Another thing they taught in driving school, don’t turn the steering wheel when the car isn’t moving. Wondering if this is True or Because the test said so.
I took driver’s ed in 1976, and the text was pretty far behind about car technology even then. The book made it seem that cars had either automatic transmissions or 3-speed on the column manuals.
Perhaps the warning to not turn the wheel is left over from the days of no power steering- it can be difficult to turn the wheel on a large car with no power steering if it’s not rolling.
This is my guess- others may speak to the mechanical aspects of your question.
I’ve always heard that turning the wheel when the car is stationary maximizes the pressure produced by the power steering pump, which is not good on the pump, fittings, and hoses.
Most cars today have power steering. This makes it easy to turn the wheels at any time. There are times, such as while parking, when it really helps to turn the wheel while not moving so as to gain the maximum turning radius. This produces slightly more wear on the tires I believe and very slightly more strain on the steering geometry. Therefore, it is better to at least be moving a little when turning.
Also, When the wheel if turned to the fully locked position right or left, the pressure in the system is at its peak. Yes, there is a pressure relief valve mechanism to avoid excess pressure. I believe the less time spent with the wheel in full lock, the better for avoiding seal leaks.
File this under ‘negligible’ effects.
When going down a road at 45 mph and you steer into a curve at 35 MPH, what exactly is easier on the pump at this point? That’s a pretty hefty job right there. 2 tons barreling straight ahead at 35-45 MPH and the pump has to get the wheels to turn, hold that turn for the length of the curve and resist the desire to self center, then it might have to react and curve the other way. It’s a-working pretty good right there.
Parking? I think you might hear the pump yawn.
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While I’d be pretty surprised if turning the wheels while stationary posed any significant danger to modern power steering systems, it’s pretty obvious that holding the wheels in a 45mph turn requires less force than turning the wheels while stationary. Just try doing both in a car without power steering. That increased effort at low or no speed? That’s extra force that the power steering system has to deliver.
Agreed. I have driven cars without power stearing and it takes little force on the stearing wheel to turn a car while moving.
A standard issue Saginaw pump in a Chevy truck will make somewhere between 0 and 200PSI in a rolling turn and up to 1000-1200PSI in a static turn.
In the pre-PS days, the Rolls Royce chauffeurs’ school requested “no dry steering”, meaning no turning of the wheel when not rolling. I never figured out whether it hurt the car, the tires, or messed up the gravel driveways.
given those cars were junk made out of expensive materials, I’d wager it was the first.
its actually very bad on the tires. When the car is rolling the friction requrred to turn the wheel (from tire meeting road) is very small. When the car is sitting still, the weight is on a fixed area. If you store a car the tires actually get flattened—not out of air, but a flat spot and there is no way to correct it short of buying new tires. Its hard on the power steering since its designed to be used with hydraulic pressure, but its very hard on the tires.
I’m sorry, are we begging the question here?
Wear is PSI or … wear?
Posted too early.
What I mean is… are we begging the question?
The OP approaches this as though strain on the pump is going to lead to failure, so others pursue attempts to determine what produces the most strain. But is the issue at hand wear… from use, wherein as long as strain is within the designed range, the actual driving and turning and doing this over and over and back and forth is the real issue at hand.
Or… nevermind…
I heard it was because of pump pressure, but I’d be interested in any reason not to turn the wheels when the car is stationary.
I second what gypsy100 said. The reason you do not want to turn the steering wheel when the car is absolutely stationary is that you do not want to flat spot the tire. At the contact point (where the rubber meets the road) you can wear that spot enough that it will cause the tire to be out of round at that spot and cause a vibration, at highway speeds.
In reality to get a tire to flat spot you would need to be on asphalt or rough concrete and go lock to lock a few times.
If I am working on a car and if I want to bleed the power steering system I sometimes have to go lock to lock many times in the steering wheel in which case I will either raise the wheels off the ground or put cardboard under the front wheels so there is no relative motion between the tires and the surface it is sitting on. The cardboard takes all the wear.
It may have been easier at one time to flat spot tires since even in the past 10 years tires have improved significantly.
ETA The power steering pump and the power steering rack are deigned to handle the loads it would encounter on a daily basis. I do not think (even at max pump pressure) there is any significant strain on the pump. As for the tie rods and tie rod ends, I don’t think the extra strain is significant either. They are pretty rugged even on my small Toyota.
tires can last 60,000 miles these days. you really think a few turns while stationary will flat-spot the tires enough to be noticeable?
I think the issue they were dealing with was one of safety. That it isn’t bad for the car, but that it’s unsafe. You won’t know which direction the car is pointed when you step on the gas. Personally I think it’s overkill. Except for one case: You should NOT turn the wheels while waiting to turn at a light or stop sign in case you’re hit from behind, it’ll push you into oncoming traffic.
All other things, its strain on the power steering pump and or tires etc., are negligible.
Some cars are more sensitive to front wheel imbalances than others. On some cars as little as 1/2 an ounce of imbalance in one of the front wheels will cause a noticeable shimmy in the steering wheel at 65 mph.
So yes I do think a few turns MAY be enough to make a flat spot on a tire which will cause a noticeable vibration.
I should add that I do not know what makes some cars more sensitive to wheel imbalances than others but I have seen it happen.
Cost benefit - if you don’t live in a city where you’re lucky to have a foot maneuvering room, why not roll while you turn?