| Mykl | 12-19-2006 08:40 PM |
Caster and wheel lift
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I'm trying to understand the effect that caster has on rear wheel lift.
My setup...
ZZYZX coilovers, 450 lb/in front springs, 400 lb/in rear springs
Cobb swaybars, rear @ full stiff
245/45-17 RT615's on 17x8 +48 wheels
Noltec camber/castor plates
Alignment...
Camber: -2.5f / -1.5r
Toe: 0/0
Caster: +6.8
Ride height: ~13.75f, ~13.75r (as measured from center of hub to fender)
At this point wheel lift is not a "problem" with my car. But it has been observed that on corner entry I do get a bit of wheel lift. I'm extremely happy with my car right now. Transient response is good, mid corner leans towards controllable oversteer, and on corner exit the car goes where I point it. The only time wheel lift hinders my transition from the brake pedal to the go pedal is when I make a pretty big mistake.
The reason I ask is because the wheel lift is right on the edge of being an actual problem, and at the point that I upgrade the tires to V710's I'll have to do something about it. Right now the plan is to change to Whiteline 24mm swaybars when I buy race tires. But I'm not yet sure if that'll be enough.
The other potential suspect is my big caster number. I understand how a lack of roll stiffness on one end of the car can cause wheel lift on the other end. But I've read that caster aggravates a rear wheel lift problem and I don't know how or why and I'm not even 100% sure that that statement is true.
If I lowered the caster number what effect would this have on wheel lift?
My setup...
ZZYZX coilovers, 450 lb/in front springs, 400 lb/in rear springs
Cobb swaybars, rear @ full stiff
245/45-17 RT615's on 17x8 +48 wheels
Noltec camber/castor plates
Alignment...
Camber: -2.5f / -1.5r
Toe: 0/0
Caster: +6.8
Ride height: ~13.75f, ~13.75r (as measured from center of hub to fender)
At this point wheel lift is not a "problem" with my car. But it has been observed that on corner entry I do get a bit of wheel lift. I'm extremely happy with my car right now. Transient response is good, mid corner leans towards controllable oversteer, and on corner exit the car goes where I point it. The only time wheel lift hinders my transition from the brake pedal to the go pedal is when I make a pretty big mistake.
The reason I ask is because the wheel lift is right on the edge of being an actual problem, and at the point that I upgrade the tires to V710's I'll have to do something about it. Right now the plan is to change to Whiteline 24mm swaybars when I buy race tires. But I'm not yet sure if that'll be enough.
The other potential suspect is my big caster number. I understand how a lack of roll stiffness on one end of the car can cause wheel lift on the other end. But I've read that caster aggravates a rear wheel lift problem and I don't know how or why and I'm not even 100% sure that that statement is true.
If I lowered the caster number what effect would this have on wheel lift?
| sciolist | 12-19-2006 08:54 PM |
We're talking about autoX here, correct? With all due respect, the lifting adventure doesn't even begin until you put race tires on.
No, the bars won't be enough. I suspect you're going to be rethinking your camber settings and spring rates, and whether you even want a rear bar. Lowering the caster would be about the last thing I'd do.
No, the bars won't be enough. I suspect you're going to be rethinking your camber settings and spring rates, and whether you even want a rear bar. Lowering the caster would be about the last thing I'd do.
| Mykl | 12-19-2006 09:08 PM |
[QUOTE=sciolist;16382778]We're talking about autoX here, correct? With all due respect, the lifting adventure doesn't even begin until you put race tires on.
No, the bars won't be enough. I suspect you're going to be rethinking your camber settings and spring rates, and whether you even want a rear bar. Lowering the caster would be about the last thing I'd do.[/QUOTE]
Yeah, autocrossing. As you can see I've pretty much set it up as a "general purpose" car. The spring rates I chose combined with the bars are great for street tires. As I've said, I couldn't be more happy with the car as it sits right now.
I understand that I'm going to want to go stiffer with race tires, but how much stiffer am I going to need to go with 245/45 V710's? The car won't be set up for monster 275+ width tires any time soon.
Concerning camber, are you suggesting that I should consider more?
...so caster isn't an issue?
No, the bars won't be enough. I suspect you're going to be rethinking your camber settings and spring rates, and whether you even want a rear bar. Lowering the caster would be about the last thing I'd do.[/QUOTE]
Yeah, autocrossing. As you can see I've pretty much set it up as a "general purpose" car. The spring rates I chose combined with the bars are great for street tires. As I've said, I couldn't be more happy with the car as it sits right now.
