[kshivaa]

Hi,

Regarding the cruising speeds of Thar, I was able to accelerate upto 120 Kmph effortlessly on Suruttapalli - Puttur highway, on relatively straight stretches.

The issue / concern, as others have mentioned is the steering feeling very light. There is no tightening / stiffening of steering after 80 Kmph speed.

Regarding the braking, while depressing the brake pedal once is not effective, a pumping action with 2-3 pumps improves the braking quite significantly - thanks to Rajith, who suggested this to me during JT7A meet. The highway had speed breakers, and with 2-3 pumps, the braking was significantly improved.

thanks,
Siva

[headers]

Originally Posted by kshivaa

Regarding the braking, while depressing the brake pedal once is not effective, a pumping action with 2-3 pumps improves the braking quite significantly - thanks to Rajith, who suggested this to me during JT7A meet. The highway had speed breakers, and with 2-3 pumps, the braking was significantly improved.

Yup..the booster brake is effective if pumped..but who has time to pump under panic braking?

[gthang]

Originally Posted by headers

Yup..the booster brake is effective if pumped..but who has time to pump under panic braking?

Am I hearing right? It's 2012, and you're suggesting having to pump the brakes for effectiveness on a brand new vehicle? Wow!!
What happened to the master cylinder?

Unless you meant "Threshold Braking", right?

Cheers

[Red Liner]

Originally Posted by gthang

Am I hearing right? It's 2012, and you're suggesting having to pump the brakes for effectiveness on a brand new vehicle? Wow!!
What happened to the master cylinder?

Unless you meant "Threshold Braking", right?

Cheers

No ABS...so you pump to mimic it...or it will lock. Pump when you're driving and actively need to brake.

Edit: Ouch, didn't read the posts above. So it doubles up as both -ABS and actually stopping :P

[Harbir]

Originally Posted by kshivaa

Regarding the braking, while depressing the brake pedal once is not effective, a pumping action with 2-3 pumps improves the braking quite significantly

This means that there is air in the braking system, which needs to be bled out.

If bleeding air out of the system does not cure this in the thar, then its a badly designed system.

Bleeding air out of a system is a laborious process and is rarely done. It requires either a gravity feed system that flows a lot of fluid through the system, collecting at the wheel hubs, in the hope that all the old fluid with the air and moisture bubbles in it will be flushed out. THe next best system is a power bleeder that applies a heavy pressure of brake fluid at the reservoir, allowing you to losing the bleed screw and just let the old fluid flow out. WHen you see fresh clean fluid starting to flow out at the bleed point, you tighten the bleed screw and then you're done. repeat for all 4 corners.

If you don't have a gravity feed and you don't have a power bleeder, then you need a buddy, a bleed kit, and a good communication system. Fill reservoir with fresh fluid. Have buddy get behind the wheel, shout "on!" to signal he should push the pedal. when he's got the pedal pushed, he says "on!" and you loosen the bleed screw and the fluid starts to pour into the hose and into the container. At this point, the fluid brake pedal will sink to the floor. as soon as it reaches the floor, your buddy says "stop!", you tighten the bleed screw, and say "release!". you buddy then releases the pedal, and it starts over again. ( you say on, he presses and says on, you looosen the bleed screw..... and on on). You can stop when the fluid coming out the bleed screw is nice and fresh. I used to use ATE super BLue Type 200 fluids that were the same chemically, but one had orange dye, the other had blue, and I would alternate. SO when there is blue in the system and orange starts to come out of the bleed screw, I know that corner is done. REpeat for all 4 corners. Fluid coming out of the bleed screw should be visible in the transparent hose (from the bleed kit) and any bubbles that you saw in the old fluid when you started the corner, should be gone and you should have clear whole fluid.

ABS equipped vehicles can use some extra steps to ensure the ABS system is bled properly without damage. Google it.

If after all this, you don't get a firm pedal, then I am sorry to say that either you have a faulty component or just crappy design.

[amartya sinha]

THAR is a vehicle with so much possibilities, that it requires separate threads for separate technical modifications / clarifications. We already have one for Air conditioning, started by none other than the father of THAR, Mr. Dhabar himself, then we have for hardtop designs, exhaust fumes et all. Over the past few posts from various users, this braking subject has crept up repeatedly, Mr. Dhabar in one of DKG's post has also mentioned how to improve braking abilities in the THAR. I would request if a dedicated thread in the 4x4 technical section can be started by the gurus, or 'THE MAN' himself, for layman like us to understand the issue better, and get the relevant data in one single place. A dedicated thread for drive line improvisation and braking is definitely a welcome!

[KkVaidya]

Originally Posted by Red Liner

No ABS...so you pump to mimic it...or it will lock. Pump when you're driving and actively need to brake.

How can you mimic ABS by pumping the pedal?
Come on guys, ABS works in mil-seconds and we are trying to press the pedal with a human foot at speeds less then a second!
If pumping improves the braking practically, then it should be a problem of the braking system.

Originally Posted by Harbir

This means that there is air in the braking system, which needs to be bled out.

If the brakes are not properly bled, wont that make the pedel feel spongy?

BEHRAM DHABHAR: Are you reading this????

[Red Liner]

Originally Posted by KkVaidya

How can you mimic ABS by pumping the pedal?
Come on guys, ABS works in mil-seconds and we are trying to press the pedal with a human foot at speeds less then a second!
If pumping improves the braking practically, then it should be a problem of the braking system.

That is exactly what you used to do in the old pre-ABS era days. Pumping is the wrong word - what you do is feather touch braking - brake, let go, brake, let go, brake, let go. This allows you to keep the car in a straightline, do minor steering adjustments where necessary. If you brake hard continually, you'll lock the wheels up...and boom.

