Steady State Understeer and Stiffer Rear Springs
07-03-09, 11:52 AM
#1
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Steady State Understeer and Stiffer Rear Springs
Hey all,
After researching causes and solutions, I feel my best bet is to change my spring rates. Currently on Tein SS's, I have 8/6 F/R. We could go into a book, I know, on solutions but don't really want to do that in this thread. Let's just focus on springs.
Question: Is it best to increase the rear spring rate or lower the front spring rate? My initial thinking is to go to 8/7.
Ben
After researching causes and solutions, I feel my best bet is to change my spring rates. Currently on Tein SS's, I have 8/6 F/R. We could go into a book, I know, on solutions but don't really want to do that in this thread. Let's just focus on springs.
Question: Is it best to increase the rear spring rate or lower the front spring rate? My initial thinking is to go to 8/7.
Ben
07-03-09, 01:02 PM
#2
Senior Member
iTrader: (3)
Join Date: Sep 2004
Location: CA
Posts: 258
Likes: 0
Received 0 Likes
on
0 Posts
I'm surprised you have steady state understeer with those spring rates.
Some more info would be helpfull:
Is this on an FD?
What are the tire sizes?
What sway bars are on the car?
Some more info would be helpfull:
Is this on an FD?
What are the tire sizes?
What sway bars are on the car?
07-03-09, 03:14 PM
#3
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Being that this is an LT1 conversion, and the bias is now 52/48 may have something to do with it.
Lets see if this helps:
FC
Camber set for good tire temps at track (-3/-1.5)
245 front / 255 rear
1-1/8 bar up front/bar delete in the rear
Lets see if this helps:
FC
Camber set for good tire temps at track (-3/-1.5)
245 front / 255 rear
1-1/8 bar up front/bar delete in the rear
07-03-09, 04:07 PM
#4
What kind of wheel rates are you getting with those springs?(it looks like you may have your corner weight info) My first thing to try would be to soften the front bar if you can. The rear springs would be the next on the list if your ride rates won't get too far out of whack.
07-06-09, 01:29 AM
#5
Senior Member
iTrader: (3)
Join Date: Sep 2004
Location: CA
Posts: 258
Likes: 0
Received 0 Likes
on
0 Posts
Since my RX7 experience is with a rotary powered FD, I can't offer specifics, but here's some general thoughts.
It sounds like you have done some good work in alignment tuning, getting good tire temps! Way ahead of many.
What's easiest to do for you?
Adding a rear sway bar should help.
You are correct in that either softer front or stiffer rear springs will help understeer. As for which to do in your case, hmmm... How's the overall stiffness of the car? Too stiff leads to compliance problems over bumpy sections of track, and you don't want the springs stiffer than your shocks can deal with. Is it more for track use (leans one to stiffer rear) or street (comfort says softer front).
Ahh, the endless suspension tuning game goes on!
It sounds like you have done some good work in alignment tuning, getting good tire temps! Way ahead of many.
What's easiest to do for you?
Adding a rear sway bar should help.
You are correct in that either softer front or stiffer rear springs will help understeer. As for which to do in your case, hmmm... How's the overall stiffness of the car? Too stiff leads to compliance problems over bumpy sections of track, and you don't want the springs stiffer than your shocks can deal with. Is it more for track use (leans one to stiffer rear) or street (comfort says softer front).
Ahh, the endless suspension tuning game goes on!
07-06-09, 09:45 AM
#6
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
What kind of wheel rates are you getting with those springs?(it looks like you may have your corner weight info) My first thing to try would be to soften the front bar if you can. The rear springs would be the next on the list if your ride rates won't get too far out of whack.
07-06-09, 09:51 AM
#7
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Adding a rear sway bar should help.
You are correct in that either softer front or stiffer rear springs will help understeer. As for which to do in your case, hmmm... How's the overall stiffness of the car? Too stiff leads to compliance problems over bumpy sections of track, and you don't want the springs stiffer than your shocks can deal with. Is it more for track use (leans one to stiffer rear) or street (comfort says softer front).