I understand that I'm going to want to go stiffer with race tires, but how much stiffer am I going to need to go with 245/45 V710's? The car won't be set up for monster 275+ width tires any time soon.
Concerning camber, are you suggesting that I should consider more?
...so caster isn't an issue?
| sciolist | 12-19-2006 09:17 PM |
[QUOTE=Mykl;16382904]I understand that I'm going to want to go stiffer with race tires, but how much stiffer am I going to need to go with 245/45 V710's? The car won't be set up for monster 275+ width tires any time soon.
Concerning camber, are you suggesting that I should consider more?
...so caster isn't an issue?[/QUOTE]
Monster? I thought this was a BSP car.
I'm saying that I think you should consider camber as a F/R tuning device, and no, I do not think caster is the place to look for solutions to wheel lift problems.
Concerning camber, are you suggesting that I should consider more?
...so caster isn't an issue?[/QUOTE]
Monster? I thought this was a BSP car.
I'm saying that I think you should consider camber as a F/R tuning device, and no, I do not think caster is the place to look for solutions to wheel lift problems.
| Mykl | 12-19-2006 09:35 PM |
[QUOTE=sciolist;16382992]Monster? I thought this was a BSP car.
I'm saying that I think you should consider camber as a F/R tuning device, and no, I do not think caster is the place to look for solutions to wheel lift problems.[/QUOTE]
It may as well be an SM car for all it matters. Going to the next level of competition isn't worth the increased financial burden so I'm going to use this time to learn.
That's an idea that I had not considered. Less bar and less camber in the rear. I might have to toy around with this later. That big-ass Whiteline front bar may be useful after all.
I'm saying that I think you should consider camber as a F/R tuning device, and no, I do not think caster is the place to look for solutions to wheel lift problems.[/QUOTE]
It may as well be an SM car for all it matters. Going to the next level of competition isn't worth the increased financial burden so I'm going to use this time to learn.
That's an idea that I had not considered. Less bar and less camber in the rear. I might have to toy around with this later. That big-ass Whiteline front bar may be useful after all.
| crystalhelix | 12-19-2006 11:58 PM |
[QUOTE=sciolist;16382778]We're talking about autoX here, correct? With all due respect, the lifting adventure doesn't even begin until you put race tires on.
[/QUOTE]
ROFL...:lol:
[/QUOTE]
ROFL...:lol:
| zzyzx | 12-20-2006 01:27 AM |
Some observations:
1) Your front roll stiffness is not enough to keep the rear tire planted. I'd suggest 550 lbs. in the front which will not produce a drastic ride comfort
change on the street.
2) Ditch the rear bar, or set it to full soft. As you migrate to Rs, the rear bar will only cause significant wheel lift issues.
3) You could use more front neg. camber. I'd recommend -2.8. With zero toe, tire wear shouldn't be an issue. Rotate regularly.
4) Try lowering the rear 1/2". If there is a significant increase in push, raise it up 1/4" - test again - and back to your current heights if the balance isn't what it is now.
Rs will change things drastically. You are what I consider at the low end of roll stiffness for an STU car. BSP STis are running rates [i]significantly[/i] higher than yours.
Either way, drop me an email to discuss more details if you want.
- Steve
[url="http://zzyzxmotorsports.com"]Zzyzx Motorsports[/url]
1) Your front roll stiffness is not enough to keep the rear tire planted. I'd suggest 550 lbs. in the front which will not produce a drastic ride comfort
change on the street.
2) Ditch the rear bar, or set it to full soft. As you migrate to Rs, the rear bar will only cause significant wheel lift issues.
3) You could use more front neg. camber. I'd recommend -2.8. With zero toe, tire wear shouldn't be an issue. Rotate regularly.
4) Try lowering the rear 1/2". If there is a significant increase in push, raise it up 1/4" - test again - and back to your current heights if the balance isn't what it is now.
Rs will change things drastically. You are what I consider at the low end of roll stiffness for an STU car. BSP STis are running rates [i]significantly[/i] higher than yours.
Either way, drop me an email to discuss more details if you want.
- Steve
[url="http://zzyzxmotorsports.com"]Zzyzx Motorsports[/url]
| afpdl | 12-20-2006 01:29 AM |
In stu I had a horrible wheel lift issue when I ran stiff rear and soft front set up with butloads of caster and my rsb on soft. I then swapped my springs around and it became more manageable. I am now running less caster than stock with the rsb on full stiff and dont have any of the complications of rear wheel lift.
<<now hates caster.
