I'm an idiot...

[MX793]

Two wheels spinning at the same speed will move you better in a straight line rather than one wheel spinning in an unequal fashion. (To the other)

Besides, most LSD's that aren't performance oriented are viscous........so there shouldn't be too much of an abrupt power shift.

On a crowned road (as almost 100% are), both rear wheels breaking loose under power when traveling in a straight line will cause the rear end to immediately swing out of line towards the ditch/curb.  With an open diff, only one wheel will typically break loose under power while the other will maintain rolling traction.  This generally reduces the tendancy for the back end to step out of line.  Although from experience, this will still happen with an open diff as well.  I remember my car crabbing a bit when trying to scale slippery hills when I had my 240SX.  Even on my FWD with an open diff, the front end will tend to seek the side of the road when the fronts break loose and start to spin.

[Rupert]

Wow, gocougs is hilarious

What else is new?

[GoCougs]

An open differential will spin whichever wheel is easiest to break loose, typically the inside drive wheel (regardless of which direction you're cornering).  Jack up either drive wheel on an open diff, and the car will not move, it will just spin whichever wheel is up in the air.  It will not act like a limited slip when one wheel is jacked up but like an open diff if the other is the lifted wheel.

The turn I looped it on was a right-hander, BTW.  My car also did not favor left handers to right handers when doing donuts in the snow, as it would if the differential behaved differently depending on the direction the car was turning.

As a hint: when accelerating in a straight line, with equal traction under both tires as on pavement, why is it ALWAYS the right tire that spins with an open diff? The answer here explains why on a left hand turn an open diff will generally act like an LSD.

[sportyaccordy]

As a hint: when accelerating in a straight line, with equal traction under both tires as on pavement, why is it ALWAYS the right tire that spins with an open diff? The answer here explains why on a left hand turn an open diff will generally act like an LSD.

Only explanation I can think of is the fact that the road is banked would pull the car to the right...


But if your car always pulls right... it's prob cause of unequal length driveshafts

[GoCougs]

Only explanation I can think of is the fact that the road is banked would pull the car to the right...

Actually, it will happen on a perfectly flat surface.

In all instances, straight (right tire spins), right turn (right tire spins), left turn (both tires spin), the open differential is doing exactly as it was designed, if that's any hint.

[sportyaccordy]

Actually, it will happen on a perfectly flat surface.

In all instances, straight (right tire spins), right turn (right tire spins), left turn (both tires spin), the open differential is doing exactly as it was designed, if that's any hint.

Can't be the case on every car. I will try this on my car tonight.

[GoCougs]

Can't be the case on every car. I will try this on my car tonight.

On a FWD car, with a transverse engine especially (hint, hint), I doubt you'd see it.

This more or less started because of the discussion regarding RWD; and my commentary was related only to RWD.

[MX793]

There is nothing in the differential that should favor the right wheel.  The only asymmetrical feature in the device is the ring gear that holds the pinions, and that isn't fixed to either of the half-shafts, it can spin at a different speed from either of the outputs.  And I'm 99.9% positive I've had only my left wheel spin when I had my RWD car.

And like I said, it didn't favor one direction when doing donuts.  If it acted like a limited slip in a left turn but not in the right, it would snap oversteer when making a left but not when making a right.  It didn't do that.  I've also witnessed semis with open differentials only spin the left sides when stopped on ice.  I've even seen them spin the left side on one axle and the right on the other.

The only thing I can think of that would favor the right drive wheel spinning is the fact that the left side of the car is generally heavier than the right (for a LHD car, at least).  On a uniform surface, that would mean that the right wheel would have less traction than the left and would be the first to break loose.

[GoCougs]

Yes, you're 100% correct that nothing inside your average open diff favors the right wheel, yet as we all know, the right wheel will always spin under a loss of traction when in a straight direction, like a hard launch from a stop sign.

The hint to Sporty was the transverse engine - a longitudinal engine w/clockwise crank rotation (as viewed from the front of the engine) as all modern engines are will load the pinion in the clockwise direction - this will plant the left tire and unload the right tire; ergo, the tell-tale sign of the peg-leg, right-wheel burnout.

