What are you towing with your 2014?

[TXS Heat]

I think we are stuck on the Lacrosse 318bhs. We haven't pulled the trigger and most like wont for another month due to crazy schedules. Who knew buy a trailer was so dang difficult haha - we have bought houses with less stress

 

 

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[sugarjohnson]

I think we are stuck on the Lacrosse 318bhs. We haven't pulled the trigger and most like wont for another month due to crazy schedules. Who knew buy a trailer was so dang difficult haha - we have bought houses with less stress

 

 

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We have owned two Primetime products with our current trailer being a Tracer 250 Air. At 5100 its a perfect weight for my 6.2L and a nice tow. Good luck on the Lacrosse. I really like Primetime products. By the way we just got back from a long trip and stopped at the Primetime factory and actually saw the Lacrosse production line. New exterior color and front cap coming this fall. Shh i wasn't supposed to tell..

[calgator73]

I think we are stuck on the Lacrosse 318bhs. We haven't pulled the trigger and most like wont for another month due to crazy schedules. Who knew buy a trailer was so dang difficult haha - we have bought houses with less stress

 

 

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If you liked the 308... Check out the lacrosse 329bht. If our dealer wasn't such a pos I would have bought that.

[TXS Heat]

If you liked the 308... Check out the lacrosse 329bht. If our dealer wasn't such a pos I would have bought that.

Correction - we originally were looking at the 318 lacrosse but after seeing yours we looked at the 329bht in comparison online - our dealer doesn't have one but expects to have. 2015 this month - we believe this is the model we are going with.. I just have 318 stuck in my mind because we have looked at it so many times.

 

I wish lacrosse did the massive horseshoe shaped couch

 

 

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[calgator73]

Correction - we originally were looking at the 318 lacrosse but after seeing yours we looked at the 329bht in comparison online - our dealer doesn't have one but expects to have. 2015 this month - we believe this is the model we are going with.. I just have 318 stuck in my mind because we have looked at it so many times.

 

I wish lacrosse did the massive horseshoe shaped couch

 

 

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Nice RV....you might be able to upgrade to that kind of dinette http://www.glastop.com/rv-furniture-detail.asp?id=604 I'll go over mine and see if there is any kind of mfgr tag

[Jon A]

 

The ONLY thing that bags do is stiffen up the rear suspension, returning it to mid-travel, and generally speaking improving the look of the tow vehicle itself. What they CANNOT physically do is alter the response of the front suspension to force and movement applied behind the rear axle. If the front end bounced before the bags, it will bounce after the bags and yes, possibly even more so.

 

If only vehicle dynamics were so simple. I’ll try and keep this short.

 

You have a single chassis with bending and torsional stiffnesses very high relative to that of the suspension on each corner. This means the chassis will react to all inputs as a single unit. What you do to one end most certainly does affect what’s happening on the other—and just as importantly, how the passenger perceives what’s happening.

 

One of the more important aspects of suspension design as it pertains to ride quality is the relative stiffnesses between the front and rear suspensions. Not merely from an absolute wheelrate standpoint, but relative to how much mass is being carried by each. This is expressed as the Undamped Ride Frequency.

 

Generally one shoots for the rear suspension to have a frequency 10-20% higher than the front for the most pleasing “flat ride.” Pickups tend to overshoot that in the rear by a bit because they generally have stiffer springs in the rear than you would otherwise put on a passenger vehicle in anticipation of carrying a load. This is why pickups almost universally ride better with a moderate load in the back—it lowers the frequency of the rear suspension closer to that 10-20% range above the front you’d shoot for with a sedan.

 

However, if you put a very large amount of mass on the rear of the chassis, you lower this frequency too far—putting it below the frequency of the front.

 

These frequencies matter because they dictate how each end (and thus, the entire chassis) reacts to large bumps or dips at highway speed. The rear hits the bump after the front so it’s starting the cycle with a delay—they are out of phase. Exactly how far out of phase depends upon the frequencies and the vehicle speed.

 

If the rear frequency is lower than the front, this out of phase condition gets worse to the point it can reach or at least approach 180 degrees out of phase with the front in the first or second cycle (which are the most important because the shocks haven’t damped them out yet—they have the largest amplitude).

 

When you reach 180 degrees, you have the front of the chassis hitting its peak when the rear of the chassis is hitting its valley or visa versa. This means the chassis is pitching (brake dive/acceleration squat type motion except due to hitting a bump and oscillating back and forth). Passengers generally describe this feeling as the “front end bouncing all over hell!” or the like because they perceive chassis pitch as mostly the front end moving (brake dive is usually made up of just as much or more “rear lift” but people only notice the “front dive” part). Not only does this give an uncomfortable feeling, it can make the vehicle feel out of control or even unsafe if it’s bad enough. And it’s not just a matter of feeling—in measured tests you will have less control of the vehicle when it’s doing this (less grip on the pavement). It is very undesirable.

 

Increasing the rear spring rate to restore its frequency to above that of the front will prevent this problem from occurring.

 

When the rear frequency is higher than the front, the out of phase condition for the first couple of cycles is constantly decreasing from the moment you hit the bump—even to the point the two are “in phase” soon after the bump giving the vehicle a very “controlled” feeling. And a “level ride” which is where the phrase comes from—you are keeping the chassis from pitching back and forth with this setup.

 

That’s why adding mass to the rear end can cause the front end to seem to bounce much more than it did before and why increasing rear spring rate can reduce/prevent the condition.

 

And all that was merely addressing the “front end bouncing” issue and how airbags can help reduce that. There are a bunch of other things that happen when you add a bunch of mass to a chassis with soft wheelrates. When you do that, dynamic load changes will cause exaggerated chassis movements. Much like the above, these can give the vehicle an “uncontrolled” feeling to the point of being unsafe if extreme enough. There will be measurable degradation in trailer sway damping, braking stability, etc tests. There’s a reason tow vehicles employ stiff springs—they simply work better as loads get higher.

 

 

But in nearly all cases more spring rate isn't what's needed and will most likely cause more problems. .

 

That’s precisely the opposite of the correct answer for the reasons stated above. When you add mass to the rear of the chassis, you will affect the ride characteristics. In order to get the ride characteristics back as close as possible to what they were before, increasing the rear spring rate is the answer. That’s not an opinion, it’s the answer to the math question presented.

 

 

Our trucks have plenty of spring rate. .

 

For the way most people use them, sure. Do they have the optimum springs for the times they’re loaded to levels considered “3/4 ton territory” not so long ago? No, not even close.

 

 

One must simply apply the proper weight at the proper locations to allow the springs that we have to handle the load. A lot of these trucks can tow 9,600lbs. That doesn't mean you can throw it all in the bed..

 

But it is all in the bed—or at least it should be. Even when using a WD hitch, 100% of the tongue weight should be on the rear axle (Front Axle Load should be unchanged). If you’re actually adjusting the hitch to place a portion of it on the front axle, you’re going too far.

 

Without a WD hitch, a lot more than 100% of the tongue weight is on the rear axle—this weight is removed from the front axle due to the fact the hitch is behind the rear wheels (levering up the front of the chassis). Naturally this is not the most desirable setup.

 

A WD hitch should be used to restore the front axle load to what it is with an empty vehicle (which is 100% Front Axle Load Restoration)—or at least closer to it. I believe both GM and Ford now recommend 50% as does the SAE when the manufacturer doesn’t specify. This means ½ of the weight removed from the front axle by hooking up the trailer is restored by the WD hitch, but there’s still less weight on the front wheels than there was before the trailer was hooked up. Total rear axle load actually increases more than the tongue weight.

 

If you’re actually increasing the front axle load compared with the empty vehicle, you are distributing some of the tongue weight to the front axle—you are exceeding 100% Front Axle Load Restoration ratio. While this may improve ride quality, it makes the vehicle less stable and more prone to jackknifing, etc, during braking, sharp turns, etc and is not recommended.

 

I know in the past many WD hitch manufacturers used to recommend setting them up such that you’d exceed 100% by quite a bit since that can give a nicer ride and “feel better,” but many have now changed their recommendations and those that haven’t yet surely will soon as this setup has been found to be less safe.

 

In short, thanks to lots of SAE testing in recent years, we know the safest setup is to use a WDH to only transfer a pretty small amount of weight. People get it in their heads they’re “equally distributing” the tongue weight to the front and rear axles (and the WDH manufacturers sometimes encouraged people to set them up in such a way) but that’s just not a very safe setup.

