Diff Fluid and Oversteer

[freerunner]

Originally Posted by Racecomp Engineering

Agreed on the slight rear toe in being helpful.

Damper changes (stiffer front, softer rear) would be helpful on corner entry and exit.

- Andrew

Sorry to disagree. Koni yellows have adjustable _rebound_ damping only.

In this case, a stiffer front setting induces more oversteer on corner exit and a softer rear induces corner entry oversteer.

reason for edit: typo

[cdrazic93]

wait, diff fluid causes oversteer? well I'll be damned

[Turdinator]

Originally Posted by cdrazic93

wait, diff fluid causes oversteer? well I'll be damned

If it's on the track rather than in the diff it might...

[ansibe]

Why do drifters lock their axles together? Why do McLaren and lotus resist using mechanical diffs? Why can't forum contributors answer honest questions or just stay out of the thread?

Yes my car was aligned by a professional shop, and I have the final readouts.

OE tires.

I chose FRS rear springs in an attempt to balance the car. Same for the alignment specs. I just have trouble believing the changes I made moved the grip so far forward.

[DarkSunrise]

I count three changes you made that would contribute to more oversteer.

(1) -rear springs swapped to OE FRS (stiffer)
(2) -Aligned to -1.5 camber
(3) -0 toe all around.

Individually they're not drastic changes but done all at once, they would have a pretty noticeable effect. I think people have made useful suggestions.

First try playing with damper settings since it's free. Here's a flow chart for dealing with oversteer (keeping in mind that Koni single adjustables appear to alter rebound only):



If that doesn't solve your issue, try adding slight rear toe-in (and/or more rear camber). Alignments are relatively cheap.

And if that fails, try an adjustable front sway bar.

One thing to keep in mind is that if you change to track tires, your opinion on the car's balance might change as well.

[cdrazic93]

I feel like flaming someone , but i dont want a temp ban. So I'll keep my mouth shut.

[solidONE]

Originally Posted by cdrazic93

I feel like flaming someone, but i dont want a temp ban. So I'll keep my mouth shut.

I seriously don't get the point of this. That you even feel the need to "flame someone" aka be a douche. Do you get internet troll "brownie points" or something? lmao

[solidONE]

Originally Posted by ansibe

I made several changes to my BRZ at once, and now I have a slight oversteer problem. Mods:

-dampers changed to Koni Yellow
-rear springs swapped to OE FRS (stiffer)
-Aligned to -1.5 camber and 0 toe all around.
-Diff fluid changed to Amsoil 75w-90 GL-4
-No change to the sways. I'm on OE BRZ

I Think the component changes are pretty conservative, so I'm surprised how much more oversteer I have. It's fun, but I'm not a drifter so I want grip.

Could this be caused by the diff locking early because of the fluid I'm using? I think I should have used GL-5.

I've personally ran BRZ front and FRS rear springs with factory dampers and im a bit surprised you are getting oversteer. My alignment was a bit different though. The result was a bit of understeer at entry. Maybe those Konis along with your alignment has something to do with your resulting oversteer.

My alignment with the set up (apporx with camber bolts and rear lower control arms):

-3 camber 0 toe front
-2.5 camber 1/16" toe rear

[cdrazic93]

Originally Posted by solidONE

I seriously don't get the point of this. That you even feel the need to "flame someone" aka be a douche. Do you get internet troll "brownie points" or something? lmao

No, but pointing out the defense has holes in it about diff fluid from OP...I would have probably chosen less than nice words for stupid questions haha.

[FRSBRZGT86FAN]

Originally Posted by ansibe

Why do drifters lock their axles together? Why do McLaren and lotus resist using mechanical diffs? Why can't forum contributors answer honest questions or just stay out of the thread?

Yes my car was aligned by a professional shop, and I have the final readouts.

OE tires.

I chose FRS rear springs in an attempt to balance the car. Same for the alignment specs. I just have trouble believing the changes I made moved the grip so far forward.

Why do drifters lock their axles together?
Because drifters care very little about handling, they want both wheels locked together so they spin at the same time and at the same speed. Alternatively they may go for 2 way LSDs

Come on dude, you're pushing it, in what world would the Diff fluid effect over-steer on this car? have you owned other cars that induced over-steer because of the fluid? What led you to that conclusion?

Also your mclaren and lotus examples don't even apply here

McLaren P1: They use frictional balancing with brakes/electric motors so they don't need an LSD system as they can be more precise without it.

Mclaren MP4,670s, 570 etc: Use brakes on the inner wheels at times moments, also the suspension is adjusted on the fly, they also have NO sway bars everything is connected electronically or hydraulically and adjusted in split second intervals (this is in the P1 as well)

For the lotus: A limited slip differential matters more in wider, heavier cars than it does in narrow lightweight cars, FYI, because the different radius paths of travel are smaller, and the distribution of weight left-right during a corner is smaller as well. They are famous for saying it here:
http://www.lotustalk.com/forums/f25/...06/#post552007

[ansibe]

Originally Posted by DarkSunrise

I count three changes you made that would contribute to more oversteer.



Individually they're not drastic changes but done all at once, they would have a pretty noticeable effect. I think people have made useful suggestions.

First try playing with damper settings since it's free. Here's a flow chart for dealing with oversteer (keeping in mind that Koni single adjustables appear to alter rebound only):

If that doesn't solve your issue, try adding slight rear toe-in (and/or more rear camber). Alignments are relatively cheap.

And if that fails, try an adjustable front sway bar.

One thing to keep in mind is that if you change to track tires, your opinion on the car's balance might change as well.

This is very helpful, thanks.
I will definitely experiment with the damper settings. I have been adding "stiffness" to the front to get traction at the rear, but now I see I've been going at it backwards!

I'm also due for tires, so I'll try something stickier. The extra roll will get me some camber at the back which should help.

[ansibe]

Originally Posted by solidONE

I've personally ran BRZ front and FRS rear springs with factory dampers and im a bit surprised you are getting oversteer. My alignment was a bit different though. The result was a bit of understeer at entry. Maybe those Konis along with your alignment has something to do with your resulting oversteer.

My alignment with the set up (apporx with camber bolts and rear lower control arms):

-3 camber 0 toe front
-2.5 camber 1/16" toe rear

We have almost identical setups. The Koni's seem to have far less compression damping than OE, which may be allowing the front to drop with corner loads.

Your alignment is more aggressive than mine, but you don't seem to be having any trouble. What tires are you running?

[irax]

LOL changes springs and doesn't understand that it will affect handling characteristics.

Your brain fluid needs to be changed.

Look, from the fact that you know the FRS springs are stiffer and you changed them on the rear it should be no surprise to you that it would induce oversteer.

Why would you even think that its related to the fluid ?

[mav1178]

Originally Posted by ansibe

I just have trouble believing the changes I made moved the grip so far forward.

Because you made a TON of changes all at once... that's where I would start.

I have no problems with oversteer on my car, and my alignment is

F -3.6 camber, 0 toe
R -2.7 camber, 1/16" toe in

-alex