<<now hates caster.
| silver arrow | 12-20-2006 02:01 AM |
650lbs, 3.5 neg camber, 1/4 toe out, 32mm FSB on the front
550lbs, 1.5 neg camber, 0 toe, stock RSB on the rear
On an STU car. Very little rear wheel lift even with the crappy no droop Teins. Car is consistent and very easy to set up handling wise.
My setup is very close to the set up used on the Nationals winning STU car except he's running 650 rear too, so I can't be to far off.
550lbs, 1.5 neg camber, 0 toe, stock RSB on the rear
On an STU car. Very little rear wheel lift even with the crappy no droop Teins. Car is consistent and very easy to set up handling wise.
My setup is very close to the set up used on the Nationals winning STU car except he's running 650 rear too, so I can't be to far off.
| crystalhelix | 12-20-2006 11:21 AM |
also - there is a method of attack that works to keep the tires planted although you may lift a front when you are generating enough grip....
..make your brake zones a little earlier and in a straighter line...then accellerate through the turn...too often people are too hot for the corner entry and are still trying to brake to get the speed down a little, this makes the doggy style a little worse...moving my brake zones up for me worked well this year..
..make your brake zones a little earlier and in a straighter line...then accellerate through the turn...too often people are too hot for the corner entry and are still trying to brake to get the speed down a little, this makes the doggy style a little worse...moving my brake zones up for me worked well this year..
| Mykl | 12-20-2006 11:25 AM |
Thanks Steve, I'll send you an eMail later! I didn't send one to begin with because at this point I'm not really trying to fix a problem with my car so much as I am trying to plan my next move.
[QUOTE=afpdl;16385484]In stu I had a horrible wheel lift issue when I ran stiff rear and soft front set up with butloads of caster and my rsb on soft. I then swapped my springs around and it became more manageable. I am now running less caster than stock with the rsb on full stiff and dont have any of the complications of rear wheel lift.
<<now hates caster.[/QUOTE]
At what point did you bring the caster setting down? Was this after you had tried the stiffer front spring setup or did you bring the caster down at the same time you swapped the springs?
Here's what I'm trying to understand...
How much of an effect does the increased caster angle up front have on the diagonal weight transfer of my car? It seems reasonable to believe that higher positive caster numbers means faster weight transfer from the rear to the front of the car.
Since I'm only lifting a wheel on corner entry, and it's sitting back down at some point before I get on the throttle tells me that I currently have enough roll stiffness for the tires at the front.
So it seems that varying combinations of these two things are occuring...
1. Weight transfers so fast that the front is compressed too much and then pushes back, decompresses a bit, and puts the rear tire down. This only seems to be the case when I make a mistake and have to ask more of the outside front tire than I should.
2. Damper rebound too strong and/or too much rear bar slowing the rate that the spring decompresses.
When I increase the adhesion between the car and the track by going to race tires, I will also increase body roll if all else remains constant. I will also increase the speed in which I can transfer weight. With more body roll up front the rear suspension needs more droop travel, and with faster weight transfer and higher cornering speeds that means the rear suspension needs to decompress faster.
It seems that there are four things that can be done...
1. Increase front roll stiffness
2. Decrease weight transfer speed
3. Increase rear suspension decompression speed
4. Increase rear droop travel
1 is easy and pretty self explanatory (I will try a bigger bar first). 2 can be done by reducing positive caster (won't help if there isn't enough roll stiffness, wheel will just lift later rather than sooner). 3 can be done by using less bar. 4 is not an option for me.
It seems like the best thing for me to do (should I get stickier tires) would be to go with more bar up front, no more bar than I already have in the rear (in relation to spring rate), and maybe increase the spring rates in the rear by a small amount (+50 lb/in) to keep the roll stiffness balance between the front and rear where I want it.
I'm not against bringing up the spring rates in the front a little, but I'd like to see what effect a larger bar will have first since the one on my car isn't significantly stronger than stock.
[QUOTE=afpdl;16385484]In stu I had a horrible wheel lift issue when I ran stiff rear and soft front set up with butloads of caster and my rsb on soft. I then swapped my springs around and it became more manageable. I am now running less caster than stock with the rsb on full stiff and dont have any of the complications of rear wheel lift.
<<now hates caster.[/QUOTE]
At what point did you bring the caster setting down? Was this after you had tried the stiffer front spring setup or did you bring the caster down at the same time you swapped the springs?
Here's what I'm trying to understand...
How much of an effect does the increased caster angle up front have on the diagonal weight transfer of my car? It seems reasonable to believe that higher positive caster numbers means faster weight transfer from the rear to the front of the car.
