re: Limited slip differentials

[Dana Loomis <dloomis@domain.elided>]

>Maybe some of the racers out there can let us know what they use.  I'm
>particularly interested for the 105 series, 4 cyl. cars.

I'm familiar with two solutions that are common on vintage race cars.  One
is to use a factory limited slip axle from a 2-liter 105/115 car and
increase the degree of lockup by adding shims to the pack.   Dedicated race
cars are usually adjusted for 75% lockup, rather than the stock 25%.  This
is how my my 71 GTV race car is set up.  Some wheelspin is still possible
in rare, and predictable, situations, but driveability remains good.

The other commonplace approach is to weld up the differential so it's
permanently locked.  This is a crude  solution well known to American
circle trackers.  It's cheap and effective, but wouldn't be practical for a
street-driven car.  On a race car, a locked rear requires adjustments in
driving style, because the car tends to push at corner entry, but you
can--in wheelspin-limited corners--get on the power earlier.  An important
disadvantage of welded differentials for vintage racing is that they  are
illegal under some historic rules, including FIA Gr. 2. 

There are probably other, more elegant technologies, but anyone thinking
about modified differentials needs to recognize that driving technique and
design and tuning of the suspension are also important determinants of
wheelspin.  

Dana Loomis

--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided