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Low maintenance Suspension mods - timbren / helper spring / other?


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#11 JHanson

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Posted 14 February 2021 - 03:07 PM

RamblinChet,

 

I appreciate your experience in the racing world, but I'm not sure how extensively it translates to the world of slide-in campers. Certainly, increasing the rear spring rate or roll stiffness on a car without doing anything else will increase understeer—I've experienced the effects myself on a Porsche 911 and a BMW 2002. But doing so on a pickup truck on which you've just plopped a 1,000-2,000-pound camper is a different matter. Even on a 3/4-ton pickup doing so is going to alter the balance built-in at the factory to some extent. The majority of the camper weight is going to be over the rear wheels, so it only makes sense that there is where the majority of the alterations need to be done. It's easy to suggest buying a truck that has "been engineered to carry your particular load on a regular basis," but the fact is that few trucks are actually made to do so on a regular basis, and since camper weight goes up with size, even the balance of an F250 will be altered if you put a 2,000-pound camper on it. Much less a Tacoma and a 1,000-pound camper. Not everyone wants or can afford an F350.

 

In my own most recent example, we put a Four Wheel Camper on our 2012 Tacoma. I added Boss air bags to the stock rear springs, and adjustable Boss shocks—thus allowing us to adjust the ride height, spring rate, and shock rebound depending on whether the camper was on or not. I did not do anything to the front suspension, as I consider the stock Tacoma front suspension to be far too stiff to begin with. The truck rode and handled safely with this configuration—and trust me, I tested the emergency handling when a car pulled out in front of me on a two-lane highway as I was heading toward it at 60 mph, and I had to swerve hard enough to break a turnbuckle and stress-crack the skin of the camper. I wrote about it here. Other mid-size trucks might be different, but altering the front suspension on that truck would have been a mistake.

 

I recently helped a friend mount a FWC Grandby on a 3/4-ton Ram, which is rated to carry more than this weight. Nevertheless, the truck sagged in the rear enough to completely throw off the headlamp alignment. Adding slightly firmer rear springs was enough to re-balance the truck. Again we saw no need to alter the front; all we did in essence was to re-calibrate the rear roll stiffness to where it should be.

 

Edit: I actually thought of a race car analogy. Remember the Renault R5 Turbo, the outrageous rally car of the 1980s? Renault started with the mild-mannered, front-engined front-drive R5, ripped out the existing powerplant and instead stuck a turbo race engine in the back. They flared the rear fenders and bolted on wider wheels—and I'm willing to bet they also installed stiffer springs and shocks back there to increase rear roll stiffness.


Edited by JHanson, 14 February 2021 - 09:33 PM.

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#12 ntsqd

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Posted 14 February 2021 - 09:35 PM

Take the Timbrens out and report back on how the truck rides and behaves. At least some of the harshness is likely caused by them and the bouncy is the result of the damping being designed for leaf springs and they can not cope with a rubber 'spring'.

 

What load range tires and what cold tire pressure do you operate with? E range tires run at 80 psi would be all of your harshness.

 

If you go the add-a-leaf route the easy way to decide on which one is to choose the longest that is closest to the same thickness as the existing leaves. If you are anywhere near the lower Left Coast I can recommend a shop that can dial you in.


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Thom

Where does that road go?

#13 JHanson

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Posted 15 February 2021 - 04:27 AM

Well, I was saddened to read your final statement, and I completely disagree with it. You invalidated the aspirations and fiscal realities of thousands of travelers, which I will not do. I'd rather help them set up their vehicles for safe travel, rather than archly telling them they bought the wrong truck and are making "excuses." We can agree completely that overloading a vehicle is not wise, but claiming that the only way to safely carry a load is to buy a vehicle capable of carrying exactly twice that load is a facile argument not supported by your own references.

 

You contradict your argument regarding roll stiffness etc. with the assumption that a vehicle designed to carry 4,000 pounds is ideal for a 2,000-pound load. How so? What sort of dynamic tests did you conduct to arrive at that precise figure? You're speaking of a ton of compromise in both directions, which violates your own notion of an accurately engineered suspension. Using your argument, removing the camper between trips would then make that vehicle dangerous.  Meanwhile, I'm arguing in favor of modifying a vehicle's suspension to suit the load. And if the increased load on a vehicle is largely biased toward the rear, the modifications to carry that load need to be oriented largely toward the rear as well. That's not just my N=1 experience; it's backed up by thousands of owners and vehicles.

 

As it happens I have a copy of Gillespie's book around here somewhere with my other performance books, and I don't recall him discussing pickup trucks and campers. However I might be wrong on that.

 

If you'd like the last word you may have it; I don't want to continue with pointless back and forth. As I said I'm respectful of your racing experience. However, in terms of overlanding vehicles, I'm confident enough of what I've learned doing this for some time with a bunch of different vehicles, both owned and loaned for review, and also of what I've learned from others with even more experience than I, to continue trying to encourage those looking for advice, rather than simply telling them they bought the wrong truck.


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#14 ntsqd

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Posted 15 February 2021 - 03:22 PM

All too often it is assumed that what works and happens in racing directly translates to driving on the street or in the dirt. While the hard physics of it all still apply and do not change, the environment is not as exact and the vehicles in question aren't tuned to the knife's edge like any decently competitive race car. As such those hard and fast rules in racing aren't so hard and fast out here in the real world. Pushed to the very limits those racing rules become much more applicable, but when not pushed to even 70% of what is possible those rules loose their hard and fastness. They still apply, but since we're not treading on the very outer edges of the traction circle their effects are much more subdued.

 

You want to frighten yourself, do the CG analysis post camper install & loaded for a trip. If nothing else will, that should slow you down.


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Thom

Where does that road go?

#15 JHanson

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Posted 15 February 2021 - 09:43 PM

Sigh . . . Chet, perhaps you missed the part where I said I agree with you on the dangers of overloading a vehicle. But I said I'd give you the last word, so please go on as long as you like about how wrong I am.


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#16 CamperSam

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Posted 19 February 2021 - 05:54 PM

Hi guys,
Removed the Timbrens and swapped for Hellwig Pro add on springs. Have driven about 400 miles.

Night and day difference, the suspension is a little softer and suspension travel has increased so the ride is a lot more compliant, especially on square edged hits. I still need to spend some time dialing in the pre-load (U bolt tension) since the rear sags approx 0.5” to the front.

E rated tires at 45/55Psi F/R - didn’t change these pressure set points between the suspension mods.

Without wishing to reopen the vehicle dynamics discussion....
One thing to note is that the truck being level and not sagging at the rear is also a factor in the balance and traction (since the effective CoG will shift rearward if the rear suspension is sagging).

This set up works well for us, especially with the Bilstein 5100’s. A future mid May be to swap out the front shocks also, but that doesn’t seem like a necessity right now.
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#17 JHanson

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Posted 19 February 2021 - 11:49 PM

Very nice! Glad to hear you noticed such an improvement. I haven't heard anything bad about the Hellwigs.


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#18 penner

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Posted 20 February 2021 - 12:00 AM

Are the Hellwigs somewhat adjustable? Just wondering what they would be like with the camper off? 


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#19 rubberlegs

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Posted 20 February 2021 - 06:14 AM

(since the effective CoG will shift rearward if the rear suspension is sagging).


Im curious what you mean by this.
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Tacoma/Fleet 2018.


#20 JHanson

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Posted 20 February 2021 - 02:15 PM

Are the Hellwigs somewhat adjustable? Just wondering what they would be like with the camper off? 

Yes, they do have a range of adjustment.


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