Can someone explain to me how LSD helps?

[Throckmorton]

Read this thread and watch the old black and white video http://www.expeditionportal.com/forum/showthread.php?t=55018

 

[SparkyJJO]

LSDs don't "slam" power to the other wheel. Street cars generally have torque-sensitive differentials and lockup tighter as you apply more throttle, so at 50% throttle they may be 30% locked and at 75% throttle it may be 60% locked etc etc, they don't suddenly jerk from unlocked to locked. It sounds like you were coming in too hot and the car's traction control or stability control surprised you when it shifted power to the wheel with traction.

Maybe wrong choice of words on my part. Point is, if it breaks traction on one wheel and transfers power to the other it can break traction on both. And on a turn when it is wet, that can be a bad thing. Just be careful is all I'm saying.

My car had no traction or stability control stuff on it. It was a 98.

Or just don't drive like an idiot on public roads. Problem solved.

I wasn't driving like an idiot. I was driving around a bend on a highway interchange, going about 50 mph, which is the posted "recommended" speed of the ramp anyway. Yes I probably was still going a bit fast for conditions, but I wasn't driving like some moron. Part of the issue too is the road design, the banking is done all wrong and I'm not the only one who has slid on that turn. There are a few other marks on the concrete from other vehicles doing the same thing, actually.

It was my first real accident that wasn't someone hitting me, in 6 years of driving, I wasn't cited due to bad road conditions causing accidents all over the place and just me involved, and I've never had any moving violations, ever. I'd venture to say I probably drive safer than the vast majority of people here. Did I make a mistake in this case? Yes. Was I driving like an idiot? No.

 

[Howard]

Yes I probably was still going a bit fast for conditions, but I wasn't driving like some moron.

Don't want to be an asshole, but that right there is a contradiction, and the rest of your post is just excuse after excuse.

 

[SparkyJJO]

I never equated driving the recommended speed as driving like a moron before. Whatever. Fact still is, road is banked wrong, I was driving the recommended speed for the turn, which was still too fast for the road was wet, and the LSD allowed both wheels to break free easier, and I wrecked my car due all that working against me. Yes it was preventable had I slowed it down more.

Would you guys prefer if I said it was 100% my fault and the road is 100% perfect or something? Geez.

 

[Howard]

I never equated driving the recommended speed as driving like a moron before. Whatever.

<shrug>

While you're at it, get out of my fast lane.

 

[SparkyJJO]

While you're at it, get out of my fast lane.

I don't cruise in the fast lane. I stay in the other lane unless I'm passing someone going under the speed limit.

 

[kornphlake]

I don't know anyone who refers to automatic locking differentials as an LSD and I've never heard them used interchangeably though I admittedly do not pay attention to much outside of sports cars. I also don't know of any modern RWD vehicle which uses an automatic locker other than for off road vehicles and large trucks/suvs, and most of those aren't automatic, they are selectable.

Most locking diffs are found on trucks and SUVs, GM, Ford, and I believe Dodge, do offer locking differentials as factory equipment on RWD trucks and SUVs. I have no idea what they offer on passenger vehicles and sports cars. I don't believe a selectable locking differential is available as a factory option except on 4wd models. Like I said automatic locking differentials are often referred to as limited slip because they offer a limited amount of slip before locking.

Torque-sensitive differentials don't have to have a clutch, many use helical gears.

Like I said there are other systems aside from the clutch type posi with clutches and went on to explain the Haldex system. I'm not familiar enough with the AWD and sports oriented vehicles to cite every available design.

 

[PricklyPete]

this video is cool

http://www.youtube.com/watch?v=K4JhruinbWc

LOVE quality old videos like that!

 

[Throckmorton]

Most locking diffs are found on trucks and SUVs, GM, Ford, and I believe Dodge, do offer locking differentials as factory equipment on RWD trucks and SUVs. I have no idea what they offer on passenger vehicles and sports cars. I don't believe a selectable locking differential is available as a factory option except on 4wd models. Like I said automatic locking differentials are often referred to as limited slip because they offer a limited amount of slip before locking.





Like I said there are other systems aside from the clutch type posi with clutches and went on to explain the Haldex system. I'm not familiar enough with the AWD and sports oriented vehicles to cite every available design.

A limited slip diff and an auto locking diff are two different things. A limited slip is open, but has resistance. But I do know that Jeep calls the locking diff in the Grand Cherokee a "limited slip", apparently so they don't scare away soccer moms.

 

[EightySix Four]

A limited slip diff and an auto locking diff are two different things. A limited slip is open, but has resistance. But I do know that Jeep calls the locking diff in the Grand Cherokee a "limited slip", apparently so they don't scare away soccer moms.

