2001 V6 Convertible: Drives like a boat

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

Interesting. Most people don't find a huge difference. On my convert, sfcs and shocks made substantially more difference.

This was the first modification. It made me realize just how much flex was there. I am certain that if I had just installed sfcs the difference would be much more dramatic than the stb. I say the difference was huge because I had no idea that chasis flex was THAT much of an issue.

This is an A4 convertible so it will not be used for autocross. However, I NEED the car to be able to handle great so I might as well set it up for autocross :) .

I've got my eye on Sumitomo's HTR Z
.

$74/tire 255/50WR16 from tirerack.com

[ArticRider]

Re: 2001 V6 Convertible: Drives like a boat

When I added a STB to my vert, I only noticed the front end becoming a little bit stiffer and firm on turning. It was slightly noticeable changing lanes on the highway.

For SFC's, I've read that Don Goetz makes some excellent ones. Check out the chirpthird f-body convertible forums. They don't have their older posts from the old board, but there are some posts here where you can find his contact information:

http://www.chirpthird.com/vb/showthread.php?t=970
http://www.chirpthird.com/vb/showthread.php?t=2232

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

update...

F-Body Chassis & Suspension Guide

this link is dead now. i have this guide mirrored until someone can get something more permanent going... http://www.clinteatswood.com/fbodysuspension

the car no longer handles like a boat. it is very flat (feeling) on turns/curves/lane-changes after the following modifications:
shock tower brace
275/40/17 falken tires on 17x9 rims (as opposed to all flexing, all season 235/55/16)
35mm eibach front sway bar with poly bushings (really jacks up the spring rate on the outside wheel while cornering)
the front sway bar is perfect. it allows for the right amount of weight transfer while keeping the wheels flat on the road.

the eibach kit came with a rear sway bar too, but it is a 25mm bar and it would be suicide to put that thing in with stock springs as we are about to get a lot of rain. i plan on getting the eibach pro kit springs within a month or two - the rear spring rate is relatively soft and should compliment the large rear sway bar.
i am still undecided on the shocks. i was thinking bilstein HDs but i hear they are not so great these days unless you get the revalved ones from sam straino. any suggestions on a good shock to go with the eibach springs? i'm considering KYB AGX shocks ("adjustable").

i did not get sub frame connectors yet because i have not found a decent weld shop. i have an idea where i might get the shocks/springs installed, so maybe i'll see how they do with those and then inquire about their welding experience.

[V6Bob]

Re: 2001 V6 Convertible: Drives like a boat

update...


this link is dead now. i have this guide mirrored until someone can get something more permanent going... http://www.clinteatswood.com/fbodysuspension

the car no longer handles like a boat. it is very flat (feeling) on turns/curves/lane-changes after the following modifications:
shock tower brace
275/40/17 falken tires on 17x9 rims (as opposed to all flexing, all season 235/55/16)
35mm eibach front sway bar with poly bushings (really jacks up the spring rate on the outside wheel while cornering)
the front sway bar is perfect. it allows for the right amount of weight transfer while keeping the wheels flat on the road.

the eibach kit came with a rear sway bar too, but it is a 25mm bar and it would be suicide to put that thing in with stock springs as we are about to get a lot of rain. i plan on getting the eibach pro kit springs within a month or two - the rear spring rate is relatively soft and should compliment the large rear sway bar.
i am still undecided on the shocks. i was thinking bilstein HDs but i hear they are not so great these days unless you get the revalved ones from sam straino. any suggestions on a good shock to go with the eibach springs? i'm considering KYB AGX shocks ("adjustable").

i did not get sub frame connectors yet because i have not found a decent weld shop. i have an idea where i might get the shocks/springs installed, so maybe i'll see how they do with those and then inquire about their welding experience.

Strong advice. The 25 rear is too stiff for anything except a roadrace car with 700 front springs. Maybe even too stiff for that. The rear bar doesn't stiffen anything much. It's a tuning device. Too big is worse than too small.

