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Rough Ride on Washboard Roads

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38K views 110 replies 29 participants last post by  frater secessus  
#1 ·
Hi,
Have had our 136 WB, `high roof 1500 camper conversion since 2014 and now have 43K miles on it.

We use it on some backroads (500+ miles on our Yukon trip), and generally its fine -- ground clearance and traction are fine for us. The ride can be a bit rough over rocks and such, but to be expected on backroads -- just go slow and its fine.

The one thing that is really bothersome is its ride on wash boarded roads -- its just really really rough. Feels like the van is about to come apart. Can slow down to 3 or 4 mph and that helps a lot, but if you have 10 or 20 miles to go, its kind of slow.

Have driven many vehicles on back roads since the 60's, and have never had a vehicle that was quite so jarring on wash boards.
It feels like a resonance phenomenon and seems to be at its worst and 15 to 20 mph you would like to travel over the wash boards.

Any ideas on what might be effective to get a better ride on wash boarded roads?

Shocks, springs, other suspension changes?

I'm fine with making some changes, but don't want to just randomly try things.

I have tried reducing tire pressure and this does help some.

Thanks --Gary
 
#2 ·
When I did my Baja trip last year I encountered plenty of washboard. Soulution I used, air down the tires. I’d drop all the way to 30psi and most of the washboard jarring disappeared. Of course, you need to have some equipment (and time) - auto tire deflators (unless you like to spend a lot of time on your knees playing with the valve stems) and a good 12v air compressor. AND, you shouldn’t plan on going anywhere in a hurry, I normally cruised the washboards at 45mph or so.
 
#4 ·
Reduce the spring rate can help. I pulled the secondary leaf on my 1500 136” and this too is better.
 
#5 ·
We found the ride improved immensely when backing down the road. So this leads me to think the spring rate is the key. Set up too harsh and too unsophisticated to be comparable to any modern pickup. Makes me wonder how they ride when loaded up to 50% of payload capacity.


Sent from my iPhone using Tapatalk
 
#6 ·
Thanks for the suggestions.

Guess I will get a better quality 12 volt compressor and try airing down more.
Maybe to the secondary leaf removal.

Any thoughts on whether new/different/softer(?) shocks might help on the rear?

edit: I wonder about having custom springs made for the rear? Or, is it the layout of the rear suspension that is the problem?

Gary
 
#7 ·
.....cut.....
It feels like a resonance phenomenon and seems to be at its worst and 15 to 20 mph you would like to travel over the wash boards.

Any ideas on what might be effective to get a better ride on wash boarded roads?

Shocks, springs, other suspension changes?

I'm fine with making some changes, but don't want to just randomly try things.

.....cut.....
You're correct that the problem is caused by resonance. When the forcing frequency from the road (based on washboard pitch and vehicle speed) matches the suspension's natural frequency (depends on mass and spring), the vehicle will bounce around at even greater amplitude than the road surface irregularity.

I think it's wise on your part to avoid random modifications without knowing how they will affect the results. If your interested in the basic math let me know and I'll try to post a graph that shows how these things relate.
 
#12 · (Edited)
Did quite a few miles on rough oil field roads as a mud engineer at high speeds, course the vehicle wasn't mine, and experience in oval dirt track racing. Just let'er rip and raise a little up off your seat and flex your knees as you would on a dirt bike. :D Jus' kiddin'. ;)

Actually, I don't know if I'd do that in a tall van with a stiff suspension with a relatively light load especially if I owned it. Seems a little scary and could see how you could easily lose control especially on a gentle or not so gentle curve unless you're an experienced dirt track racer and can control a power slide. In one race we would tear up the right front tire and there was always welds coming loose. I think your van at high speeds on washboard terrain would vibrate some stuff loose and wear your tires and your suspension out prematurely. Am too old to go fast anymore, so maybe less tire pressure and go slow or just find a better smoother path.:)
 
#14 ·
P.S. -- By the way, if your worst speed is between 15 and 20 MPH, then at just below 30 MPH the ride should start to feel no worse than going slowly. Note curves all pass by 1.0 magnification when forcing frequency is at 1.41 that of natural frequency. Beyond that speed it should start to smooth out more. Another variable that makes this more complicated is that front and rear suspensions often have different natural frequencies, and different levels of unsprung mass. Also it makes a difference when front and rear tires hit bumps at same time versus one axle at a time.
 
#15 ·
Hi,
We were in Big Bend NP last couple days and got a chance to try the go faster method a bit. Things do seem to settle down some at 30 mph. But, problem is that 30 mph is pretty fast for a lot of back roads (at least where we go) -- things like sharp rocks strewn over the road, turns, dips for dry streams all make going faster a bit more of an adventure than I like -- the chances of ending up in the ditch or with a blown tire seem too high to me. I guess going faster could work well on flat straight sections where the washboarding is the only issue.

Chance: thanks for the info -- took a quick look, but will look through it carefully when we get back home.

Gary
 
#16 ·
How tough are our PMs when it comes to washboard roads and going faster?

I traveled some washboard a bit in my minivan (Dodge Caravan, 2011) and I didn't want to damage it so I avoided gravel roads. I remember thinking at the time: "I wish I had a jeep". Can our PMs handle it? Are they body-on-frame vehicles like trucks?
 
