I was just reading about torque steer and how it caused by unequal length half shafts and their respective unequal driveshaft angle. Apparently these inequalities produce unequal moments about the steering axis and then you get torque steer. Since the fiero is essentially a FWD set up in the rear is it possible to experience torque steer even though our rear tie rods are fixed? Or do the fixed tie rods make it almost negligible?

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no, TQ steer comes from the the wheels that determin direction and movement. IE the front wheels. the fiero is a transverse transmission in the rear and will do the same thing a longitudal transmission with out a LSD (limited slip differential) rear end would do, just spin one tire.

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[This message has been edited by americasfuture2k (edited 12-09-2009).]

Thats kind of what I figured, but I recall seeing some engine swaps on here with guys who install what I think is called a "layshaft?" that would eliminate the unequal driveshaft angles... what would be the benefit of that on the fiero?

This answer refers to the original post:

That's correct. The fixed tie rods transfer the load to the cradle, so torque steer isn't relevent on the Fiero unless your tie rods or control arm bushings are worn. As for the control arm bushings, under hard acceleration they will flex altering the toe of the rear wheels. As long as they are good, the amount that each wheel toes in or out under hard accleration or deceleration should be roughly equal and opposite in magnitude on either side of the car and cancel out.

[This message has been edited by Bloozberry (edited 12-09-2009).]

From my understanding of it, I would have to say that both arent entirely true.

The phrase "torque steer" implies that the turning force (torque) produces a tractive force which, when unequal between two wheels that have steering capability, will result in the vehicle pulling left or right. So it does have to do with the spinning of the wheels AND the turning of the wheels. So in a fiero, the spinning obviously can come from the fact that its FWD in the rear, and the steering can come from wear/flex in the suspension components in the rear.

So neglecting wear of the components, and eliminating torque steer, my question becomes, whats the benefit of a layshaft to equalize the driveshaft angles in a fiero?

[This message has been edited by doublec4 (edited 12-09-2009).]

quote Originally posted by doublec4: I recall seeing some engine swaps on here with guys who install what I think is called a "layshaft?" that would eliminate the unequal driveshaft angles... what would be the benefit of that on the fiero?

Also called a jack-shaft. The reason people do this is to create equal and opposite forces on both sides of the car due to the component of torque that would result in torque steer. Although with fixed rear tie rods the torque steer is essentially eliminated, it still produces a force which is exerted on the frame. If you can equalize these forces then they cancel out and the frame flexes less.

I don't buy the unequal length argument. It's not like the CV joints are binding at any normal angle.
It's the suspension geometry.

quote Originally posted by americasfuture2k: the fiero is a transverse transmission in the rear and will do the same thing a longitudal transmission with out a LSD (limited slip differential) rear end would do, just spin one tire.

Fieros won't lift one rear wheel, unless something is wrong... my stock open diff Fiero will lay down 2 nice parallel peel-out traces.

Not all longitudinal cars will lift one rear wheel (and spin one as a result). Only the ones with live rear axles and no torque tube.

I guess that would make more sense... I was thinking about implementing something like this but I probably wouldn't notice the difference. Would be a lot more useful for a FWD car though.

The other benefit is less need to accomodate the movement of a long axle for tight installations.

I wouldn't call a jackshaft an improvement, more weight and complexity, for what? It can help with packaging.

On this equal length half-shaft topic, Cadillac CTSs have equal length half-shafts.

But, they're different diameters.

I guess there was some kind of resonance problem, and the different diameters was a way to tune out the excess resonance.

quote Originally posted by pmbrunelle: Fieros won't lift one rear wheel, unless something is wrong... my stock open diff Fiero will lay down 2 nice parallel peel-out traces.

Getrag right?

My understanding is the Getrag is the only fiero trans capable of laying down 2 lines during hard acceleration. Because how the diff is setup though the exact explaination escapes me at the moment.

My 4speed will only lay one line no matter what. Same went with my isuzu before it broke. No matter which one I'm driving I have never felt any real amount of torque steer no matter how much torque is put down. This is with a 4.9 ran behind all 3 trans at different times. Not something I would concern myself with.

