Why you need a LSD if you like cornering!

[ZDan]

Originally Posted by Captain Snooze

I'm thinking that an aftermarket diff is a plug and play item. I don't have the money or experience to be experimenting with diff settings. (I'm guessing a few people would fall into this group.) So long as there is some benefit straight out of the box I would be happy.

It's not a yes/no question. Whether or not there will be a benefit depends on a number of things.
Street, track, autoX, drift?
What's your suspension setup? (spring rates, sway bars, alignment settings)
What tires are you running?

[wparsons]

Originally Posted by s2d4

You must be suberman.

He most definitely is.

[mike156]

Originally Posted by CSG Mike

Lets say that the suspension is set up to maximize the rear grip, with a balanced car. Now add a clutch type LSD. Now the rear grip is improved, and the car is able to power out better, but when that extra power is applied, now the front pushes. You compensate by softening the front rates slightly, restoring the balance. Now you can fully utilize the increased rear grip, and increase net corner exit speed.

Absolutely correct, the suspension's job is to keep the tires in contact with the ground, but under cornering, if the inside load is reduced enough, you can still spin the inside tire, temporarily reducing the stock toresen to an open diff.

Absolutely. I think? Not sure if we are thinking the same or not honestly. I'm making the argument that for performance applications with no regard to noise and maintenance, clutch type LSDs are superior in all cases simply because nobody races on perfect tracks. The perfect solution to an imperfect problem.

However, I have a dispute with an idea used in your post. You say you decrease front (spring) rates. I feel you should be decreasing front roll stiffness, not implicitly spring rate. A spring rate change should be based on ride frequency, not roll stiffness.

[CSG Mike]

Originally Posted by mike156

Absolutely. I think? Not sure if we are thinking the same or not honestly. I'm making the argument that for performance applications with no regard to noise and maintenance, clutch type LSDs are superior in all cases simply because nobody races on perfect tracks. The perfect solution to an imperfect problem.

However, I have a dispute with an idea used in your post. You say you decrease front (spring) rates. I feel you should be decreasing front roll stiffness, not implicitly spring rate. A spring rate change should be based on ride frequency, not roll stiffness.

But how many people understand ride frequency? We could start a whole different discussion on that topic, and reducing spring rate + adjusting damping is more feasible for most people.

[mike156]

Softer sway bars seems as/more feasible than spring rate changes?

I mention this as it's kind of the limiting factor to what ZDan is suggesting? Yes, you could soften the front spring rate and then add more lock up and end up in some endless cycle...but your front/rear ride rates are going to get so out of wack that it's going to stop you from pushing into some endless loop.

[Captain Snooze]

Originally Posted by ZDan

It's not a yes/no question. Whether or not there will be a benefit depends on a number of things.
Street, track, autoX, drift?
What's your suspension setup? (spring rates, sway bars, alignment settings)
What tires are you running?

Biased towards track. 6k springs f&r atm but awaiting feedback from MCS (Australian distributor) as to what to go with in near future. 25mm/19mm sways atm but will be looking to go back to oem with new springs on new dampers.
Front toe 0, camber -3.62/-3.74, rear toe +0.9mm/+0.9mm, camber -2.85/-2.95. Kumho v710.

[ZDan]

Originally Posted by Captain Snooze

Biased towards track. 6k springs f&r atm but awaiting feedback from MCS (Australian distributor) as to what to go with in near future. 25mm/19mm sways atm but will be looking to go back to oem with new springs on new dampers.
Front toe 0, camber -3.62/-3.74, rear toe +0.9mm/+0.9mm, camber -2.85/-2.95. Kumho v710.

Dem some sticky tires and good camber numbers, so you should be cornering hard and unloading the inside wheels a lot. But then again your springs are very front-stiffness biased, 5.4/3.4 wheel rates ~62F/38R on wheel rates vs. ~54F/46R weight distribution.

For sure you shouldn't consider the investment a "plug-and-play" deal. Go to school on how these custom diffs work before you invest $$$$ into one.

If your car is pretty well developed and you like how it handles now, but feel you could get better drive out of corners, I would go with light preload, which will still clamp better than the Torsen with the inside wheel unloaded and won't upset balance as much as a tight clutch-type.

[CSG Mike]

Originally Posted by mike156

Softer sway bars seems as/more feasible than spring rate changes?

I mention this as it's kind of the limiting factor to what ZDan is suggesting? Yes, you could soften the front spring rate and then add more lock up and end up in some endless cycle...but your front/rear ride rates are going to get so out of wack that it's going to stop you from pushing into some endless loop.

Not everyone has a stiffer swaybar that can be softened up...

[mike156]

I guess I'm confused where you're going there. Buy softer springs or buy an adjustable swaybar? You're buying something either way to change the roll stiffness up front.

[Ubersuber]

Originally Posted by mike156

I guess I'm confused where you're going there. Buy softer springs or buy an adjustable swaybar? You're buying something either way to change the roll stiffness up front.

