Factory rear sway bar upgrade options

CSVT6 · Jun 15, 2021

Power6 said:
Hey thanks for chiming in that is helpful! Maybe a running change... I'll update the first post. Could you possibly PM me your VIN, and if you did look under your car...could you look again and grab the part number off the sticker on the bar? I'll try to keep the info up to date with what we know.

PM sent

V60CCR40 · Jun 18, 2021

Looking to possibly upgrade on a 2020 V60CC. Just talked with parts guy at Volvo and said 2021V60CC sway bar has the same part # for each model year, but for some reason could not determine 19 or 22mm.

zerocover · Jun 20, 2021

Power6 said:
I did some reading about bonded sway bar bushings, this design can make the action of the bar more efficient, %20-50 stiffer than a traditional sliding bushing. Something to keep in mind with aftermarket upgrades that may not use this design.

Are you saying the KCDesign bar will no longer be bonded? As such it won't be an upgrade at all?

If anything it would eliminate the non-linear additional spring force in on the rear, that might be a good thing.

Power6 · Jun 20, 2021

zerocover said:
Are you saying the KCDesign bar will no longer be bonded? As such it won't be an upgrade at all?

If anything it would eliminate the non-linear additional spring force in on the rear, that might be a good thing.

It appears so yes. The instructions are to cut apart the OEM bracket and you reuse that to hold the new bushing. I'm not aware of any aftermarket bonded bushing sway bars so that seems typical, just maybe a bit cheap on their part that they didn't fab a replacement bracket so you could leave your stock bar intact. I'm sure this will still be an upgrade, the stiffness is in the bar mostly. Now we could get into if it's an "upgrade" does it actually improve performance to increase the roll stiffness, but I should digress ha, reduced body roll has a nice psychological effect and that is probably good enough!

It's hard to say what the effect is. Bonded bushings, fairly new to sway bars but traditionally on suspension arms, they have always added some amount of spring rate. But it's rarely quantified, we just know you lose some when you replace with sliding urethane. My guess is the spring rate is not much, probably never notice it. I tried to find some OEM quotes talking about the benefits of the bonded bushings, to get some insight. I found Ford mentioning this on the GT500 Mustang, claiming that the bonded bushing provide "quicker response" in the sway bar. Not really sure how that figures. As always we are second guessing engineers, I would suspect the use for Volvo is less chance of squeaks and noise since there is flex but no rubbing parts with the bonded bushing.

MDicnMan · Jun 23, 2021

It would appear that the 2021 V60CC must have gone to a 22mm after week 26.

Sent from my SM-G960U using Tapatalk

V60CCR40 · Jun 24, 2021

Interesting! Now, I want one on my 2020.

CSVT6 · Jun 24, 2021

MDicnMan said:
It would appear that the 2021 V60CC must have gone to a 22mm after week 26.

Sent from my SM-G960U using Tapatalk

Our V60 CC was built 3/21 and is equipped with a 22mm rear swaybar.

Power6 · Jun 29, 2021

I updated the first post to reflect the 22mm bar coming on the V60CC, perhaps it's a '20 vs '21 thing.

Voytech · Jun 30, 2021

Power6 said:
I updated the first post to reflect the 22mm bar coming on the V60CC, perhaps it's a '20 vs '21 thing.

Not sure if this is useful to anyone but I measured a hair less than 22mm on my '20 V60CC with a build date of 3/20.

Jack Watts · Jun 30, 2021

Part of me trading my Golf R for a V60 was a desire to take a break from such things as swapping out swaybars... I think the car handles just fine for my intended purposes as-is!

For those who are modding this stuff, though--two questions:

1) is the FWD and AWD bar the same? Seems this would be surprising from a packaging standpoint, but this seems to be the case

2) I hear lots of talk about the diameter--but what's the construction of these bars? I'm assuming they're hollow. If so, I'm wondering if folks know that actual wall thickness? It's not uncommon for manufacturers to use the same diameter but use thicker walled tubing--which would toss the stiffness estimates out the window...

Power6 · Jul 4, 2021

See how that happens you can take the car guy out of the VW but you can't stop him from wanting mods ha. I was totally definitely just going to drive my S60 and leave it alone lol. Honestly that did guide me fairly well though. I didn't accept a car that I thought I could "fix" later. I insisted on dealer finding me a sport chassis equipped car because I knew if I didn't I would be wanting that later and it would become a "project" ha, gotta know yourself. The fact is you could just drive anything, be it a Golf R, and just leave it alone, but funny how that is hard sometimes!

I welcome anyone else who is doing the research but I think I am it for now ;-) All I can do is compare part numbers in VIDA and of course anyone who can measure their bars as a data point. From what I have compared it does seem the T5 FWD bars are the same as the AWD cars. There does not seem to be much size variation even though there are many part numbers, but can't be sure at this point. The front bar is larger on the sport chassis at 26mm, shared with the PE model. I don't know the other front bar sizes just they are different.

