Take care of your Tyres

A recent study in the UK revealed that over 40% of its motorists badly neglected their tyres – knowing fully well that their lives depended on them !

So let’s explore the various pro’s and con’s of elementary tyre care that every motorist should ensure without fail – lest it costs him dearly. We’ll do it in 2-parts so that it doesn’t tax the readers’ patience much !!
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I) ARE TYRES TURNING KILLERS IN CAR CRASHES?

The Economic Times carried an Article some times back on this issue, asking its readers what they thought caused the spate of road accidents involving
deaths of some high profile personalities like WorldTel chief Mark Mascarenhas,
stock broker Nirmal Bang and Priyanka Gandhi's sister-in-law Michelle Vadra?

Poor quality of tyres, according to one theory that is hard to dismiss.

Pune-based Rajshree Parmar Memorial Foundation, which has studied accidents occurring on the Mumbai-Pune Expressway, holds tyre manufacturers responsible for accidents involving tyre bursts.

Their findings state that "Between January 1 and December 31, 2001, there were a total of 340 accidents on the MPE leading to 85 deaths and over 1,000 injuries, out of which 50 per cent were caused by tyre bursts."

Which means the quality of tyres currently available in the Indian market is
simply unsuitable for high speeds that the new generation of cars can achieve
on expressways like the MPE, the Delhi-Jaipur highway or the Delhi-Agra highway.

The friction generated by high speeds causes overheating of tyres, leading
to tyre bursts. And the friction is much higher on concrete surfaces.

This theory is vehemently opposed by the domestic tyre manufacturers. The Secretary General of the Automotive Tyres Manufacturers Association of India states that "All Indian tyres meet European standards and the norms set by the Bureau of Indian Standards."

J K Tyres is more specific. They state that "While cross ply nylon tyres are rated for speeds up to 135 km/hr, the other nylon tyres are rated for speed of up to 160 km/hr. And passenger car radials are rated for speed of up to 180 km/hr."

Tyre Manufacturers squarely blame poor maintenance of tyres – particularly their recommended ‘cold’ inflation pressures - and the unregulated import of tyres for tyre bursts.

However, Parmar Foundation counters this by arguing that, "These speed ratings might work on regular asphalt roads but on the concrete roads like the Mumbai-Pune expressway, the outer layer or tyre soles starts peeling off at sustained speeds of over 80-90 km/hour. In Europe and the US, tyre manufactures use 70 per cent synthetic rubber and 30 per cent natural rubber, but in India this ratio is reverse. Synthetic rubber increases the durability and speed endurance of tyres".

On the other hand, "Both the tyres and the vehicle involved in the accident leading to the death of Mascarenhas were foreign," says the marketing director of MRF Tyres.

So where does it leave the hapless motorist ?

(II) On Maintaining and choosing Replacement Tyres

In my practice, I often come across queries such as -
“Which tyres would you recommend for my Maruti Esteem car? My driving is mainly in the city with occasional trips to Pune & Panchgani”.
And my standard response to them is -
I'm glad you asked such a Q, as most Motorists are blissfully unaware of the crucial role the Tyres play in the overall satisfactory performance of a car, including fuel efficiency - assuming all other parameters are in their proper places.

For your kind of duty, I'd recommend that you stick to the OE Specs i.e.
"155/80-R13". Of the various brands available in the market, I find 'Bridgestone' a good value for money, from their Ride Quality AND 'Tread Noise' points of view.
'JK Ultima' is also quite good.

Besides, whatever be their make, you must also ensure the following :

1) That they are atleast "T" Rated - given 120 kmph+ sustained cruising speeds now afforded by most 'Express Ways'.

2) ALL the 5-wheels must be in good 'Dynamic Balance' all the time. It's a fallacy that the Rear/Spare ones need not be balanced.

3) Besides above, immediately after fitting a new Set, you must get a "4-Wheel Alignment" done at a reliable place, preferably having the 'Infrared' type of Computerised M/C - as opposed to the now obsolete 'String' Type. In normal course of usage, it's worthwhile to get the same redone every 10,000 km to get max pleasure/life out of one's Tyres.

