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Old 28th August 2009, 22:15   #16
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well in my experience fatter tyres inflated to the normal pressure definitely enhance the stability of the SUV around corners because of the inherently wider stance. I never over-inflate or under inflate. The footprint/ contact patch should always be kept at the optimum level.
I ve found this to be true in the Bolero and in the Scorpio AND in my old Gypsy which had fat 215/75/15 radials. The old MM540 with standard Jeep HT 75 tyres used to squeal around bends in the Nilgiris even at speeds like 50KMPH.

With the advent of the radial tyres this changed a bit, but still that vehicle should NOT be driven at rally type speeds around bends in the hills unless of course the driver harbours a secret wish to join his forefathers!

however, to reiterate once again as I have mentioned in many posts before this one - one simply cannot and should not drive an SUV the way one drives a sports sedan. its innately high stance, high ground clearance and otherwise ponderous proportions cause a much higher centre of gravity and hence a higher likelihood of turning turtle or toppling and this fact MUST be respected.

For example in my opinion, taking an SUV like a Scorpio around the bends in the hill roads like say Ooty or Coorg or somewhere, one should keep to lower speeds in lower gears most of the time, atleast this ensures you have enough torque kicking in to take you out of trouble should you encounter some.

the ideal drive gear would be 3rd and 2nd ,sometimes 1st around bends as per the specific characteristics of the bend. Optimum speed for taking bends in 3rd would be around 50-60 MAX, 2nd would be 40 Max and 1st would obviously be 20 Max. In any case at higher speeds than this, one's engine will strain and let you know its displeasure in no uncertain terms. The optimum speeds can be of about 70-80 Max on the straight bits.

Driving in the correct gear reduces un-necessary strain on the engine and avoids over usage of brakes - as described in my post about taking bends on the Sigur Ghats on the Linea trip to Ooty thread. Also while we may like to believe otherwise, not all of us are as blessed with the driving control skills that a Sebastian Loeb has!

Ive driven for years in the hills in a selection of different cars and jeeps and thus believe I know what can and cannot be done in different types of vehicles.

there is a trick to taking bends - the shortest LINE through the curve is the most enjoyable way to take a curve- it can be done at night when there is no one on the road and one can see miles ahead with the headlights. Not recommended around Blind Curves though since you never know, there may be some poor chap whose vehicle has broken down sitting there with no lights! On our roads in the current dispensation, it is far better to adopt slightly defensive and more responsible driving techniques than otherwise. One more pointer - when driving SUV's or any other vehicle in the hills especially, the typical observation I have made, is that most of the plains drivers tend to stick to the right side lane -this is an absolute NO NO - simply because around the next curve the driver may have a date with destiny in the form of a large bus or truck, who is quietly buzzing along on the correct (left) side of the road, and who cannot stop in time to avoid the idiot who is in the wrong side. Remember also that our hill roads are rather narrow.
another thing -

again - I would suggest that we always remember the responsibility we drivers owe to ourselves, our passengers and of course our fellow road users.

Quote:
Originally Posted by freewheelburnin View Post
I found this line in the article
"But tires which are operated at the maximum pressure tend to have reduced contact area and thus produce less cornering force which is good for SUV's and 4 x 4s"
Is it true that wider tires will produce more cornering force and hence cause the vehicle to topple, but lesser contact area and harder tires with more air filled will oversteer and prevent toppling?If this is true what would be the advantage of wider tyres?

Last edited by shankar.balan : 28th August 2009 at 22:22.
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Old 29th August 2009, 10:32   #17
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Even i follow the fastest path method around curves which have visibility.It reduces body roll and provides more control to gracefully enter and exit a curve without much drama.
+1 to that even I think being responsible to passengers and fellow drivers is a good motivation to drive safer..

Quote:
Originally Posted by shankar.balan View Post
well in my experience fatter tyres inflated to the normal pressure definitely enhance the stability of the SUV around corners because of the inherently wider stance. I never over-inflate or under inflate. The footprint/ contact patch should always be kept at the optimum level.
I ve found this to be true in the Bolero and in the Scorpio AND in my old Gypsy which had fat 215/75/15 radials. The old MM540 with standard Jeep HT 75 tyres used to squeal around bends in the Nilgiris even at speeds like 50KMPH.

With the advent of the radial tyres this changed a bit, but still that vehicle should NOT be driven at rally type speeds around bends in the hills unless of course the driver harbours a secret wish to join his forefathers!

however, to reiterate once again as I have mentioned in many posts before this one - one simply cannot and should not drive an SUV the way one drives a sports sedan. its innately high stance, high ground clearance and otherwise ponderous proportions cause a much higher centre of gravity and hence a higher likelihood of turning turtle or toppling and this fact MUST be respected.

For example in my opinion, taking an SUV like a Scorpio around the bends in the hill roads like say Ooty or Coorg or somewhere, one should keep to lower speeds in lower gears most of the time, atleast this ensures you have enough torque kicking in to take you out of trouble should you encounter some.

the ideal drive gear would be 3rd and 2nd ,sometimes 1st around bends as per the specific characteristics of the bend. Optimum speed for taking bends in 3rd would be around 50-60 MAX, 2nd would be 40 Max and 1st would obviously be 20 Max. In any case at higher speeds than this, one's engine will strain and let you know its displeasure in no uncertain terms. The optimum speeds can be of about 70-80 Max on the straight bits.

