Comp coupe anti-roll bar Qs

[Grant]

I'm looking at the different parts available, trying to figure out the best way to prep my '08 ACR for the 2009 One Lap of America.

So, does anyone know...

1) The diameter of the VCC bars?
2) If they are hollow, and their weight?
3) How many adjustment settings are available? 3?
4) If they are insanely expensive?

Since I'm guessing the answer to #4 is "yes", I'll probably just end up getting adjustable links to take out any preload and stick with the stock bars. I think a 315 front tire (adding 1.5" to the front wheel, to a 18x11.5) will take out some of the push without needing to change spring rates or anti-roll bars, but it would still be nice to have some adjustability as well as lighter (hollow) bars.

 

[j-rho]

Grant, I did a bit of digging, but never picked up the phone to talk to Dodge Racing, who will probably be the only ones able to credibly answer your questions.

That aside - I believe there are two flavors of CC bars out there. One set are a stock-style, but stiffer than stock, set. Non-adjustable, and not expensive.

The other were blade-adjustable bars made by Roush. These are true blade-adjusted bars, most people aren't familiar with this style of bar, I can explain further if interested. I've been quoted $1800 for this bar from the Viper racer I bought my car from.

I ended up building my own front bar using a 37.5" Speedway center section and some spherical mounts that bolted up to the factory locations. I then bent a pair of the 30-degree steel Speedway arms in a press. This style bar construction allows for nearly infinite adjustment via arm length and replacement center sections. At the moment I am using the 1.25" bar stepped up to 1 3/8" in the middle. I had to grind down a bit of that "step" up to fit the standard 1.25" diameter chassis-side mounts. Some simple brackets and rod-ends complete the a-arm side mounting.

Overall my bar weighs (guessing) 5-6 pounds more than stock, should be similar to what the CC blade piece weighs. Hard to say without knowing wall thickness, the CC blade bars are probably all custom made.

FWIW, my car (otherwise stock '04) works pretty darn well with that bar and 315fr/345rr Hoosier A6s. I'm going to try 335's up front next, but this is for autocross where rotation is paramount, and besides alignment, the front bar is the only suspension mod the rules allow me to make. For a track car the 315/345 combo would probably be just right, though I would be ready with some additional front roll stiffness through a bigger bar, or slightly higher spring rates, if needed to maintain balance. The net result should have quite a bit more front grip, and a bit more front roll stiffness will help put power down.

Here's a pic of my bar, this one I actually bent the arm too far, had to re-do with less bend, but you get the idea.
[media]http://www.jrho.com/viperswaybar1.jpg[/media]


The only place I've seen pics of the CC blade bar on a car are on this guy's site:
e85viper.

As you can see below, the front one does not appear to mount in the standard location.

You must be registered for see images attach

 

[Grant]

j-rho,

Thanks a lot for the information. It sounds like I've got better things to put money and time into than anti-roll bars, given that the One Lap starts in 4 months.

I'm not sure how much oversteer will be added with 20mm more tire and 1.5" more wheel up front. Whatever the case, the nice thing about the ACR is the ability to add in a bit more understeer at high speeds, where oversteer is usually more difficult to deal with.

I think I'll give Dodge racing a call anyways.

 

[j-rho]

I think the car gets a lot better with more front tire, and you'll be quite happy with it. My suggestion to have a bit more front bar/spring standing by is in case you start to have diff issues out of low-speed corners. Increased front grip without an increase in front % of roll resistance means you'll be further unloading the inside rear. It'll be a lot less of an issue for you with an '08 ACR vs. my '04, as the '08 has the better diff and the ACR is lower so it transfers less weight overall. Plus One Lap tires aren't quite to Hoosier grip levels.

Have fun at One Lap! I did OTC (the west-coast version) in 2003, was a total blast!

 

[Jeff Monheim]

I totally didnt understand a thing you guys said, but loved it all anyways!
Good luck at One Lap of America!!

 

[Viper X]

Grant,

If this is a dup, sorry.

If you have a 08 ACR, you already have the base CC sway / roll bars. They are solid compared with hollow bars for the non-ACR.

I'd recommend you add adjustable CC end links, about $300 from Evernham. These will allow you to remove the pre-load and properly corner weight the car. I also added greaseable nylon / poly sway bar bushings, about $50 front / rear from just about any auto parts store. These will stiffen up the front and rear roll resistance a bit.

This should do it for most track driving.

If you are a serious racer, you may want to buy the adjustable CC sway bar pieces. Lots of dough and you really need to know what you're doing to adjust them.

I've been fine with the above.

Also, the ACR's tend to push quite a bit, so I'd recommend you increase the front spring rates, which are way too soft IMHO and go to a bigger front tire (Hoosier R/A 6 in 315's or VRL in 305's) work well. PS2's are available in 315 too.

Good luck,

Dan
09 ACR just arrived, setting up now.

 

[Grant]

Thanks for the info j-rho and Viper X.

I called Dodge Racing and was told the adjustable front bar was $1200 (ouch!), and came in at 1.25" (31.75 mm). I stupidly forgot to ask if it was hollow, but at that price I don't think it matters. The One Lap is totally open as far as mods go, so I think I'd be better off spending that amount of money on something else (such as a quaife, or weight reduction) anyways.

