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Old 18th March 2011, 08:52   #1291
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Janjua View Post
I have driven the Thar with company recommended 35 psi and found the ride to be quite bouncy. Now, I am driving the Thar at 30 psi and the ride is very decent indeed. I think I will need to do a couple of more 'Hit & Trials' to get the ride quality near perfect.
You can stick to 30 PSI at front and 32 PSI at the rear (when loaded), this will keep handling in "under-steer" region.

Spike

Last edited by SPIKE ARRESTOR : 18th March 2011 at 08:53.
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Old 18th March 2011, 12:09   #1292
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by SPIKE ARRESTOR View Post
You can stick to 30 PSI at front and 32 PSI at the rear (when loaded), this will keep handling in "under-steer" region.

Spike
Dear Spike Arrestorji,

Can you please explain how? I'd really like to know how this works? What happens in under and over inflated situations and why?

If in have same pressure back and front, what happens?

If i have front tyres inflated more than rears, will it over steer?
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Old 18th March 2011, 12:31   #1293
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Default Re: Mahindra Thar : Test Drive & Review

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Can you please explain how? I'd really like to know how this works? What happens in under and over inflated situations and why?
If tire pressure is more on front tires (lesser contact patch), front tires loose traction first -> Understeer.


Quote:
If i have front tyres inflated more than rears, will it over steer
Yes theoretically, of-course it depends on the drive set up, weight distribution, suspension set up etc. Tire pressure is the simplest thing you can play around with.

Quote:
If in have same pressure back and front, what happens?
Tends to neutral steer.

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Dear Spike Arrestorji
Why this Ji Sir JEE ? Excuse me!

Spike

PS- There are more elaborate reasons for Under-steer / Over-steer, this is the simplest I can think of.

Last edited by SPIKE ARRESTOR : 18th March 2011 at 13:04.
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Old 18th March 2011, 13:17   #1294
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by SPIKE ARRESTOR View Post
If tire pressure is more on front tires (lesser contact patch), front tires loose traction first -> Understeer.
...
Spike, I hope you meant oversteer. They loose traction and turn more easily.

When the air pressure in the front tires is less, it increases the contact patch and in turn increases the resistence to turn. So it should tend to understeer.

When the tire pressure is more, the reverse happens and it will tend to oversteer.

In vehicles with power steering, this may not be very pronounced. But in the old jeeps (vehicles with bigger tyres and without power steering), one should be able to experience it while driving.

And having a greater air pressure in the back tires should help one to get the back to slide out more easily during hard cornering.

Last edited by pjbiju : 18th March 2011 at 13:25.
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Old 18th March 2011, 14:05   #1295
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Default Re: Mahindra Thar : Test Drive & Review

Oops, that was a typo! ^^

Mods- Correct the above post if possible. Thanks.

Spike
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Old 18th March 2011, 17:12   #1296
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by pjbiju View Post
When the air pressure in the front tires is less, it increases the contact patch and in turn increases the resistence to turn. So it should tend to understeer.

When the tire pressure is more, the reverse happens and it will tend to oversteer.
I don't think this is correct at all!

Oversteer and understeer are linked to TRACTION and not how heavy the steering wheel is to turn, or how quickly you can turn it.

Even if the steering is a bit heavier to turn due to lower tyre pressure, it will only be a fraction of a second slower than as with proper tyre pressure.

Either way, even if it took 5 whole seconds more to turn all the way, that still wouldn't be considered understeer, as the car would still be going where you point it (just not where you want it to go).

Quote:
Originally Posted by SPIKE ARRESTOR View Post
Oops, that was a typo! ^^
Are you sure?

cya
R

Last edited by Rehaan : 18th March 2011 at 17:14.
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Old 18th March 2011, 17:44   #1297
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Default Re: Mahindra Thar : Test Drive & Review

Couple of pounds change the contact patch? or changes the suspension equation, as in overall stiffness or softness, due to the flexing sidewall.

As far as under or over steer, this is from wiki Understeer - Wikipedia, the free encyclopedia

Quote:
In standard terminology defined by the Society of Automotive Engineers (SAE) J670[1] and the International Organization for Standardization (ISO) 8855[2], understeer and oversteer are based on differences in steady-state conditions where the vehicle is following a constant-radius path at a constant speed with a constant steering wheel angle, on a flat and level surface. If the speed is increased slightly for the same radius path and, after settling into steady state, the same steering is measured, then the vehicle is said to have neutral steer. If more steering is needed at the higher speed to maintain the same radius of curvature, then the vehicle is said to have understeer. If less steering is needed at the higher speed, then the vehicle is said to have oversteer.
Oversteer - Wikipedia, the free encyclopedia

Quote:
Generally, oversteer is the condition when the slip angle of the rear tires exceeds that of the front tires, even when they are both small. Limit oversteer occurs when the rear tires reach the limits of their lateral traction during a cornering situation but the front tires have not, thus causing the rear of the vehicle to head towards the outside of the corner.
So in real life if front is losing out it is understeer and if rear is losing out its oversteer?

EDIT 1: To take it one step further, "if" by reducing pressure contact patch increases "then" it will oversteer atleast theoretically. EDIT 2: in front tyre i mean. Which is not really good thing in Thar, if you ask me.