#17 ·
No they are the more rugged unit body so such vibrations are transferred to the body directly. Don’t take that to mean it cant take the washboard, it can.
I spend lots of time on desert roads that require 4wd and high clearance and have hundreds of miles of unavoidable washboard. I have had three vehicles over the past 18 years used for at least 3,000 to 4,000 miles of it a year including some rock crawling across the roads of lava fields and washes in the Pinacate of Mexico (look it up). I have not seen any damage to suspensions except for two broken sway bar links on my current 4 runner. They had been badly corroded by my daughters owning it in the salt of NH for 10 years and the replacements have been fine. I have pushed through running washes up to the top of the tires, jacked myself off a high center once with my F150 with the camper on it, traveled some roads the jeeps we saw could not believe we could go and that they were reluctant to try (scratches you know). I am not timid but I don’t rush these things except for finding the magic speed on washboard. Steve (of "The Backroader” fame) stopped on his return from the Baja in his 159”. He described his van’s limit in some challenging situations. The van is limited by it’s being 2wd and a bit by it’s clearance but not by it’s ruggedness. Go forth and wander- dirt!
 
#20 ·
Thanks Gary bis for starting this thread!

So, as I understand the above advice, air down, go faster, maybe? take a leaf out? I'm already looking for a good, economical compressor.

I too traveled a lot of Baja washboard this winter. Too many miles at 10 mph. The van just shook itself to death when I tried to go faster as I had done on previous vehicles. Remember that I was driving these roads with highway air pressure. I won't make that mistake again! I also won't have the Nexen highway tires. Maybe some BF Goodrich AT?

Please explain spring rate and how you reduce it.

And, how much of this applies to soft sand?
 
#21 · (Edited)
Lower the spring rate by having more flexible springs. How can you do that inexpensively? Pull the secondary rear leaf, re-aim the headlights and you will enjoy the ride. Don’t expect to carry thousands of lbs. of load though unless you bag it. If you do, run the bags at 10 psi or so, or the ride will be just as bad. I have avoided the bags and with 9,000 miles and two trips cross country I am happy, happy, happy. Its your fault for not stopping in AZ and taking a ride when you were nearby, shame on you.
 
#22 ·
Hi,
We are up in Yukon/Alaska and doing many hundreds of miles on gravel roads in last couple weeks.



Just before we left, I installed the Bilstein shocks that KOV recommended and this has resulted in quite a good improvement on gravel roads with washboards and lines of potholes that the gravel roads up here seem to develop. Would not have thought that shock absorbers would make that much difference, but they really help.
Thank you KOV!



Finally got to do the Prudhoe Bay (Dalton) highway after many years of thinking about it. Really nice even though we got lots of rain. Van has been converted from white to mud tan :).


Gary
 
#23 ·
Just before we left, I installed the Bilstein shocks that KOV recommended and this has resulted in quite a good improvement on gravel roads with washboards and lines of potholes that the gravel roads up here seem to develop. Would not have thought that shock absorbers would make that much difference, but they really help.
Thank you KOV!

Did you just replace the rear shocks with bilstein's or did you do the front struts also? I read the whole thread and didn't see a specific p/n rear shock mentioned. Bilstein makes a lot of shocks. Can you share the part numbers? I visited their webpage and they don't list for the 2500.
 

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#25 ·
Expense not withstanding, is there a reason many people seem to only change/upgrade the rear shocks and not the front ones? In selecting a new shock for these vans, what features should one be looking for? Ie., what distinguishes the Bilsteins mentioned here from the Fox shocks I've seen mentioned elsewhere and what makes them better options than the shocks that come standard with the van?
 
#26 · (Edited)
I replaced all 4 shocks/struts. The rears will take about 30 minute but the fronts will take 6-8 hours depending on your skill level. Bilstein makes 2 shocks/struts for this van, the standard replacement B4 which are like the stock shocks and the upgrade B6 which has better valving and high pressure nitrogen filled shock. The original shocks were fine in my opinion but they gave up rather quickly. By 70k miles they were ready to be replaced. The replacement price of the original shocks is ridiculous, I think the fronts were around $300 each.

As far as features go, nitrogen filled high pressure gas is fairly important as it keeps the oil from foaming under high stress situations. The drawback is I noticed Bilstein shocks on my previous van were a little stiff in cold weather, after a few miles they were fine. Other than that you really need to ride in a vehicle with the particular shocks your considering to see if you like the valving. I replaced our minivan shocks once with Monroe and that was a total waste of time as the new shocks valving was so poor that it was hardly an improvement over the old worn out shocks. I’ll never buy Monroe again.
 
#30 · (Edited)
I have not ordered any shocks and can't give any advice on shock quality.

Bilstein has been around for a while. They only have OE B4 or Performance B6 models for the PM. Even has cheap as I am I would pay the small increase to get the B6, again I have no experience with Bilstein.

Make sure the p/n fit the vehicle. Most sites have a "does this p/n fit your vehicle" entry.

The link you had I think was for a Ram 1500 pickup truck.

Tire Rack has a better price.
 
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