Zr2 front suspension

[Epsilon Plus]

On 9/16/2025 at 2:48 PM, Chuck FB said:

So was a price of a Cognito bar vs a GM bar set ( go with US prices ) get established to compare ? 

 

This also then goes back to my watching a youtuber in Texas who had a Duramax and his truck I believe would have had the 5600 lb rated factory bars and he installed a set of the Cognito bars ( which now with this info are highly likely to be the 44000 lb rated bars ) and he raved at the ride as did him claiming his wife was blown away and questioning what had he done to the truck to make it ride way better. Shows what happens when a softer bar is installed in a front end heavy diesel truck and turn the keys more to get the same ride height back.  Hard to say how much of a noticeable difference there is in a gas truck that has the 4800 standard units and dropping to the 4400 bars, it would be something but I assume not drastic. 

 

Oh and Epsilon, you've done very well ... and in the process managed not to get thrown in jail by some company thinking you were attempting to steal parts off their work truck LOL. 

 

With the constant -20off discount parts.gmparts has, like currently, they are available picked up at dealer after tax for ~520 something vs the new price of $944.95 for Cognito. They used to be $899.99 like last month. This might point to a foreign tariffed part and not Made in the USA like stated. 

 

I don't know that I'm ready to throw $500 to drop 400lb rate. I could see the difference on a 5600 bar diesel but something tells me I would notice nothing on my truck.

 

I got lucky and a Milgard window warranty service truck was at the house and I asked if I could peak at the door sticker. Even after explaining why I'm sure the dude had no idea what I was on about.

 

 

On 9/17/2025 at 9:50 AM, revrnd said:

Possible. Does anyone know if Cognito paints them a different colour or applies their own decal to them?

 

They look painted black from the picture gmcnewbie posted. 

 

Maybe if it's a foreign part that's how they are getting around the made in USA tag line. They arrive raw, and then they paint them. Wala. Kind of like China garbage going to France or Spain before coming to US to avoid tarrifs.

[AndrewF]

I don't have the ZR2 suspension but I switched from 6k lb bars on my 24 WT Gasser with the plow package to 4800 lb bars.  Which is how the truck would've been configured without the plow package.  I was surprised that the plow package on a gas regular cab WT (essentially the lightest front end configuration available) still resulted in the strongest 6k bars so I switched. The 6k bars still rode very well but I was hoping for more front end travel when "off road" (AKA field or logging road) on uneven terrain. 

 

The jury is still out whether it was worth it.  Ride is maybe slightly better but again I thought the 6k bars (and truck overall) rides pretty darn good to start with. Especially for an HD truck. Maybe it is because my truck before this was an 1985 K30 1 ton instead of a newer 1500. Now that was a rough ride.

Edited September 19, 2025 by AndrewF

[kylant]

the cognito bars are painted just like the OEM. they appear literally the same as OEM bars just without the part number stickers. 

 

i honestly don't feel they made a big difference in ride quality. 

the problem is: since the bars are lighter spring weight, the torsion keys need to be cranked more to get the same ride height. the increase cranking, negates the softer spring rate (IMO). 

just person seat of the pants observation obviously 

[Chuck FB]

3 hours ago, Epsilon Plus said:

 

With the constant -20off discount parts.gmparts has, like currently, they are available picked up at dealer after tax for ~520 something vs the new price of $944.95 for Cognito. They used to be $899.99 like last month. This might point to a foreign tariffed part and not Made in the USA like stated. 

 

I don't know that I'm ready to throw $500 to drop 400lb rate. I could see the difference on a 5600 bar diesel but something tells me I would notice nothing on my truck.

 

I got lucky and a Milgard window warranty service truck was at the house and I asked if I could peak at the door sticker. Even after explaining why I'm sure the dude had no idea what I was on about.

 

 

 

They look painted black from the picture gmcnewbie posted. 

 

Maybe if it's a foreign part that's how they are getting around the made in USA tag line. They arrive raw, and then they paint them. Wala. Kind of like China garbage going to France or Spain before coming to US to avoid tarrifs.

