Preloading Sway Bar

[DGRacing]

Gasp!! What??? Preloading a swaybar?? You're not supposed to do that!!!

Yes, that is usually what is recommended but hear me out (this is a pet theory I want some feedback on).

So maybe some of you notice this, but since I'm a big fella I notice it a lot. My car turns left much more balanced and planted than it does right.
Not that its bad turning right at all, but at the limit there is more tire slip in the front than i care for.

Now this is primarily a result of the driver weight on the left side of the car. Oddly enough I turned my best lap with a full tank of gas and was only 1 second shy of that with pufferfish in the passenger seat. So I do believe performance favors balance over weight up to a point.

But I want my cake and eat it too. So here is my theory.

If I pre-load the front sway bar, it simulates weight on a given side of the car, offsetting the driver side weight difference. I've never tried this or done it before, so two questions.

1) Which side do I pre-load and how? I _think_ I need to add length to the endlinks on the driver side. Not 100% sure
2) What are the anticipated effects on left turns if I pre-load to distribute weight towards the right? more or less understeer?

That is all. Appreciate any input.
Darren

EDIT: I suppose the best thing to do is corner balance the car with my weight in the driver seat and adjust the sway bar until the cross weight is 50%. lol. Well, your input is still appreciated!

 

[VoodooBoss]

I know nothing about this so...

I just had my Boss corner weighted by a race shop at Sonoma Raceway in conjunction with CorteX installing their Xtreme Grip kit. They used ballast in the drivers seat. They do this with the sway bars disconnected and then check it with them connected. I was told if the rear bar adds too much "weight" when connected that means it's bent and needs to be replaced. Fortunately mine was within tolerance and didn't add much. On the front they installed an adjustable sway bar end link so it doesn't add preload. While the corner weighting did improve it's still far from evenly balanced. While I wanted this done because I wanted it setup as best as possible I question if I'll be able to notice the difference.

In theory what you're suggesting makes sense to me but again I know nothing about this.

 

[DGRacing]

Couple good info tidbits there Rick! I'm actually gathering the necessary tools and DIY stuff to do full alignments and corner weighting/balancing in my garage[1] and will start a how to thread about that once I get it all working. Some tools are essential, others are pretty straightforward or can be replicated with stuff lying around the garage surprisingly.

Front/back balance (in my car at least) will never happen. However the more important balance measure is "cross weight" (diagonally). And that is relatively easy to achieve with corner balancing. I was looking for my x-balance diagram from Phoenix, but can't find it right now. It's somewhere between 49-51%. They were going to ballast my passenger side but I told them not to just yet. I think using the sway bar I can simulate torsional rigidity (weight). Maybe I'll just do a diary of this over time. It does remove a big hassle for me, at least, since getting my car to a shop for a $100 alignment is a big hassle.

[1] http://www.hotrod.com/how-to/chassis-suspension/hrdp-0411-wheel-alignment-guide/

 

[VoodooBoss]

Have you checked to see if your sway bars are currently neutral? Member YoPauly, who lives a couple of miles from me, added adjustable front sway bar end links and with him in his car I set his sway bar with no preload. Attached are my corner weights and alignment.

 

[DGRacing]

I haven't checked them since Pheonix setup the car last fall but when I put everything back together (no engine right now) I'll set it to no load and experiment with loading one end link. The side that creates weight on the passenger side.

I see your cross weight is 50.3% which is spot on!

 

[Flyboygsxr]

When you corner balanced your car did you do it with you in the car or with ballast?

 

[VoodooBoss]

When you corner balanced your car did you do it with you in the car or with ballast?

Ballast although they were about 10 lbs too light. :

 

[Grant 302]

Great topic, Darren!

Not 100% sure, but I think you have it right on the link to lengthen for what you're trying to do. I'm really interested in hearing wether it works in practice. I'm still running a panhard bar, so I'm not looking to be able to fix my left turn bias just yet.

 

[WinterSucks]

Since you are talking about sway bar pre-load: I was told by Sam Strano that the front sway bar OEM mounts grab the bar tight and adds some resistance to suspension movement. I have not had the chance to get on a track or even AutoX after switching to his adjustable front, so I don't know if I will get noticeably more nose movement or not. I did notice that it seemed to be a bit pre-loaded (evenly both sides) with the suspension loaded. I did notice on a hairpin right turn that I had much less push with even a light passenger on the OEM bar and staggered tires.

I realize most of you discussing this thread are probably not on the OEM bar, but I figured this was worth mentioning if you still have a stock suspension otherwise. I am wondering if anyone has noticed better articulation in the front with the OEM mounts replaced for something that does not impede movement.

 

[JScheier]

Since you are talking about sway bar pre-load: I was told by Sam Strano that the front sway bar OEM mounts grab the bar tight and adds some resistance to suspension movement. I have not had the chance to get on a track or even AutoX after switching to his adjustable front, so I don't know if I will get noticeably more nose movement or not.