I have an Isuzu.

Fieros don't naturally have a tendency to lift one rear wheel, but there can be other factors which affect the left-right traction balance.
Weight distribution, and rear wheel camber are the ones that come to mind.

To clarify:
They can spin one wheel due to those factors and nothing's wrong.

They're all open diffs, they should all be the same with regard to the one-wheel spin. Even the automatics.

[This message has been edited by pmbrunelle (edited 12-09-2009).]

CTS's are rear wheel drive... so it wouldn't matter. Unless you're talking about the AWD, and AWD cars don't really get torque steer.

Yes, hypothetically the fiero will see some sort of the torque steer one wheel turning faster than the other and play in the rear suspension could give you torque steer. In my years of driving manual and automatic 2.5 through 3800SC fieros I have never once gone "oh **** torque steer".

As I understand it, torque steer is feedback through the steering wheel caused by engine torque. Since the rear wheels in the Fiero are not connected to the steering wheel, and the front wheels are not driven by the drivetrain, then by definition the Fiero cannot experience torque steer.

That said, with a powerful enough engine, the forces exerted on the rear tie rods may be enough to damage the tie rod mounting brackets. I'm not sure how much power would be required to do that, though. And I doubt the length of the drive axles is going to make a difference in that.

To sum it up, there's no pressing need to have equal length drive axles in a Fiero.

There's alot of misunderstanding of torque steer here. Torque steer has nothing to do with one wheel turning faster than the other or loss of traction. Torque steer is soley the result of torque being applied to an angled shaft. I can post the math, but essentially the angled shaft results in the torque being broken down into two components, the largest component rotates the wheel in the forward direction, but a smaller portion of the torque gets applied to the hub in the steering axis. The greater the angle to the road surface, the greater the proportion of the torque that is applied in the steering axis.

It follows then that if two axle shafts are different lengths as a result of the transmission being offset to one side, then the axles will be at different angles in relation to the road. The shorter axle will have a greater angle and thus create a greater force in the steering axis than the hub with the longer axle. The forces are in opposite directions from one side of the car to the other, so they act through the steering tie rods on the rack in opposite directions. If they aren't equal forces, then the rack is forced in one direction or the other, which is why in a FWD car you feel the steering wheel tug in your hands.

Unequal TRACTION on the other hand results in asymmetric thrust along the centerline of the car. When the traction of the drive wheels is unequal, it produces a moment about the center of gravity of the car which results in yaw. Like torque steer, it rotates the car in the steering axis... it's just not called torque steer.

I didn't think about the angle of the shaft causing a force on the knuckle, that part flew by me. Interesting.

Another thing though that would cause torque steer is a non-zero scrub radius. You would get a moment around the steering axis when flooring it. When going straight, both left and right tie-rods would be equally pushed/pulled. However, when turned, the tie-rods won't be equally pushed/pulled. This is because the steering arms are not parallel.

Edit to include my amazing work with mspaint; a pic is worth 1000 words:


A small note to add on the unequal traction - the asymmetric thrust shouldn't happen with an open diff, which always splits torque equally between the wheels.

[This message has been edited by pmbrunelle (edited 12-09-2009).]

if by an open diff you mean any garden variety non lsd type differential , then an open diff does not distribute the load evenly between both wheels .the wheel with the least traction will always get the torque or turning force .best illustrated by being stuck in the snow , one wheel spins , the other just sits there .LSD in a front driver reduces torque steer but does not elliminate it , and only gear type lsd's (non clutch pack) can be used in a front driver .the fiero does not suffer from torque steer .i really dont know why my fiero will lay down 2 strips of rubber ,other than with the open diff , if both tires are equal and the pavement is the same under each tire then you should get equal traction .but most of the time , road and tire condition vary from side to side .

quote Originally posted by wftb: if by an open diff you mean any garden variety non lsd type differential , then an open diff does not distribute the load evenly between both wheels .the wheel with the least traction will always get the torque or turning force .best illustrated by being stuck in the snow , one wheel spins , the other just sits there.

