Neutral at the Limits - Changing the Front Sway Bar Only
06-27-2013, 02:02 PM
#1
Pro
Thread Starter
Neutral at the Limits - Changing the Front Sway Bar Only
I have been toying with the idea of swapping the front bar but can't seem to find anyone that has posted any feedback on it.
My experience on track with other cars that are a bit tail happy is to change the front bar for a much stiffer one. On an S2000 for instance, especially the early models, the front bar has a lower spring rate than the rear ( 393 lb/in Front and 427 lb/in rear). So to make the car more neutral I put in the lowest rate bar I can find for the rear and highest rate for the front (600 lb/in to 311 lb/in). This combination makes the car much more neutral.
Really there are a lot of similarities between the setups between the two as the S2000 also has a 50/50 weight distribution (Mine balanced out within 7lbs across all (4) tires) and also runs staggered tires. That being said I can't seem to find why the physics would be any different on a C5 or C6.
After reviewing the chart produced by PFADT (see below) it appears the OEM bars for all models have a higher rear rate than the front. So my thought was to throw on a front bar that is at least 75% firmer than my stock C6 Z06 bar in the front thus calming the car down. It appears that PFADT is doing just this with their kits. I am going to bet that the Johnny O'Connell setup which many commented "Is More Neutral" is almost purely a function of the larger sway bar spring rate ratio (F/R) and that the shocks play a very minor role, as compared to my stock 09 Z06 suspension.
Some back ground on the car. It is on street tires with increased camber and corner balance. The tires are all wearing right to the triangles at the sidewalls and tire temps have a small gradient across the tread. So I don't think an alignment is the answer. I know that coil overs, more specifically spring rates changes, would also help but this car is 100% stock and I don't want/need to make any big changes. I am not professional and have no problem admitting my laps times will be benefited by a "Driver Mod" more than anything at this point. However confidence in the car always seems to help quite a bit.
My experience on track with other cars that are a bit tail happy is to change the front bar for a much stiffer one. On an S2000 for instance, especially the early models, the front bar has a lower spring rate than the rear ( 393 lb/in Front and 427 lb/in rear). So to make the car more neutral I put in the lowest rate bar I can find for the rear and highest rate for the front (600 lb/in to 311 lb/in). This combination makes the car much more neutral.
Really there are a lot of similarities between the setups between the two as the S2000 also has a 50/50 weight distribution (Mine balanced out within 7lbs across all (4) tires) and also runs staggered tires. That being said I can't seem to find why the physics would be any different on a C5 or C6.
After reviewing the chart produced by PFADT (see below) it appears the OEM bars for all models have a higher rear rate than the front. So my thought was to throw on a front bar that is at least 75% firmer than my stock C6 Z06 bar in the front thus calming the car down. It appears that PFADT is doing just this with their kits. I am going to bet that the Johnny O'Connell setup which many commented "Is More Neutral" is almost purely a function of the larger sway bar spring rate ratio (F/R) and that the shocks play a very minor role, as compared to my stock 09 Z06 suspension.
Some back ground on the car. It is on street tires with increased camber and corner balance. The tires are all wearing right to the triangles at the sidewalls and tire temps have a small gradient across the tread. So I don't think an alignment is the answer. I know that coil overs, more specifically spring rates changes, would also help but this car is 100% stock and I don't want/need to make any big changes. I am not professional and have no problem admitting my laps times will be benefited by a "Driver Mod" more than anything at this point. However confidence in the car always seems to help quite a bit.
06-27-2013, 04:39 PM
#2
Drifting
yes it will help. My last 2 track cars (c5 z) had/have T1 front bar with stock z06 bar in back.
06-28-2013, 12:37 AM
#4
Safety Car
Maybe I'm just used to my car, but it hasn't really tried to kill me yet. It seems to give me warning signs (except for my one baja excursion) and I rarely feel on edge, but I am on NT05s. Does the pucker factor go up on DOT R's?
06-28-2013, 09:38 AM
#5
Melting Slicks
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The famous Pfadt sway bar graph isn't actual rate, it's relative. You can't compare the front bars to the rear on the graph. The actual rate of a front T1 bar is somewhere in the 900 lb/in range and the rear is somewhere around 400 lb/in. The Pfadt graph is useful in comparing front bars to fronts and rear bars to rears. Since you are running street tires increasing the stiffness of the stock front bar would just make the front end push sooner, (better balance - maybe, better overall grip negative) you're better off softening the rear bar to get the bite you are looking for. I've had C6Z customers really like the C5Z06 rear bar to help get them a little more bite in the rear. If you have access to one I would try installing one and see how you like it. (Rear bars are also easier to change than fronts.)