When turning right, this planting of the left tire is compounded by left-sided body roll as the vehicle negotiates the turn, further guaranteeing spinning only the right wheel.

When turning left, this planting effect is counteracted by right-sided body roll as the vehicle negotiates the turn, evening traction between right and left, thereby letting both tires spin.

This phenomenon in my experience is at least 95% reliable, and reaches across all RWD vehicle types that I've had; raised trucks, standard height trucks, and cars big and medium. A poor man's LSD is to use an air shock, block in the spring, or even a one-sided roll bar, to prevent this planting action.

This being the holiday season, I won't even charge NACar nor Psilos for their edumacation.

[Rupert]

Esqueeze me? Where did I disbelieve you?

I'm stilling waiting to pass judgment until I see someone who knows about these things (not saying you don't...) responds.

[MX793]

Yes, you're 100% correct that nothing inside your average open diff favors the right wheel, yet as we all know, the right wheel will always spin under a loss of traction when in a straight direction, like a hard launch from a stop sign.

Usually, but not always.  On ice and snow, you'll find that it doesn't necessarily favor the right wheel as consistantly as on dry or otherwise more uniform surfaces.  Partly due to less uniformity in traction, and partly because when traction is low, it doesn't take much torque to break the tires loose and you don't get as much torque induced weight transfer from left to right.  If the left is on the slicker surface or otherwise easier to spin (e.g. jacked up in the air), the left will be the one that spins.

Case in point, this V6 gen 3 Camaro:

http://www.youtube.com/watch?v=PtNVJRbGvy0

Or, if you watch this E46 3 series doing donuts in the snow and watch the rooster tails off the wheels, you'll see that it's typically the inside wheel that is the one throwing snow regardless of which way the car is turning.  Even when straightening out after a drift or donut, you can see the rooster tail switch between tires (sometimes both will throw a tail simultaneously).

http://www.youtube.com/watch?v=jAJmsuDfkVA&feature=related

[GoCougs]

Usually, but not always.  On ice and snow, you'll find that it doesn't necessarily favor the right wheel as consistantly as on dry or otherwise more uniform surfaces.  Partly due to less uniformity in traction, and partly because when traction is low, it doesn't take much torque to break the tires loose and you don't get as much torque induced weight transfer from left to right.  If the left is on the slicker surface or otherwise easier to spin (e.g. jacked up in the air), the left will be the one that spins.

Case in point, this V6 gen 3 Camaro:

http://www.youtube.com/watch?v=PtNVJRbGvy0

Or, if you watch this E46 3 series doing donuts in the snow and watch the rooster tails off the wheels, you'll see that it's typically the inside wheel that is the one throwing snow regardless of which way the car is turning.  Even when straightening out after a drift or donut, you can see the rooster tail switch between tires (sometimes both will throw a tail simultaneously).

http://www.youtube.com/watch?v=jAJmsuDfkVA&feature=related

So then you agree with me?

Sure there are anomalies ("95%").

FWIW, it was not uncommon for V6 gen 3 Camaros to be outfitted with an LSD: http://www.youtube.com/watch?v=sz9ntwoLjVA&feature=related

[3.0L V6]

Side note: That 2.8L V6 sounds just utterly awful.

[MrH]

So then you agree with me?

Sure there are anomalies ("95%").

FWIW, it was not uncommon for V6 gen 3 Camaros to be outfitted with an LSD: http://www.youtube.com/watch?v=sz9ntwoLjVA&feature=related

Honestly, I don't agree with you at all.  Both from experience and from a mechanical sense, I don't agree with what you're saying.

[sportyaccordy]

There is

Yes, you're 100% correct that nothing inside your average open diff favors the right wheel, yet as we all know, the right wheel will always spin under a loss of traction when in a straight direction, like a hard launch from a stop sign.

The hint to Sporty was the transverse engine - a longitudinal engine w/clockwise crank rotation (as viewed from the front of the engine) as all modern engines are will load the pinion in the clockwise direction - this will plant the left tire and unload the right tire; ergo, the tell-tale sign of the peg-leg, right-wheel burnout.