Since I'm only lifting a wheel on corner entry, and it's sitting back down at some point before I get on the throttle tells me that I currently have enough roll stiffness for the tires at the front.
So it seems that varying combinations of these two things are occuring...
1. Weight transfers so fast that the front is compressed too much and then pushes back, decompresses a bit, and puts the rear tire down. This only seems to be the case when I make a mistake and have to ask more of the outside front tire than I should.
2. Damper rebound too strong and/or too much rear bar slowing the rate that the spring decompresses.
When I increase the adhesion between the car and the track by going to race tires, I will also increase body roll if all else remains constant. I will also increase the speed in which I can transfer weight. With more body roll up front the rear suspension needs more droop travel, and with faster weight transfer and higher cornering speeds that means the rear suspension needs to decompress faster.
It seems that there are four things that can be done...
1. Increase front roll stiffness
2. Decrease weight transfer speed
3. Increase rear suspension decompression speed
4. Increase rear droop travel
1 is easy and pretty self explanatory (I will try a bigger bar first). 2 can be done by reducing positive caster (won't help if there isn't enough roll stiffness, wheel will just lift later rather than sooner). 3 can be done by using less bar. 4 is not an option for me.
It seems like the best thing for me to do (should I get stickier tires) would be to go with more bar up front, no more bar than I already have in the rear (in relation to spring rate), and maybe increase the spring rates in the rear by a small amount (+50 lb/in) to keep the roll stiffness balance between the front and rear where I want it.
I'm not against bringing up the spring rates in the front a little, but I'd like to see what effect a larger bar will have first since the one on my car isn't significantly stronger than stock.
| Mykl | 12-20-2006 11:30 AM |
[QUOTE=crystalhelix;16388929]also - there is a method of attack that works to keep the tires planted although you may lift a front when you are generating enough grip....
..make your brake zones a little earlier and in a straighter line...then accellerate through the turn...too often people are too hot for the corner entry and are still trying to brake to get the speed down a little, this makes the doggy style a little worse...moving my brake zones up for me worked well this year..[/QUOTE]
That's basically how I drive, I get most of my braking done in a straight line and when I start to turn the car I'm moving my foot to the go pedal. But I'm generalizing, there are some times where I drag the brakes into a turn a little longer. But this mostly happens on turns that decrease in radius to some degree.
..make your brake zones a little earlier and in a straighter line...then accellerate through the turn...too often people are too hot for the corner entry and are still trying to brake to get the speed down a little, this makes the doggy style a little worse...moving my brake zones up for me worked well this year..[/QUOTE]
That's basically how I drive, I get most of my braking done in a straight line and when I start to turn the car I'm moving my foot to the go pedal. But I'm generalizing, there are some times where I drag the brakes into a turn a little longer. But this mostly happens on turns that decrease in radius to some degree.
| afpdl | 12-20-2006 11:32 AM |
[QUOTE=Mykl;16388999]
At what point did you bring the caster setting down? Was this after you had tried the stiffer front spring setup or did you bring the caster down at the same time you swapped the springs?
[/QUOTE]
It progressed like this.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.
At what point did you bring the caster setting down? Was this after you had tried the stiffer front spring setup or did you bring the caster down at the same time you swapped the springs?
[/QUOTE]
It progressed like this.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.
| Mykl | 12-20-2006 11:41 AM |
[QUOTE=afpdl;16389104]It progressed like this.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.[/QUOTE]
:cool:
With my current setup, I honestly don't notice the wheel lift. As I said, the only time it's an issue is when I screw up. The only reason I know it's happening with any amount of frequency is because I was told by an observer that it was happening a lot.
It seems like increased caster is beneficial, but there are negative side effects of pushing the angle a little too far. Fortunately with the Noltecs I can fine tune it.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.[/QUOTE]
:cool:
With my current setup, I honestly don't notice the wheel lift. As I said, the only time it's an issue is when I screw up. The only reason I know it's happening with any amount of frequency is because I was told by an observer that it was happening a lot.
It seems like increased caster is beneficial, but there are negative side effects of pushing the angle a little too far. Fortunately with the Noltecs I can fine tune it.
| silver arrow | 12-20-2006 12:13 PM |
[QUOTE=afpdl;16389104]It progressed like this.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.[/QUOTE]
In theory, caster should allow you to run less static camber and still retain camber mid corner. Less negative camber allows for better braking and acceleration. In practice, I'm not sure how helpful it is. I think the guy with the driving tips is probaby the closest to avoiding wheel lift.