Drive a jeep today, and you'll know what I'm talking about. Ofcourse, maintaining saner speeds is a lot more intelligent when you know the braking is highly inadequate.

[Harbir]

Originally Posted by KkVaidya

If the brakes are not properly bled, wont that make the pedel feel spongy?

if there is air in the system, yes. Thats the complaint I was responding to.

[KkVaidya]

Originally Posted by Red Liner

That is exactly what you used to do in the old pre-ABS era days. If you brake hard continually, you'll lock the wheels up...and boom.

I still do not get the point. In Pre-ABS days, if the pedal is feather-touched it makes very very less difference to the car speed. That too depends on the car you drive - if it is a non-servo brake, it hardly makes any difference.
Say I am doing 80kmph in a car with servo-assisted brakes, feather touching the pedal wont help me cut much of a distance. I agree that stomping on the brake pedal will surely lock the wheels but you cannot mimic ABS practically. Yes you can jerk-brake but that is only for the mental assurance or a planned stop - otherwise it wont help in an emergency situation.

[DHABHAR.BEHRAM]

Originally Posted by KkVaidya

How can you mimic ABS by pumping the pedal?
Come on guys, ABS works in mil-seconds and we are trying to press the pedal with a human foot at speeds less then a second!
If pumping improves the braking practically, then it should be a problem of the braking system.


If the brakes are not properly bled, wont that make the pedel feel spongy?

BEHRAM DHABHAR: Are you reading this????

Dear Vaidyasaab - I AM READING EVERYTHING. Even if I did not read, I still know exactly what the issue is and what is the PCA (Permanent Corrective Action) to set it right. It is not bleeding. As far as brakes are concerned, I had expressed my reservations many times in all forums as the Thar CRDe is a fast car by any stretch of the imagination, but due to two reasons as I am mentioning below, things did not get implemented.

1. Present system meets cost target.
2. Present system meets CMVR and there is a certificate for it.

However on MH01V521, I had done the complete system upgradation. It does not need any drilling, cutting or welding because boundary dimensions are common with other models, so are all the aggregates. With my flatout driving style and with my speed consistently high, the production brakes just could not stop the vehicle.

There is something which is much more important than cost target and CMVR. I hope that the brakes get upgraded soon. This should have been done as a package on the recently released vehicle.

Best regards,

Behram Dhabhar

[gthang]

Is there no such thing as ethics in this country?

How can someone put into production a vehicle knowing fully well that the brakes are inadequate, on account of cost control and paperwork hassles?

Human life apparently has no value over a quick rupee. Sad thing is that this practice is not new, and makes one wonder what the farce with a new R&D center and other so-called charitable acts really translate to.

Nice that such a forum exists where such death traps can be advertised for free and gather a fan following even.

Cheers.

Originally Posted by KkVaidya

I still do not get the point.

It's called "Threshold Braking". Google it.

[4x4addict]

Thar owners who drive fast should upgrade to Scorpio mhawk brake set up with dual piston calipers and bigger rear drum. It will cost about 30K but well worth it.

[Harbir]

Originally Posted by DHABHAR.BEHRAM

know exactly what the issue is and what is the PCA (Permanent Corrective Action) to set it right. It is not bleeding.

as I said: "If bleeding air out of the system does not cure this in the thar, then its a badly designed system."

And while I am sorry to hear that its the result of a bad engineering decision, I am not surprised. Honestly, I feel that the engineering culture at Mahindra and Tata reflects too much of the jugaad that indians are so proud of.

but perhaps I am being too harsh. Mahindra and Tata excel at very low prices. You get what you pay for. You can't expect Fortuner/Pajero grade engineering at Thar/bolero/scorpio/safari prices.

[Aroy]

Originally Posted by KkVaidya

I still do not get the point. In Pre-ABS days, if the pedal is feather-touched it makes very very less difference to the car speed. That too depends on the car you drive - if it is a non-servo brake, it hardly makes any difference.
Say I am doing 80kmph in a car with servo-assisted brakes, feather touching the pedal wont help me cut much of a distance. I agree that stomping on the brake pedal will surely lock the wheels but you cannot mimic ABS practically. Yes you can jerk-brake but that is only for the mental assurance or a planned stop - otherwise it wont help in an emergency situation.

The job of brakes is to slow the vehicle down - the brake slows the wheel, which in turn slows the vehicle. In case the adhesion between the wheel and the road is lost, the vehicle will skid and skate instead of stopping.

ABS is to prevent the brake lock.

Brake lock is when the brake locks the wheel, but due to loss of adhesion between the tyre and the road, the tyre starts skidding on the road. If you release the brake at the point of skidding, the wheel regains adhesion (well mostly, exceptions are oil and ice etc), and then you apply the brakes to slow the vehicle.

Manually you can do a fairly good job by so called "pumping" of brakes, where you press and release the brake paddle rapidly. ABS does this automatically at a much higher frequency, so can do a better job in general. Please note that ABS requires the sensors in system - brake rotation, brake pedal depression and speed, to be functional as well as the control system to detect when the brakes are locking to activate the ABS.

Each manufacturer has a different algorithm for detection and activation of the ABS, hence in some cases the ABS will activate at speeds as low as 30 km/h on apparently normal surface at curves, in other case it may activate at a much higher speed on much more slippery surface.

Though most of us do rely on ABS, where available, we should also be proficient with emergency braking procedures when the ABS fails, especially those who love to drive extremely fast. You must also be aware where excessive speed is catastrophic as you cannot brake efficiently on those surfaces, thin snow/ice and water running on a hill slope are some that come to my mind.