Rear Diff Options - Power Oversteer Found Here
to chime in I should mention when I was having all my crazy power oversteer I was on some crappy tires and I was running toe in the front.. I forget how much though.
I would start out with -3.5 up front and -1.2 in the rear.
If you have 2.5" ID springs 03whitegsr...lmk I have some 850 Hyperco's I'll sell ya. Put the 12k up front and the 850's out back
If you have 2.5" ID springs 03whitegsr...lmk I have some 850 Hyperco's I'll sell ya. Put the 12k up front and the 850's out back
I finally got out on R-comps at an auto-x today and it has changed my perspective a bit.
On narrow street tires, it is magical. Makes the car step out nicely and predictably. Even if you go in too hot, you can throttle steer the car to help recover.
On wider tires (275 in my case) it isn't going to be as noticeable. You over drive the car into a corner, it is still going to understeer into oblivion. The way the car acts on the street left me thinking I was going to be able to throttle steer the car out of anything and the first run was horrible, understeer EVERY WHERE.
I went back to typical AWD "slow in fast out" type driving and I did notice I could get on the throttle pretty early and the car tended towards oversteer on the exit. This being the first event on decent tires in the car, I have no idea if this is due to the diff or not though.
Conclusion, on street tires this diff is very noticeable and makes the car a riot to drive. On good wide rubber, I probably could not tell the difference, but I am not the best driver.
On narrow street tires, it is magical. Makes the car step out nicely and predictably. Even if you go in too hot, you can throttle steer the car to help recover.
On wider tires (275 in my case) it isn't going to be as noticeable. You over drive the car into a corner, it is still going to understeer into oblivion. The way the car acts on the street left me thinking I was going to be able to throttle steer the car out of anything and the first run was horrible, understeer EVERY WHERE.
I went back to typical AWD "slow in fast out" type driving and I did notice I could get on the throttle pretty early and the car tended towards oversteer on the exit. This being the first event on decent tires in the car, I have no idea if this is due to the diff or not though.
Conclusion, on street tires this diff is very noticeable and makes the car a riot to drive. On good wide rubber, I probably could not tell the difference, but I am not the best driver.
I was running kumho ecsta xs last season, on stock evo 8 wheels. I frequently had to spray the tires down as I could easily get them too hot. This season Im making the same hp, ~273awhp, but now Im running 18x9 w/ 255/35 star specs. I dont easily overheat these tires with my power and setup Im running. At this point I know if I go any wider, or even stay the same width but with R compounds, I would be slower because I know I couldnt heat up the tires. Unless your at least 350 awhp I wouldnt recommend going to a 275 street or especially R compound.
I think exactly the reason you stated you had heavy understeer is because you have much more available traction so either you need more power or less tire. Just imagine how much more understeer you would be having if you had the stock diff back there.
What R compound tires were you running exactly? Keep in mind alot of R compound tires have harder compound so they are generally meant for a road course on a 3000 lb+ car (2.2 mile lap many times vs a .5-.75 lap one time). Unless you are on hoosier A6 which are softer and meant for autox as opposed to the R6. I beleive Yokohama has different compounds for their R tires as well. If your running an autox with something similar to a hoosier R6, with 275 width its gonna be hard to warm them up so your not getting the full benefit of the tire. It was just like my post earlier where I stated that GENERALLY, a wider tire isnt always faster.
I was running kumho ecsta xs last season, on stock evo 8 wheels. I frequently had to spray the tires down as I could easily get them too hot. This season Im making the same hp, ~273awhp, but now Im running 18x9 w/ 255/35 star specs. I dont easily overheat these tires with my power and setup Im running. At this point I know if I go any wider, or even stay the same width but with R compounds, I would be slower because I know I couldnt heat up the tires. Unless your at least 350 awhp I wouldnt recommend going to a 275 street or especially R compound.
I think exactly the reason you stated you had heavy understeer is because you have much more available traction so either you need more power or less tire. Just imagine how much more understeer you would be having if you had the stock diff back there.
I was running kumho ecsta xs last season, on stock evo 8 wheels. I frequently had to spray the tires down as I could easily get them too hot. This season Im making the same hp, ~273awhp, but now Im running 18x9 w/ 255/35 star specs. I dont easily overheat these tires with my power and setup Im running. At this point I know if I go any wider, or even stay the same width but with R compounds, I would be slower because I know I couldnt heat up the tires. Unless your at least 350 awhp I wouldnt recommend going to a 275 street or especially R compound.
