niteriderc5

Hello everyone, I'm trying to figure out how i can eliminate more body roll without sacrificing overall grip, ride quality is not an issue for me i could care less as long as it feels planted.

I know it will be a combination of different things and more importantly alignment, just not sure where to start.

Also what is everyone's opinion on PFADT's C6 poly control arm bushings? I know it will increase steering feel and response but will it help with the roll?

Here is my current chassis setup.

Base 1LT non Z51

Goodyear F1 GS RF street tires all around

Factory Caster settings

-1.7 front camber 0 toe

-1.0 rear camber 0 toe

Front C6 Z06 spring and base rear spring <- which uses a higher rate than z51.

08 C6 Z06 shocks all around

Front and rear Z06 sway bars

thanks in advance

2000BSME

I'm thinking the cheapest, easiest, least labor intensive thing you could do is put some stiffer sway bars on. Like maybe T1's.

C6400hp

niteriderc5

Will putting T1s induce understeer on street tires and mild alignment?

John Shiels

poly on roll bar will make a slight difference. Stiffer springs.

0JoshS

Sway bar bushings will not increase your roll resistance. Roll resistance is driven by suspension geometry, springs, sway bars and the center of gravity of the car.

Agreeing with the previous comments, sway bars will make a great improvement to the handling of the car with out sacrificing ride quality. Also, with your current setup it will be important to buy sway bars that are adjustable. This is because you are running a different combination of springs that bars such as the T1's were not designed for. So it is quite possible that non adjustable sway bars will induce abnormal understeer/oversteer.

All of the Pfadt sway bars offer a multitude of adjustment settings. Allowing you to adjust the balance of the car to your particular driving style and setup.

Please don't hesitate to call us with any questions about your particular setup.

Have a great weekend!

niteriderc5

Appreciate the responses guys

And thank you Josh, you guys at pfadt, including Aaron are always helpful .

I will be ordering your control arm poly bushings before the end of this month. The chassis/steering communication and response Im assuming is positively drastic with the poly bushings? also make sure to send me a couple of 'PFADT Race Engineering' stickers...i have have a small scratch on the lower rocker panel that would hide it and go well as far as looks are concerned

As far as the adjustable sway bars go, Im sure they work great, but i want to avoid fiddling with the suspension, i want to get to the point where Im always happy with it whether I'm on the track or street, so far, overall im happy with the way the car feels minus a few small things stated above and in the original post.

i forgot to mention that I have lowered car maxing out the bolts front and rear without cutting any bushings . I know there needs to be a rake but I cant stand the drag racer looks If i go with longer bolts in the rear how far can i go down without messing up the dynamics of the vehicle?

gkmccready

I was running 0 toe front and rear for a while... you really NEED to try running some rear toe-in 1/16th or 1/8th inch will make the car seem unbelivably planted compared to running 0 toe. You'll be shocked at how that simple change totally transforms the car...

With 0 toe and Z06 rear bar isn't the car super tail happy? Especially at corner exit when you roll on the power? What tires do you have?

2000BSME

David Farmer swears by toe OUT on the front. 1/16th is a suggestion. I'm going to try that next season.

gkmccready

Yup. Farmer, Hoffman, Popp all like toe-out up front. Randy@DRM likes toe-in. I'll experiment with front toe now that I'm happy with 1/16-1/8th toe-in in the rear. :-)

The rear toes OUT under acceleration and toe-out in the rear is unfun so you need enough static toe-in to control the dynamic toe-out. Or so I've been told. All I know for sure is running some toe-in in the rear rather than 0 toe makes the car a joy to drive...

niteriderc5

Your not the first one to tell me that!

I will be going back to my alignment guy soon, so i will deff give him new specs

so far 0 toe and z06 bar can be very tail happy, most of the time its just my poor throttle application all that power on exit takes getting used to... maybe its not me though...maybe its the alignment, yeah thats it!

John Shiels

I still think poly bushins vs a wore stock or soft one will make the bars work better hence less roll how ever slight it may be,

0JoshS

I would say the oversteer is partly because of the setup you are running. Normally for people that want the low dollar or factory part option we suggest changing out the rear Z06 sway bar to the Z51 rear sway bar. The Z06 and Z51 front bar are the same. We feel that the rear bar on the Z06 is too stiff for the front bar, making the car excessively tail happy. However, since you are running a stiffer spring in the rear, this oversteer tendency will be increased. I would say change the springs to both Z51 or Z06 and then swap your rear sway to the Z51. This will be a much more balanced setup.

Also, I look forward to your order of control arm poly kit. Feel free to talk to us about your setup when you call.

gkmccready

This'll let the bars act earlier but won't change the overall effectiveness. Once the stock rubber bushings deflect/compress to their maximum they'll be just like having the poly bushing.

Unless the stock bushings continue deflecting so far that you could actually measure more lean outboard, but that seems unlikely to me since there just isn't enough material in the bushing to really allow the bar itself more travel?

But I am talking in theory (aka a guess)... the poly sway bar bushings should help make the bar take effect earlier (less deflection) but I'm not convinced about them increasing the overall roll stiffness.

Where're our mechanical engineering friends?

gkmccready

You'll be very surprised at the difference. In fact, I had put a base model rear bar on my C6 Z51 to try to get better balance. Now that I've found the magic of rear toe-in I'm thinking about going back up to the Z51 bar... at least I'm going to test it at some point.

I think it's the Van Steel catalog that listed different alignment specs for cars with and without poly control arm bushings, by the way. With the poly bushings they suggest running 0.25deg less camber on each corner, plus slightly vary the toe suggestions.

ghoffman

OK, Glen, one of your ME's here! The question(s) I have is/are are you speaking of corner entry, mid corner or coming out of the corner? They are totally different problems and solutions. In addition, is this an auto-x application, track days, street use?

gkmccready

Er, your questions make me question my thinking. :-)

At turn-in once the car takes a set don't you keep load on the swaybar the entire time? The only way [I can see] poly increasing overall roll stiffness in this situation is if the load on the rubber bushing isn't enough to completely compress it such that its spring rate doesn't go "infinite".

And once you get the car to take a set at turn-in isn't your goal to use maximum grip throughout mid-corner and corner-exit thus keeping maximum loading on the swaybar (and its bushing)?

Or are your questions targetted at overall roll resistance questions and not just the poly vs rubber bushings? In which case, I'm less confused, and I see a spring rate versus swaybar versus shock damping discussion coming since all three have the ability to control body roll.

So I guess a question to the original post is this: is it the amount of roll you don't like? or the rate at which the roll occurs?

ghoffman

I do try...
Exactly, and what is it about the roll you don't like? Is the total grip lacking or just is the feel is "wooly" (to quote David Yu!)? I really recommed Carroll Smith's "Engineer in a Pocket". It is a great little set of flip charts that are easy to read.
http://www.carrollsmith.com/books/pocketbook.html

niteriderc5

The roll isn't horrible...in fact its progressive...initially the turn in is tight 80% of the time exibiting a flat feel <- usually thats around tight short corners. My issue is with longer bends and that as i approuch and clip the apex using power to exit, the amount of lean that occurs is what i dislike. I'm sure better chassis/steering feel would help balance it out and i can overlook this issue all together ... I hope that makes sense

niteriderc5

Im looking forward to re-doing my alignment As far as measuring toe, is there a formula to transfer it into degrees?