Why some low-slung cars can handle bad roads better

It’s not always a factor of ground clearance alone that accounts for a car’s ability to handle bad roads. True, cars with higher ground clearance have a better chance of negotiating speed breakers and potholes, but in some cases there are cars with lower ground clearance that are better off as well.

The recent Union Budget has put the spotlight on ground clearance of cars as it’s one of the three factors that determine if a car should be taxed at 30% excise duty or not. The government’s definition of a vehicle that qualifies to be taxed at 30% excise duty instead of 24% – are vehicles which are more than 4 metres in length, have an engine capacity of over 1,500 cc (whether petrol or diesel) and should have ground clearance of over 170 mm. In Finance Minister Chidambaram’s words, vehicles meeting all three criteria are SUVs. Also read: Hatchbacks for rough roads

By this definition a Honda Civic should be a car that should easily handle bad roads, as it comes under the big, bad SUV tax definition. It has 170 mm of ground clearance, it is 4,545 mm in length and has a 1.8 litre petrol engine. Yet, it is one of the poorest when it comes to bad roads and is notorious for scrapping its underbelly. In contrast, take a Maruti Alto – a diminutive car at only 3,395 mm in length, engine capacity of only 800 cc and ground clearance of 160 mm. Yet, it is the highest selling car in India, and especially if you look at rural India, it’s one of the most common cars around, happily negotiating potholed roads and mud tracks, and unfazed by city speed breakers. (The Alto also attracts only 12% excise duty because it qualifies as a small car.) Also read: Budget impact: SUVs become more expensive

What makes the Maruti Alto with lesser ground clearance better to handle bad roads compared to a Honda Civic? The answer is in two factors – the wheelbase of the car and the nature of the suspension.

A Honda Civic has quite a long wheelbase of 2,700 mm, which accounts for ample cabin space and a comfortable ride. But this long wheelbase is also its undoing, as it reduces the “breakover angle” of the car. This means that once the front wheels of the car go over an over-sized speed breaker, it takes a while before the rear wheels encounter the speed breaker, at which point, if the height of the speed breaker is anywhere above 150 mm it will hit the centre of the car. This has also got to do with the fact that the Civic has a soft suspension tuned for comfort and tends to “sit down” when loaded. Once the front wheels cross the speed breaker, the car dips to absorb the impact, with the suspension compressing at least 20 mm, and because of that it scrapes its bottom. Also read: Big and tough premium hatchbacks for rough roads

With a Maruti Alto, the wheelbase is only 2,360 mm, which means that the rear wheels encounter the speed breaker much earlier, before the chassis has a chance to touch. Also the Alto has a fairly stiff suspension, which doesn’t compress as much and hence it has a better chance of clearing a speed breaker than a Honda Civic. In fact, most of the Maruti cars have stiff suspensions, across its range from the Wagon-R to the Ritz and Swift. Hyundai cars have softer suspensions, although the Hyundai Santro and Hyundai i10 are exceptions. Fiat cars have best of both – stiff suspensions and high ground clearance, clearly well suited for rough roads. Also read: Best cars for heavy city usage

So the next time you are looking to buy a car that will be driven on rough roads, don’t just go by ground clearance figures, also look at reviews as to what kind of suspension the car has and its wheelbase, as these play important factors in the car’s ability to handle bad roads.