1999 Hard steering at idle
- Thread starter Outdrdude
- Start date
Qyota
New member
Munkey, no one is arguing that whacking bumps whilst driving isn't hard on the steering. My point is that turning the wheel while stopped is more stressful to the steering and tires than turning the wheel while rolling. Get it? That's all I'm saying.
But, assert whatever you want. It's a free country, and a free forum. Go nuts!
But, assert whatever you want. It's a free country, and a free forum. Go nuts!
TheDurk
Elite Member
The idea of not turning power assisted wheels when the car is stopped has been around for a very long time. The concern is, I believe, not with the mechanical side of the system, but the hydraulic. If you go lock-to-lock while stopped, the hydraulic system has a hard time keeping up and the pump will be throwing maximum pressure at the system for several seconds while encountering maximum resistance. Nothing like this occurs in normal motion, even off-roading (unless a wheel is stuck between two rocks, but that means you are stopped. You should know better than to force your hydraulics in that situation, too.)
The concern here is that you are over-stressing the HYDRAULIC system, and you might achieve an over-pressure situation, causing something to pop.
That said, when I go to DC or NYC (or São Paulo in my HiLux) or any parallel parking environment, I do this all the time. I turn the wheel slowly enough that the system stays 'caught up' and pressure does not spike (not all that slow--just don't spin it way ahead--some people do.) If the wheels keep turning after you let go of the steering wheel (to 'catch up'), that's not good.
The concern here is that you are over-stressing the HYDRAULIC system, and you might achieve an over-pressure situation, causing something to pop.
That said, when I go to DC or NYC (or São Paulo in my HiLux) or any parallel parking environment, I do this all the time. I turn the wheel slowly enough that the system stays 'caught up' and pressure does not spike (not all that slow--just don't spin it way ahead--some people do.) If the wheels keep turning after you let go of the steering wheel (to 'catch up'), that's not good.
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So you've seen a situation where the vehicle is stationary, there are no steering inputs, yet the wheels keep turning? I can see this being possible in a fully hydraulic system, but how can this happen on a hydraulic assisted system that has solid mechanical linkages from the steering wheel to the wheels?
I seriously want to know, not trying to start crap on here...this whole thread has made me go :wtf: numerous times and I want to find out the correct answers for my sake, and any other poor soul who starts thinking about these things as well.
I understand the stresses applied to the pumping system; and hopefully the pumps relief valve is working so nothing will go POP. I've seen a few pump specs and testing procedures; I was always under the assumption that the pump pressure is determined by the amount of steering input; small input, low pressures, high inputs (wheel cranked all the way) high pressures. Should not the steering stops be setup in such a manner to LIMIT the motion of the wheels to a point before the pump reaches its max pressure and thereby avoid damaging the system?
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TheDurk
Elite Member
I don't get your first sentence. I am saying when you are tuning the wheel as fast as you can, putting max pressure to the rack piston, by twisting the torsion bar, it takes a split second for the wheels to catch up and the pressure to equalize. It is solid--sort of. If it were totally solid, the hydraulic system would never activate and there would be no power assist. If you keep turning, the system never catches up, until you either stop turning or hit the lock.
You have more confidence in by-pass valving than I do. Continuous use of the by-pass relief will cause super-heating of the fluid and the combination of temperatures and pressure beyond design parameters can cause something to go POP. I am by no means saying that doing this once will explode your system. I am saying that you are stressing the system beyond design parameters if you keep it up for too long and do it too often. I have been operating maintaining and repairing hydraulic farm equipment all my life and putting a pump into by-pass is not good for it or the other components.
When testing pressure in the Toyota system, the FSM instructs you to hold the wheel to lock for 2-3 seconds. Then in BOLD it says: Do not maintain lock position for more than 10 seconds and Do not let the fluid temperature become too high. Wonder why that is?
I guess you failed to grasp that I posted in part to AGREE with you that the mechanical stresses in stationary steering are no real concern. But I do have a concern about the hydraulic side. These things fail enough that avoiding a high stress load makes sense to me. Where's the BS in that?