06-28-2013, 09:42 AM
#6
Burning Brakes
I don't think the relative rates are the same for front and rear on the Pfadt chart. All the options the front bar is stiffer than the rear. Look of the charts with the diameters of the bars posted elsewhere on the forum.
06-28-2013, 06:23 PM
#7
Pro
Thread Starter
The famous Pfadt sway bar graph isn't actual rate, it's relative. You can't compare the front bars to the rear on the graph. The actual rate of a front T1 bar is somewhere in the 900 lb/in range and the rear is somewhere around 400 lb/in. The Pfadt graph is useful in comparing front bars to fronts and rear bars to rears. Since you are running street tires increasing the stiffness of the stock front bar would just make the front end push sooner, (better balance - maybe, better overall grip negative) you're better off softening the rear bar to get the bite you are looking for. I've had C6Z customers really like the C5Z06 rear bar to help get them a little more bite in the rear. If you have access to one I would try installing one and see how you like it. (Rear bars are also easier to change than fronts.)
I actually am going to look at a C5Z tomorrow morning with a friend. If he buys it I might just have to put it up on my lift and borrow it ;-)
1.) OEM bars change on many cars through the years, model..... So unless you specify that brand XXXXX bar is XX% stiffer than a year and model then the data is useless.
2.) Bar diameter might be one indicator but it does not tell if the bar is hollow or solid, the type of material used for the bar and if the fulcrum/lever positions are the same (This is what is changed on adjustable bars)
I did talk with Eric @ PFadt and they agreed a front bar would make the car more neutral. They recommended the C6Z SS bar but my experience with setup's like this are that they tend to be a bit much for a street car. I still have and race the S2000, the Z06 is my street car and as such I don't want to make any drastic changes. That being said I ended up picking up a set of the Johnny O'Connell bars today and will report back.
06-28-2013, 09:34 PM
#8
Burning Brakes
The famous Pfadt sway bar graph isn't actual rate, it's relative. You can't compare the front bars to the rear on the graph. The actual rate of a front T1 bar is somewhere in the 900 lb/in range and the rear is somewhere around 400 lb/in. The Pfadt graph is useful in comparing front bars to fronts and rear bars to rears. Since you are running street tires increasing the stiffness of the stock front bar would just make the front end push sooner, (better balance - maybe, better overall grip negative) you're better off softening the rear bar to get the bite you are looking for. I've had C6Z customers really like the C5Z06 rear bar to help get them a little more bite in the rear. If you have access to one I would try installing one and see how you like it. (Rear bars are also easier to change than fronts.)
06-28-2013, 11:33 PM
#9
Safety Car
This is really a preference on how the car is setup not a problem with the setup, if that makes sense. I personally prefer that the car be more neutral or even push a just a tiny bit. For me it's just a comfort thing and the more comfortable I am the faster I believe I will be.
06-29-2013, 08:12 AM
#10
Drifting
Here is my personal setup for 100% neutral feeling in my car to me.
- PFADT racing sway bars, Light Rate, #2 hole up front, #1 hole in rear.
- Nitto Invo tires, 265/35/18 up front, 305/30/19 in rear
On the street or track I have 100% confidence in the balance of the car and traction.
I have barely squeeled my tires, if ever, through aggressive driving on the street, and only squeeled my tires a few times in the hardest of turns at Road Atlanta.
Yes, I am still a novice and not pushing 100%, pushing about 90%, but I am within my safety factor and have no worries about traction or balance.
Brakes are a much bigger issue.
- PFADT racing sway bars, Light Rate, #2 hole up front, #1 hole in rear.
- Nitto Invo tires, 265/35/18 up front, 305/30/19 in rear
On the street or track I have 100% confidence in the balance of the car and traction.
I have barely squeeled my tires, if ever, through aggressive driving on the street, and only squeeled my tires a few times in the hardest of turns at Road Atlanta.
Yes, I am still a novice and not pushing 100%, pushing about 90%, but I am within my safety factor and have no worries about traction or balance.
Brakes are a much bigger issue.