Viper X, I've used adjustable bars, links and harder bushings on other cars, but I admit I never thought to use harder bushings on one end to tune balance, thanks.

I'm currently planning on going with 315/30/18 and 345/30/19 Kumho XSs (as I must run street tires) on 18x11.5 and 19x13 wheels. If it ends up too tail happy with the 315 fronts (and I kind of doubt it will, given how much it understeers currently), I'll look to bushings and then bars as solutions.

 

[j-rho]

Grant, you can probably have the center be solid, or hollow with a wall thickness of your choice. You can check out the components to build one yourself here:
Genesis Technologies Cockpit Adjustable Race Car Sway Bar Kits
Race Car Cockpit Adjustable Swaybars and Components

Note, you probably meant to type 1.25", not 3.25". 1.25", which is a pretty standard swaybar diameter, is about 32mm. Also, one of the neat things about the cockpit-adjustable bars I linked to above, you have the ability from the driver's seat to produce large changes in understeer/oversteer balance by moving a lever. Might be nice at One Lap where you have limited (or no!) time at a given track to put the car in the air and make adjustments. Something like that might have saved the Viper team last year on the wet skidpad.

There really isn't much magic to the way these things work - stiffening the front bar will change the balance towards understeer, softening it will tend towards oversteer. The blade style bars work by making the arm a spring. Think of it like a plastic knife - when you press the cutting edge against something, it is very stiff; when you press it on its side, it flexes easily. With a blade ended bar, you can rotate the arms from inside the cockpit to soften/stiffen the bar using that same principle, any time you want.

Dan, stiffening the front springs will tend to make the car understeer, for the same reason increasing front swaybar stiffness does. In roll, the front tires take more of the load transfer, overloading the outside front tire more. There are some special cases where increasing front spring or bar will decrease understeer, but that generally only applies to cars with really bad suspension geometry on really sticky tires. A Viper on street tires meets neither of those conditions.

Have fun Grant, I'm jealous!

 

[Grant]

Whoops, typo fixed.

Grant, you can probably have the center be solid, or hollow with a wall thickness of your choice. You can check out the components to build one yourself here:
Genesis Technologies Cockpit Adjustable Race Car Sway Bar Kits
Race Car Cockpit Adjustable Swaybars and Components

I'd absolutely love an in-cockpit adjustable bar. All the cars I've had in the past didn't look like they could fit those sorts of bars without some serious work, and I hadn't thought the Viper was an exception. But I suppose the center section is perfectly straight, isn't it? Do you think the blade would clear over the tie rod? Once my ducting is in, there won't be any room under it... Forgive me is this is a stupid question; I haven't really wrenched on the ACR (or any Viper) yet.

There are some special cases where increasing front spring or bar will decrease understeer, but that generally only applies to cars with really bad suspension geometry on really sticky tires.

I think the most common cause of this is just bottoming out of the front damper travel. I've had this happen (in a Supra) from excessive rebound damping, among other things.

I am, by the way, not a complete n00b

 

[j-rho]

Sorry, didn't mean to imply you were - I attempted to address that paragraph to Dan (Viper X). I don't think stiffer front springs are a proper prescription to remedy understeer unless you already knew said understeer was the result of a bottoming condition. Even then, stiffer springs usually aren't the right remedy for that.

As for the blade bar, without having tried it, I don't think you could make it work well with the bar center in the stock location, would be better off mounting it below the steering arm as pictured above. Even with the bent Speedway arms, interference with the steering boot at full droop is a big problem on my car. This may be mitigated somewhat with the ACR's shortened shocks, not sure.

You might consider doing a cockpit-adjustable rear bar first, as it would be a lot easier to implement without all the steering and ducting complications.

 

[Viper X]

Sorry, didn't mean to imply you were - I attempted to address that paragraph to Dan (Viper X). I don't think stiffer front springs are a proper prescription to remedy understeer unless you already knew said understeer was the result of a bottoming condition. Even then, stiffer springs usually aren't the right remedy for that.

J-rho,

I recommended as below:

"Also, the ACR's tend to push quite a bit, so I'd recommend you increase the front spring rates, which are way too soft IMHO and go to a bigger front tire (Hoosier R/A 6 in 315's or VRL in 305's) work well. PS2's are available in 315 too."

After about 12,000 track miles on my 09 ACR and quite a bit of experimentation / development, I can tell you that the Gen IV ACR needs stiffer front springs and larger front tires to increase front grip and get closer to neutral on the track at speed. Tire wear and braking are also improved. I've found that with the OE front ACR springs, I could bottom the front of the car under heavy braking at some tracks if I set the car up at "smooth track" ride height.

In addition, I have now lowered the car a bunch and have added Moton triple adjustable shocks along with stiffer rear springs among other things.

As you know, when you change one thing in a suspension system, it will almost always lead you to change another.

Also, FYI, the Viper Cup ACR X cars come OE with significantly stiffer front springs and stiffer rear springs.

I've not spent much time as an Auto Crosser, so cannot comment much on that aspect of the car's set up, but your bar looks cool.....and the idea of being able to adjust it from inside the car would be a big benefit to most.

Good luck Grant,

Dan