You have more confidence in by-pass valving than I do. Continuous use of the by-pass relief will cause super-heating of the fluid and the combination of temperatures and pressure beyond design parameters can cause something to go POP. I am by no means saying that doing this once will explode your system. I am saying that you are stressing the system beyond design parameters if you keep it up for too long and do it too often. I have been operating maintaining and repairing hydraulic farm equipment all my life and putting a pump into by-pass is not good for it or the other components.
When testing pressure in the Toyota system, the FSM instructs you to hold the wheel to lock for 2-3 seconds. Then in BOLD it says: Do not maintain lock position for more than 10 seconds and Do not let the fluid temperature become too high. Wonder why that is?
I guess you failed to grasp that I posted in part to AGREE with you that the mechanical stresses in stationary steering are no real concern. But I do have a concern about the hydraulic side. These things fail enough that avoiding a high stress load makes sense to me. Where's the BS in that?
100% correct; from your earlier post I had taken it as you would stop turning the steering wheel, and still have noticeable movement at the wheels; "Hey my hands are off the wheel but the wheels are still turning, weeee!" The movement of the torsion bar will always have the system in 'catch up' just like you say. I was thinking about the macro-view of the steering system as a whole, and I guess you were thinking about the micro pertaining to the steering box internals.
Exactly, thats why I said hopefully the relief valve is working. With your posts and work experience, you know what is going on, and like I said before, I'm not trying to start any arguments, I've got serious questions, and am seeking serious exact answers (which you're providing). I guess I'm just dealt with too much sheeple mentality that I immediately question why something is 'bad' or 'good'. I want to know why is it bad/good, and to what extent.
The steering gear is locked; akin to closing a valve in the pipe leading back to the pump. Should the steering stops not be set to limit the travel, keeping the steering gear from being fully locked, and thereby prevent pump damage?
The mechanical stresses are a moot point; when you posted about the hydraulic stresses, the wheels turning etc it brought up more questions in my mind, and like I said in my earlier post, I'm seeking answers not a B.S. forum argument. I always like to know the exact reason 'why' behind everything.
:boink:
TheDurk
Elite Member
Okay, we are on the same page except for this paragraph. It has to lock sooner or later, at the rack/pinion, the piston, or elsewhere, and if somebody is still trying to turn the steering wheel, the system will go to max pressure. I don't think that will change until we go to steer-by-wire (which is coming). You would have to add a lot to the system to avoid that; it is not a matter of 'setting the stops', whatever you mean by that. I know what it is on a tractor, but steering wheels/shafts don't have stops, they just keep turning until the rack ends.
I'm talking about the steering stops on the knuckle. Maybe I'm misunderstanding the way the torsion bar works inside the steering box.
I though the torsion bar twists relative to the amount of steering input; when the steering wheel is straight, there is equal pressure seen at either side of the piston on the rack. It the wheel is turned to the right, then the torsion bar twists, closing off or narrowing the passages to the 'left' side of the piston decreasing the pressure, and opens up the 'right' side increasing the pressure, and turning the wheels to the right. I thought the amount you turn the wheel was relative to the amount that the torsion bar opens or closes right/left sides. Full right turn, end of rack, then the 'left' side is completely closed, and 'right' side is fully open.
I had always though that another function of the steering stops on the knuckle was to prevent one 'side' of the torsion bar from reaching a fully closed position, thereby not allowing the pump to be operating in a fully locked, end of rack, position. Is this not another reason (besides limiting the turning of the wheel) to properly set the steering stops if my original idea of how the torsion bar works is correct?
LOL, is this making sense?
:nerd:
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TheDurk
Elite Member
Ahh, so it springs back to the neutral position when there is no steering wheel movement, makes sense now! My assumption about the steering stops was wrong; now I need to go back and dig through a mountain of technical data from where I thought I had read that and figure out what it really says!
Hey thanks for clearing this up! It's always nice to have someone such as yourself to FULLY explain things!
:thanks:
