Custom sway bars

[ayousef]

yes im bored, but no really been spoiled by cars like the GT3 RS which have no body roll at all even with much softer springs vs the ACR.

Viper specs sheet.jpg

Based on the image above, you can find out that all models have spring rates that are exactly 2.5 times stiffer in the rear, except for the ACR.

so:

- SRT Viper: 500/200 = 2.5

- GT/GTS: 550/220 = 2.5

- TA: 600/240 = 2.5

- ACR: 1300/600 = 2.16

Perhaps there is something magical about this ratio of front to rear spring rate split on this platform especially if one were to calculate the spring's natural oscillation frequency and how that effects the drivability and handling on track.

My question is if the ACR spring rates were exactly where they have to be or if this is the best compromise they managed to come up with due to the effects of front vs rear downforce. To get the same ratio the ACR would require 1500lbs springs in the rear or 520lbs springs in front.

Also if we were to compare the sway bar stiffness settings between the SRT/GT/GTS vs the TA we would come up with the following:

- SRT/GT/GTS: Front bar is %43 stiffer than rear.

- TA/ ACR: Front bar is %48 stiffer than rear.

This difference might be simply due to how sway bars are made in that sizes go up a minimum of one millimeter. Reducing the percentage above will have the benefit of increasing load transfer on the rear axle, which should help with some of the inherent weakness of the front end.

My solution for this is to buy a set of stock ACR/TA sway bars and send them over to a swaybar manufacturer (which im already working on). Measure both bars and duplicate them while increasing the front bar 1mm and the rear bar by 2mm. This would help neutralize the car's handling much more in addition to the added benefit of reducing body roll.

I did some preliminary number crunching and came back with good results. I just want to confirm the stock bar diameters before I post anything however. I am making those for myself but I spoke to the swaybar manufacturer and anyone who wants those will be able to order them directly. Will need a few weeks though.

What do you guys think?

[Racingswh]

I think body roll on the ACR-E is minimal and find the car quite neutral already when corner balanced properly and damper settings optimized.

The GT3 RS is a fun, lively car but certainly not as quick as the ACR-E. I found it to be less poised than the ACR-E and the one I drove hung the tail off every corner. Super fun nonetheless.

[ayousef]

I think body roll on the ACR-E is minimal and find the car quite neutral already when corner balanced properly and damper settings optimized.

The GT3 RS is a fun, lively car but certainly not as quick as the ACR-E. I found it to be less poised than the ACR-E and the one I drove hung the tail off every corner. Super fun nonetheless.

Well the ACR has very high limits that once you reach the limits it does start to roll, and by that I mean approaching 1.5 G's. Other cars have much lower performance ceiling and so the car starts to slide before it could sway. The difference those bars would make is small yet noticeable but the biggest change would be how they would throw more of the load transfer bias towards the rear axle.

I am curretly using some shock damping to control fast cornering transitions, id like to dial down the damper a tad by relying more on the sways. My calculations included taking into consideration the ACRs spring rates and sway bar rates and these are the figures I came up with. They would probably cost about $500 a piece, maybe slightly less so given a small investment its always easy to revert back to stock.

[ayousef]

I think body roll on the ACR-E is minimal and find the car quite neutral already when corner balanced properly and damper settings optimized.

The GT3 RS is a fun, lively car but certainly not as quick as the ACR-E. I found it to be less poised than the ACR-E and the one I drove hung the tail off every corner. Super fun nonetheless.

also, what wing setting do you use and what are your alignment settings? I want to be able to dive into the higher wing settings since my car is slightly modiffied and can push through the drag better than a stock car and given I dont reach very high speeds where the drag could hurt performance. Hope this makes sense

[Arizona Vipers]

Great post, but I knew it wouldn't get much action.
ACR's and regular Gen 5's could benefit greatly from adjustable, blade style bars. Especially if you do many different tracks frequently.
Any big name experienced race suspension shop could get these made for you, but will cost $5000+, maybe $10K all in with shock dyno time etc.

[ayousef]

Great post, but I knew it wouldn't get much action.
ACR's and regular Gen 5's could benefit greatly from adjustable, blade style bars. Especially if you do many different tracks frequently.
Any big name experienced race suspension shop could get these made for you, but will cost $5000+, maybe $10K all in with shock dyno time etc.