An open diff does split torque equally - in cases like the snow example, both wheels get practically nothing.
Don't confuse the wheel speed with the torque!

A LSD on the other hand, does not distribute the torque evenly - you can have one wheel on a slippery surface just along for the ride, and the other handling most of the torque.

I can tell you that if you have worn or loose components you CAN and WILL get torque steer.

If you don't believe me go out and drive my Indy on the freeway and punch it, the car will dive to one side, then let up and it will dive back the other direction.

quote Originally posted by jscott1: I can tell you that if you have worn or loose components you CAN and WILL get torque steer. If you don't believe me go out and drive my Indy on the freeway and punch it, the car will dive to one side, then let up and it will dive back the other direction.

I was just going to say if you have worn out components you can experience torque steer

If "Torque Steer" is defined as "a change in the direction of travel of the car as the result of increasing or decreasing the torque applied to the transverse drivetrain" then yes a Fiero will torque steer.

Come take a ride in my Fiero. You will believe that it happens. :-)

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Steve AT 88GTP DOT com
88 GT\3800 SC\4T65E-HD

Torque steer in a FWD vehicle is something completely different than what you would experience in a Fiero. I do believe that in some Fieros you can accelerate and the car goes to one side, then let off and the car goes to the other, but that is caused by worn suspension parts or some other underlying problem. In a FWD car, you have a short shaft on one side and a long shaft on the other side, the car always pulls to the side with the longer shaft, meaning the side with the short shaft is trying to accelerate faster. With more torque applied to one side of the car, the steering wheel will try to pull to the one side. This cannot happen in a Fiero as the drive wheels are not the steering wheels.

Also, this has nothing to do with the differential. An open differential applies the same amount of power to both axles under normal traction. When enough torque is applied to break one tire loose, it can because the spider gears will begin to spin. When going in a straight line the spider gears are not spinning on their bearings. When you take a turn one tire is spinning faster than the other and the spiders will allow the smooth transition.

One way to tell that the diff has nothing to do with it is simple. If you have a FWD car that torque steers, then add a jack shaft, the torque steer goes away using the same diff. It only has to do with the axles lengths and angles.

-Joe

Torque steer in Fiero?
Yes But not the half shaft, ie fwd, version.

Torque and rubber cradle mount can cause this because of the dog bone. Dog bone make the right side of the cradle more than the left side when it accelerate or decelerate. Stick tranny does it more then auto tranny but auto can do it to, especially if the cradle is soft.

Twist the cradle and cradle going nut in steering alignment. A arm and tie rod is connected to cradle, top of strut to frame....

That's why how a cradle mount method is importance in 84-87 Fiero... Polly is less but Metal stops that cold.

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quote Originally posted by joesfiero: meaning the side with the short shaft is trying to accelerate faster. With more torque applied to one side of the car, the steering wheel will try to pull to the one side. This cannot happen in a Fiero as the drive wheels are not the steering wheels. -Joe

This part isn't true Joe. One axle is not trying to accelerate faster than the other, nor is more torque being applied to one side of the car... even you contradict yourself when you say that "an open diff applies the same amount of power to both axles". Also, torque steer doesn't HAVE to act through the front wheels in order for it to be called torque steer, and so it CAN and DOES happen in a Fiero with worn rear tie rods. Take a look at the old four wheel steering Honda Preludes of the late '80's early 90's to see that it only takes a very small deflection in the rear wheels to produce a large steering input. That's one of the reasons the system didn't provide any inputs above parking lot speeds. I think the Preludes had something like a maximum of 4* of steering. You can easily get this kind of change in rear toe due to torque steer with worn rear tie rods and or control arm bushings on a Fiero undergoing acceleration.