This is true. You can remove some of that resistance by either a) removing some of the base material on the sway bar busing or b) adding washers under the sway bar bushing mounting bracket to space it away from the chassis. There is a significant amount of sticktion in those bushings... enough so that I queried Ford at the roundup and asked if the purposely added that to affect the spring rates (Boss / Mustang Roundup in Hastings).

 

[BigTaco]

The OP is actually correct in assuming that sway bar preload/unload(?) is important.The Boss 302S came with an adjustable front sway bar link to compensate for driver weight.

"Service replacement on the Boss 302S Mustang road race car! One adjustable link on your front swaybar is all you need to adjust pre-load on your race car and compensate for driver weight. The Boss 302S race cars come standard with one fixed sway bar link (driver’s side) and one of these adjustable sway bar links on the passenger side. Assembled with precision-machined aluminum couplers and high-quality MOOG joints, these adjustable sway bar links have been tried and tested with years of abuse on the race track. Sold individually."

This is right from Watson Racing's web site (original builders of the 302S). Pretty cheap as well ($149.00)

 

[DGRacing]

Oh cool. Yeah, the more I was thinking which way the bar should twist to add passenger weight I started thinking the passenger side link should be extended. Maybe I'll ping watson for more details. Don't want to throw off the whole setup.

 

[Grant 302]

Oh cool. Yeah, the more I was thinking which way the bar should twist to add passenger weight I started thinking the passenger side link should be extended. Maybe I'll ping watson for more details. Don't want to throw off the whole setup.

I think you're original post is still correct. I'm reading that as shorten the passenger side. Same difference.

 

[DGRacing]

I think you're original post is still correct. I'm reading that as shorten the passenger side. Same difference.

Oh. Yeah that's right. I have to fiddle with my fingers in the air to visualize it.

 

[Grant 302]

Oh. Yeah that's right. I have to fiddle with my fingers in the air to visualize it.

;D Yeah, last night I had to wonder if my wife thinks I'm crazy...or that I can't do 'itsy bitsy spider' correctly. :

 

[VoodooBoss]

If Phoenix is doing work on your car ask AJ as I'm sure he knows how to setup our cars properly.

 

[blacksheep-1]

IMHO preloading the sway bar is a bad idea, I know we all do it, but....it throws another variable into the suspension mix, I would balance the car w/o the bars attached, then attach them and re-weigh the car, this will tell you if the bar is bent once it is tightened. I would work on getting the bar parallel to the plane of the lower ball joint looking from the side of the car. The bar should not run up or down hill. Same with the tire rods. Once everything is in a happy place, you can adjust on one end of the bar while the car sits on the scales and watch the weight change. At that point you can try to raise or lower the car to simulate suspension movement and measure the change in weight across the arc and see if it is linear. For those of us without a "shaker" lift you can have someone sit on the corner of the car, add weight..whatever and measure the distance the suspension moves vs the weight change. Do it without the bar to create a baseline.
and yes, I would take AJ's recommendations to heart

 

[DGRacing]

IMHO preloading the sway bar is a bad idea, I know we all do it, but....it throws another variable into the suspension mix, I would balance the car w/o the bars attached, then attach them and re-weigh the car, this will tell you if the bar is bent once it is tightened. I would work on getting the bar parallel to the plane of the lower ball joint looking from the side of the car. The bar should not run up or down hill. Same with the tire rods. Once everything is in a happy place, you can adjust on one end of the bar while the car sits on the scales and watch the weight change. At that point you can try to raise or lower the car to simulate suspension movement and measure the change in weight across the arc and see if it is linear. For those of us without a "shaker" lift you can have someone sit on the corner of the car, add weight..whatever and measure the distance the suspension moves vs the weight change. Do it without the bar to create a baseline.
and yes, I would take AJ's recommendations to heart

I hear you. Joe and AJ already were going to put ballast on the right side of the car. Couple problems with that. 1) I'm not racing in a spec class so every extra pound is lost performance and 2) My race class is occupied by 700hp cars. I intend to compete with my n/a motor and if I put 200lbs of ballast in the right seat there goes my acceleration.

So this build is not the typical by-the-book build. I have to pull out all the tricks and tweaks I can to compete. As it already seems Watson recommends pre-loading on the 302s to avoid adding weight I think its worth exploring. But every race team has their own recipes. It might come down to ballast at some point.

I'll hit AJ up on FB and see what he's doing for his PWC car, since my car is using a lot from that spec.

 

[steveespo]

I would also consider replacing the stock frame bushings with greaseable aluminum pillow block mounts. There is a lot of bind and sticktion in the stock mountings that I am sure adds some unpredictable variation in spring rate. Adjustable end link is a band-aid for unwanted preload, but I imagine it serves the purpose well.

 

[BMRTech]

Like I told you previously, Darren, I am not a fan of using bar preload to compensate actual weight distribution through the chassis.

It can be done, and as mentioned, we all do or have done it.

The proper way to balance the car, is to add weight for spec in the right places, or if you are wanting to remain the same weight - move your weight around. There are many ways to skin a cat, but I prefer balancing the car with the weight, and not by the load/force in between the chassis and the suspension.

And not sure what was said above, as it confused me slightly, but lengthening the end link will apply more weight to that corner.