The bars do not appear to be hollow at least not having the "crushed end" look. Not a guarantee though, don't know unless we slice one open. Hollow bars are used as they are lighter. The premise is the physics of how the outer radius contributes more spring stiffness than the inner radius. There is not actually much stiffness lost as you hollow out the bar. At any rate that would matter if we are trying to calculate the actual spring rate of the bar. When comparing two different bars, like 22mm vs 23mm, the comparative stiffness like "20%" is plenty close enough for our purposes of comparison.

GordonCs · Jul 5, 2021

So I checked with VIDA and there is a KC design 24mm solid rear sway bar. My Volvo has a 22mm hollow. According to Viva, the 24mm is approximately 81% stiffer than the OEM. They also are saying that since the rears are leaf springs, spring travel is unaffected and ride quality will not be impacted, i.e., the rear end will not be harsher when going over bumps. I sent this info to my service parts manager and asked for his opinion on this. I don't know...81% seems like a big jump.

Power6 · Jul 8, 2021

GordonCs said:
So I checked with VIDA and there is a KC design 24mm solid rear sway bar. My Volvo has a 22mm hollow. According to Viva, the 24mm is approximately 81% stiffer than the OEM. They also are saying that since the rears are leaf springs, spring travel is unaffected and ride quality will not be impacted, i.e., the rear end will not be harsher when going over bumps. I sent this info to my service parts manager and asked for his opinion on this. I don't know...81% seems like a big jump.

Was the "hollow" based on what Viva said? I just don't know that to be true, but they may know better. Maybe someone has cut the sway bar to see.

81% sounds more than expected. It's pretty simple to compare, if both bars were solid then this would apply https://www.whiteline.com.au/docs/bulletins/Update BL-281.pdf which is where the 42% comes from in the OP. We would have to know the wall thickness if the OEM is in fact hollow to truly compare. 81% seems high though.

We're comparing relative stiffness, i.e. "181% of unknown" so it doesn't tell us anything definitive. Actual rate of the bar depends on the shape, the attachment points and motion ratio. I have estimated the OEM 22mm at about 153lb-in of spring rate. It's not a stiff bar. The front (sport chassis/PE) 26mm bar, I have estimated at 360lb-in.

The explanation of why ride quality isn't affected doesn't hold any water. The leaf spring is completely independent of the sway bar. Sway bars do not affect spring travel. The ride quality effect will be the same situation as it is on any car. The sway bar is a torsion spring that links two sides of the independent suspension. It is only engaged when there is a difference in travel between right and left wheels. As we know that is when you are negotiating a corner. It reduces the body roll. You go over a speed bump, with both wheels on an axle, it does nothing. Single wheel bumps though, those engage the sway bar. And that does reduce the ride quality since the sway bar links the two sides. As suspension geeks like to say it "reduces independence". The results are subjective though, you may not notice or care, or the benefits of the sway bar outweigh the downsides. A sway bar is still a nice way to add roll stiffness without stiffening the main spring, which would take a bigger bite out of ride quality. Usually when I have swapped out sways it's for 150% stiffer or more. It takes quite a bit more stiffness to be noticeable, so even 81% sounds like a lot but not particularly so in my experience.

GordonCs · Jul 11, 2021

Power6 said:
Was the "hollow" based on what Viva said? I just don't know that to be true, but they may know better. Maybe someone has cut the sway bar to see.

81% sounds more than expected. It's pretty simple to compare, if both bars were solid then this would apply https://www.whiteline.com.au/docs/bulletins/Update BL-281.pdf which is where the 42% comes from in the OP. We would have to know the wall thickness if the OEM is in fact hollow to truly compare. 81% seems high though.

We're comparing relative stiffness, i.e. "181% of unknown" so it doesn't tell us anything definitive. Actual rate of the bar depends on the shape, the attachment points and motion ratio. I have estimated the OEM 22mm at about 153lb-in of spring rate. It's not a stiff bar. The front (sport chassis/PE) 26mm bar, I have estimated at 360lb-in.

The explanation of why ride quality isn't affected doesn't hold any water. The leaf spring is completely independent of the sway bar. Sway bars do not affect spring travel. The ride quality effect will be the same situation as it is on any car. The sway bar is a torsion spring that links two sides of the independent suspension. It is only engaged when there is a difference in travel between right and left wheels. As we know that is when you are negotiating a corner. It reduces the body roll. You go over a speed bump, with both wheels on an axle, it does nothing. Single wheel bumps though, those engage the sway bar. And that does reduce the ride quality since the sway bar links the two sides. As suspension geeks like to say it "reduces independence". The results are subjective though, you may not notice or care, or the benefits of the sway bar outweigh the downsides. A sway bar is still a nice way to add roll stiffness without stiffening the main spring, which would take a bigger bite out of ride quality. Usually when I have swapped out sways it's for 150% stiffer or more. It takes quite a bit more stiffness to be noticeable, so even 81% sounds like a lot but not particularly so in my experience.

