Miata Mailing List: July 1992, Message #13
sponsored by



     


   From: (none)
Subject: Limited Slip Differentials
   Date: (none)

> So, miata owners on the net, what exactly IS the purpose of the
> Limited Slip Differential option?  All the magazines say "oh, it
> prevents one tire from spinning too much faster then the other..."

Precisely.

> but I've never had that problem with any of my other (family-style)
> cars.  Why is the miata any different?

Because you probably don't race your station wagon.

> Does LSD help when doing jackrabbit starts from stopsigns?

It might.  As long as both rear tires remain adhered to the road the LSD
won't come into play.  If you break one of the tires free (say it's on loose
sand) the LSD will keep that wheel from spinning wildly and will apply at
least some of the force from the engine to the other wheel which still has
traction.  Of course, that wheel might then break free also, in which case
you're just going to sit in place and make lots of smoke.

> Does LSD help when taking corners too fast in mall parking lots?

Only if you're cornering so furiously that the inside rear wheel comes off
the ground, and you're trying to accelerate.  This is not uncommon during
autocrosses.  Then the LSD will keep the inside wheel from spinning and will
apply some force to the outside wheel which will allow you to accelerate like
you wanted to.  Probably a better way to solve this particular problem is to
get stiffer sway bars (to keep the tire on the ground in the first place),
not a LSD.

> Does LSD help when the roads are wet?

It might.  This is basically the same situation as the jackrabbit start you
asked about above.  In both cases you're trying to turn the tire faster than
friction sticks it to the road surface (one because the tire spins too fast
and the other because the road is wet and slippery) and something breaks
free.

> Does LSD help when the roads are covered in ice?

Well, if both rear wheels are on ice, probably not because you won't have
much traction in the first place and both tires will tend to spin.  But if
you momentarily hit an ice patch with one drive wheel while the other is on
bare asphalt, the LSD will help.

I think you probably understand now.  If you're in a situation where both
rear wheels are on the ground and sticking, it doesn't matter if you have a
LSD.  Once you lose traction on one of those tires, though, without the LSD
the free tire will spin freely with the engine and none of the force will go
to the sticking tire.  The LSD keeps the unstuck wheel from spinning and so
applies drive force more evenly.  This also assumes you're trying to
accelerate while the tire is unstuck.
--
Michael J. Abbott		mja@kpc.com
Kubota Pacific Computer Inc.	Santa Clara, CA		408-987-3303