You are correct in that either softer front or stiffer rear springs will help understeer. As for which to do in your case, hmmm... How's the overall stiffness of the car? Too stiff leads to compliance problems over bumpy sections of track, and you don't want the springs stiffer than your shocks can deal with. Is it more for track use (leans one to stiffer rear) or street (comfort says softer front).
It has been stated that you adjust the area that is giving you problems. understeer, adjust the front. So from my point of view, I don't want to soften the front but stiffen the back. This is counter to good racer logic and wanted to hear from others on this.
Appreciate it,
Ben
Trending Topics
07-06-09, 11:17 AM
#9
Easiest at this point would be to try adding stock rear bar and see how that goes.
Or, I'll be the first in the thread to mention driving style... A steady state understeer may not be a bad thing with an LT1, you have enough power to bring the rearend out at will. A slight oversteer is just a right foot away!
Or, I'll be the first in the thread to mention driving style... A steady state understeer may not be a bad thing with an LT1, you have enough power to bring the rearend out at will. A slight oversteer is just a right foot away!
07-06-09, 11:38 AM
#10
F**K THE SYSTEM!!
HE has no rear swaybar because he was tyring to get grip out of it?
I have heard of evos using tein springs and getting some fugly undesteer. Stock springs are way better than tein for evos.
I have heard of evos using tein springs and getting some fugly undesteer. Stock springs are way better than tein for evos.
07-06-09, 07:37 PM
#11
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
It has been indicated on this board to try it with an FC and in my case, it did work to keep the rear planted when exiting the corner. Times went down because I was able to apply more power sooner. It was indicated that it has something to do with the rear suspension dynamics of an FC.
07-06-09, 07:42 PM
#12
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Easiest at this point would be to try adding stock rear bar and see how that goes.
Or, I'll be the first in the thread to mention driving style... A steady state understeer may not be a bad thing with an LT1, you have enough power to bring the rearend out at will. A slight oversteer is just a right foot away!
Or, I'll be the first in the thread to mention driving style... A steady state understeer may not be a bad thing with an LT1, you have enough power to bring the rearend out at will. A slight oversteer is just a right foot away!
I would agree going with 255's all around probably would come close to solving the problem but right now that is not a cheap option as I would need new rims. Only 8" up front.
07-07-09, 11:49 AM
#13
F**K THE SYSTEM!!
Irentat. I had the same problem on my last event.
MY conclusion came down to getting a 9" rim up front with 255 or 245. I also run a 255 on the rear.
I know how u feel. U hit the gas. The chassi sits on the rear wheels and pushes the front with nasty understeer.
MY conclusion came down to getting a 9" rim up front with 255 or 245. I also run a 255 on the rear.
I know how u feel. U hit the gas. The chassi sits on the rear wheels and pushes the front with nasty understeer.
07-07-09, 03:18 PM
#15
Toe settings shouldn't make a huge difference in steady state cornering. It mainly effects: tire wear, high speed stability, and corner entry. You could always try some toe out and see if it helps, but I would check your tire temps and see if you need more camber.
07-07-09, 03:28 PM
#16
Too much toe-out turns you in to a snow plow, with enough power you'd never notice going straight, but you'd really notice it fighting you through the corner.
I agree with jgrewe, though, that the most common cause of apex and corner exit understeer is driving style... with a V8 in the car hitting the gas at the apex should result in some nice oversteer, and not further understeer, though, unless you really over-cooked it, or there's a set up issue. But chasing this with rear spring seems like the wrong approach since the rear sounds great right now, it's planted. It's front grip that's the issue...
07-07-09, 08:51 PM
#17
Lives on the Forum
Disagree. It can explain corner entry (as you said), steady state and corner exit understeer (or oversteer), too. And don't forget part of toe is getting the thrust angle correct. And we haven't even talked about the affects of rake, yet.