I think exactly the reason you stated you had heavy understeer is because you have much more available traction so either you need more power or less tire. Just imagine how much more understeer you would be having if you had the stock diff back there.
I completely disagree. Following your reasoning, a superlight miata with 100HP would NEVER run R-comps of any size. If you throw on a set of R6's you would probably be a couple seconds faster per lap, but they will take a few laps to get up to temp. Also, the difference in one tire overheating and another not overheating can be completely due to the rubber compound. Even in autocross for a low-powered Civic on street tires - there are some that get too hot and greasy after a couple runs, and others that don't. All has to do with construction and compounds. . .
Spec miatas arent running 285/35/18 R comps though.
The fact that at some point you will be slower by adding a wider tire is not because you can't get heat into it, it is due to the extra rotating mass and the extra aero drag from the wider tires.
https://www.evolutionm.net/forums/au...-autobahn.html
Just wanted to post a link to that - dropped almost 2 seconds with just the upgraded diff and moustache bar delete
Just wanted to post a link to that - dropped almost 2 seconds with just the upgraded diff and moustache bar delete
General question:
As I'm sure most of us have anything from a faint clicking to a semi violent shudder (me) at low speed, I was curious what is happening/what the diff is trying to do? My extremely general understanding with clutch type diffs is that it tries to shuffle the torque the the wheel with more grip - and this is what gives us our power oversteer yes?
so what is happening when the car is turning at low speeds? Does the diff "know" which way the wheel is turned and is attempting to shift the power to the outside wheel? that doesn't really make sense considering what a diff does. both wheels are nowhere near the limit of grip.
is the diff simply accounting for the difference in distances traveled between the wheels? it must be, it only happens when im actually touching the throttle during these low speed turns (ie turning left from a stop light or whatever).
As I'm sure most of us have anything from a faint clicking to a semi violent shudder (me) at low speed, I was curious what is happening/what the diff is trying to do? My extremely general understanding with clutch type diffs is that it tries to shuffle the torque the the wheel with more grip - and this is what gives us our power oversteer yes?
so what is happening when the car is turning at low speeds? Does the diff "know" which way the wheel is turned and is attempting to shift the power to the outside wheel? that doesn't really make sense considering what a diff does. both wheels are nowhere near the limit of grip.
is the diff simply accounting for the difference in distances traveled between the wheels? it must be, it only happens when im actually touching the throttle during these low speed turns (ie turning left from a stop light or whatever).
General question:
As I'm sure most of us have anything from a faint clicking to a semi violent shudder (me) at low speed, I was curious what is happening/what the diff is trying to do? My extremely general understanding with clutch type diffs is that it tries to shuffle the torque the the wheel with more grip - and this is what gives us our power oversteer yes?
so what is happening when the car is turning at low speeds? Does the diff "know" which way the wheel is turned and is attempting to shift the power to the outside wheel? that doesn't really make sense considering what a diff does. both wheels are nowhere near the limit of grip.
is the diff simply accounting for the difference in distances traveled between the wheels? it must be, it only happens when im actually touching the throttle during these low speed turns (ie turning left from a stop light or whatever).
As I'm sure most of us have anything from a faint clicking to a semi violent shudder (me) at low speed, I was curious what is happening/what the diff is trying to do? My extremely general understanding with clutch type diffs is that it tries to shuffle the torque the the wheel with more grip - and this is what gives us our power oversteer yes?
so what is happening when the car is turning at low speeds? Does the diff "know" which way the wheel is turned and is attempting to shift the power to the outside wheel? that doesn't really make sense considering what a diff does. both wheels are nowhere near the limit of grip.
is the diff simply accounting for the difference in distances traveled between the wheels? it must be, it only happens when im actually touching the throttle during these low speed turns (ie turning left from a stop light or whatever).
I think its the clutches grabbing, trying to turn the rear wheels. Diff fluids with lsd additive let the clutches slip more so the diff becomes quieter, but also less effective since the clutches slip more. Ya, I think its basically accounting for the differences between wheels.
Last edited by TommiM; Sep 20, 2010 at 07:12 PM.