The OEM tyre choice will usually have a speed rating of more than the rated top speed of the car, as per the spec sheet of the car.
BHPian prash2606 recently shared this with other enthusiasts.
Hello BHPians,
This is my first post and it comes with a curiosity for which I believe I couldn’t find an answer in the posts. Please pardon me if a response already exists.
Query: At times I’ve observed that the top speed mentioned on the car speedo meter is northwards of 180kmph even in a hatch back or a <10lacs sedan, however, the tyres provided by manufacturer may not be a suitable match for those speeds, even though the car is not capable to climb up to those theoretical speeds mentioned on the meter. Has anyone come across such scenarios on any make/model and if yes, then can we legally pull up the dealer/manufacturer to provide the tyres more suitable for such acclaimed theoretical speeds?
Here’s what BHPian Amrik Singh had to say on the matter:
Suitability or adaptability of tyres cannot be related to the car only. Another factor is the road and temperature. The road surfaces are of different types. The manufacturers test their products on their own tracks which are not exactly the same elsewhere. So any attempt to hold them liable for this anomaly will probably fall flat.
Here’s what BHPian Dr.AD had to say on the matter:
The top speed marked on the speedometer has no meaning. That is not the top speed of the car. Forget the tyre speed rating, the car itself is often not capable of reaching that speed. The car manufacturer does not even claim that the car will reach that speed. They provide car’s rated top speed in the spec sheet, which is often a number much below the top marking in the speedometer dial.
The OEM tyre choice will usually have a speed rating of more than the rated top speed of the car, as per the spec sheet of the car. And thus, there is nothing wrong with this practice. The top number on the speedometer has no bearing on this equation, and has no meaning as such.
Here’s what BHPian Jeroen had to say on the matter:
Other members have already explained how this works. Cars just don’t reach the maximum speed of the speedometer. But they do have a maximum speed obviously. And it would be safe practice to have tyres fitted that are suitable for that speed.
Whether that is a legal requirement in India I don’t know, I am sure other members will chip in. In some countries it is a legal requirement in some it is not.
In my home country it isn’t anymore. We did away with that requirement many years ago. So my Jaguar can do speeds in excess of 265 Km /h. So I like to have the appropriate speed rated tires, just because occasionally I have been known to hit that speed on the German Autobahn.
I am not sure why the Dutch government did away with this rule. I am a liberal at heart, so the less rules and regulation and keeping people responsible for their own actions is great. But most people would not have a clue there is even such a thing as a speed rating for their tires. Ensuring with a simple rule/law that the speed rating of the tires need to match the car maximum speed seemsvery simple and straightforward to me. Almost impossible to make mistakes.
But I could fit much lower speed rated tires and save myself an awful lot of money. Up to my own discretion and responsibility. I do know that certain insurers require the speed rating of the tires fitted to match the maximum speed of the vehicle. Usually, on super cars and so on.
Irrespective it is advisable to have all four tires the same speed rating. If you have two sets with a different speed rating, put the ones with the lowest rating on the front wheels. That will ensure you will have the best grip on the rear wheels.
Here’s what BHPisn Sankar had to say on the matter:
The car manufacturer always fit a tyre with a speed rating that is rated for the maximum speed vehicle is capable of doing (not the speedometer max value).
For eg:
- Most Maruti Suzuki 1.2K engine cars will do a true top speed of 175KPH, the Apollo tyres fitted as OE are T rated which is good for 190KPH. The numbers printed on the speedometer may go beyond 200 but it is irrelevant.
- Innova Crysta will do a true top speed of 180KPH and the bridgestone tyres fitted as OE are H rated which is good for 210KPH. Highest value on the speedometer is 200.
For any new car you can find out its manufacturer specified true top speed (from the specifications or other sources) and find the speed rating of the OE fitted tyre (which is usually there on the tyre itself – T, H, V, W etc) and check if they are under or over rated for the speeds capable. Don’t go by max numbers displayed on the speedometer and compare that to the OE tyre its pointless.
Keyword: Differences: Maximum speed rating of OEM tyres vs the car's top speed