I got my sfcs welded at a shop that does mostly performance exhaust work. Right expertise, right tools and lifts. I did inquire as to whether they had anyone with sfc experience and found the right guy.

Bilstein HDs are pretty good regardless, IMHO guys are making too much about revalving. It's useful but not revolutionary. I'd simply ask your spring manufacturer what they recommend.

[DAS BOOT]

Re: 2001 V6 Convertible: Drives like a boat

'd look into upgrading to 17X9s and going with 275/40/17s


Also a tip, if you are having issues before you buy stuff, go out and check all your sway bar endlinks. Its not too uncommon for a stocker to break, and really makes the handling ****ting on the f-body.

[Niko97RS]

Re: 2001 V6 Convertible: Drives like a boat

strut tower brace, sways bars but def SFC

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

'd look into upgrading to 17X9s and going with 275/40/17s

funny you suggest that, because i am running 17x9's with 275/40/17s right now

Strong advice. The 25 rear is too stiff for anything except a roadrace car with 700 front springs. Maybe even too stiff for that. The rear bar doesn't stiffen anything much. It's a tuning device. Too big is worse than too small.

I got my sfcs welded at a shop that does mostly performance exhaust work. Right expertise, right tools and lifts. I did inquire as to whether they had anyone with sfc experience and found the right guy.

Bilstein HDs are pretty good regardless, IMHO guys are making too much about revalving. It's useful but not revolutionary. I'd simply ask your spring manufacturer what they recommend.

the eibach pro-kit has 600lb front springs, so i'm betting that will balance out the rear bar to a degree, but i won't put in the 25mm rear bar unless i feel it absolutely needs it after springs/shocks are put in. i'll be crawling under the car this weekend to retighten the bolts on the front bar and put in the poly endlink bushings on the stock rear - i think that will be sufficient.

i'm feeling a little twist towards the rear when taking some sharper corners at higher speeds. that could be body roll, body flex, or a little bit of both. at this point, i think i'll get sfcs welded in before i put the 25mm bar in.

THANKS FOR THE ADVICE!!! :tup:

[V6Bob]

Re: 2001 V6 Convertible: Drives like a boat

the eibach pro-kit has 600lb front springs, so i'm betting that will balance out the rear bar to a degree, but i won't put in the 25mm rear bar unless i feel it absolutely needs it after springs/shocks are put in. i'll be crawling under the car this weekend to retighten the bolts on the front bar and put in the poly endlink bushings on the stock rear - i think that will be sufficient.

i'm feeling a little twist towards the rear when taking some sharper corners at higher speeds. that could be body roll, body flex, or a little bit of both. at this point, i think i'll get sfcs welded in before i put the 25mm bar in.

THANKS FOR THE ADVICE!!! :tup:

The stock rear bar (15) will be small with those other changes. The 25 is almost 8 times stiffer, too big a jump. You're not increasing front roll stiffness anywhere near that, and because of the suspension design, increases in rear roll stiffness affect the balance more. (Sway bars are very complicated) Something in between would be best. Unfortunately I can't say more than that.

You might want to talk to Sam Strano about shocks, and get his advice on bars also.

Note though the rear bar has very little effect on overall body roll. The front springs and bar do 80+% of it, the rear springs maybe 10%. The rear bar, maybe 5%.

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

yeah, the sway bar stiffness increase is not proportionate at all:
the front bar goes from 28mm to 35mm for a 25% increase
the rear bar goes from 15mm to 25mm for a 67% increase

this takes the stock front/rear sway bar ratio from 1.87 to 1.4 ... that is pretty dramatic.

consider eibach's pro-kit spring setup...
stock front goes from 257lb to 377-600lb for a 46-133% increase
stock rear goes from 114lb to 80lb-137lb for a -29% - 20% increase
essentially taking the stock setup which had the front springs 225% stiffer than the rear to a setup that has the front srpings 470-440% stiffer than the rear.

i went to put in the endlinks and poly bushings then decided to take the bar off to show the size difference between the stock rear and the eibach rear...




i threw the eibach rear bar in and took a drive through some residential streets at around 25-35mph. i did not notice much more than a slight decrease in rear roll (i'd say about 5% as you suggested) and a hint of oversteer. it's going to rain here soon, so i'll have to wait to reinstall the stock paper clip - i mean sway bar. the front bar is perfect, but at the moment, i am thinking the individual who designed the rear sway bar to be this stiff wasn't the brightest. you don't want to meet your limit of adhesion with this setup.

any ideas on what sort of driving will bring out the flaws in the 35/25 sway bar setup (on stock shocks/springs)?