When turning right, this planting of the left tire is compounded by left-sided body roll as the vehicle negotiates the turn, further guaranteeing spinning only the right wheel.

When turning left, this planting effect is counteracted by right-sided body roll as the vehicle negotiates the turn, evening traction between right and left, thereby letting both tires spin.

This phenomenon in my experience is at least 95% reliable, and reaches across all RWD vehicle types that I've had; raised trucks, standard height trucks, and cars big and medium. A poor man's LSD is to use an air shock, block in the spring, or even a one-sided roll bar, to prevent this planting action.

This being the holiday season, I won't even charge NACar nor Psilos for their edumacation.

I don't agree with this... if you goose the gas in a turn on a slick surface w/an open diff, the inside tire will slip. Left or right. The only explanation for one side breaking loose before the other is the tranny placement making for uneven driveshaft lengths.... and even with that the lengths have to be significantly different.

I don't have much experience w/RWD or AWD cars,  but all my FWD cars have had relatively unequal length setups, and haven't really ever peg legged during a burnout or quick start.

For RWD I could see this being possible as the engine twists the chassis to load one side during acceleration... but within the realm of non-dragsters, and ESPECIALLY in low-torque situations like when its snowing out this should be a non issue...

I dunno... I'm not convinced...

[MX793]

So then you agree with me?

Sure there are anomalies ("95%").

I agree that on flat, dry pavement, it's usually the right tire that breaks loose first (as you said, probably 95% of the time, if not more).  It occured to me after posting that the ring gear is almost always on the left/driver's side of the pumpkin, which would result in the torque from the driveshaft causing a tendancy for the right wheel to want to lift and the left to plant.  I'm not sure the effect is as prominent on IRS cars as it is with a live axle, though anecdotal evidence on youtube and the like would indicate that even IRS equipped vehicles with open diffs favor the right wheel when doing a brake stand.

From personal experience, I can think of times when I took a hard left on dry pavement with the throttle planted and only the left tire was burning out (the car wasn't really drifting like it would have if both were lighting up).  In fact, I don't think I ever got both wheels to burn when cornering in good traction.  So I do not agree that you'll always burn both tires when making a left as though the car had a limited slip.  It may take harder cornering when turning left than right to initiate the one-wheel-peel, but a left handed one-wheel-peel will occur on a car with an open diff.

And on slick surfaces like snow and ice, the open diff definately does not behave like a limited slip when making a left.  For that matter, I think you'd find that it favors the right wheel a far lower percentage of the time when going straight.  When traction is that low, lateral weight transfer caused by torque from the driveshaft will be minimal.  You'll spin one of the tires well before you transfer enough load to make a difference in traction.  When turning, you'll usually spin only the inside wheel.

[GoCougs]

Uh, so you guys are commenting in the negative, and save for MX793, no one has even anecdotal experience?

By my guestimate I've logged about 300,000 miles in RWD, open diff vehicles - the phenomenon is very, very consistent, in most conditions.

The physics are relatively basic, too - you can't not load up the left and unload the right, by definition it must happen.

As to Sporty's FWD hint, a lateral-mounted engine the application of torque to the axles doesn't come in counter clockwise and at a right angle, so I doubt you'll see consistency as you do with RWD.

[MrH]

I don't believe your explanation on the loading of the pinion explain how it loads one side.  While I'll agree it might favor one wheel while accelerating in a straight line, in order for the car to not spin the inside wheel coming out of corner, the amount of fiction necessary to ensure that the inside wheel spins as fast as the outside would be ridiculous.  If that much friction existed, all open differentials would be horribly inefficient.

The difference in the amount of available friction between two wheels while trying to accelerate through a corner is tremendous.  To insist that an open differential will still divert torque equally between the two wheels means that both wheels are experiencing equal forces.  For that to happen, there has to be a huge amount of resistance in the drivetrain to the inner wheel.  That kind of friction simply isn't there, it'd be too inefficient of a design.