1. Stiff rear soft front lots of caster = horrid wheel lift
2. Got a front bar and put rear bar on soft, still had wheel lift on corner exit.
3. Swapped springs and it would only lift time to time
4. Flipped my camber plates the wrong way to get rid of caster and put the rsb on full stiff and I haven't noticed any wheel lift since.
I don't really see the benefit of caster in our cars. I have all the static camber I could ever need. AFAIK all caster does is increase weight transfer, make the steering a little heavier and gain camber when you turn.[/QUOTE]
In theory, caster should allow you to run less static camber and still retain camber mid corner. Less negative camber allows for better braking and acceleration. In practice, I'm not sure how helpful it is. I think the guy with the driving tips is probaby the closest to avoiding wheel lift.
| Mykl | 12-20-2006 04:22 PM |
A funny note on caster... I'm finding a ton of useful information on kart racing web sites and very little on actual automobile racing web sites.
According to these web pages my car handles "properly" for a kart. Inside rear wheel lift at initial turn in, resulting in a center of gravity change that basically places more weight on the other three tires allowing for sharper turn in.
According to these web pages my car handles "properly" for a kart. Inside rear wheel lift at initial turn in, resulting in a center of gravity change that basically places more weight on the other three tires allowing for sharper turn in.
| zzyzx | 12-20-2006 04:52 PM |
[QUOTE=Mykl;16388999]4 is not an option for me.[/QUOTE]
:confused: Why not?
:confused: Why not?
| Mykl | 12-20-2006 04:55 PM |
[QUOTE=zzyzx;16393743]:confused: Why not?[/QUOTE]
I already have your coilovers? :lol:
I already have your coilovers? :lol:
| zzyzx | 12-20-2006 05:02 PM |
[QUOTE=Mykl;16393783]I already have your coilovers? :lol:[/QUOTE]
You [i]can[/i] adjust droop/bump travel on my coilovers... :)
Not that you'd need to, however:
[img]http://zzyzxmotorsports.com/pics/stompy/pic4.jpg[/img]
My coilovers offer more rear droop than most applications can utilize.
You [i]can[/i] adjust droop/bump travel on my coilovers... :)
Not that you'd need to, however:
[img]http://zzyzxmotorsports.com/pics/stompy/pic4.jpg[/img]
My coilovers offer more rear droop than most applications can utilize.
| omaha03wrx | 12-20-2006 05:04 PM |
You might be better off going with the Whiteline 27mm adjustable front bar instead of the 24mm one. I installed one right before my last autox in KC and didn't have any inside tire lift. It used to do it quite frequently. I wish I would have done it A LOT sooner than I did. Also like Steve said ditch the rear bar. I haven't had one since day of running his coilovers.
| Mykl | 12-20-2006 05:07 PM |
[QUOTE=zzyzx;16393903]You [i]can[/i] adjust droop/bump travel on my coilovers... :)[/QUOTE]
Absolutely. I've been playing with that. Up front I had a problem with bottoming out over a very nasty bump it seems that the course designers enjoy making us drive over. I gave myself a little more bump travel up front, but I haven't been back to see if I have enough yet.
Absolutely. I've been playing with that. Up front I had a problem with bottoming out over a very nasty bump it seems that the course designers enjoy making us drive over. I gave myself a little more bump travel up front, but I haven't been back to see if I have enough yet.
| Mykl | 12-20-2006 05:13 PM |
[QUOTE=omaha03wrx;16393944]You might be better off going with the Whiteline 27mm adjustable front bar instead of the 24mm one. I installed one right before my last autox in KC and didn't have any inside tire lift. It used to do it quite frequently. I wish I would have done it A LOT sooner than I did. Also like Steve said ditch the rear bar. I haven't had one since day of running his coilovers.[/QUOTE]
I can see why he recommends removing the bar every time I lift both rear tires off the ground at the same time for maintenance or adjustments. When I lift just one side the bar keeps the side that's off the ground from extending as far as it could. I think the difference is something like two inches.
The reason I don't want to skip straight to the 27mm bar is mostly due to my curiosity. For testing purposes I would like to see how the car handles as I gradually increase bar strength. If I find out that I don't need the big bar to get the inside rear to the ground when it needs to be there, all the better.
I can see why he recommends removing the bar every time I lift both rear tires off the ground at the same time for maintenance or adjustments. When I lift just one side the bar keeps the side that's off the ground from extending as far as it could. I think the difference is something like two inches.