 

Here’s a simplified example using rounded off numbers to keep it simple:

 

A truck with a 150” wheelbase, 50” from the rear tires to the hitch and 1000 lbs of tongue weight:

 

With a straight weight carrying setup, the 1000 lbs tongue weight puts 1333 lbs on the rear axle, removing 333 lbs from the front. According to GM, Ford, SAE, etc, the proper setup is to adjust the WD hitch to transfer 167 lbs back to the front leaving 1167 lbs on the rear (technically slightly less than that as a little bit will go to the trailer but we're trying to keep things simple for the moment). 100% FALR would be transfering 333 lbs back to the front.

 

While that’ll certainly be an improvement, it’s not exactly a dramatic difference. If the trailer was throwing the truck around before that, it’s going to still do it to some extent. It’s just not that much of a difference in the big picture.

 

Use the WDH to transfer 400-600 lbs to the front and it will be a more dramatic difference and might feel like it drives better in some ways. But it’ll be less safe in others.

 

 

 

In any case, I expect many peoples’ eyes glazed over and they skipped reading the above. That’s OK, they don’t need to take my word for it. Seeing is believing. Airbags are only a couple hundred bucks for a basic setup and adding air only takes a few seconds.

 

The only people skeptical that airbags (or helper springs, etc) can improve handling ills (much less make things worse) that were caused by adding a bunch of mass to one end of the chassis are those who don’t have them.

[calgator73]

I agree with some of what you say... But equalizer disagrees with your assessment of only transferring 1/2 the load you lost on the front. They set that as their minimum amount of distribution with full load restoration as the max IF your rear suspension compresses at least 1.5". This prevents unloading of the rear axle. Where did you find manufacturer recommendations? Certainly not in the towing guides. In regards to transferring more than stock axle load to the front. I can see where that will be a problem if you are not loading your rear suspension correctly or if you're exceeding fgawr.

[Jon A]

Where did you find manufacturer recommendations? Certainly not in the towing guides.

 

The owners' manual for one. It clearly states 50% distribution for our vehicles and describes how to set that up (front wheelwell height 1/2 way between unloaded and loaded heights). Going over 100% is not a safe setup regardless of any other factor.

[calgator73]

You are correct on the 50% according to the manual. (9-92) This is different than the wd hitch instructions where it shows that 1/2 the distance is the minimum distribution with factory ride height being the max. Well written post btw. One problem with using 1/2 the distance as your goal is that you are unloading your front axle compared to stock. Everyone here knows that the front end on these trucks float and bob down the interstate like an old Caddy. My opinion is that they don't have enough shock damping for the spring rate and that the tires are too soft which act like springs of their own. This gets magnified when you unload the front end...a lot. By using factory ride height as a goal for the front end while ensuring your rear fender height does not exceed unladen height you are considered "safe" according to the hitch mfgr. My unloaded front height is 36 1/2 and my rear is 38 3/8. Initial loading with 1/2 fender height as target resulted in my RAW hitting 4060 and my FAW hit 3400. This would literally make people sick in the truck as the already underdamped front end was literally moving like a pogo stick. After targeting front factory ride height I ended up at 3700F (factory front axle weight btw) and 3800R. My rear fender is now precisely 36 1/2 as well. I now get the factory float (magnified at times by the WD arms...but settles within two bobs) while not exceeding either axle's weight rating. Additionally my headlights aren't blinding people. My only other adjustments were to tire pressure. My first trip I bumped the front to 35 PSI to get max load rating for SL tires on the front. After talking to Goodyear I should see more improvement by bumping the tires a little more to 40psi. This will result in less dynamic tire flex and should further refine the ride. After these tires and shocks are worn I'm going for a LT tire and 5100 shocks. Nice debate. Cheers.

[bdbake01]

 

If only vehicle dynamics were so simple. I’ll try and keep this short.

 

 

W.O.W. Ok, where should I start. First, maybe I'll just say that we are basically on the same page here in theory. I agree with most of your points here, so know that we are on the same team. FYI, I think you failed on the "keep this short" part.