Last edited by Jaggu : 18th March 2011 at 17:58.
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Old 18th March 2011, 18:12   #1298
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Rehaan View Post
I don't think this is correct at all!

Oversteer and understeer are linked to TRACTION and not how heavy the steering wheel is to turn, or how quickly you can turn it.

Even if the steering is a bit heavier to turn due to lower tyre pressure, it will only be a fraction of a second slower than as with proper tyre pressure.

Either way, even if it took 5 whole seconds more to turn all the way, that still wouldn't be considered understeer, as the car would still be going where you point it (just not where you want it to go).
...
One of the improtant things (among the many) that contribute to understeer/oversteer condition is the cornering stiffness of the tyre. Reduced air pressure means reduced cornering stiffness of the tyre. Cornering stiffness is the ability of the tyre to take you in the direction you want to go. This is one of the parameters used for measuring understeer/oversteer characteristics of a vehicle. So with reduced air pressure, the ability of the vehicle to go in the direction you want it to go, reduces. That is understeer. To stay along the same curve at a given speed, you will need to turn the steering more with reduction in tyre pressure. You can try to search for some SAE papers on this to get a better idea.
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Old 18th March 2011, 20:54   #1299
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Default Re: Mahindra Thar : Test Drive & Review

Quote:
Originally Posted by Rehaan View Post
Oversteer and understeer are linked to TRACTION and not how heavy the steering wheel is to turn, or how quickly you can turn it.

Even if the steering is a bit heavier to turn due to lower tyre pressure, it will only be a fraction of a second slower than as with proper tyre pressure.
Oversteer happens in a fraction of a second. I agree they are linked to TRACTION and it also depends on how heavy your steering wheel is to turn.

Try a simple example of taking a 90 degree turn in the
Quote:
samevehicle with equal load, equal tyre pressure front and rear as first run and unequal ones as second run at the same speed,
to understand the phenomena better.
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Old 21st March 2011, 11:37   #1300
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Default Re: Mahindra Thar : Test Drive & Review

On a side note from all the technical details....got a call from a dealer in Bangalore on Saturday. Thar bookings are back on and they are bringing the Thar home for a test drive on Thursday.

Good news. Now at least I can drive it before I make the decision...

Thanks,
Manas
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Old 21st March 2011, 11:56   #1301
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Default Re: Mahindra Thar : Test Drive & Review

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Good news. Now at least I can drive it before I make the decision...

Thanks,
Manas
You wont be disappointed - Go for the THAR! Keep us posted on the delivery schedule..
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Old 21st March 2011, 12:07   #1302
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by manasm View Post
On a side note from all the technical details....got a call from a dealer in Bangalore on Saturday. Thar bookings are back on and they are bringing the Thar home for a test drive on Thursday.

Good news. Now at least I can drive it before I make the decision...

Thanks,
Manas
Which dealer? Even I am planning to take a test drive.
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Old 21st March 2011, 17:11   #1303
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Default Re: Mahindra Thar : Test Drive & Review

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Which dealer? Even I am planning to take a test drive.
Even I got a call today (from Sireesh Auto, Yelahanka) offering to bring the vehicle home for a TD. From 24th onwards, the vehicle would be stationed at their Hosur Road showroom it appears. When asked on delivery timelines she said it would be 3 months waiting.
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Old 22nd March 2011, 11:04   #1304
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Default Re: Mahindra Thar : Test Drive & Review

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Which dealer? Even I am planning to take a test drive.

Got the call from Sireesh Auto...

Will start a discussion on loans for vehicle + mods for the Thar...
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Old 22nd March 2011, 11:24   #1305
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Default The Thar -- Buying it, Living with it, Modding it

Hi All,

Well, I have 50% made up my mind about the Thar and the remaining 50% will be made up by the wife on Thursday after a test drive! If all goes well, the deposit and booking will be completed on Thursday itself.

I have some questions for those who have bought or are buying the Thar...

1. Car loans
  • what is the going interest rate right now?
  • any recommendations on which bank would be the best bet? Who have you guys used? The dealer did mention that I have to go through them, but I am a bit skeptical on that
  • anything else I should look out for?
2. Mods

After buying the Thar, some mods are required - at least as far as I am concerned. As far as possible, I would prefer the cheaper option, but also do not want to lose warranty. It would help immensely if owners/potential owners could provide costs for the below and if possible, best places in Bangalore to get these done.
  • A/C - best from dealer or can I get it done outside?
  • Rollcage - from dealer seems like the only option
  • Hard Top - am working on my own design. completed design and looking for fibre plastic vendors who would be interested in quoting for manufacture - hope to have a prototype in hand before delivery of the vehicle
  • Security - steering lock, gear lock? what other options are there?
  • Tyre/rim - what is the suggested tyre/rim combo replacement from stock?
  • Rear seat replacement - want to replace the rear seats with individual front facing seats (as in attached pic) - i would also need to add seat belts to the rear seats...
  • Front sear replacement - captain seats
  • Cigarette lighter - for GPS, charging phone etc...
Any other simple mods anyone can think of?

Later on, would look at mods like snorkel and performance mods. For right now, this is what I would like/need before I can drive the Thar around.

P.S. I am looking at the Thar as a tourer - where I can take family on long(ish) trips and do a bit of off road to get where I need to go...

Thanks in advance for the help and advice.

Cheers,
Manas
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