The reason I don't want to skip straight to the 27mm bar is mostly due to my curiosity. For testing purposes I would like to see how the car handles as I gradually increase bar strength. If I find out that I don't need the big bar to get the inside rear to the ground when it needs to be there, all the better.
| bdi | 12-20-2006 08:17 PM |
This is a good thread.
[QUOTE=zzyzx;16385472]Some observations:
Either way, drop me an email to discuss more details if you want.
- Steve
[url="http://zzyzxmotorsports.com"]Zzyzx Motorsports[/url][/QUOTE]
Steve is there anyway that I could email you a few questions that I have about my setup?
Thanks
[QUOTE=zzyzx;16385472]Some observations:
Either way, drop me an email to discuss more details if you want.
- Steve
[url="http://zzyzxmotorsports.com"]Zzyzx Motorsports[/url][/QUOTE]
Steve is there anyway that I could email you a few questions that I have about my setup?
Thanks
| Mykl | 12-20-2006 09:12 PM |
. oops
| afpdl | 12-21-2006 01:23 AM |
[QUOTE=silver arrow;16389716]In theory, caster should allow you to run less static camber and still retain camber mid corner. Less negative camber allows for better braking and acceleration. [/QUOTE]
According to my gtech braking is unaffected up to -3.8 of static camber (I got equal lateral gs to braking gs) Above that and braking starts to fall off slightly. As for acceleration, I can see that being helpful in wrxs or fwd cars but I have never had a huge issue with front wheel spin in a sti.
According to my gtech braking is unaffected up to -3.8 of static camber (I got equal lateral gs to braking gs) Above that and braking starts to fall off slightly. As for acceleration, I can see that being helpful in wrxs or fwd cars but I have never had a huge issue with front wheel spin in a sti.
| silver arrow | 12-21-2006 06:03 AM |
[QUOTE=afpdl;16398851]According to my gtech braking is unaffected up to -3.8 of static camber (I got equal lateral gs to braking gs) Above that and braking starts to fall off slightly. As for acceleration, I can see that being helpful in wrxs or fwd cars but I have never had a huge issue with front wheel spin in a sti.[/QUOTE]
That's why I said "In theory". I haven't really felt any difference in braking or acceleration either
That's why I said "In theory". I haven't really felt any difference in braking or acceleration either
| crystalhelix | 12-21-2006 09:10 AM |
[QUOTE=afpdl;16398851]According to my gtech braking is unaffected up to -3.8 of static camber (I got equal lateral gs to braking gs) Above that and braking starts to fall off slightly. As for acceleration, I can see that being helpful in wrxs or fwd cars but I have never had a huge issue with front wheel spin in a sti.[/QUOTE]
have you tried this when it's wet or cold out? just curious...also - from the info in the ghetto g-meter thread the g sensors loose accurracy with body roll, so would they also loose accuracy with dive or squat....I am not saying your wrong but it's something to consider...how stiff of a setup are you running (ie..do you have a lot of dive)
have you tried this when it's wet or cold out? just curious...also - from the info in the ghetto g-meter thread the g sensors loose accurracy with body roll, so would they also loose accuracy with dive or squat....I am not saying your wrong but it's something to consider...how stiff of a setup are you running (ie..do you have a lot of dive)
| afpdl | 12-21-2006 11:54 AM |
Yes they loose info with body roll, but when I am only changing the camber/caster settings body roll is going to have the same effect on the numbers as it did before.
For a year every event I went to with 3 different sets of tires resulted in an even round friction circle and equal (within +- .05) peak gs for braking and lateral. Nothing changes when its wet or cold other than the size of the friction circle. I see that as proving itself pretty consistent. The moment camber goes past -3.5 I start seeing a difference in braking vs lateral gs.
But no I dont have a whole lot of dive, front springs are 550lbs, and Im on street tires. The gtech does have some roll correction figured in that you can adjust, I have it set the way it came. At the drag strip it measures about .2sec slower than actual so it seems to be slightly underestimating forces.
For a year every event I went to with 3 different sets of tires resulted in an even round friction circle and equal (within +- .05) peak gs for braking and lateral. Nothing changes when its wet or cold other than the size of the friction circle. I see that as proving itself pretty consistent. The moment camber goes past -3.5 I start seeing a difference in braking vs lateral gs.
But no I dont have a whole lot of dive, front springs are 550lbs, and Im on street tires. The gtech does have some roll correction figured in that you can adjust, I have it set the way it came. At the drag strip it measures about .2sec slower than actual so it seems to be slightly underestimating forces.
| crystalhelix | 12-21-2006 12:03 PM |
neat..
| solo-x | 12-21-2006 01:09 PM |
[QUOTE=Mykl;16393309]A funny note on caster... I'm finding a ton of useful information on kart racing web sites and very little on actual automobile racing web sites.