 

I'm all for sharing information and working through issues together in a public forum where everyone can benefit from the discussion. Seriously, I think it's probably one of our greatest modern accomplishments. That said, my concern here is that an explanation taken to this level of excruciating detail will be deterimental in the long run, particularly to those who are not interested or deeply experienced in the field of statics & dynamics or strictly vehicle suspension system design. I'm an electrical engineer by education, training & experience, but I don't have to explain the the quantum physics behind the liberation of valence electrons to explain how flipping the light switch should = light in the room. I'm not trying to patronize anyone here, my apologies if it seems that way, but I also don't ask my physician to explain the biochemistry behind why an antibiotic only supports recovery from a bacterial infection and will do nothing for my rhino virus. Get a second opinion if you wish, and I recommend you do if you have concerns, but that's their field of study not mine. I've had an interesting career covering a range of experience from food manufacturing to automotive engineering, mechanical, civil, chemical, you name it I've worked with it. I'm probably one of the few electrical engineers who has personaly welded on coded pressure vessels operating at >1,500 psi and >1,000F and passed UT/X-Ray inspection. I can discuss details on the affects of high/low pH on flow accelerated corrosion, the differences in grain boundaries in various nickel/chromium stainless steels, beam loading calculations, boiler chemistry, etc. etc. list goes on. I actually own a "calibrated hammer", pun intended, complete with integrated load cell for the purpose of measuring system resonant frequencies.

 

My point is, there's little to no benefit in dazzling with a 2 page in depth explanation of why I'm clearly wrong. Just stick with the helpful stuff. You even eluded to this yourself here:

 

In any case, I expect many peoples’ eyes glazed over and they skipped reading the above. That’s OK, they don’t need to take my word for it. Seeing is believing.

 

 

You're welcome to disagree, but I get concerned when I see so many (not pointing out anyone in particular in this thread, this is a general statement) thinking that freezing up the rear suspension on a truck with bags/springs/bumps/etc. fixes all of their issues because their buddy said so. Maybe bags are the answer, in some cases they are. But think it through first.

 

At the most finite level possible, throwing a roll of toilet paper in the bed of the truck changes its handling characterstics. Period. Does it matter in practice? Clearly it doesn't, but throwing 9,000lbs around in various locations becomes signficant and should be taken seriously if for no other reason than I may be passing you some day with family in tow and I'd rather you stay on your side if a cross wind happens to pick up at the wrong time.

No offense to the OP or any other, but think it through. GM and other manufacturers have to try to hit a middle of the road since it's physically impossible to have a suspension system that infinitely perfect for every load. WD hitches can, properly set up, assist with this as can bags. But my bet is that for Joe the Weekend Warrior, the WD hitch will hit the mark more often than the bags, and they are certainly a more flexible option. I never said that "distributing" weight to the front axle was a good idea. If you want to get detailed, I'm with you. You should "transfer" the ORIGINAL loading (and no more) back to the front axle which is what most WD hitch manuals try to do with some margin of error. The shadetree method of doing this is measure the front before, load her up, and then restore that ride height. The load, should be carried by the rear suspension and the trailer's suspension provided you do not exceed any axle ratings. If you do, well, this may not be workable my friend.

As for "The only people skeptical that airbags (or helper springs, etc) can improve handling ills (much less make things worse) that were caused by adding a bunch of mass to one end of the chassis are those who don’t have them.", careful there Skippy as others may have had some experiences that don't quite line up with yours. I've had them, don't have a need for them now, but I've had great experience with them in the proper application. It's never been while adding mass to the far back end of a chassis, but there's really no sense in killing that dead horse again.

To the OP...sorry for starting a fight in your black panther party... And I have no idea what happened to the font there. Something with the quote function I think.

 

 

 

 

[bdbake01]

When I said:

 

"One must simply apply the proper weight at the proper locations to allow the springs that we have to handle the load. A lot of these trucks can tow 9,600lbs. That doesn't mean you can throw it all in the bed.."

 

I was literally saying you can't place 9,600lbs of, say, concrete in the bed of the truck and expect it to stay on the road.

[blacksvt]

First pic was before I had he WDH dialed in. This truck pulls SO MUCH better than my 2011 CC Z71

[calgator73]

First pic was before I had he WDH dialed in. This truck pulls SO MUCH better than my 2011 CC Z71

Nice setup!

[Jon A]

Initial loading with 1/2 fender height as target resulted in my RAW hitting 4060 and my FAW hit 3400. This would literally make people sick in the truck as the already underdamped front end was literally moving like a pogo stick.

 

The cause of that ride problem is exactly what I described above. Stiffer rear springs attack the cause of the problem.

 

I agree the stock shocks aren’t great and it’s a good idea to replace them with something better (for many reasons), but they will only be camouflaging the problem, not addressing its cause. E rated tires pumped to 60+ psi in the rear actually will increase the rear ride frequency slightly and help things, but they’ll only make a pretty small change compared with airbags—but again are a good idea for lots of reasons.

