Sway bars, how to set them up?

[vlad01]

Thought I might start a thread about sway bars and question I have, and hopefully these important suspension components are better understood for me and others.

I am looking to upgrade mine on my to be daily white VP.

I had for years stashed a rear FE2 bar that is 20mm where the stock for these cars is 18mm

I was looking for a thicker front bar to upgrade as well, but options now are kind of limited, 27mm arm mounted, K-mac have a 27 and and 30mm stock mounting type (to the strut). Stock is 26mm, strut mounted.

So I started looking for FE2 front bars but came up negative handed if that's the right word for how useless search engines are now.

Anyway, later today I was organising stuff in the shed and have all my cars in there now, and I thought, well I have the VP S that is FE2, I measured the front bar as a sanity check to make sure I was looking at the right upgrades, but had to do a tripple take, 25mm! actually legitimately thought I measured wrong as I am sure the FE2 was 27mm for the front, nope, 25! So less than the stock models.

So I thought maybe the year, but my shitbox is older and it like the late VP and the VR have all 26mm ones.

But I know the rear on the S is 20mm, so it appears the FE2 spec is smaller than standard at the front and bigger than standard at the rear.

I was always told it was better to have a bigger bar up front.

Even suspension specialists say this. But once I came across an article in the states that said for better turn in and weight transfer on a front engine, rear wheel car it was better to stiffen the rear bar and loosen the front one, which in it's logical explanation made sense, but I dismissed it as it was an outlier compared to all other sources, that was a few years ago now.

But now I am thinking, maybe they were onto something and the manufactures with their millions in R&D know better than a shop selling parts.


I am interested to hear anyone's experience and if anyone worked for a car manufacture that knows a bit about the sway bar design choices.

Just for some extra data points, I have a VN wagon in my hands atm as I have been custom tuning it (modded engine) and I measured the front bar as 24mm, smaller yet again, I will check the rear tomorrow and report back, but I am guessing it will be smaller than VP as were 1st gen commodores, VN still had geometry of the first gen for the most part so it could be a similar thing with the bars.

[immortality]

It's all about balance of the car front to rear which effects oversteer/understeer.

Factory cars are generally set up with understeer as it''s safer for most drivers as all you need to do is reduce speed to regain car control. Oversteer is much harder to control if you are not used to it. Manufacturers are much happier when a car slides straight rather then swapping ends.

I do believe with the FE2/SS models the cars were aimed more at the "enthusiast" driver so a little more "oversteer" than your normal family sedan.

Edit:
I was actually discussing this not long ago with a guy at my local suspension place and he said something I hadn't really considered. Fitting much larger bars sure will help the car corner flat because it is much stiffer but conversely if you hit a big pot hole or other hazard the potential for damage is much greater.

[Holden202T]

i used to have a website that calculated what differences in diamater made, like 24mm to 26mm doesnt seem like a lot but its nearly 10% increase .... and then adding the rear to it changes it all as well.

i personally have found too stiff in the rear without the front to complement it, just lifts the inside rear wheel off the ground and i went from an 18mm to 15/16mm in the rear and it actually had better drive out of a hard corner!

this too obviously all depends on the weight balance of the car and un-sprung weight etc, theres certainly alot more to it than just jamming the biggest bar in you can find!

[immortality]

There is this chart from Whiteline

https://www.rtsauto.com/wp-content/uplo ... schart.pdf

Something I read a long time ago said the sway bars should be the last item you change, get all the other stuff (springs/shocks) sorted first and then use the bars to "tune" the suspension/handling.

On my old VN I didn't change the sway bars, I did change the sway bar links from the factory strut mounted type back to the early Commodore type that mounts directly to the control arm and I fitted a strut brace which helped stiffen the whole front chassis and improved turn-in without stiffening the suspension.

[Wade]

Don’t no all the in’s and out’s unfortunately. I do remember measuring bars back in the day and noticed differences just like your finding now. I fitted white line solid mount adjustable fr + rr sways bars on 1 of my old vl turbo’s and hated it. Up and down drive ways ect would have everything binding up. But I think having the adjustability was a good thing. One of my old rotaries had an adjustable rear sway bar and would hook up quite well off the line. But that’s about alls I can add.

