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Excessive Wheelspin In The Wet

benro2

By benro2,
in R Series (R30, R31, R32, R33, R34)

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benro2 Community Regular

benro2

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I was having a discussion with a friend today about LSD's, and it made me think up a few questions. I know that when a tyre spins, it makes the car want to pivot around that axis (the tyre), so wouldn't that mean that a car *without* an LSD would tend to lose the rear end (ie: fishtail) *more* than a car with an LSD (ie: it is more dangerous in the wet than with a car with an LSD)?

So, with my original situation where I was going around a LH turn at a constant 50 km/h up a hill, the inside (LH) rear tyre would be the most likely to spin since it has the least weight on it and it has drive torque passing through it. I was under the impression that once the LSD senses that tyre spinning, it would lockup the diff to a certain percentage, thereby allowing some drive torque through to the RH rear tyre. That should stop the LHR tyre spinning, thereby correcting the slide (well, this should all happen before the car starts sliding, but anyway...). So, the only reason that I would be sliding is because the drive torque passing through the RHR tyre has overpowered the amount of grip available, and now *both* rear tyres are spinning, thereby causing the car to lose rear end grip and thus oversteer? Basically, what I'm asking is, did my car start to slide because only the LHR tyre was spinning (the first paragraph), or because *both* rear tyres were spinning? If it's the former, then would that make my LSD stuffed? If it's the latter, I presume my LSD is working, but wouldn't that mean that cars equipped with LSD's are actually more dangerous to drive in the wet than with cars that have open diffs? I'm all confused now... :happy:

And finally, what about when you see two tyre marks left on the road as a result of a burnout? That means that the tyre with the least grip has lost grip, which has sent torque to the other rear tyre, which was then overpowered by that torque? But why do both tyre marks look about the same "darkness"? Shouldn't one be much darker because that tyre is spinning faster than the other (ie: the wheel that initially lost grip)?

Kinks Grand Master

Kinks

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What did you mean by Skylines having better balance, therefore equalling more wheelspin? Do you mean front/rear weight distribution, or having more "neutral" handling characteristics, ie: not as understeer-biased as the Calais?

Yes, more neutral. If a car is understeer biassed and you put your foot down the rear grips, the front scrubs and you go straight ahead. If a car is neutral and you put your foot down the back wheels spin and you get oversteer.

Now re your above post... Your comment about the car pivoting around the spinning wheel is false IMO.. I don't believe it works that way.

When you have no LSD then the tyre with the least grip will spin. The thing is, this is unpredictable and the spinning tyre can change from moment to moment. Hence, yes, you can fishtail and lose it with an open diff in the wet because when you correct, the weight shifts and the other wheel spins up, making it snap back on you.

A V-LSD is in some ways almost as bad because the LSD action is related to SPEED differential. Not applied torque from the engine. So you must have some wheelspin in order for the LSD to start working. Again, if you have small amounts of wheelspin it can behave like an open diff. My R33 is really quite twitchy in the wet sometimes.

A clutch type LSD operates on torque - the more torque the more LSD action so they are much better LSDs.

Then you've got locked diffs - by which I mean there is no differential action both wheels always rotate at the same speed. This is bad for handling, bad for tyre wear and bad for your rear bushes. Not to mention really bad for grip unless your wheel is pointed dead straight. HOWEVER, with a locked diff you always know that any wheelspin means both wheels are spinning, and they are very predictable in that respect. Of course, if you don't know how to drive then you WILL end up reversing it into a tree because you thought that giving it a hit around a wet corner was a smart idea. Totally dangerous and illegal. But fun. Apparently. :rofl:

Regarding your rain problem, I'd say you spun the inside wheel, as it had less grip. Then the V-LSD saw a speed differential between the wheels and started transferring torque to the outside wheel. Since the engine is now revving harder through the spinning wheel you've got more torque available and this overpowers the other rear wheel and then you're going sideways.

benro2 Community Regular

benro2

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Regarding your rain problem, I'd say you spun the inside wheel, as it had less grip. Then the V-LSD saw a speed differential between the wheels and started transferring torque to the outside wheel. Since the engine is now revving harder through the spinning wheel you've got more torque available and this overpowers the other rear wheel and then you're going sideways.

Hmm... that's exactly what I originally thought was happening. But then I started thinking about the "inside wheel acting as a pivot" concept and it started to make sense. I mean, thinking about the initial corner, I wasn't really applying all that much throttle, so was it really possible for the other wheel to become overpowered? That's the bit I was getting confused with. I would understand if I were applying WOT or I was in a low gear, but I wasn't. I was literally just trying to maintain a constant speed, albeit on a relatively steep hill and turning a (gentle) corner.

With "V-LSD", are you referring to a viscous-type LSD? Because I was under the impression that these were an option on the GTS-T, and are quite rare? They are apparently the same type of diff as used in the GTR. So that would mean that I should have the more common, and theoretically, more secure, clutch-type LSD?

Anyway, is there any way to check to see if my diff is stuffed? I mean, a proper, controlled test, not just one where I go to the nearest corner, stomp on the accelerator and see if I still have drive? Well, the answer to that last part is "yes", I can still feel drive going to the tyre with the lesser grip, but whether the amount of torque being transferred is how much it's supposed to be, I don't know. This is what I want to find out. And if my LSD is stuffed, how much am I looking at to get it fixed or replaced?

scathing Grand Master

scathing

Posted
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Yep, he offered me an "excellent price". I had no idea of their going price, but I was planning to buy some performance Bridgestones (can't remember which but I think they'd just placed highly in a Wheels or Motor tyre test) and these Nexens were close to half price. He told me stories of how previous customers had also come in wanting to buy expensive tyres but had supposedly taken his advice and bought the Nexens, even with a money-back guarantee, and he'd only heard good feedback from them. I wasn't overly keen on spending $1000+ on tyres at the time, so I went with the ~$550 Nexens. Guess I'll know what to say next time eh?

I think its quite obvious how much respect I have for salespeople, especially commission-based ones, so I won't go into a massive rant.

"Good customer feedback" without some kind of auditable paper trail means about as much as "new and improved taste" or "if you only see one movie this year....."

**JaR** Grand Master

**JaR**

Posted
Posted

tis the tyres for sure.

the stockies have shit tyres on em ( i killed the other ones, and couldnt be f**ked spending heaps on tyres for the gay stockies so meh ).

hence why i try to avoid driving if its heavy rain... coz i tend to go nowhere fast except sideways or wheelspinning. :D

Kinks Grand Master

Kinks

Posted
Posted
With "V-LSD", are you referring to a viscous-type LSD? Because I was under the impression that these were an option on the GTS-T, and are quite rare? They are apparently the same type of diff as used in the GTR. So that would mean that I should have the more common, and theoretically, more secure, clutch-type LSD?

yes, viscous. they are standard on GTS-t models, active LSD (A-LSD) was an option on them - it is a computer controlled clutch type diff and you will have a dash light inside your tacho if you have it. Unless someone has replaced the diff in your car then there's a 95% chance you have a viscous LSD in it.

The GTR has a mechanical (clutch type) rear diff, that much I am certain of. I'm not sure about the front diff.

LTHLRB Grand Master

LTHLRB

Posted
Posted

driving a powerfull car in the wet with a light rear end is absolutely dangerous if your a fool like me and stab the throttle everywhere... Wheelspinning in 4th is pretty bad. So just take it easy in the wet and drive slow.

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