At the limit suspension settings are a black art. There is no right answer.

There is good information on this thread and some not so good.

Have a look at F1: two very, very talented drivers, say Hamilton and Rosberg driving the same car (supposedly) on the same track on the same day. One day Hamilton is faster and the next Rosberg is faster. Change tracks and it all starts over.

Conventionally you deal with the problem of getting the power down at the rear by stiffening front roll or softening rear roll. Or, you could tighten up the lsd but that may or may not work for you.

One thing is for sure, the more power you have to deal with the more you bias roll resistance to the front axle, unless you are dealing with fwd or awd.

For these cars for street use the Torsen is pretty good. To go faster on whatever tires you have chosen to run you should first fit better shocks, as Subaru/Toyota have just done for 2015.

Next consider increasing front roll stiffness relative to the rear as these cars are tail happy from the factory, even the BRZ which is the tamest of the 3 settings released into the World markets.

If you fit a clutch type lsd then be ready for some serious understeer under heavy power applications. Once that lsd locks up the chassis will push unless it is already well turned in.

Too bad this isn't made for our cars, yet:

http://www.wavetrac.net/technical.htm

Torsen also makes one: the T2R which incorporates a clutch type pre-load slip limiting device within the Torsen diff.

http://www.torsen.com/products/T-2R.htm

One wonders why Toyota/Subaru didn't spec one....

[Apoc]

Originally Posted by Ubersuber

At the limit suspension settings are a black art. There is no right answer.

There is good information on this thread and some not so good.

Have a look at F1: two very, very talented drivers, say Hamilton and Rosberg driving the same car (supposedly) on the same track on the same day. One day Hamilton is faster and the next Rosberg is faster. Change tracks and it all starts over.

Conventionally you deal with the problem of getting the power down at the rear by stiffening front roll or softening rear roll. Or, you could tighten up the lsd but that may or may not work for you.

One thing is for sure, the more power you have to deal with the more you bias roll resistance to the front axle, unless you are dealing with fwd or awd.

For these cars for street use the Torsen is pretty good. To go faster on whatever tires you have chosen to run you should first fit better shocks, as Subaru/Toyota have just done for 2015.

Next consider increasing front roll stiffness relative to the rear as these cars are tail happy from the factory, even the BRZ which is the tamest of the 3 settings released into the World markets.

If you fit a clutch type lsd then be ready for some serious understeer under heavy power applications. Once that lsd locks up the chassis will push unless it is already well turned in.

Too bad this isn't made for our cars, yet:

http://www.wavetrac.net/technical.htm

Torsen also makes one: the T2R which incorporates a clutch type pre-load slip limiting device within the Torsen diff.

http://www.torsen.com/products/T-2R.htm

One wonders why Toyota/Subaru didn't spec one....

The T-2R looks like it is designed for SUVs and RWD trucks. Maybe thats why

[Sleepless]

Originally Posted by Apoc

The T-2R looks like it is designed for SUVs and RWD trucks. Maybe thats why

It is quite popular for road racing GM and Ford race cars. I had one in a 2003 Mustang Cobra and it is an excellent hybrid of a Torsen and clutch LSD. However, it seems they are larger than would be appropriate for our cars. Plus, it is obviously more expensive than the Torsen and for 90% of the owners the Torsen is just fine; probably more like 95%.

[CSG Mike]

Originally Posted by Ubersuber

At the limit suspension settings are a black art. There is no right answer.

There is good information on this thread and some not so good.

Have a look at F1: two very, very talented drivers, say Hamilton and Rosberg driving the same car (supposedly) on the same track on the same day. One day Hamilton is faster and the next Rosberg is faster. Change tracks and it all starts over.

Conventionally you deal with the problem of getting the power down at the rear by stiffening front roll or softening rear roll. Or, you could tighten up the lsd but that may or may not work for you.

One thing is for sure, the more power you have to deal with the more you bias roll resistance to the front axle, unless you are dealing with fwd or awd.

For these cars for street use the Torsen is pretty good. To go faster on whatever tires you have chosen to run you should first fit better shocks, as Subaru/Toyota have just done for 2015.

Next consider increasing front roll stiffness relative to the rear as these cars are tail happy from the factory, even the BRZ which is the tamest of the 3 settings released into the World markets.

If you fit a clutch type lsd then be ready for some serious understeer under heavy power applications. Once that lsd locks up the chassis will push unless it is already well turned in.

Too bad this isn't made for our cars, yet:

http://www.wavetrac.net/technical.htm

Torsen also makes one: the T2R which incorporates a clutch type pre-load slip limiting device within the Torsen diff.

http://www.torsen.com/products/T-2R.htm

One wonders why Toyota/Subaru didn't spec one....

All 3 cars understeer. Any oversteer is driver induced.

[troek]

Although mike dosnt realy need the support of a novice, i have to agree. Everytime ive gotten oversteer ive done something to cause it.