[MX793]

Here's a good, clear example of a left-handed one-wheel-peel I managed to find.

http://www.youtube.com/watch?v=07_QALXv6xE&feature=related

And another, though it's not quite as clear

http://www.youtube.com/watch?v=t_Kj6-nuIlg

[Soup DeVille]

Studded tires also aren't legal everywhere, unfortunately.  Studs are illegal in Michigan and Minnesota (two states where they'd be really useful).

As far as I can tell though, the only penalty for running studs in Michigan is a $60 or fix-it type ticket, which is well worth the risk.

Oh, and Tire Rack will ship you tires with the studs pressed in, that seems to be the easiest way to do it.

[Soup DeVille]

Yes, you're 100% correct that nothing inside your average open diff favors the right wheel, yet as we all know, the right wheel will always spin under a loss of traction when in a straight direction, like a hard launch from a stop sign.

With a solid rear axle, yes. Other independant type suspensions are not so predictable as that.

[GoCougs]

I don't believe your explanation on the loading of the pinion explain how it loads one side.  While I'll agree it might favor one wheel while accelerating in a straight line, in order for the car to not spin the inside wheel coming out of corner, the amount of fiction necessary to ensure that the inside wheel spins as fast as the outside would be ridiculous.  If that much friction existed, all open differentials would be horribly inefficient.

The difference in the amount of available friction between two wheels while trying to accelerate through a corner is tremendous.  To insist that an open differential will still divert torque equally between the two wheels means that both wheels are experiencing equal forces.  For that to happen, there has to be a huge amount of resistance in the drivetrain to the inner wheel.  That kind of friction simply isn't there, it'd be too inefficient of a design.

If you believe it for straight-line scenario, why not for a left-hand turn? A differential doesn't know anything about speeds, turns or the like - it knows only forces. If the traction force is approximately equal left to right, why wouldn't both tires spin? The practical result is that the inside tire will spin approximately at the same speed as the outside, and bring the car around.

I have done many, many, many left-hand donuts (read: both tires spinning) in open-diff vehicles.

[GoCougs]

Here's a good, clear example of a left-handed one-wheel-peel I managed to find.

http://www.youtube.com/watch?v=07_QALXv6xE&feature=related

But notice that the Miata has to make it around a full 360 before anything starts spinning - it's so far pitched onto the right it has not chance but to spin the left.

http://www.youtube.com/watch?v=t_Kj6-nuIlg

But notice that 80% of what happens is a left-hand slide by benefit of the phenomenon I described (both tires spinning) - as he slows and tightens the turn the car pitches toward the passenger side, unloading the driver side tire, and sending only it up in smoke.

[MX793]

But notice that 80% of what happens is a left-hand slide by benefit of the phenomenon I described (both tires spinning) - as he slows and tightens the turn the car pitches toward the passenger side, unloading the driver side tire, and sending only it up in smoke.

I don't think both were burning.  Maybe very briefly at the initial transition when the left started to break loose.  Momentum alone can get the back end to slide around during a 1-wheel-peel.  The fact that only one tire has rolling friction at the back makes it all the easier to get it to swing around.  Hence why the BMW drifting in the snow that I posted earlier was able to swing the tail around in a left handed slide despite only one rear wheel (the inside) throwing a rooster tail.  Holds true in the dry too.

[GoCougs]

I don't think both were burning.  Maybe very briefly at the initial transition when the left started to break loose.  Momentum alone can get the back end to slide around during a 1-wheel-peel.  The fact that only one tire has rolling friction at the back makes it all the easier to get it to swing around.  Hence why the BMW drifting in the snow that I posted earlier was able to swing the tail around in a left handed slide despite only one rear wheel (the inside) throwing a rooster tail.  Holds true in the dry too.

It never would have slid on pavement at such slow speed and with relatively little steering input without both tires spinning.

What I saw in that BMW video was both rear tires spinning - there's no way you're going to get such low speed over-steer without that.

[J86]

I'd like to retire the "I'm an idiot" thread and redirect positive energy to the "New Car!!" thread instead