Too much toe-out turns you in to a snow plow, with enough power you'd never notice going straight, but you'd really notice it fighting you through the corner.
I agree with jgrewe, though, that the most common cause of apex and corner exit understeer is driving style... with a V8 in the car hitting the gas at the apex should result in some nice oversteer, and not further understeer, though, unless you really over-cooked it, or there's a set up issue. But chasing this with rear spring seems like the wrong approach since the rear sounds great right now, it's planted. It's front grip that's the issue...
Too much toe-out turns you in to a snow plow, with enough power you'd never notice going straight, but you'd really notice it fighting you through the corner.
I agree with jgrewe, though, that the most common cause of apex and corner exit understeer is driving style... with a V8 in the car hitting the gas at the apex should result in some nice oversteer, and not further understeer, though, unless you really over-cooked it, or there's a set up issue. But chasing this with rear spring seems like the wrong approach since the rear sounds great right now, it's planted. It's front grip that's the issue...
07-08-09, 10:09 PM
#18
Full Member
Thread Starter
iTrader: (1)
Join Date: Jan 2008
Location: Phoenix
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Disagree. It can explain corner entry (as you said), steady state and corner exit understeer (or oversteer), too. And don't forget part of toe is getting the thrust angle correct. And we haven't even talked about the affects of rake, yet.
Too much toe-out turns you in to a snow plow, with enough power you'd never notice going straight, but you'd really notice it fighting you through the corner.
I agree with jgrewe, though, that the most common cause of apex and corner exit understeer is driving style... with a V8 in the car hitting the gas at the apex should result in some nice oversteer, and not further understeer, though, unless you really over-cooked it, or there's a set up issue. But chasing this with rear spring seems like the wrong approach since the rear sounds great right now, it's planted. It's front grip that's the issue...
Too much toe-out turns you in to a snow plow, with enough power you'd never notice going straight, but you'd really notice it fighting you through the corner.
I agree with jgrewe, though, that the most common cause of apex and corner exit understeer is driving style... with a V8 in the car hitting the gas at the apex should result in some nice oversteer, and not further understeer, though, unless you really over-cooked it, or there's a set up issue. But chasing this with rear spring seems like the wrong approach since the rear sounds great right now, it's planted. It's front grip that's the issue...
Before these tires, I had toe 0 with 225/255 F/R. With that setup, I had lots of understeer in steady state but could swing the back around with the V8 torque on exit.
Referencing this discussion and continued understeer issues, I went with 245/255 with some toe out...approximately 5/16". I did not realize that my toe out could cause pushing (again newbie to road racing).
Based on the new advice, I will change to 0 toe to determine if this makes a difference before I go with springs.
Ben
07-08-09, 11:48 PM
#19
5/16" !? Damn, that's *a lot* of toe-out. I wouldn't even run 5/16" toe-in in the back to keep oversteer under control.
Try somewhere between 1/32" toe-in and 1/16" toe-out in the front. 1/4" toe-out *might* work on an autocross. Try somewhere between 0 and 3/16" toe-in on the back.
Keep in mind that I'm just coming back to my FC, but those numbers are where I'm going to play to start with. Maybe somebody else can pipe up a bit.
Also, you could raise the rear a bit, or drop the front a bit, to get more front bite. Rake can play a huge role in this stuff. Have you done a corner weight?
Try somewhere between 1/32" toe-in and 1/16" toe-out in the front. 1/4" toe-out *might* work on an autocross. Try somewhere between 0 and 3/16" toe-in on the back.
Keep in mind that I'm just coming back to my FC, but those numbers are where I'm going to play to start with. Maybe somebody else can pipe up a bit.
Also, you could raise the rear a bit, or drop the front a bit, to get more front bite. Rake can play a huge role in this stuff. Have you done a corner weight?
Thread
Thread Starter
Forum
Replies
Last Post
diabolical1
2nd Generation Specific (1986-1992)
30
01-30-16 05:50 AM
