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Old 2nd March 2010, 14:54   #1
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Default Compact city car - Dimensions vs Turning Radius

I searched the forums and couldn't really find a topic that discusses this. I would like to point out the differences or rather relevance of "width" of the car as against "turning radius".

Many of us living in congested cities, especially those of us used to handy two-wheelers, look for a really small and compact car. Options like WagonR, Santro and Alto take preference. We know that even if a car does great on the highways (like Palio), our usage will be more than 90% inside the city's narrow lanes. The top reason in our mind is the turning radius.

However, I have been pondering a bit on this, lately. What got me thinking was driving my friend's Santro for a couple of days. I am used to driving my Indica in the city roads, and with Santro's small turning radius of 4.4m, I expected a huge difference. But I didn't really find that much difference.

Now here's my point: When does the "minimum turning radius" really matter?
1. When taking a U-turn
2. When parking
3. Rarely, when caught so close behind another vehicle but realize too late that the vehicle in front is not going to move, and it is better to switch "lanes".

In normal driving, does turning radius ever come into play? I think not, because we never go down to the minimum radius when actually driving. So that difference doesn't really come out. Most of our steering actions get to the just needed steering level, not to the extreme.

What does make a difference, however, are two other factors:
1. Length and width of the car
2. Engine responsiveness in lower RPMs

When overtaking in a narrow lane, a smaller width will make a whole world of difference. Smaller width and length also allows me to dart in between vehicles because I need less space to occupy. The engine responsiveness becomes very important too, because when I find that space to dart in between, I need the quick pick-up to do it.

So the more I think about it, it seems to me that dimensions and responsiveness are more important factors when choosing a city car, than the actual minimum turning radius.

Examples: Palio has a higher turning radius than Swift, but it is narrower. Same can be said of Santro and WagonR. Santro's turning radius is less, but WagonR's width and length are less than Santro's.

Note: I am not advocating reckless driving, switching lanes and darting in between vehicles. Just thinking, what type of car will be easiest to drive under such conditions.
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Old 2nd March 2010, 15:26   #2
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I prefer car which have a small turning radius as it is easy to take U-turns and getting out of tight parking situation.
If the turning radius is more it makes things really difficult in tight situations.
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Old 2nd March 2010, 17:32   #3
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Quote:
Originally Posted by rajushank84 View Post
Now here's my point: When does the "minimum turning radius" really matter?
1. When taking a U-turn
2. When parking
3. Rarely, when caught so close behind another vehicle but realize too late that the vehicle in front is not going to move, and it is better to switch "lanes".
It should come into play for all 3 situations, though more important for the first & second.
Switching lanes & overtaking will also depend a lot on engine peppiness, sensitivity of the steering too [I mean the number of full rotations lock to lock]

Quote:
Originally Posted by rajushank84 View Post
What does make a difference, however, are two other factors:
1. Length and width of the car
2. Engine responsiveness in lower RPMs

So the more I think about it, it seems to me that dimensions and responsiveness are more important factors when choosing a city car, than the actual minimum turning radius.
You've given quite a bit of thought to the topic & it really shows
In a nutshell, a TD will show how eager the car is move in either direction which should help you gauge how nimble it is.

The length of the car minus the wheelbase will play an important role in city conditions cause the boot is late to follow-through when you turn & can scrape something along the way (Just see how late bus drivers have to start turning at a curve to avoid their rear end over-running the dividers).

This can turn out to be quite an interesting thread. Would love to know what others think
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Old 2nd March 2010, 21:55   #4
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Yes, I would especially love to hear from people who have driven:
1. Both Swift and Palio
2. Both Santro and WagonR

In fact I am planning to replace my two-wheeler with the most chuckable city car, sometime next year. Getting the thought process rolling already...
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Old 2nd March 2010, 23:04   #5
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you might want to look at power steering and its response. then radius. then size
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Old 3rd March 2010, 01:16   #6
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I do agree with your prognosis. I would however like to bring your attention to two other parameters that determine the ease of driving/parking in congested traffic.

It is what is commonly referred to as overhang and form. Even if you have a good turning radius, a large overhang and a bluff form will nullify its benefits....