I didn't realize the online gm parts and a dealership were connected in any way, I've never had anything to do with GM online parts but it seems there is a Canadian website as well. So does GM the online parts store pay for shipping to the dealership or do you get that fee tacked on as well ?. But as to the price and if they are the same bars or perform the same, its obvious as to which one costs less and then shipping costs dependent as well. 

 

It is a good question as to what one would notice in a ride difference with ratings being so close, what a stock suspension would react like as per factory shocks and factory weight tires vs a higher end shock and heavier tires ... a few variables thrown into the mix and hard to know unless a lot of swapping and testing was done which again goes back to the seat of the pants feel without having some fancy measuring system to calculate the performance. 

 

Amusing about the truck you found, literally came to your house and no surprise that the driver had no idea what you were even talking about, its a company truck for one thing and not everyone would have a clue what a torsion bar even is, never mind that GM has 5 different ratings on this series of truck. 

[Chuck FB]

2 hours ago, AndrewF said:

I don't have the ZR2 suspension but I switched from 6k lb bars on my 24 WT Gasser with the plow package to 4800 lb bars.  Which is how the truck would've been configured without the plow package.  I was surprised that the plow package on a gas regular cab WT (essentially the lightest front end configuration available) still resulted in the strongest 6k bars so I switched. The 6k bars still rode very well but I was hoping for more front end travel when "off road" (AKA field or logging road) on uneven terrain. 

 

The jury is still out whether it was worth it.  Ride is maybe slightly better but again I thought the 6k bars (and truck overall) rides pretty darn good to start with. Especially for an HD truck. Maybe it is because my truck before this was an 1985 K30 1 ton instead of a newer 1500. Now that was a rough ride.

Perhaps in hindsight had you realized there was one series of torsion bar lower rated that the stock configuration that you may have tried it instead as definitely if a 4800 bar is just fine for a crew cab short box fully loaded up with crap ( I mean options ... ) it certainly can hold up the front end of a single cab truck. 

 

However I have a question in how you set up the keys ( the trucks height ) compared to the factory equipped plow package bars. I am wondering if you have some leeway to raise the truck slightly to possibly use the suspension travel to be more effective. Put another way, if the suspension is bottoming out for example, raising it a little to gain up travel before it smashes against the jounce bumpers hard when hitting a bump but not to the degree of loosing the proper amount of down travel. "Leveling" a truck like what some want to do though is not that wise of a plan or I don't think so anyway, that messes up the ride and causes a short life of a lot of suspension/steering parts. What I am wondering is, what your front measurement is from the center of your front hubs to the underside of your fenders. Measuring that way eliminates all issues with tire size or air pressures your carrying and so if its a heavy front end diesel or a lighter single cab gas, that measurement stays the same. 

[Joe97281]

I have been meaning to graph the contribution torsion bar vs jounce bumpers to draw conclusions about ride stiffness. I was too cheap to buy a a line pot for a data acquisition unit, so I never got anywhere. 

 

It would be very easy to do for someone with access to basic mechanical instruments at a college, tech school, or employer. 

 

The question to answer: What is the spring rate of the jounce bumper?

 

With that info you can make decisions about modifying it to get a lower overall effective spring rate. Maybe drilling a hole down the center of the bumper solves all problems and no one needs new torsion bars.

 

Pic attached demonstrates the concept of overall spring rate. At some distance of suspension travel, the jounce bumpers make contact with the control arms and the overall spring rate of the suspension is increased. This is the blue shaded portion of the graph. 

 

If anyone knows spring rates of the torsion bars or equivalent conversions as if it was a coil spring, that would help as well. 

 

Also, I have always understood the spring rate of torsion bars to be linear, therefore cranking the keys does not change ride quality, all it does is lift the suspension.  This is a common misconception from people with cranked keys because the upper control arms kit the service stops on down travel, making for a crap ride. The concept of "preload" for linear coil springs and torsion bars resulting in a rougher ride has no merit. This is not true for a progressive rate coil spring. 

 

Fingers crossed someone here is a physics teacher and measures and generates a graph accounting for the torsion bar,  and 2 jounce bumpers corrected for motion ration. 