Thanks for response. Yes, the "independence" of the leaf springs will be affected by the stiffer sway bar. I should have been clearer when I said there was no impact to ride quality. As to the 81%, that was comparing to the 22mm hollow vs 24mm solid. I don't know how they came up with it, but I've read that a 22hollow is comparable to a 21solid - with the caveat that all things being equal - so if you take the difference of 24 -21 = 3 to the 4th power, you get 81%. This is probably completely wrong but I think that's where the Viva's number came from.

Anyway, the part is on its way and I will install it next week. Will let you know my subjective impressions on any change to the roll stiffness.

GordonCs · Jul 13, 2021

So the KC Design 24mm solid was installed. I decided to see how it handled speeding up a curved on-ramps on the interstate and doing circle 8"s in an empty parking lot. Overall, less body roll and it gave me more confidence in cornering. So definitely a noticeable change in body roll. Admittedly I did not go fast enough to really test the limits, but for what it's worth, there was definitely less oversteer. Going over bumps and potholes on a paved road did not seem any different than before the switch out. I am sure if you are taking it off-road there will be less "forgiveness" in the rear.

I have to say, that I think the change was worth it, especially if you are planning on towing anything. I am thinking of purchasing a teardrop trailer so it will definitely make the rear end more stable. I also decided to go from the 19" standard rim to a 18" rim because I wanted a little more sidewall. I am now running 235/50 R18, which is the same diameter as the 235/45 R19 so no impact on TPMS, ABS, AWD, speedometer and whatever else is managed by the Volvo software. I went with Michelin A/S 4 Pilot for the higher load factor and a 45K mile warranty. I got 35K on the original tires. You can check out https://tiresize.com/caculator to run comparisons on different tire sizes if you are interested.

So a little less precise handling due to the higher sidewall, but more than offset by the stiffer rear sway bar.

I would definitely recommend this product if you are looking to reduce oversteer and body roll.

S60-1800ES · Jul 14, 2021

GordonCs said:
So the KC Design 24mm solid was installed. Admittedly I did not go fast enough to really test the limits, but for what it's worth, there was definitely less oversteer.
.....
I would definitely recommend this product if you are looking to reduce oversteer and body roll.

Maybe I missed something here, but I am having difficulty understanding how a stiffer rear bar resulted in less oversteer.

Power6 · Jul 14, 2021

S60-1800ES said:
Maybe I missed something here, but I am having difficulty understanding how a stiffer rear bar resulted in less oversteer.

I'd have trouble with that too. The general convention is that adding stiffness decreases overall grip of the axle that you add it. More rear bar, decreased grip, more oversteer. It seems counterintuitive that stiffer bar increases weight transfer and reduces overall tire grip, but it does. Each car is different though, specific quirks to suspension design that might benefit from less roll.

I don't know about this "oversteer" stuff people be throwing that around too much. Ain't no oversteering Volvo lol. We need a some words to describe the shades between "understeer" "neutral" and "oversteer"...

S60-1800ES · Jul 14, 2021

Power6 said:
I don't know about this "oversteer" stuff people be throwing that around too much. Ain't no oversteering Volvo lol....

Oh, yes there are... I've owned several of them.

Power6 · Jul 24, 2021

S60-1800ES said:
Oh, yes there are... I've owned several of them.

Ahhh you got me, I wasn't thinking far back enough in history...

S60T6P · Apr 15, 2022

Power6 said:
I've got some drive time in with the new bar now. It's all subjective of course I got the good feelings from having done an upgrade. I like it though. Front heavy AWD can always use a little more roll stiffness in the rear. I was reminded what a hidden gem the sport chassis is ripping around yesterday!

I did some reading about bonded sway bar bushings, this design can make the action of the bar more efficient, %20-50 stiffer than a traditional sliding bushing. Something to keep in mind with aftermarket upgrades that may not use this design.

Anyways I'm happy with the upgrade! Let me know when you are coming to get the bar for your CC sundstmp ;-)

I was wondering if you have noticed any change in chassis vibration since changing the rear sway bar. I had the dreaded 70+ vibration on my S60 but finally got it 75% better. I was thinking of grabbing the 23mm sway bar for mine but I am worried it might bring back some of the vibration by stiffening things up.

Factory rear sway bar upgrade options

CSVT6

V60CCR40

zerocover

Power6

MDicnMan

V60CCR40

CSVT6

Power6

Voytech

Jack Watts

Power6

GordonCs

Power6

GordonCs

GordonCs

S60-1800ES

Power6

S60-1800ES

Power6

S60T6P

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