According to these web pages my car handles "properly" for a kart. Inside rear wheel lift at initial turn in, resulting in a center of gravity change that basically places more weight on the other three tires allowing for sharper turn in.[/QUOTE]
now, if you had a spool for a rear diff like a kart does, then you'd be on to something. karts have to lift the inside rear tire to turn since they have a common axle that drives both of the rear tires at the same time. if you ever watch kart races though, you'll see the fast guys are just barely lifting their inside rear tires. why? raise the cg, increase load transfer, reduce grip, go slower.
my DL1 shows only very minimal decrease in braking and acceleration on my civic going from -2.7 to -4.0 degrees static. we're talking .01 reduction in both, easily offset by the .02 increase in lateral grip. this was a very ghetto test i did too since all i did was drop the car. i was running on the bumpstops with maybe all of 1/4" of bump travel from compressing the bumpstop available before the uca and tire hit the strut tower.
According to these web pages my car handles "properly" for a kart. Inside rear wheel lift at initial turn in, resulting in a center of gravity change that basically places more weight on the other three tires allowing for sharper turn in.[/QUOTE]
now, if you had a spool for a rear diff like a kart does, then you'd be on to something. karts have to lift the inside rear tire to turn since they have a common axle that drives both of the rear tires at the same time. if you ever watch kart races though, you'll see the fast guys are just barely lifting their inside rear tires. why? raise the cg, increase load transfer, reduce grip, go slower.
my DL1 shows only very minimal decrease in braking and acceleration on my civic going from -2.7 to -4.0 degrees static. we're talking .01 reduction in both, easily offset by the .02 increase in lateral grip. this was a very ghetto test i did too since all i did was drop the car. i was running on the bumpstops with maybe all of 1/4" of bump travel from compressing the bumpstop available before the uca and tire hit the strut tower.
| Mykl | 12-21-2006 02:06 PM |
[QUOTE=solo-x;16403540]now, if you had a spool for a rear diff like a kart does, then you'd be on to something. karts have to lift the inside rear tire to turn since they have a common axle that drives both of the rear tires at the same time. if you ever watch kart races though, you'll see the fast guys are just barely lifting their inside rear tires. why? raise the cg, increase load transfer, reduce grip, go slower.
[/QUOTE]
Would the 2-way limited slip differential out back have a similar, if somewhat lessened effect?
Obviously the effect is going to be greater if you tie the two wheels together by taking the differential out of the equation (weld the diff or whatever). But since the rear diff in the STi is a 2-way, even if it only locks up to 40%, getting the inside rear off the ground at turn in should enhance the transitional properties of the car just a bit.
Just a thought, I don't know how big of a difference it actually makes.
[/QUOTE]
Would the 2-way limited slip differential out back have a similar, if somewhat lessened effect?
Obviously the effect is going to be greater if you tie the two wheels together by taking the differential out of the equation (weld the diff or whatever). But since the rear diff in the STi is a 2-way, even if it only locks up to 40%, getting the inside rear off the ground at turn in should enhance the transitional properties of the car just a bit.
Just a thought, I don't know how big of a difference it actually makes.
| afpdl | 12-21-2006 02:12 PM |
There is no need to lift a rear wheel on turn in unless you have a welded diff/solid axle.
| Mykl | 12-21-2006 02:21 PM |
I am not implying that there is a *need* to with our cars. What I am saying is that with a 2-way limited slip there should be a difference in how the car behaves at turn in when you have the inside rear tire weighted on the ground and when you have it in the air.
When I made the comment about the kart initially I wasn't really trying to make a statement or a real comparison. I didn't actually understand why you would want a kart to behave that way. Now I do. :)
When I made the comment about the kart initially I wasn't really trying to make a statement or a real comparison. I didn't actually understand why you would want a kart to behave that way. Now I do. :)
| silver arrow | 12-21-2006 02:35 PM |
[QUOTE=afpdl;16404591]There is no need to lift a rear wheel on turn in unless you have a welded diff/solid axle.[/QUOTE]
I do get some wheel lift due to the lack of droop in the Teins Flexs I run. They were all I could afford and do a decent job, concidering the Nationals winning car was running OTS Flex's with 12k/12k setup. I would prefer a set of zzyxx's but can't afford it. We make compromises when on a budget. I run the Azenis because they are cheaper, not better than the Yoko's. I did suspension and exhaust, because I thought they were the best bang for my buck. Will get tuned this year and P&P exhaust manifold and replace stock pads when they wear out. Blanket statements like yours don't add much to the thread.