[revrnd]

On 9/19/2025 at 10:51 AM, Epsilon Plus said:

 

With the constant -20off discount parts.gmparts has, like currently, they are available picked up at dealer after tax for ~520 something vs the new price of $944.95 for Cognito. They used to be $899.99 like last month. This might point to a foreign tariffed part and not Made in the USA like stated. 

 

I don't know that I'm ready to throw $500 to drop 400lb rate. I could see the difference on a 5600 bar diesel but something tells me I would notice nothing on my truck.

 

I got lucky and a Milgard window warranty service truck was at the house and I asked if I could peak at the door sticker. Even after explaining why I'm sure the dude had no idea what I was on about.

 

 

 

They look painted black from the picture gmcnewbie posted. 

 

Maybe if it's a foreign part that's how they are getting around the made in USA tag line. They arrive raw, and then they paint them. Wala. Kind of like China garbage going to France or Spain before coming to US to avoid tarrifs.

Someone said they had the same end markings as the OEM bars.

 

Also I think you meant 'voila' rather than wala...

[Chuck FB]

49 minutes ago, revrnd said:

Someone said they had the same end markings as the OEM bars.

 

Also I think you meant 'voila' rather than wala...

Or perhaps upon the excitement of the findings "Eureka !" ... or .... Holy FU%$ ( after he hit his head under the truck )

[Chuck FB]

This video has a good example of a torsion bar cranked right up to the point where there is almost zero droop before the upper control arm hit the steel frame stop as well as the severe angles of the cv shaft and tie rods, and for that matter the upper and lower control arms. Also note they are using the hub center to underside of the fender for measurement comparisons and for the GM they are stating around 24 inches from factory, the Chev has a different fender profile and all I can say is that mine "averaged" about 24 1/2 inches and the high side was 24 3/4. I put mine to 25 inches and in checking the droop by jacking up the truck I am at around 2 3/4 to 2 7/8 for droop. I would say my cv and tie rod angles look very good, its not out much from the factory height, yet it gained 3/4 of an inch of height on my low side from the factory due to their lopsided adjustment. Perhaps that is just enough additional up travel before the jounce bumpers really start taking effect on smaller bumps on the highway and cause a less harsh hit feel to a bump. Trucks with some miles on may very well be sagging a little vs what the new height had been and with it the ride doesn't feel as good anymore and needs a slight turn of the keys and perhaps new jounce bumpers to bring the ride back and those jounce bumpers probably tend to get harder with age although I can't claim that, they sure can wear out though if smashed into enough times when driving crappy roads. 

 

 

[kylant]

shocks:

 

 

[Chuck FB]

22 minutes ago, kylant said:

shocks:

 

 

Are those the 2.5 series and wondered what one gets them for in the states, if its less than the listed price on the fox site. 

 

Also do they use the same shock valving for the gas HD as they do for the Duramax or is there a reason or even ability to get a custom tuned shock for the front ( the rear would have the same potential loads on either engine version ). 

[kylant]

8 minutes ago, Chuck FB said:

Are those the 2.5 series and wondered what one gets them for in the states, if its less than the listed price on the fox site. 

 

Also do they use the same shock valving for the gas HD as they do for the Duramax or is there a reason or even ability to get a custom tuned shock for the front ( the rear would have the same potential loads on either engine version ). 

they retail for $346 in the states. I haven't seen any discounts on them, but I'm sure there can be some found.

valving is standard, it is the same for gas and diesel. There's no adjustability to them. They cannot be revalved as far as I know

[GMCnewbie]

38 minutes ago, kylant said:

they retail for $346 in the states. I haven't seen any discounts on them, but I'm sure there can be some found.

I bought mine last year during the Black Friday sales thru shocksurplus.com and got maybe $100 off.  It wasn't a great deal but it was the best available at the time.

[Epsilon Plus]

Tirerack has them for money off. They took a few weeks as they are likely drop shipped but I saved a good bit. Think I paid like $276 each. Right now they have them at $315 each.

[GMCnewbie]

38 minutes ago, Epsilon Plus said:

Think I paid like $276 each.

Damn!  Great price considering I paid around $1,200 for a set last Nov.  And mine was discounted.