Driving in the correct gear reduces un-necessary strain on the engine and avoids over usage of brakes - as described in my post about taking bends on the Sigur Ghats on the Linea trip to Ooty thread. Also while we may like to believe otherwise, not all of us are as blessed with the driving control skills that a Sebastian Loeb has!

Ive driven for years in the hills in a selection of different cars and jeeps and thus believe I know what can and cannot be done in different types of vehicles.

there is a trick to taking bends - the shortest LINE through the curve is the most enjoyable way to take a curve- it can be done at night when there is no one on the road and one can see miles ahead with the headlights. Not recommended around Blind Curves though since you never know, there may be some poor chap whose vehicle has broken down sitting there with no lights! On our roads in the current dispensation, it is far better to adopt slightly defensive and more responsible driving techniques than otherwise. One more pointer - when driving SUV's or any other vehicle in the hills especially, the typical observation I have made, is that most of the plains drivers tend to stick to the right side lane -this is an absolute NO NO - simply because around the next curve the driver may have a date with destiny in the form of a large bus or truck, who is quietly buzzing along on the correct (left) side of the road, and who cannot stop in time to avoid the idiot who is in the wrong side. Remember also that our hill roads are rather narrow.
another thing -

again - I would suggest that we always remember the responsibility we drivers owe to ourselves, our passengers and of course our fellow road users.

Last edited by freewheelburnin : 29th August 2009 at 10:49.
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Old 29th August 2009, 10:42   #18
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You have hit a few good points.But regarding wider tyres or better rubber, they definitely improve the handling of a sedan.But in an SUV more grip around a corner will lead to a topple.Here is my argument....

1)More grip will try to counter the oversteer generated at the rear tyres as a result of cornering force.
2)When the rear tyres do not slip out of line(Remember it is rear wheel drive), the force acts on the body and increases body roll.
3)Excessive body roll force can topple the car easily.
4)In short more grip at the rear can prove disastrous...



Quote:
Originally Posted by MudMover View Post
On my weekly trips to TN I've often been involved in 'tight situations' with other SUVs on the B'lore-Mysore highway. I've noticed the following bad habits among most SUV owners/drivers:

1.Over-dependence/over-use of brakes: constant use of wheel brakes instead of using engine-braking, steering-braking, roadsurface-braking. SUVs are huge things, and it's dangerous to rely only on the wheel brakes alone to slow/stop these monsters.
2.Poor gearing judgement: I've seen a lot of uncles desperately trying to push their beasts up a hill in the 4th or 5th whereas they should've downed into the 3rd. Such 'ducks' then lose energy near the top of the hill and invariably end up neck-to-neck with some auto/tractor/scooter, thus blocking trailing traffic.
3.The small-car mentality: a couple of SUV owners like myself are erstwhile small-car owners . Such folk tend to slow/brake or take wild evasion actions even for small speedbreakers/potholes not realising that SUVs are built to take on such things in their stride and not realising that there's somebody behind them coming at high speeds.
4.Poor concentration levels: SUVs are huge things which require good driving skills> good driving skills require good concentration. I've seen a lot of SUV drivers who're smoking, talking business with the co-driver, playing with the bachcha party - all while thundering across the countryside at 100+ kmph. That's a definite OUCH! scenario.

Much of the above maybe repetitive, but these are some things I've learned by 'driving and getting the feel' of things like hrag mentioned.
Quote:
Originally Posted by watashi75 View Post
Just to clarify a couple of myths here -

Myth 1: wider tyres = more contact area

Myth 2: more contact patch = more grip

Reference: Browser Warning

Most of the misconception arises because people also opt for better rubber when they upgrade to wider tyres.

Wider tyres do not provide any additional grip in straightline acceleration or braking. Cornering grip is different. Cornering force depends on the ability of the rubber to deform, producing what is called slip angle.

Reference: Definition of tyre Slip Angle

Wider tyres have a shorter contact patch which means there is less tread deformation for a given force (less slip angle). This leads to better cornering grip.

Reference: Chosing A Tire | Build A Faster Car

So, to answer your question, wider tires will produce more cornering force and hence cause the vehicle to topple, but for reasons other than contact patch or tyre pressure.

Last edited by freewheelburnin : 29th August 2009 at 10:44.
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Old 29th August 2009, 13:03   #19
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Quote:
But regarding wider tyres or better rubber, they definitely improve the handling of a sedan.But in an SUV more grip around a corner will lead to a topple.
Every vehicle has a limit to how much lateral Gs it can pull before it topples. On low slung cars, the COG is much lower (with a larger track to height ratio) than an SUV so their "Rollover Threshold" is much higher and tyres would start losing traction well before it is achieved.

As the COG gets higher and TOHR gets lower, it becomes easier to topple a vehicle. If you notice racing trucks, they look like normal trucks but they can pull far more Gs, bcoz even thought their height remains the same, they are redesigned to hold most of their weight as low as possible.