[vlad01]

i used to have a website that calculated what differences in diamater made, like 24mm to 26mm doesnt seem like a lot but its nearly 10% increase .... and then adding the rear to it changes it all as well.

i personally have found too stiff in the rear without the front to complement it, just lifts the inside rear wheel off the ground and i went from an 18mm to 15/16mm in the rear and it actually had better drive out of a hard corner!

this too obviously all depends on the weight balance of the car and un-sprung weight etc, theres certainly alot more to it than just jamming the biggest bar in you can find!

It certainly is more complex than that. To complicate things more, the work of a sway bar is done at the surface of the material, the inner part does little. This is why hollow bars are a thing and I've even heard of hollow springs. They reduce the weight and inertia and change the harmonic dynamics when it comes to springs mainly. The stiffness is mostly a function of circumference, so it's not linear with diameter increase.

I always found with the commodore, that high speed turn in and handling is great, and not much is needed other than good poly bushes (nolathane don't count as good ), however the slow speed turn in up front on these cars is must to be desired, sharp corners at low speed when your steering angles sharpen up quickly makes these cars understeer, bad enough that they sometimes head off in a straight line, only to suddenly grip and turn in right at the last sec once the weight transfer at the rear finally catches up.

And this is what I speculate the factory might have been doing on the S and SS models, helping the front have a better turn in at slow speeds with aggressive manoeuvring.


Interestingly, on my red VP, I have an adjustable 31mm bar up from and fixed 22mm on the rear, and the shocks are Bilstein, springs were suppose to be stock replacements, but ended up being FE2 height at the rear and country pack raised height up front (thanks King!) So that needs fixing still, was put on the back burner years ago and still haven't had the money or motivation to do that.

But regarding the bars, I honestly didn't feel them being much stiffer than stock, the body rolls and handling apart from the sticky tyres feels similar to my usual stock + superpro combo. I think that much of the stiffness in the front bar was lost due to it being mounted to the control arms and not the struts, since having them on the arms increases leverage and decreases the effectiveness of the bars, making their rating the same as a smaller bar mounted to the strut. The increase leverage also increases the load on the sway bar link bushes, reducing their load transfer efficiency, giving them a more of a sluggish response.

I personally found that having stiffer link bushes and bar mounts on the stock front bar, dramatically improves the response in small steering movements and the response from alternating steering directions, like weaving through back streets etc... All that is lost when going to a control arm mounted setup, unless you can substitute it with ball jointed links. That said, I have a purpose made stock replacement link bars for the VN-VS from RoadSafe that are ball jointed, I have not fitted them, but I am keen to try them as the poly bush z link upgrades really heaps a lot.

[immortality]

Fairly much all my Commodores now have the ball joint upgraded link arms fitted + poly bushes on the sway bar mounts.

Discovered them when we still had our old VS, got sick of replacing bushes every year.

[vlad01]

These are the ones I have sitting aside.

Screenshot 2024-09-14 at 12-30-08 Sway Bar Link - Front Roadsafe.png (81.9 KiB) Viewed 6871 times

[vlad01]

This explains it really well, and looks like holden were on the money with the S and SS models, smaller front, bigger rear gives better front grip, lessens under steer and increases overseer. Exactly what I want. having overall less stiffness also reduces lateral vibration/harshness and juddering across the road, commodores do that I found. So rather than just stiffening the rear as the video suggests, softening the front should help in other aspects mentioned.

Now to find a factory front 25mm FE2 bar! should be a lot easier as urban myth is the front are bigger, so they are harder to find and much more $$, a thinner one should be cheaper.


https://www.youtube.com/watch?v=vNr7_9oN3CU&t=708s

[Wade]

A few people I know have re drilled and mounted the lower control arms out 20mm. Apparently helps with turn in. The older commodores you could get offset strut tops. But if you look at all the commodore through the years they slowly kept moving the strut top further back. By the time the vf come around I think holden pretty much nailed it in terms of suspension setup. ( well they did in the redlines anyway) on turn in the inside tyre rolls over and limits grip. That’s why the above helps so much. My go to has always just been good quality gas shock and Polly bushes for the caster and sway bars. From there you really need to look at getting better geometry and moving some components.