quote Originally posted by Bloozberry: This part isn't true Joe. One axle is not trying to accelerate faster than the other, nor is more torque being applied to one side of the car... even you contradict yourself when you say that "an open diff applies the same amount of power to both axles". Also, torque steer doesn't HAVE to act through the front wheels in order for it to be called torque steer, and so it CAN and DOES happen in a Fiero with worn rear tie rods. Take a look at the old four wheel steering Honda Preludes of the late '80's early 90's to see that it only takes a very small deflection in the rear wheels to produce a large steering input. That's one of the reasons the system didn't provide any inputs above parking lot speeds. I think the Preludes had something like a maximum of 4* of steering. You can easily get this kind of change in rear toe due to torque steer with worn rear tie rods and or control arm bushings on a Fiero undergoing acceleration.

I am going to have to say Bloozberry is right he has explained it more than once now. Also I would like to add my .02 and say that I have experienced torque steer as well on worn out components.

No one mentioned the effect that torque has on the axle itself as the length increases. In a perfect plain with an axle as long as what's found in the manual Fiero, you may still experience some torque steer if it were in a front wheel drive car. With the axles fixed perfectly parallel to the ground, on hard acceleration a longer axle can twist more between both joints than a much shorter more rigid axle. If you have access to a pair of axles you can confim this, unless one of mine was an aftermarket replacement. The passenger side shaft is noticeably thicker than the driver side shaft. Perhaps that has as much to do with it as axle angle. From a trigonomic stand point I would expect the effect to favor changes going in the direction of motion which in this case is forward. The instantaneous torque would result in more twisting deflection in the longer shaft before actual movement of suspension occured where the shorter shaft would have much less and result in the wheel it is attached to starting its rotation an instant quicker slightly turning the steering wheel to the opposite side. I'm just reasoning from something I apparently read about the subject many years ago, not stating this as a factual cause. I'm sure unequal suspension angle has its effect to.

Actually, bloozeberry, I am correct. I have done some extensive research and a little bit of testing with torque steer.

The part where you say I contradict myself - let me clarify. An open diff DOES put out equal power to both sides while both tires have traction. However, the length of the axles affects the amount of torque applied at the HUB. A longer shaft, unless it is substantially thicker to the point it is as rigid as the shorter shaft (which is not the case in any car that feels torque steer) will deflect enough to rob torque at the hub. You can verify this with just a ratchet and two different length extensions. The longer extension will apply less torque at the bolt than the shorter one with equal torque at the ratchet. Thus, less torque is applied to one side of the car under acceleration causing torque steer.

And you really dont have to educate me on 4 wheel steering, I drive a Silverado with Quadrasteer. At low speeds the rear wheels turn 12 degrees in the opposite direction of the fronts. At higher speeds they turn the same direction. As I already stated, I know a Fiero can pull to one side under acceleration if it has worn suspension or steering components. However, this is a whole different feeling than torque steer. You must drive both kinds of cars to understand the difference, torque steer will try to pull the steering wheel out of your hand, worn suspension components will simply move the car where it wants to go. You can correct it by steering the wheel the opposite way, but thats not where the force is being applied by the torque of the engine.

-Joe

quote Originally posted by joesfiero: A longer shaft, unless it is substantially thicker to the point it is as rigid as the shorter shaft (which is not the case in any car that feels torque steer) will deflect enough to rob torque at the hub. You can verify this with just a ratchet and two different length extensions. The longer extension will apply less torque at the bolt than the shorter one with equal torque at the ratchet. Thus, less torque is applied to one side of the car under acceleration causing torque steer.