4) Last but not the least, you should have your own good quality and easy to read 'Dial Type' TP Gauge (available at most Tyre/Accessories Shops) and never rely on the wayside ones. The TP's given on the DS/'B' Pillar Sticker are "When Cold". This means BEFORE you start Rolling. Since the latter is somewhat impractical, here's what you can do to overcome this :

a) Buy yourself a good foot pump or better still a Battery operated one, freely available at above shops for ~ Rs: 500/-, and do the exercise at home once a fortnight before you roll off. These can be carried in the Car all the time, as you never know when you may need them.

b) If not interested in (a), then inflate your tyres to "+10%" of the recommended pressure using your own gauge, if checking at a Wayside Facility, after having rolled a few kms to get there. This will more or less ensure that they are 'down' to the correct levels when cold, the next morning.

c) You should check/correct your tyre pressures once a week in a similar manner.

I hope the foregoing will be of interest and use to you and your friends for all times to come.

(End of Part-1)

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(III) TYRE CLEANING

There's more to cleaning tires than you might think. Exterior rubber fades, cracks and eventually loses its mechanical properties from exposure to ultraviolet (UV) light. This process is called photo-degradation. Tires should be cleaned occasionally to remove brake dust, road oils and grime and other contaminants that will cause a browning effect on the surface of the tire.

Chemicals and road pollution present another danger to synthetic and natural rubber products. Hastened by the effects of UV light, this environmental soup can cause dry rot and eventually sidewall failure on tires that are not regularly used.

Modern tire sidewalls have a coating that helps protect them from normal wear and tear. Problems arise when caustic wheel cleaners and other harsh chemicals that one tends to use remove this protective coating.

The first step to reclaiming the original tire luster is a proper cleaning. Choose an appropriate rubber cleaner or a mild, all-purpose cleaner/degreaser.
You can also use a soft scrub brush to maximize the effectiveness of your cleaner. Avoid brushes with very stiff bristles. They can scratch rubber as well as the nearby wheel.

The second step to restoring natural luster is the application of a high-quality rubber dressing. Choose one that's not too sticky or not apt to sling off on the car. If you can use your dressing on vinyl, then you can almost be sure it's a safe bet for the tires.

If you have washed or rinsed your tires, they should be dry before applying any such dressing. These dressings should be allowed to penetrate the rubber before wiping off the excess. Repeat this process periodically to maintain luster and prevent drying or cracking of the rubber.

Properly maintained rubber should have a rich, dark sheen and be smooth to the touch.

(IV) Speed vs Mileage

It’s a common knowledge that ‘mileage’ drops as speed increases and for the present day cars, ~ 60-80 mph is the most fuel-efficient cruising speed. Let’s see how exactly it works, taking a real life example –

Getting 21 kpl @ 60-70 kph and 18+ @ > 100 kph out of an Mpfi Zen is as good as it can be.

The variation experienced is quite normal, for it's a well known fact that wind resistance goes up with speed in a complex manner - starting with square of it and going up to the power of 4 - depending on its magnitude.

In other words, say at a cruising speed of 50 kph, 40% of the engine power may go towards over coming the rolling resistance and the remaining 60% to overcome the wind resistance. Assume it's 5 and 7.5 = 12.5 Bhp.

Further, assuming that the rolling resistance remains more or less constant beyond 50 kph, at 100 kph the engine will have to produce 5 + (7.5 x 4) = 35 Bhp. So as far as the engine is concerned, for 2x the speed, it has to produce 3x the power.

Therefore, in terms of 'Specific Fuel Consumption' defined as 'grams per Bhp per hr' - that's how the engine sees it - its FC stands to go up by 3x but then, at 2x the speed, it also has to run for half the time to cover the same distance - or effectively the FC stands to go up by 1.5x to cover the same distance. In other words, if it was doing say 25 kpl @ 50 kph, at 100 kph it stands to do ~ 17 kpl.

And mind you, the 'SFC' that we just talked about above also varies with the absolute Bhp demanded from it - coz an ICE's 'fuel efficiency' drops above and below its peak torque rpm.

Further, since an ICE's max rpm AND Bhp is limited, 59 Bhp in this case, it follows that at 100 kph, it's got only 59 - 35 = 24 Bhp left to propel it any faster and going by the above relationship, this will get used up by another 40 kph or so - leading to its top speed 'capability' of ~ 140 kph.

To sum-up, to get the best 'FE' (as opposed to absolute Fuel Consumption/kpl) out of your Car, cruise as close to its peak torque rpm as practicable.

(End of Part-2)