For years, I have been driving cars and a lot of it on highways. To me the most important element which decides the safety of the passengers are tyres. Those 4 rubber donuts are what keeps us on ground.
It is very important to select the right tyres for your car.
IMPORTANT: STICK TO THE FACTORY SPECIFICATIONS OF TYRES UNLESS YOU VERY WELL KNOW WHAT YOU ARE GETTING INTO
Agree. The company spec tyres are mostly a compromise based on factors such as:
- Fuel efficiency 2. Weight of the automobile 3. Class of car(Commercial \ Personal \ Premium \ Segment A\B\C etc.) 4. Looks & Road Grip 5. impact of other safety features such as ABS, EBD, Traction control etc
Yes. Road grip is not the foremost priority for automobile manufacturers. Please do not blame them. It is us who demanded cheaper automobiles over safe vehicles, which influenced such a manufacturing pattern.
Now on selection of tyres. To select a tyre we need to know what different parameters are to be considered.
For example: 175/65 R14 T84 or similar is what we get to see on tyre walls. What is this?
175= Tyre width
65 = sidewall profile: the measurement between the tyre’s contact area with ground and the wheel rim
R = Radial construction. Most tyres are radials these days which is a better technology than cross ply(old Ambi \ Premier car tyres)
14 = Wheel Rim size. 14inch wheels. Some reference: Maruti 800 \ Eon used 12" rim, WagonR uses 13 inch rim, Ford Figo uses 14 inch etc
T = Max speed rating. E.g., S 180km/h; T 190km/h; U 200km/h; H 210km/h; V 240km/h
84 = Load rating. Max load permissible per tyre. E.g, 84= 500kg per tyre. 85= 515kg per tyre etc
Now that we learnt what these ratings are, let us discuss about tyre compound.
Tyre compounds commonly found for regular use are hard, medium and soft rubber based.
The modern day cross polymer tyres have as less as 10% natural rubber. The polymers include natural and synthetic polyisoprene, polybutadiene along with with reinforcing fillers(carbon black or silica), sulfur(the crosslinking agent), antioxidants and processing oils. Okay so much of technical stuff. What does this mean. The ratio of these compounds determine the hardness of a tyre.
Hard tyre= longer tyre life by minimal tyre wear, fewer punctures while hitting sharp rocks etc. But they offer less grip in wet or winters.
Soft tyre = Superior wet\winter grip, better initial pickup etc. But they wear off pretty soon and are more prone to get punctured(towards the last few mm of tread thickness)
Medium = Best compromise between longer tyre life(than soft rubber) and better grip(than hard rubber)
Simple, for Indian road conditions Medium hard rubber tyres are the best. However, discretion is requested basis the vehicle you drive. E.g., If you own a Mahindra MM540 jeep for travelling on rocky\off road terrain, a medium hard rubber may not be best. For most city driven vehicles, the medium hard rubber is good.
Which brand: Almost all brands sell medium rubber based tyres. However there are few brands which still could not find the perfect medium hard tyres for India. E.g., MRF tyres are harder than Michelin.
Other critical facts :
a. Tubeless or tubed: Tubeless tyres have better thermal efficiency than tubed tyres. They can be driven even with small punctures without damaging the tyres much. They are easy to repair too. However, once if you have extremely large punctures, getting a tube inside the tubeless tyre will help you take your car back home(make sure to replace the tyre soon as possible with a fresh tyre). Also, tubeless tyres do not bulge or burst as much as tubed tyres do.
b. Tyre upsizing: If you are increasing the tyre width(say from 175 to 185) essentially the tyre width will increase, thus providing better grip and a small increment in ground clearance of the vehicle. However, this put more pressure on the wheel bearings and reduce the fuel efficiency. Normal 10mm increment in tyre width is okay with most manufacturers. However, extreme upgrades will void manufacturer warranty and sometimes even insurance claims.
A lot of new age hatchbacks in India(Polo\Figo etc) have low ground clearance. Suggestion is to increase the sidewall profile from 65 to 70 or move from 175\65 to 185\65 tyres. Thus you need not change the wheel rims and will improve the ground clearance at cost of slightly decreased fuel mileage. Also, this means that the speedo readings too will vary.
c. Tyre noise: Another important aspect to look for is tyre noise. The tread pattern on the tyres affect the tyre noise, especially when cars cross 80kmph speeds. Note that hardness of tyres generally have no impact on tyre noise. The width and tyre pattern are the factors here.
d. Alloy wheels: The lighter wheels help in better fuel efficiency, acceleration and also helps in keeping the tyres cool during longer highway runs when cars generally do in excess of 90kmph. Alloys have better thermal conduction, thus taking off the excess heat better than steel wheels. Alloys are better for faster cornering too. However, they tend to crack during big impacts, where as steel wheels will bend, which could be repaired.
e. Normal or Nitrogen: Nitrogen is best for places like Chennai where temperature is quite high throughout the year or to places like Rajasthan where temperature varies heavily between day and night since it expand less in comparison with oxygen. Thus N2 not lead to tyre bursts on hot highway runs. However, normal tyres can withstand almost 25% more air pressure than what we normally fill in. To reach such high pressures, the car need to run full load for extremely long duration on hot asphalt. Nitrogen permeation(leaks) thru rims are also marginally less than normal air. Nitrogen is non-combustible and does not trigger corrosion of rims. If you fill nitrogen(my car tyres do have nitrogen) and unfortunately get a puncture, the puncture shop guy may not have nitrogen with him. This means that I need to bring it back to a tyre shop and purge the normal air off to refill with nitrogen. Not quite worth the effort. Conclusion: Unless you own an aircraft, it is okay to run tyres with normal air.
Always maintain the tyre pressure prescribed by your car manufacturer for best mechanical, braking, grip, fuel efficiency and comfortable journeys
f. Treadwear: It is very important to replace tyres at the proper time to avoid damage to your vehicle and life. Though the tyres can run with moderate grip until the last 1.5mm of tread, it is suggested to replace them at 3mm itself. A couple of thousand kms less on your old tyres could mean safer drive for us.
Hope this write-up addressed most of your tyre related questions. Else pls ask in the comments section.
Have a safe journey!