I already bought a set of stock ACR Sway bars and im sending them over to a swaybar manufacturer, we will put the bars on a test bench to measure them (independently from the information provided by Dodge), then work out how much stiffer we want the new bars to be. If im not mistaken the bars should cost about $500 each since its a very low production, so if you're interested let me know

This will be a small incremental change only, 1mm additional in front and 2mm additional in the rear. win-win

So yes im working on it as we speak.

[stradman]

I already bought a set of stock ACR Sway bars and im sending them over to a swaybar manufacturer, we will put the bars on a test bench to measure them (independently from the information provided by Dodge), then work out how much stiffer we want the new bars to be. If im not mistaken the bars should cost about $500 each since its a very low production, so if you're interested let me know

This will be a small incremental change only, 1mm additional in front and 2mm additional in the rear. win-win

So yes im working on it as we speak.

Great Ayousef! I'd be interested in a set if if works out beneficial.

[Bruce H.]

Any concern for loosening up the rear as you tighten up the front, and trading some corner exit speed for entry speed?

[Arizona Vipers]

Any concern for loosening up the rear as you tighten up the front, and trading some corner exit speed for entry speed?

This is why we need adjustable ones. I was just underneath a brand new 2018 Porsche Cup car and the set up was amazing. Cockpit adjustable, similar to these- https://rennlist.com/forums/porsche-...y-bar-set.html

[Bruce H.]

Those look pretty slick! Good luck to you and ayousef with this project. Be pretty interesting to see at NVE if done and bringing that car.

[ayousef]

Any concern for loosening up the rear as you tighten up the front, and trading some corner exit speed for entry speed?

Hi Bruce,

I dont think it will be that big of a difference to cause massive oversteer or anything like that. What this will require is an alignment change however. It seems that this should enable the use of more negative camber in the rear, or less in the front accompanied by higher downforce settings on the rear wing. I think the perfect trade off would be to have the vehicle oversteer in the very slow corners, and slightly understeer at higher speeds as the big aero kicks in (due to it being mostly concentrated in the rear).

I am also swapping the fronts to 18" Forgelines with R888R 315 front tires (wider and larger sidewall) and 19's in the rear. Might be less grippy than the Kumhos but should have more even wear and last longer.

This is an experiment based on my limited knowledge and I will share my findings, good or bad

[kriskyk]

What width wheel are you running the 315 R888Rs on?

[ayousef]

What width wheel are you running the 315 R888Rs on?

approved wheel widths for this tire are 10.5 to 11.5 inches wide. It has a 1 inch wider tread width vs the stock tires, and 0.5 inches taller diameter.

[Arizona Vipers]

approved wheel widths for this tire are 10.5 to 11.5 inches wide. It has a 1 inch wider tread width vs the stock tires, and 0.5 inches taller diameter.

If you are having the wheels built, go for 11.5" wide, that will make the actual contact patch of the 315 much wider than it would on a 10.5" wheel.

[kriskyk]

Is there any advantage of running 315 on 10.5 wide wheel vs the typical 295?

[Bruce H.]

Hi Bruce,

I dont think it will be that big of a difference to cause massive oversteer or anything like that. What this will require is an alignment change however. It seems that this should enable the use of more negative camber in the rear, or less in the front accompanied by higher downforce settings on the rear wing. I think the perfect trade off would be to have the vehicle oversteer in the very slow corners, and slightly understeer at higher speeds as the big aero kicks in (due to it being mostly concentrated in the rear).

I am also swapping the fronts to 18" Forgelines with R888R 315 front tires (wider and larger sidewall) and 19's in the rear. Might be less grippy than the Kumhos but should have more even wear and last longer.

This is an experiment based on my limited knowledge and I will share my findings, good or bad

With all those changes to wheels, tires, suspension, alignment and aero you're going to be busier than a mosquito at a nudist colony getting it all dialed in!

I started thinking about the range of possible effects from each individual change. Just looking at tires, swapping from the ACR's bespoke Kumho to Toyo R888R will be quite interesting at the limits. The Toyos have less grip than the Kimhos, and significantly less I'm thinking. Without any other changes that would mean lower cornering speeds, and reduced body roll. And you'll be replacing a front tire that was designed and constructed with the single purpose of maximizing grip on the front of an ACR with a Toyo that was designed for general use as a rear tire. Upsizing to the wider 315 will help offset that grip deficit between the tires but it would be interesting to see how various aspects of handling would change due to the differences in construction, compound, tread, sidewall stiffness, temperature range, ideal pressure and camber, ect.