This was the point I was trying to make.

 

[alkemyst]

wow trolling in garage now.

 

[Zenmervolt]

Maybe wrong choice of words on my part. Point is, if it breaks traction on one wheel and transfers power to the other it can break traction on both. And on a turn when it is wet, that can be a bad thing. Just be careful is all I'm saying.

And the point everyone else is making is that the way an LSD transfers power to the wheel with traction is gradual, not in any way sudden. If your car spun out with an LSD, you were already past the point where you would have spun out with an open differential.

ZV

 

[thescreensavers]

My car has a vlsd, it takes time for it to engadge

 

[Vic Vega]

And the point everyone else is making is that the way an LSD transfers power to the wheel with traction is gradual, not in any way sudden. If your car spun out with an LSD, you were already past the point where you would have spun out with an open differential.

ZV

Nonsense, it couldn't possibly be his fault, obviosly the car is to blame.

This guy could be a professional racing driver.

 

[Gillbot]

wow trolling in garage now.

And if it continues to derail this thread, I'll lock it up.
KEEP the BS out of here and in OT where it belongs.
AT Mod
Gillbot

 

[SparkyJJO]

Nonsense, it couldn't possibly be his fault, obviosly the car is to blame.

This guy could be a professional racing driver.

I AM to blame, I never said I wasn't. I said between multiple factors - ME being one of them - I broke traction and wrecked.

Why did I even bother saying anything, I should have known better then to mention it on AT since everyone will instantly jump down your throat at the slightest chance D:

 

[Zenmervolt]

I AM to blame, I never said I wasn't. I said between multiple factors - ME being one of them - I broke traction and wrecked.

Why did I even bother saying anything, I should have known better then to mention it on AT since everyone will instantly jump down your throat at the slightest chance D:

What we're jumping on is the claim that the LSD "made the wheels slip easier". It didn't. It can't. If you spun out with the LSD, you would have spun out sooner with an open differential. By making blatantly incorrect claims about the effects of an LSD, you are clouding an issue and preventing the dissemination of accurate information to the OP.

That's what most of us are annoyed about.

ZV

 

[alkemyst]

If anything the LSD held you longer into going into the point of no-return than if your single tire would have broke loose earlier.

Alot of that is more dependant on tires though. On the street a tire that gradually let's loose even if it gives up some ultimate traction is safer than one with ultimate traction, but snaps at that point you go beyond it.

 

[SparkyJJO]

If one wheel breaks traction on an open diff the other one might not, but with LSD and the power transfer it may make it break the other one loose as well. Doing donuts in a RWD is an example of that, much easier to do it with a LSD than an open diff because you can get both wheels spinning, not just the one.

That was my only point is the possibility of that happening around a turn when you don't want it to...

If I was wrong, then OK, tell me and explain why, I have no problem accepting correction 🙂 Just don't attack me over it and then treat me like some troll. I'm not saying you were ZV, but some of the others.

 

[Throckmorton]

What we're jumping on is the claim that the LSD "made the wheels slip easier". It didn't. It can't. If you spun out with the LSD, you would have spun out sooner with an open differential. By making blatantly incorrect claims about the effects of an LSD, you are clouding an issue and preventing the dissemination of accurate information to the OP.

That's what most of us are annoyed about.

ZV

You have things backwards.

A tire has a certain amount of traction. That traction is split between propulsion/braking and lateral grip. That's why you break loose easier when you apply power.

With an open diff, one wheel will lose traction and the other won't because it's getting virtually no torque-- until it reaches the limit of its static friction.

With a clutch type LSD, the slipping wheel will spin, but the gripping wheel will still be getting SOME torque. So of course the gripping wheel is more likely to also lose traction.

Also, a clutch LSD is always applying force to the tires resisting differential action, so on every turn it's fighting you and trying to break the tires loose to some extent.

Think of it this way... a clutch LSD is somewhere between an open diff and a locked diff. A locked diff is horrible on the street, because on EVERY turn you must lose traction on at least one tire. On wet or icy roads, a locked diff would kill you.

 

[Zenmervolt]

You have things backwards.

A tire has a certain amount of traction. That traction is split between propulsion/braking and lateral grip. That's why you break loose easier when you apply power.

With an open diff, one wheel will lose traction and the other won't because it's getting virtually no torque-- until it reaches the limit of its static friction.

With a clutch type LSD, the slipping wheel will spin, but the gripping wheel will still be getting SOME torque. So of course the gripping wheel is more likely to also lose traction.

Also, a clutch LSD is always applying force to the tires resisting differential action, so on every turn it's fighting you and trying to break the tires loose to some extent.