 

Don’t get me wrong, at 100% you’re in the safe zone and if the rig is riding and handling how you like I don’t blame you for not wanting to mess with it. I’m just trying to describe an alternate way with which people may have more luck.

 

At 100% you’re in the safe zone, but you’re all the way to the edge of it. Everything is a matter of degree. You will have a lower threshold for jackknifing. They do test for understeer at both 50% and 100% in J2807, but at 50% they test at .4g cornering force, at 100% only .3g cornering force. And in testing for trailer sway damping they do that at 50% unless otherwise specified by the manufacturer so you have no assurance a truck would pass the test at 100% with a max load as you do if loaded to 50%.

 

That’s why it’s not an either/or answer as so many to think. The best answer is to use both a WDH and airbags/helper springs, etc. With a set of airbags fixing the ride problem (as well as the headlight problem) you describe, people can run a WDH closer to 50% and have an even better handling setup with higher margins of safety if they ever find themselves standing on the brakes while in a turn.

 

More importantly, they’ll be less tempted to exceed 100% with the WDH “because it feels better.” I’m afraid a whole lot of people do this (and in their defense, they were often told to set them up this way years ago) without knowing the risks they are taking. It may feel like it’s riding and handling great—right up to the point they jackknife it. Over-doing it with a WDH can be less safe than having no WDH at all. Unfortunately that doesn’t seem to be very common knowledge yet.

 

I think if people had been told to run WDH’s at only 50% years ago, they wouldn’t have developed the reputation as a magic cure-all they seem to have developed in some circles. As illustrated above, especially with a long wheelbase truck, a WDH at 50% isn’t really doing all that much. Giving it a more solid platform to work with in the first place can be a big help.

 

 

 

My point is, there's little to no benefit in dazzling with a 2 page in depth explanation of why I'm clearly wrong. Just stick with the helpful stuff.

 

Please understand, it’s not meant to show off, it’s meant to help. I learned long ago that simply saying somebody is "wrong" and providing the correct answer didn’t really sound any different than anybody else’s opinion, which could be pulled from thin air—and it would just as likely be ignored. If the goal is to actually help people with the correct answer, being able to explain exactly why it’s the correct answer has a better chance of success. And especially when the audience is full of Engineers (such as various road racing forums), a lot of people really are interested in learning the “why” behind an answer.

 

 

 

You're welcome to disagree, but I get concerned when I see so many (not pointing out anyone in particular in this thread, this is a general statement) thinking that freezing up the rear suspension on a truck with bags/springs/bumps/etc. fixes all of their issues because their buddy said so. Maybe bags are the answer, in some cases they are. But think it through first.

 

But adding airbags is in no way “freezing up” the rear suspension, they only give it a higher spring rate and higher ride height. Everything is relative—even with quite a bit of air in the bags a ½ ton is still relatively soft compared with a ¾ or 1 ton and that’s easily seen by how much it rises after lifting the tongue weight off. I don't consider all those trucks to have frozen rear suspensions. I guess the difference between "frozen" and "better tuned for a specific task" could be an exercise in semantics. Though I'll point out airbags allow one to change the tuning of the suspension for a different task in a matter of seconds which comes in really handy.

 

 

 

I never said that "distributing" weight to the front axle was a good idea. If you want to get detailed, I'm with you. You should "transfer" the ORIGINAL loading (and no more) back to the front axle which is what most WD hitch manuals try to do with some margin of error. The shadetree method of doing this is measure the front before, load her up, and then restore that ride height.

 

 

And I guess this is probably my biggest point on the subject: Thanks in large part to much testing in recent years by all the OEM's, the thinking about WD hitches has changed somewhat industry-wide. It's now generally accepted that the above is the absolute maximum limit of what should be put back on the front, not necessarily the best target for one to shoot for. Most are adjusting their recommendations to target somewhere closer to 50% because that has been shown in testing to be a safer setup in many ways.

 

But as noted above, 50% often will result in unacceptable ride and handling traits without the help of airbags or the like which is why an either/or answer isn't necessarily the best answer to the question. In my opinion that's very clearly "both." Better ride, handling and safety by all measures.

[RobDarden]

All I've towed is a 21ft bow rider. I have the 5.3. The truck does very well. A little slower accelerating and stopping. Gas mileage drops a bit too, but nothing unexpected. I'm happy with it.

 

 

 

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