[V6Bob]

Re: 2001 V6 Convertible: Drives like a boat

yeah, the sway bar stiffness increase is not proportionate at all:
the front bar goes from 28mm to 35mm for a 25% increase
the rear bar goes from 15mm to 25mm for a 67% increase

this takes the stock front/rear sway bar ratio from 1.87 to 1.4 ... that is pretty dramatic.

You're underestimating the degree to which this is disproportionate by using different units to compare things; mm (bars) and lbs/inch (springs). It's a common mistake.

The stiffness of the bar in lbs/inch goes up as the fourth power of the diameter. So the increase _in stiffness_ on the front bar is 1.25**4 = 250%. On the rear it's 1.67**4 or 800%. We're well past dramatic. And, because of suspension geometry (a-arms versus live axle) a balanced increase would increase the rear bar stiffness _less_ than the front.

The driving that will bring this out is wet weather (you really want to change back _before_ you drive in rain) or an emergency swerve to avoid something. But doing a test is dangerous, you could easily totally lose control.

As you said, whoever thought the 25 bar was a good idea wasn't thinking well. I honestly think your current setup is dangerous.

[Fireball27]

Re: 2001 V6 Convertible: Drives like a boat

hey jack, i've got a question for you: What's the silver car whose hood your using as a table?

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

You're underestimating the degree to which this is disproportionate by using different units to compare things; mm (bars) and lbs/inch (springs). It's a common mistake.

The stiffness of the bar in lbs/inch goes up as the fourth power of the diameter. So the increase _in stiffness_ on the front bar is 1.25**4 = 250%. On the rear it's 1.67**4 or 800%. We're well past dramatic. And, because of suspension geometry (a-arms versus live axle) a balanced increase would increase the rear bar stiffness _less_ than the front.

The driving that will bring this out is wet weather (you really want to change back _before_ you drive in rain) or an emergency swerve to avoid something. But doing a test is dangerous, you could easily totally lose control.

As you said, whoever thought the 25 bar was a good idea wasn't thinking well. I honestly think your current setup is dangerous.

i know my numbers don't translate into real world stiffness, but i wanted to try and get some kind of a feel for what eibach was doing to the stock setup.
i agree a softer bar is needed for that scenario when you attempt to correct the car's direction after swerving to avoid something - that could be suicidal.

i'm thinking about going for this 22mm addco bar
http://www.autopartswarehouse.com/pe...7&brandid=1813
or this 21mm SLP bar (probably addco too) for half the cost..
http://www.ws6project.com/user_stor/...a707f8eed6c4ea

but in the interim, i'm sticking to the stock paperclip with poly bushings

hey jack, i've got a question for you: What's the silver car whose hood your using as a table?

the silver car with the stock power bulge hood is my daily driver '98 saturn sl with the 1.9 sohc powerplant (80something fwhp). this mean silver 4-door beast rockets down the 1/4 mile in 17+ seconds. it holds all of my tools (rolling garage) and is much safer to drive in wet conditions than my camaro. i can swerve around in the rain all day in that thing.

[01PewterDropTop]

Re: 2001 V6 Convertible: Drives like a boat

Bilstein shocks, BMR Subframe connectors and sway bars will really tighten up the suspension. my BMR's are on the way so i will be posting my thoughts on them in a few weeks after the install.

[BobDoLe]

Re: 2001 V6 Convertible: Drives like a boat

i guess it is common for red camaro convertibles to drive like boats.