[ramkya1]

Hai BHPians,

Yesterday a friend told me we should keep the front wheels straight when we park at night or leave the car for a long time. He said leaving the wheels fully turned either to right or left will put pressure on the tension springs (that helps the wheels to pull back to a straight position) and is not ideal......... some of the techies out here can please advise

Ramky.

=======================

[Rudra Sen]

haven't heard this before...where is this tension spring thingeee sitting?

[amitoj]

I have heard that this is true for vehicles with non electronic power steering only.
EDIT: By that, i mean hydraulic power steering equipped vehicles only.

[ramkya1]

Originally Posted by Rudra Sen

haven't heard this before...where is this tension spring thingeee sitting?

Rudra,

Honestly......... I don'tr have the foggiest, I went under my fusion to check out, could't see one. Maybe its in the housing somewhere out of sight, that's why I posted the question.

Ramky.
============

[Ram]

Originally Posted by ramkya1

Yesterday a friend told me we should keep the front wheels straight when we park at night or leave the car for a long time. He said leaving the wheels fully turned either to right or left will put pressure on the tension springs (that helps the wheels to pull back to a straight position) and is not ideal......... some of the techies out here can please advise

Ramky.
=======================

Hi Ramky:

Let me explain one of the three important angles in steering and suspension geometry of a car.

When you turn your steering wheel, your front wheels swivel on a pivot defined in the suspension system. The angle of this pivot is called Caster.

When observed from the side of the car,
if the top of the pivot leans toward the rear of the car, the caster is positive and the steering will center after a turn. The more positive the caster angle the heavier the steering will be.

On the other hand, if the top of the pivot leans toward the front of the car, the caster is negative. Steering will be light and the car will wander all over, after a turn.

If the caster on the left side is not equal to that on the right side, the car will continually pull to the side with the less positive caster.

So, in a moving car, after completing a turn, the front wheels return to the straight-ahead position, not due to imaginary tension springs in the steering system, but due to caster.

Rest assured, there is no harm leaving the wheels fully turned either to right or left.

In fact, the California Directorate of Motor Vehicles (DMV) handbook advises that…

QUOTE
When you park on a hill:

• On a sloping driveway, turn the wheels so the car will not roll into the street if the brakes fail.
• Headed downhill, turn your front wheels into the curb or toward the side of the road. Set the parking brake.
• Headed uphill, turn your front wheels away from the curb and let your vehicle roll back a few inches. The back of the front wheel should gently touch the curb. Set the parking brake.
• Headed either uphill or downhill and there is no curb, turn the wheels so the car will roll away from the center of the road if the brakes fail.

Always set your parking brake and leave the vehicle in gear or the "park" position.
UNQUOTE

I rest my case…
Ram

[speedsatya]

Originally Posted by ramkya1

Hai BHPians,

Yesterday a friend told me we should keep the front wheels straight when we park at night or leave the car for a long time. He said leaving the wheels fully turned either to right or left will put pressure on the tension springs (that helps the wheels to pull back to a straight position) and is not ideal......... some of the techies out here can please advise

Ramky.

=======================

even i have heard about this

[ramkya1]

Originally Posted by ram

Hi Ramky:

Let me explain one of the three important angles in steering and suspension geometry of a car..................


So, in a moving car, after completing a turn, the front wheels return to the straight-ahead position, not due to imaginary tension springs in the steering system, but due to caster......................

Rest assured, there is no harm leaving the wheels fully turned either to right or left.


I rest my case…
Ram

Hai Ram,

Tnx for that one............. I'll NOT go under my car in searach....

Is this true to all cars or only to new generation power steering cars? Does that mean other than power steering there has been no revolutionary change in the steering assembly etc..?

--Ramky
=====================

[Rtech]

Maybe what was meant was the the car should not be left in the full lock position. This puts a lot of pressure on the seals in a hydraulic PS system, which, if left in that position for a length of time would cause some seals to give way, leading to a loss of PS. This is a fact though. I think...

[DRC]

Haven't heard about the tension spring ever!!

But, My Petra's Owner manual mentions to keep the wheels straight to avoid damage to the hyd Power steering.

But , I remember having read in my dad'd old DL it was mentioned to turn the steering turned completely (?) to left to avoid the car drifting into the traffic ;-(

[Ram]

Originally Posted by Rtech

Maybe what was meant was the the car should not be left in the full lock position. This puts a lot of pressure on the seals in a hydraulic PS system, which, if left in that position for a length of time would cause some seals to give way, leading to a loss of PS. This is a fact though. I think...

My, my, what Urban legends abound! Technology is based on logic not hearsay

1) Neither springs, nor Hydraulic pressure in the steering system, returns steered wheels to the straight ahead position. Steered wheels return to the straight ahead position only due to the "caster" (the British spell it as "castor") angle of the kingpin, leading the point of contact of the wheel on the road.

For this very reason, swiveling caster wheels on hospital-beds and airport baggage trolleys, straighten out when you push them straight ahead.

2) Power Steering

Case: Hydraulic Power Steering
When the engine is switched off, the power steering pump stops producing hydraulic pressure. Power steering systems are not designed with any pressure tank to hold the pressure for "next morning" steering assistance. There is no fear of any seal giving way due to imaginary pressure in the steering system when the engine is not running.
That being said, you can damage a power steering system by continuously holding the steering wheel against the travel locks at either extreme, with the engine driving the power-steering pump. When you do this, pressure applied to the steering-rack is maximized. All of the fluid output of the power-steering pump flows through the relief valve (that is the loud hum you hear). This heats up the power-steering fluid and it applies maximum pressure to the seals. The hot fluid and high pressure can damage a seal. But when you switch-off the engine in a parked car all of this no more applies!

Case: Electronic Power Steering
In a completely electric power-steering system. Sensors detect the motion and torque of the steering column and embedded software applies varying amounts of assistive power via electric motors, depending on driving conditions. Even in this case the pressure exerted disappears when the car is switched off.

3) In lands used to over a century of automobiles, (Europe and USA) it is law, that cars parked on a hill must have their wheels steered all the way to prevent rolling all the way downhill, should the parking brakes fail.

[GTO]

Very well explained, Ram. Your two posts were an eye-opener.

GTO

[jat]

If the steering has zero castor and there are springs provided for self centering then won't it give a neutral handling and also a good feedback in means of steering spring pressure? And also simpler to design?

So, how does the castor is better or why do manufacterers prefer castor?

[Boom Shiva]

What about if you park your car with one side on a higher position than the other? Like sometimes when there's debris (e.g. all over bombay) and the left wheels are resting on the elevation and the right wheels are on the road? How badly does this affect your suspension etc?

[vivekiny2k]

Originally Posted by jat

If the steering has zero castor and there are springs provided for self centering then won't it give a neutral handling and also a good feedback in means of steering spring pressure? And also simpler to design?

So, how does the castor is better or why do manufacterers prefer castor?

caster comes into play only at a resonable speed. I don't think you would have ever felt the wheels re-straightening at speed below speed of 10kmph.

spring will keep u pulling back all the time. not a good thing i feel.

[islero]

Originally Posted by Boom Shiva

What about if you park your car with one side on a higher position than the other? Like sometimes when there's debris (e.g. all over bombay) and the left wheels are resting on the elevation and the right wheels are on the road? How badly does this affect your suspension etc?

My question exactly.