I do get some wheel lift due to the lack of droop in the Teins Flexs I run. They were all I could afford and do a decent job, concidering the Nationals winning car was running OTS Flex's with 12k/12k setup. I would prefer a set of zzyxx's but can't afford it. We make compromises when on a budget. I run the Azenis because they are cheaper, not better than the Yoko's. I did suspension and exhaust, because I thought they were the best bang for my buck. Will get tuned this year and P&P exhaust manifold and replace stock pads when they wear out. Blanket statements like yours don't add much to the thread.
| afpdl | 12-21-2006 02:45 PM |
It wasn't a blanket statement, I misread his question. I didn't say if your car lifts a wheel it sucks or you cant win with it, hell i didn't even say it wasn't optimal to have a wheel up, just that cars don't have the "need" for it that karts do. My coilovers cost $900 and are assembled out of 2 different brands, I know all about compromises.
| silver arrow | 12-21-2006 03:55 PM |
[QUOTE=afpdl;16405216]It wasn't a blanket statement, I misread his question. I didn't say if your car lifts a wheel it sucks or you cant win with it, hell i didn't even say it wasn't optimal to have a wheel up, just that cars don't have the "need" for it that karts do. My coilovers cost $900 and are assembled out of 2 different brands, I know all about compromises.[/QUOTE]
That's cool, I guess I just read your comment wrong. I'm working on making my Teins a Tein/Koni Frankentien. Let you know how that turns out.
That's cool, I guess I just read your comment wrong. I'm working on making my Teins a Tein/Koni Frankentien. Let you know how that turns out.
| solo-x | 12-22-2006 11:27 AM |
a 2-way diff could have a similar affect, but it really comes down to how the diff is setup. lots of preload and really aggressive ramp angles will increase the tendancy for push on entry. the stock diff is probably not aggressive enough to really matter. a much bigger issue with a sedan like the STi is that of excessive roll and raising the cg. that's why you try to limit how much you lift the inside rear. you'll likely never get the car to keep all four on the ground during combined braking and turning. chang's civic is running stiffer wheel rates then you guys have in your subaru's and with stock swaybars still lifts the inside rear during combined dive and roll in the WET. though at this point i think the majority of the roll and dive is coming from tire deflection.... damn street tires!
| Mykl | 12-22-2006 08:35 PM |
I guess the easy way to see how much preload (if any) is placed on the disks would be to get both rear wheels off the ground, spin one wheel, and see if the other spins with it.
I had a Sentra Spec-V that was also fond of hiking the inside rear. Even on excessively ungrippy Kumho 711's.
I had a Sentra Spec-V that was also fond of hiking the inside rear. Even on excessively ungrippy Kumho 711's.
| AUTOwrXER | 12-22-2006 09:32 PM |
The situation you describe (turn-in, weight just starting to unload from the inside rear) would be corrected by reducing rear rebound. What are your shock settings?
I agree with Steve that you also need more front spring rate, and quite a bit more when you move to race tires. However, if you are just looking to keep the rear tire on the ground DURING CORNER ENTRY, reduce rear rebound.
I agree with Steve that you also need more front spring rate, and quite a bit more when you move to race tires. However, if you are just looking to keep the rear tire on the ground DURING CORNER ENTRY, reduce rear rebound.
| Mykl | 12-22-2006 11:15 PM |
Absolutely... and I'm probably running too much rebound in the back anyway. I believe I have it set at either 1 1/4 turn, or 1 1/2 turn from soft. I'm sure the swaybar isn't helping either.
But I'm not terribly worried about keeping the inside rear on the ground during turn in. It doesn't slow me down, so it's not really a problem.
Concerning my setup... my goal has been, and will continue to be, to have a neutral handling car. Right now that's exactly what I've got. If I increase the rates up front, I have to increase the rates in the back. At the point that an increase in rates becomes necessary, first I'm going to increase the front rates via a stiffer bar, and probably increase the rear via stiffer springs.
But I'm not terribly worried about keeping the inside rear on the ground during turn in. It doesn't slow me down, so it's not really a problem.
Concerning my setup... my goal has been, and will continue to be, to have a neutral handling car. Right now that's exactly what I've got. If I increase the rates up front, I have to increase the rates in the back. At the point that an increase in rates becomes necessary, first I'm going to increase the front rates via a stiffer bar, and probably increase the rear via stiffer springs.
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