Hopefully you'll have the opportunity to test each modification individually in order to evaluate their effects despite the overall plan to combine multiple changes to work together to improve performance. Will you be using a data acquisition system?

I know you've been considering changing the coilovers. I wonder if settling on a tire first and then testing a range of aero adjustments might help you decide whether to change the coilovers or not, and what changes to spring rate and damping would significantly address your handling and roll goals, and then look at adjustable sway bars just for fine tuning between tracks? I can see the sway bars as being an excellent tool for fine adjustment, and would hopefully have a broad enough range of adjustment to accommodate any other modification or adjustment. But I would think choice of bar thickness/stiffness would depend on testing of some other changes first, particularly where you end up with spring rates, assuming that's still being considered.

This is going to be exciting journey!

Bruce

[Fatboy 18]

How will this affect handling at the Wallmart or Autozone parking lot when at Cars and Coffee meets? those Speed ramps can be tricky

[ACR Steve]

No offense but the ACR is super neutral when set up right . We smoke RS's and Cup cars .(well not a GT2rs ) Get it aligned ,corner balanced and pay a real Pro Coach to work with on track . Much better investment

[Arizona Vipers]

No offense but the ACR is super neutral when set up right . We smoke RS's and Cup cars .(well not a GT2rs ) Get it aligned ,corner balanced and pay a real Pro Coach to work with on track . Much better investment

Yep, everyone on the planet can become a better/faster driver, we all know that. This post is about modifying ACR suspension/sway bars though. Why not just post on every mods post "go spend your money on pro coaching instead"? The ACR-E suspension is great for all around track use, but is still compromised. For example, 1300 lb springs in the rear have to be there for safety for cars that *might* hit 177 on wing setting #5. But for 99% of us that would never happen and a softer spring rate would make the car accelerate out of turns much better. Yousef obviously has an engineer's brain and loves tinkering with this stuff and I love hearing his ideas, especially knowing he puts them to use. I love posts like this and would never discourage them by saying the ACR is already perfect and to spend your money on pro coaching instead.
I was just down at INDE doing some suspension testing this weekend on my 9.0 liter and learned a LOT with a guy who runs 1.34's (same as Winklers ACR production car record) in a bone stock motor 408rwhp C6 with a suspension he put together (MSC, custom valved, springed, adjustable blade style bars, mild aero). This guy is usually 1 second faster than me in my well set up stock ACR and it's all due to the suspension.

[ayousef]

No offense but the ACR is super neutral when set up right . We smoke RS's and Cup cars .(well not a GT2rs ) Get it aligned ,corner balanced and pay a real Pro Coach to work with on track . Much better investment

Steve, the ACR might be amazing but its not perfect by any chance. The front end of the car is VERY weak, yes you can make it handle neutral for a few laps before the front tires give up (on low rear wing downforce setting), im not a big fan of this. I also believe that you can accept the weakness and drive around it. Im trying to fix this problem and I dont know if I will be successful but ive experimented with cars/suspensions before and thankfully those who were skeptical arent anymore

The goal would be to be able to use higher downforce settings on the rear wing, while having enough HP to push through the added drag and handling as neutrally as possible, without having to change front tires every 20minutes. In addition, the car should sway less. You also have to consider that all the mods are 100% reversible so im not messing the car while I experiment. For me, its fun and very rewarding when it works out, and I learn something new everyday!

To use the higher downforce settings, the car would need wider tires up front, reducing the load transfer on the front axle. As I stated this should be doable as well with the added control I have with the DSCSport module and Tractive Dampers since I can add more damper to the rear at higher speeds to control the understeer and/or start with softer damper in the rear in the slower corners to control oversteer.

The short answer is I like to tinker with stuff, plus the first sentence in the OP

[Arizona Vipers]

Steve, the ACR might be amazing but its not perfect by any chance. The front end of the car is VERY weak, yes you can make it handle neutral for a few laps before the front tires give up (on low rear wing downforce setting), im not a big fan of this. I also believe that you can accept the weakness and drive around it. Im trying to fix this problem and I dont know if I will be successful but ive experimented with cars/suspensions before and thankfully those who were skeptical arent anymore

The goal would be to be able to use higher downforce settings on the rear wing, while having enough HP to push through the added drag and handling as neutrally as possible, without having to change front tires every 20minutes. In addition, the car should sway less. You also have to consider that all the mods are 100% reversible so im not messing the car while I experiment. For me, its fun and very rewarding when it works out, and I learn something new everyday!

