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My synchros are starting to wear out, and it's time for the transmission to come out, so I'm thinking now's the time to install an LSD, but I'm concerned about the impact on Elise handling. Right now, I definitely start to spin a wheel coming out of some turns, so this will let me get on the power earlier, but I know that LSD's resist all turning. So, do any of you guys have experience both with and without LSD, and how would you compare the car's handling with and without?

Thanks.
 

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IMHO, the single, biggest improvement a LSD makes is the ability to _change_ grip on the overloaded (outside) drive tire.

The obvious one is "power out of corners." That's easy to feel, quantify, and gratifying - without a LSD, you might spin the inside rear into oblivion, add LSD, hey, look, all of a sudden, you can ACCELERATE out of corners! Cool!

That's fantastic. HOWEVER, I am stronly of the opinion that adding a LSD gains you MUCH more in terms of adjusting the car's balance with the throttle.

My first LSD/performance experience was in FWD - VW Rabbit, to be exact. Prior to adding the LSD (Quaife/torsen type, in this case), I would get inside wheelspin exiting corners. That went away, as expected.

A few more runs, though, we realized something - you could TOTALLY overcook entry, get the car all kinds of sideways - say, turning left, front right wheel is coutntersteering, rear wheels sliding, withOUT a LSD, you would either A) get it back or B) spin. No option C. In the process of trying to grab Option A, you lost ALL forward momentum, though.

WITH the LSD, though, ooooh, now things are getting good - upset the heck out of the car, then add ALL the throttle, send power to that outside front wheel that has all the grip in the world, and TAKE SOME AWAY via the throttle.

With a little care and practice, it made the cars MUCH faster than the added bonus of "powering out" of corners; you could turn in much more aggressively, get the car to start "rotating" (aka "spinning"), then add all kinds of throttle and instead of COUNTERSTEERING, balancing the slip angle front to rear, accelerating not just OUT of the corner, but _through_ it.

I've not driven an Elise without a LSD. I doubt the benefits are as pronounced, but they're still there - all of a sudden, you get to put power to that outside rear tire, which is a VERY useful thing to be able to do; possibly in low speed corners, certainly in the wet (careful....), and, of course, you can put power down.

IMHO, the biggest REAL advantage of a LSD is the fact that it allows you/enables you to put power to the overloaded wheel. I hardly notice the LSD in mine, but the car does exactly what I tell it to do, which tells me it is working.

In thinking about it (and this is speculation), an open diff Elise sideways = countersteering. Adding throttle just spins the inside rear wheel.

LSD car, countersteer, and while adding throttle very well may REDUCE lateral traction (increasing the "spin" piece), it very well may INCREASE aft weight transfer, which in turn would REDUCE front grip, which may well result in not-spinning - after all, that's what's happening; the front wheels are gripping WAY more than the rear, so if you can all of a sudden transfer some weight to the rear wheels, transfer some off the front, REDUCE grip at front, INCREASE at rear, hmmmm.

I have an autocross this weekend. I'll try it.



.02c!



Iain
 

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Oh - a good LSD won't resist turning. I lied, too - I drove an open diff 05 elise at a school recently, did not really notice the LSD's absence (was driving at 80-90%), but I certainly did not notice that car being more eager to turn in or anything.

You can tune turnin with toe adjustments; even if the LSD numbed turn in a bit, the positives SO outweigh the negatives; once the open diff goes "open," you've lost ALL ability to put power to the tire that likely needs it the most.



Iain
 
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