front of the screen? Do you think your tires are wide enough?
Issue 1815
Author: Chen Houze