This isn't quite true either Joe. If it were, then the longer your extension between the socket and the torque wrench, the more you would have to dial up the wrench to get the proper torque at the socket! It doesn't work that way. 30 lbft applied with a 4" extension is the same as 30 lbft applied through a ten foot extension. The longer axle (or ratchet extensions if you prefer), only act as torsion rods or springs. They transmit just as much torque to the driving end of the shaft as what is being applied to the driven end. The only effect that a longer extension or axle has here, is that under conditions of changing or dynamic torque (ie increasing or decreasing), some initial energy is taken up and stored or released by the axle as it twists or untwists, just like a spring. This effect only lasts as long as the torque is changing. As soon as the applied torque is steadystate, the torque at the other end of the axle is identical to that which is being applied. So you might argue that it's the DELAY that causes difference in torque at the wheels, which causes torque steer. It may play a role in generating torque steer, but it would be neglible compared to the amount generated by unequal angle shafts. The torque produced by unequal angle shafts is a 'constant' force proportional to the amount of torque applied at any given time, whereas the effect of a difference in torque at the wheels due to the twisting nature of the axles will only last as long as it takes for the axle to stop twisting. Given the spring rate of the axles in torsion, that effect might last a few milliseconds.

quote Originally posted by joesfiero: As I already stated, I know a Fiero can pull to one side under acceleration if it has worn suspension or steering components. However, this is a whole different feeling than torque steer. -Joe

That's only because you keep holding onto the idea that torque steer can only happen if it's applied to the set of wheels with a steering wheel attached. The steering wheel being snatched from your hands is only the 'symptom' of torque steer in a FWD car. The symptom of torque steer in a Fiero is the wandering rear end with worn tie rods. They feel very different, but they are both the result of torque steer.

Im trying to be as polite as possible because I am not a confrontational person.

However, you are incorrect when you say the same amount of torque will be applied to a bolt as is applied to a ratchet through an extension. Its all about leverage. If you have a real long extension, you are going to lose torque even when a static amount is applied through it. An exercise to determine this is to take a torque wrench, two extensions of different lengths and a bolt. First, set your torque wrench to a desired torque, say 45 ft.lbs. and tighten the bolt with a long extension, say 20-24 inches. You can hold the torque wrench with the applied torque as long as you wish. Now, put the shorter extension, say 4 inches on and without changing the torque wrench, apply the torque again, guess what? The bolt will spin, as you have less parasitic loss through the shorter extension, thus increasing the torque at the bolt. It doesnt take shock loading the extension to lose torque through it.

The same applies to longer axles vs. shorter axles. With equal torque coming out of the diff, you will have different amounts of torque at the hubs.

At this point I think its safe to say that you can really call it whatever you want. If you want to call what the Fiero does "torque steer" than so be it. I suppose you can call any pulling to one side torque steer if you really wanted to. The reason I even chimed in to this thread is because of the amount of research I have done on this topic. The term itself was coined to describe what happens to a FWD vehicle under certain conditions where the torque applied under acceleration causes the steering wheels to steer to one side. Of course there are other terms out there to describe other conditions, like bump steer which our vehicles do (84-87 mainly) and roll steer. They are all terms to describe a specific condition that affects a specific vehicle layout.

-Joe

Don't get me wrong, I'm not trying to be confrontational either. I just want to be certain that the correct information is posted here.

So, in that light, here is the equation for torque:

F x L = torque

where F is force in lbs or Newtons, and L is the moment arm in inches, feet or meters.

So for example 15 lbs applied to the end of a lever that is two feet long gives 15 lbs x 2 feet = 30 lbft of torque.

Nowhere in this equation is there a factor for how far away the force is applied, for example, using extensions vertically away from the surface of the lever. It really doesn't matter. Next time you do your test, add your extensions, tighten the bolt, wait a minute, tighten it again, and repeat once more. Then remove your extensions and try it. The bolt won't turn unless your torque wrench isn't giving you repeatable results... which is highly likely the case.

The thing about pushing on the handle of a torque wrench with an extension, is that it not only causes a twisting force, but a bending force also, depending on the length of the extension. With an extension you would have to push harder on the handle to achieve the same torque. This may be a source of confusion.

On a car driveshaft, there is no bending, so it's not even relevant.

[This message has been edited by pmbrunelle (edited 12-10-2009).]

The point of that exercise is to prove that the longer extension absorbs some of the torque, which in turn doesnt transmit all of the energy applied to the driven end.

