Question 'N' Auto

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S. Muralidhar

What is antisubmarine seat? What does it prevent and what does it protect the driver from? Do the angle of the seat and the backrest have anything to do with it? Is its availability in a car be identified by merely by looking at the seats? Do entry-level `B' segment cars in India have them?

V. S. Rajagopalan

Antisubmarine seats are of special design and construction that include an extra thick front squab to protect the driver and passenger in the event of a collision. The so-called `submarining' effect is demonstrated when during a collision at high speed or sudden brake situation, the effect of inertia drags the driver and he slides down the seat and into the well of the car under the dashboard. The laws of motion at work here could cause injury or prove fatal to the driver and/or passenger because even as he is being dragged forward, the car's chassis, engine and body panels themselves intrude into the car's passenger cabin as a result of the head-on collision.

Antisubmarine seats help avoid this eventuality by preventing the driver and passenger from sliding forward. There is no connection to the angle of the seat or backrest, but of course there is only a certain range within which the `antisubmarining' effect will be most effective. Antisubmarine seats are much more essential for front-seat passengers than for rear occupants.

Several B-segment cars have antisubmarine seats. However, it may not necessarily be evident from the looks of the seat alone. Bucket seats with adequate lumbar and thigh support are primary requirements for getting the best antisubmarine effect; higher-end sedans also offer well-supported rear bench seats.

I recently bought a 2003 model automatic transmission Hyundai Santro. The previous owner had clocked about 13,000 km and the car overall seems to be in a good condition. It came fitted with alloy wheels, which were shod with 13 R165 tubeless Pirelli tyres. I drove it with the 2.1 kg/cm2 recommended tyre pressure. But the ride was very rough.

I reduced the pressure to 1.8 kg/cm2 (26 psi), and the ride is now comfortable under the same driving and road conditions. Is it true that tubeless tyres are to be inflated to a lower pressure than recommended? When I drive it on the expressway, what pressure should I maintain to ensure that I do not compromise on comfort and safety?

Mohan Chitale

Tubeless tyres too need to be inflated to the recommended pressure level for optimum performance and to ensure that their operating life is not shortened due to uneven wear.

Tubeless tyres are also used with after market rubber tubes and inflated to lower pressure levels. This, it is felt, will help get the best in terms of ride quality from these relatively new technology tyres. This is definitely not recommended and, in most cases, the problem lies elsewhere in the car.

Tubeless tyres are more efficient and safer simply because tyre pressure does not drop suddenly in the event of a puncture. A rapid fall in tyre pressure at high speeds can lead to loss of control.

Tubeless tyres are also easier to maintain, but they need to be attended to by well-equipped mechanics; it may not be advisable to trust the roadside mechanic. Tubeless tyres do their job better when they are shod on to alloy wheels, which tend to be dimensionally more accurate and sturdier.

In your case, the real culprit for the poor ride quality could well be the suspension or the fact that the car is overdue for wheel balancing and alignment. Unbalanced wheels can damage the suspension components in the long run and amplify the effect of even minor undulations on the road. So, the ride, especially in the rear, could get pretty rough. It is also possible that the tubeless tyres that your Santro came with are low profile ones.

To improve your ride may try any or all of these: - changing over to taller profile tyres, checking wheel alignment and balancing and examining suspension components for possible damage. Lowering the tyre pressure may only lead to higher than normal tyre wear and may also end up weakening the tyre wall over time.

I am shopping for a scooter for my sister. I am unable to decide from among the Kinetic Nova 135, Honda Activa/Dio and the Bajaj Wave. My sister will be using it mostly to go to college and for the occasional jaunt in the city . My final decision will be taken after considering aspects such as fuel efficiency, service quality, value for money features, and so on.

Jijoy Abraham Verghese

From the list, our candidates would be the Honda Activa and the Bajaj Wave (not necessarily in that order though). The Activa has built a reputation of being a practical two-wheeler for both older adults and the college-goer. It is practical, sturdy and enjoys a relatively better resale value compared to the other scooterettes in the `variomatic' category.

But the Bajaj Wave DTS-i, which was launched a couple of months back, is fast catching up with the Activa in terms of popularity. That has been possible for Bajaj after the Wave, the erstwhile Safire, was relaunched with the company's now tested and effective engine technologies digital twin spark ignition and ExhausTEC.

The new Wave has a better finish and is more powerful and fuel-efficient than its predecessor. The Wave also manages to pack in about one bhp more power than the Activa, though its engine is only about 7cc more than the Honda Scooterettes' 102cc engine. In the long run, the Wave should also be able to offer a slightly better fuel-efficiency ( 45-50 kmpl) than the Activa (40-45 kmpl) in city riding conditions.

(This article was published in the Business Line print edition dated September 25, 2005)
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