To use the higher downforce settings, the car would need wider tires up front, reducing the load transfer on the front axle. As I stated this should be doable as well with the added control I have with the DSCSport module and Tractive Dampers since I can add more damper to the rear at higher speeds to control the understeer and/or start with softer damper in the rear in the slower corners to control oversteer.

The short answer is I like to tinker with stuff, plus the first sentence in the OP

Unless you are running monster horsepower, I feel anything other than the #1 setting on the wing is just going to slow down 99% of drivers. Even the guy who ran the 7.01 at the 'Ring said he was on #1 and the car would have gone much faster with less wing. When I was at INDE this weekend fine tuning my suspension, the pro guy said right after one session "too much wing" and we changed it from #2 to #1 and he still thought there was too much. And that's with a 735rwhp car. LOL. I wonder if the non extreme wing would bolt up. That combined with the extreme splitter and diffuser would probably be a better balanced car and would have gone under 7 minutes at the Ring with that same driver for sure.

[Bruce H.]

To use the higher downforce settings, the car would need wider tires up front, reducing the load transfer on the front axle. As I stated this should be doable as well with the added control I have with the DSCSport module and Tractive Dampers since I can add more damper to the rear at higher speeds to control the understeer and/or start with softer damper in the rear in the slower corners to control oversteer.

My apologies...I forgot that you had the DSC/Tractives and was confusing you with someone else considering them. I just reviewed your thread about DSC.

The DSC controller has the ability to minimize dive under hard braking, and very effectively, it should be able to do the same thing with lean under hard cornering.
Have you spoken with Mike Levitas about that or dove into the software yourself?

Bruce

[ayousef]

Unless you are running monster horsepower, I feel anything other than the #1 setting on the wing is just going to slow down 99% of drivers. Even the guy who ran the 7.01 at the 'Ring said he was on #1 and the car would have gone much faster with less wing. When I was at INDE this weekend fine tuning my suspension, the pro guy said right after one session "too much wing" and we changed it from #2 to #1 and he still thought there was too much. And that's with a 735rwhp car. LOL. I wonder if the non extreme wing would bolt up. That combined with the extreme splitter and diffuser would probably be a better balanced car and would have gone under 7 minutes at the Ring with that same driver for sure.

Did the drivers say what they meant about too much wing? was it slowing them down in the straights or was the balance off (front to rear)? Im thinking of perhaps getting the shorter diffuser strakes from Doug Shelby since I drive with them on the street and they rub alot.

So yes it would be interesting to know what those guys meant about too much downforce, the Nurburgring runs were done on bone stock Vipers obviously and depending on whether your track has long straights would determine if you could use higher settings or not. I remember you saying in a post that you were using setting 2 or 3 on your Viper race car? Is that an ACR Extreme wing?

[ayousef]

My apologies...I forgot that you had the DSC/Tractives and was confusing you with someone else considering them. I just reviewed your thread about DSC.

The DSC controller has the ability to minimize dive under hard braking, and very effectively, it should be able to do the same thing with lean under hard cornering.
Have you spoken with Mike Levitas about that or dove into the software yourself?

Bruce

I did speak to the guys at DSCSport but not Mike. I think I know the software inside out and ive done a few different things than what they have done. I reduce damper on the tire that has the least traction, and stiffen the sides that have the most load transfer. I also considered how lateral weight transfer would be larger than longitudinal weight transfer due to the difference between trackwidth and wheelbase (longer = less weight transfer). I found that the canned tune was very stiff at full tilt to the point where the car would skip over the road surface, and too soft when driving in a straight line with minimal G forces. My brain didnt register the huge shift in stiffness and I had a very time predicting the car's behavior due to this.

You can control dive/squat and roll using the dampers but only for sudden transitions, like a quick left to right transition or acceleration to sudden braking. However the vehicle will eventually give in. The only way to control sustained lateral acceleration is with springs or anti-sway bars. Only way to control dive under hard braking from say 140mph down to 50mph would be with springs and the vehicles anti-dive and anti-squat geometry.

[ayousef]

So, the custom bars are ready and have been shipped.

Front bar came in 27% stiffer than stock and rear bar is %31 stiffer than stock. I will start by installing the rear bars since my car understeers some despite the correct alignment and rake. I will report back my findings.