Shan2nu

Last edited by Shan2nu : 29th August 2009 at 13:05.
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Old 29th August 2009, 14:23   #20
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there is a fat book provided in every vehicle, its called owner's manual, read it!
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Old 29th August 2009, 19:52   #21
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Quote:
Originally Posted by Shan2nu View Post
If you notice racing trucks, they look like normal trucks but they can pull far more Gs, bcoz even thought their height remains the same, they are redesigned to hold most of their weight as low as possible.

Shan2nu
Thats a very informative piece - any simple pointers for us novices ?
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Old 29th August 2009, 20:27   #22
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Quote:
Thats a very informative piece - any simple pointers for us novices ?
On a personal level, you could try and shift some objects like spare tyre, tool kit, heavy luggage etc as low as possible.

If you look at the vid of the SUV toppling, a large part of the reason why it did so was bcoz the owner had loaded up the top most part of the vehicle with 4 surf boards. This would have drastically increased its COG. Had the surfboards been at a lower level, he might not have overturned at that speed.

Shan2nu

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Old 7th October 2009, 21:23   #23
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Someone told me that in the US, OE manufacturers are not allowed to have seating on the 3rd row for SUVs due to safety reasons - but then this is allowed in India ( eg Scorpio, Safari all have 3rd row seating). Only vans are allowed 3rd row seating in the US.

Likewise, pickup trucks are not allowed to have passengers at the back .

Anyone knows if there are such rules and regulations in the US?
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Old 8th October 2009, 10:35   #24
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Excellent thread. I'd extend these driving tips to SUV owners as well as that of MUVs. Some safe driving tips from my end:

1. MOST IMP : Understand your vehicle's limitations. SUVs, compared to sedans, have poorer handling, braking, body roll and dynamic skills (thanks to the weight, high center of gravity etc.). Also take the time out to judge your individual model's behaviour. For example, a Xylo at speed will not be as stable as say, an Innova.

2. Lower speeds : On the highway, and all things being equal, an SUV / MUV driver must be more conservative with the speedometer than in a sedan / hatchback. This suggestion is a direct output of the previous point. Also keep a longer distance between the car ahead (due to longer braking distances).

3. Go easy around corners : This is where SUVs are especially vulnerable. Best to be conservative around corners and expressway turns.

4. Don't be overtly aggressive with the steering, and don't give a sudden yank to the steering either. Smooth, rather than aggressive, is the key here.

5. Tyres : While some SUVs come well tyred from the factory (e.g. Endeavour), other SUVs could use better rubber to enhance grip / reduce braking distances.

6. In slippery conditions, use the AWD that many SUVs come standard with.

7. Do NOT overload your SUV / MUV with people / luggage. The more passengers you are carrying, the longer your braking distances and the poorer your handling.
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Old 8th October 2009, 11:10   #25
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Apart from all the techniques most accidents are due to human errors . In Indian context do not try to terrorize others and do not bite the bait thrown in by another idiot to do road racing let him pass, if he slows down and try to engage in race again stay at least 500 Meter away.

I have noticed baits are generally thrown at SUV drivers by all and sundry who have juvenile tendency to measure up against others. Sometimes you will have more enjoyable drive by allowing them to feel big .

I remember a small incidence couple of months back I was driving towards E-City in Bangalore in the early morning with my BIL. Saw a gentlemen few hundred yards ahead who was inspired by Ford Fiesta TV add and was doing all sort of stunts to demo the handling capability to all and sundry in his new black fiesta.

I was at high speed carefully changed lane and passed him maintaining more then required distance so he was kind of infuriated and increased speed We allowed him to pass after his terrorizing flashes and honks

A couple of KM later we saw his front quarter panel flaying away after a nick with a JCB, he stopped to collect the part and was kind of reflecting upon himself standing in middle of road with badly mauled panel in hand .The look on his face was priceless.

Last edited by amitk26 : 8th October 2009 at 11:12.
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Old 8th October 2009, 12:46   #26
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Last time on my way to cochin, a lady tried to cross the road between hosur and salem .I thought that she would pass ,but she stood right there in the middle of the road.I was at 120 kmph and there was hardly distance to brake and come to a halt.All i could do was to bring down the speed of the vehicle as fast as possible and then steer it away from her.I did abrupt engine braking (down from 5th to 3rd).Once i was about 6 metres aways i turned the vehicle very gently so that the bonette faced away from her.It went into a small slide.Before i could relax she jumped back again.Now i stepped on brake pedal again and released it very near to her and steered again.All this happened in few seconds.The fact that my mind was very relaxed helped and my reflexes followed my brain.It was a very scary experience because at those speeds you are controlling a Tower on wheels and a small error or misjudgement can be fatal.If Safari was my first car
I would not have been able to control it in that situation.The Lancer experience was helpful, because it was a very forgiving car and gave me time to experiment and learn.My suggestion for new drivers, please stick to cars atleast for a year or two before buying an S.U.V.
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Old 31st March 2013, 21:11   #27
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Default Re: SUV safe driving tips anybody?

With the introduction of vehicles like Duster/XUV5OO, should be interesting to give life to this thread
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