Think of it this way... a clutch LSD is somewhere between an open diff and a locked diff. A locked diff is horrible on the street, because on EVERY turn you must lose traction on at least one tire. On wet or icy roads, a locked diff would kill you.

You're over-thinking and, apparently, have little or no practical experience driving an on-road car with an LSD.

If you're going around a corner with an open differential and you spin the inside rear tire by applying too much power, guess what, you're going to spin out. The lateral grip afforded by the outside rear wheel alone is just not sufficient to prevent a car from spinning out. God knows I've spun enough RWD cars with open differentials to know that even when you only break traction with just the inside tire you're still going to make a nice visit to the runoff area and end up having to replace a couple autocross cones.

An LSD transfers torque to the outside wheel and it begins doing this early and gradually (in the case of a clutch-type LSD anyway). Because the inside wheel is not being fed 100&#37; of the torque, it doesn't break free as early as it would with an open differential. While an LSD will still cause the car to "let go" if you give it too much power, this happens later than the inside wheel of an open diff would "let go" and cause a spin out.

In fact, the practical upshot of an LSD (and even a locker) is increased power-on understeer due to the rear axle trying to push the car straight ahead. A locked diff is horrible on the street because you almost can't turn, not because you're oversteering.

ZV

 

[EightySix Four]

You're over-thinking and, apparently, have little or no practical experience driving an on-road car with an LSD.

If you're going around a corner with an open differential and you spin the inside rear tire by applying too much power, guess what, you're going to spin out. The lateral grip afforded by the outside rear wheel alone is just not sufficient to prevent a car from spinning out. God knows I've spun enough RWD cars with open differentials to know that even when you only break traction with just the inside tire you're still going to make a nice visit to the runoff area and end up having to replace a couple autocross cones.

An LSD transfers torque to the outside wheel and it begins doing this early and gradually (in the case of a clutch-type LSD anyway). Because the inside wheel is not being fed 100&#37; of the torque, it doesn't break free as early as it would with an open differential. While an LSD will still cause the car to "let go" if you give it too much power, this happens later than the inside wheel of an open diff would "let go" and cause a spin out.

In fact, the practical upshot of an LSD (and even a locker) is increased power-on understeer due to the rear axle trying to push the car straight ahead. A locked diff is horrible on the street because you almost can't turn, not because you're oversteering.

ZV

Sometimes it blows my mind that you don't just give up and ban people sometimes. 😛 The frustration level I'd have with trying to moderate ATOT:G would push me over the edge.

 

[Throckmorton]

You're over-thinking and, apparently, have little or no practical experience driving an on-road car with an LSD.

If you're going around a corner with an open differential and you spin the inside rear tire by applying too much power, guess what, you're going to spin out. The lateral grip afforded by the outside rear wheel alone is just not sufficient to prevent a car from spinning out. God knows I've spun enough RWD cars with open differentials to know that even when you only break traction with just the inside tire you're still going to make a nice visit to the runoff area and end up having to replace a couple autocross cones.

An LSD transfers torque to the outside wheel and it begins doing this early and gradually (in the case of a clutch-type LSD anyway). Because the inside wheel is not being fed 100% of the torque, it doesn't break free as early as it would with an open differential. While an LSD will still cause the car to "let go" if you give it too much power, this happens later than the inside wheel of an open diff would "let go" and cause a spin out.

In fact, the practical upshot of an LSD (and even a locker) is increased power-on understeer due to the rear axle trying to push the car straight ahead. A locked diff is horrible on the street because you almost can't turn, not because you're oversteering.

ZV

Both wheels are getting the same torque with an open diff. So unless the LSD sends the outside tire more torque, I don't see how the LSD makes the inside tire less likely to break loose in the first place. To me it seems obvious that the tire will still break loose, but the outside tire will still get the amount of torque that the clutch pack sends to it.

 

[alkemyst]

Both wheels are getting the same torque with an open diff. So unless the LSD sends the outside tire more torque, I don't see how the LSD makes the inside tire less likely to break loose in the first place. To me it seems obvious that the tire will still break loose, but the outside tire will still get the amount of torque that the clutch pack sends to it.

magnets how do they fucking work y0!

Seriously you should read the wiki on LSD's and educate yourself.

A differential does divide torque.

 

[Throckmorton]

magnets how do they fucking work y0!

Seriously you should read the wiki on LSD's and educate yourself.

A differential does divide torque.

An open diff always sends the same amount of torque to both wheels. When one wheel breaks loose, the torque it can handle drops to basically 0. It's like spinning a loose bolt with a torque wrench- the reading will never go much above 0. So with that one wheel spinning, the wheel with grip can't get any torque either.

The resistance of the clutch pack in an LSD sends power to the wheel with grip, purely by friction.