And yes, if you tighten a bolt with a long extension, then recheck the torque with a shorter extension you will find that the longer one didnt transmit the same amount of torque. Another example is a spring or torsion rod, which you mentioned yourself. If you have a torsion rod suspension on a car and the car is sitting still, there is X amount of energy stored in the torsion rods. The suspension is not moving (I.E. dynamic torque) and there is a certain amount of force applied to the control arms of the car, keeping it suspended. Now, with the same exact car, if you shorten the torsion bars you will notice the car will sit higher. This is because less energy is being stored in the torsion bar itself and more force is applied to the control arm.

Just like cutting the springs in a Fiero. The car will sit lower, but the spring rate will increase because the spring rod is shorter. If you dont believe me still, I highly encourage you to try the torque wrench example I explained. When torque is applied at one end of the extension, the same amount of torque is applied at the driven end until the resistance on the driven end is greater than the amount of "give" the extension has. The longer the extension, the more give.

While this should be pretty easy to understand with all the examples I have given, I do not claim that torque steer is due solely to axle length. The angle of the axles also plays a pretty big role in torque steer in a FWD vehicle. While I do not agree with using Wikipedia as a reference for anything since it is all user submitted, this page actually gives some pretty dead on information from all of my references. Towards the bottom of the page read where it says "Note that rear-wheel-drive vehicles do not suffer from the torque steer effects on the rear wheels, since the engine is not connected to the steering gear unless it has all wheel steering." Every bit of information I have found in my research has explained that the term "torque steer" applies only to the effect of engine torque on the steering of FWD vehicles.

-Joe

The straight green arrow pointing down shows the force of your hand.
The curved arrow shows the twisting.

The extension bends because you are pressing downwards. This wouldn't happen with a cross-type lug wrench.

quote Originally posted by joesfiero: If you have a real long extension, you are going to lose torque even when a static amount is applied through it.

quote The point of that exercise is to prove that the longer extension absorbs some of the torque, which in turn doesnt transmit all of the energy applied to the driven end.

quote Originally posted by Bloozberry: 30 lbft applied with a 4" extension is the same as 30 lbft applied through a ten foot extension. The longer axle (or ratchet extensions if you prefer), only act as torsion rods or springs. They transmit just as much torque to the driving end of the shaft as what is being applied to the driven end. The only effect that a longer extension or axle has here, is that under conditions of changing or dynamic torque (ie increasing or decreasing), some initial energy is taken up and stored or released by the axle as it twists or untwists, just like a spring. This effect only lasts as long as the torque is changing. As soon as the applied torque is steadystate, the torque at the other end of the axle is identical to that which is being applied.

I'm sorry, Joe, but you're wrong, and Bloozberry is correct. Part of the problem is that you're using the terms force, torque, power, and energy too loosely.

Assuming for a moment that you were correct, where does all that energy that is "absorbed" in a long torque tube go? Does the torque tube heat up indefinitely? No. As Bloozberry correctly stated, once steady state is reached the torque out will equal the torque in ... regardless of the length of a torque tube.

[This message has been edited by Marvin McInnis (edited 12-11-2009).]

quote Originally posted by joesfiero: The point of that exercise is to prove that the longer extension absorbs some of the torque, which in turn doesnt transmit all of the energy applied to the driven end. -Joe

Got to go with Joe on the different length extension example. He is absolutely correct. The extension will twist.

That is the principle of a torque stick.

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Steve AT 88GTP DOT com
88 GT\3800 SC\4T65E-HD

quote Originally posted by Steve25: Got to go with Joe on the different length extension example. He is absolutely correct. The extension will twist. That is the principle of a torque stick.

Steve, no one is disputing the fact that the axle will twist. What's being misunderstood here is that torque is being absorbed and LOST through the twisting motion. If this were true, then theoretically you could attach a super long axle to an engine, and keep it from turning with your bare hands. This isn't true because the twisting of the axle is only stored energy, not lost. As soon as the super long axle was done twisting (and storing the energy), I can assure you that you wouldn't be able to keep it from turning with your hands, or anything less than an opposite amount of torque the engine is producing.