Overhang is the distance from the front/rear wheel centre to the outermost point on the front/rear bumper of the car measured along the cars length.

Close observervation of the 2nd generation Honda City led me to this conclusion. Looking at the front end, one notices how short the overhang is and in the case of the City (when looked at in top view), the front of the car tapers distinctly towards the rear i.e. the bumper is furthest in the centre of the bonnet after which it recesses towards the back of the car as we approach the corners (imagine an arrowhead).......Hence as the car turns out of a parallel parking, the point of contact (with the car in front) keeps moving backwards, thereby reducing the possibility of bodywork impact.

The form and overhang thus in my opinion are equally important.

An optimised combination of the three can help close distance manouvres like parallel parking and U turns
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Old 3rd March 2010, 13:53   #7
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Quote:
Originally Posted by rajushank84 View Post
What does make a difference, however, are two other factors:
1. Length and width of the car
2. Engine responsiveness in lower RPMs
Some other factors that lead to ease of driving in the city:

1. Driveability : Superior torque = lesser gear changes.

2. A light quick steering : Boon at low speed & while parking (though I personally prefer 'em heavy).

3. Short light gear throw quality : After all, the average 10 km urban drive needs 150 gearshifts (if not more).

4. Lower the turbolag, the better. Especially relevant in the advent of diesel hatchbacks. Turbo-lag is a royal PAIN in traffic.

5. Short-throw light clutch : Long heavy units are, again, a royal pain in traffic.

6. Visibility : As important in the city as on the highway. You'd need a good side & rear view more in the city.

7. Ergonomics. At lower speeds, you'll be using controls more frequently than say, when cruising at 80 kph on an expressway.

Last edited by GTO : 3rd March 2010 at 13:55.
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Old 10th March 2010, 18:30   #8
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Quote:
Originally Posted by rajushank84 View Post
What does make a difference, however, are two other factors:
1. Length and width of the car
2. Engine responsiveness in lower RPMs

When overtaking in a narrow lane, a smaller width will make a whole world of difference. Smaller width and length also allows me to dart in between vehicles because I need less space to occupy.
Aha. Isn't that an autorickshaw you are describing? Push your nose in and get your way everytime.
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Old 11th March 2010, 16:16   #9
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Originally Posted by emil View Post
Aha. Isn't that an autorickshaw you are describing? Push your nose in and get your way everytime.
Almost . An autorickshaw-sized car with a full car-sized engine would be ideal. Petrol-based Reva?
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Old 11th March 2010, 16:36   #10
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Almost . An autorickshaw-sized car with a full car-sized engine would be ideal. Petrol-based Reva?
When you have the Nano why a petrol based Reva?!!
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Old 11th March 2010, 16:45   #11
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When you have the Nano why a petrol based Reva?!!
Well, Nano isn't that small! Its width is more than that of M800, Omni, WagonR, Alto, Estilo and Spark.
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Old 11th March 2010, 17:18   #12
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Smaller turning radius does not always mean an easier car to drive.

Its the steering ratio that dictates how quickly you can make the car change directions. But having quick response steering all the time can make the car unstable at high speeds. Thats why some modern cars come with variable steering ratios which use taller ratios at the center of the rack and get shorter as you reach the outer ends.

Shan2nu

Last edited by Shan2nu : 11th March 2010 at 17:20.
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Old 11th March 2010, 17:58   #13
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Quote:
Originally Posted by Shan2nu View Post
Its the steering ratio that dictates how quickly you can make the car change directions.
Is there a way to know the steering ratio of a car, other than by test driving it? I don't remember seeing it in any spec sheet.
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Old 11th March 2010, 18:14   #14
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gurus - i would like to know what determines the turning radius of a car?
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Old 19th March 2010, 06:57   #15
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One thing that is worth mentioning is the all around visibility that you have which really helps in city driving, To really understand this, drive any Hatchback and then WagonR and you would immediately know the difference.
Also, EPS also helps a lot in city, Also, I agree to Ameya on the overhangs, NHC and WagonR has very less overhangs and add the Tapering front Bumper, you are extremely benefitted.
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