comptiger5000
Adventurer
I'll second the 7100s. I've got a set under a Jeep ZJ at almost stock ride height (with very not-stock springs). As long as they're valved well to the springs you've got, they ride quite nicely.
Optimizing suspension for washboard?
- Thread starter Martinjmpr
- Start date
W0lfpack91
New member
With washboard the only solution is just to drive faster. As you go slower Your tires tend to dip into the washboard, If you go faster they can just skate over the top as the suspension doesn't have time to react. If you wanna look it up on YouTube mythbusters did a video about it.
Sent from my SM-G955U using Tapatalk
Sent from my SM-G955U using Tapatalk
SoCal Tom
Explorer
You just need good suspension to absorb the dips and rises that you will end up hitting at speed.
Sent from my iPad using Tapatalk
1stDeuce
Explorer
Good thread with lots of interesting reading. Some of it way off, some right on... Grab a cup of coffee, here's my dissertation on the subject.
Washboard:
Back in the late 90's, I was involved in a mobility study for the US army. They were mainly looking at CTIS, and the effects it had on mobility.
With respect to roads, what they found was that too high a tire pressure for the surface would quickly cause washboard. The faster the speed, the faster washboard would form.
By airing down appropriately for the surface, formation of washboard was eliminated, and with passage of traffic (with proper tire pressure) washboard could actually be healed to a smooth road surface again.
The moral of the story? Ideally, when you are on a non-paved surface, you should be running less tire pressure. Realistically it's not always possible, but for long stretches of washboard, it really does help, both for the ride of the vehicle, and to prevent formation of more washboard, and to heal existing washboard. Running 4wd helps a little on the level, and a lot on grades, both at preventing formation, and improving ride.
Tire Pressure:
I think this can be gathered by reading the preceding pages, but the pressure you will air down to depends HEAVILY on your vehicle, your tires, and your desired speeds. People citing any pressure without that info are well meaning, but their suggestions are pretty much useless.
For example, I have 255/85R16's on my 4k lb Jeep. I don't consider it "aired down" until I'm at or below 15psi. (Street pressure ~28psi by chalk test.) I've been down to 5psi at the dunes when it was really dry. At 15psi, washboard is liveable, but I don't have to worry about speed even on hard hard surfaces. At 10~12psi, washboard is non-existant, but I wouldn't run down a paved road for more than a few miles at lower speeds.
My GMC 2500 with camper runs the same size tire on a 17" wheel. It probably weighs ~9500 lbs, and airing down to 45psi has about the same effect as running the Jeep at 15psi. I've run it as "low" as 30psi, for heavy washboard and sand. I'd equate 30psi on the truck to ~10psi in the Jeep, as it makes washboard a non-issue, and tire bulge appears similar. For the truck, I would consider 15psi "emergency" pressure, for getting out of deep sand perhaps, and I would air up to at least 30psi immediately after I was free. At 5psi, the truck tires are still "flat", so this isn't even a workable pressure.
Aspect ratio:
Nobody much mentions this, but aspect ratio is VERY important. Anything less than about 60 is not well suited to offroad use. I would recommend staying above 70 for best performance. (IE, 265/70R17, 285/75R16, etc... NOT 265/60R20...)
With less sidewall, the tire will be less tolerant to airing down before overheating becomes an issue due to excessive flex. With a limit on how much you can air down, you're stuck with a tire that is often still too hard for the terrain, and you can't get much flotation if you can't air down. Even if you are OK with a LOT of sidewall flex, you still don't get much elongation in contact patch at lower pressures, which is the primary benefit to airing down in soft surfaces.
Shocks:
Valving is everything, and the same series or brand shock can be valved differently for different applications. This means a 5100 may be valved to your taste on a Tacoma, but not for a Jeep TJ. It all depends on the priority of the tuner, and what vehicle they used. (Ie, how heavily accessorized it was...)
Knowing the valving style for a particular shock is key, and if possible, valving the shocks to your specific vehicle and needs provides the best result. Read this article... It explains things pretty well...
In my experience with my TJ, Bilstein's 5100 series (Digressive valving) are meant for bombing around in the desert. Washboard performance was not a priority of the tuning, though with a loaded vehicle, it is somewhat tolerable. OME Nitrocharger Sport shocks also seem to me to be digressive. The old OME "comfort ride" Nitrochargers were likely linear, or progressive. They were AWESOME for washboard and cobbled trails, but a bit soft for high speed travel in the rough. (I still want a set of these!!!)
I would try a set of Fox shocks, but the ones for my application (~1.5" lift) severely limit droop travel...
Washboard:
Back in the late 90's, I was involved in a mobility study for the US army. They were mainly looking at CTIS, and the effects it had on mobility.
With respect to roads, what they found was that too high a tire pressure for the surface would quickly cause washboard. The faster the speed, the faster washboard would form.
By airing down appropriately for the surface, formation of washboard was eliminated, and with passage of traffic (with proper tire pressure) washboard could actually be healed to a smooth road surface again.
The moral of the story? Ideally, when you are on a non-paved surface, you should be running less tire pressure. Realistically it's not always possible, but for long stretches of washboard, it really does help, both for the ride of the vehicle, and to prevent formation of more washboard, and to heal existing washboard. Running 4wd helps a little on the level, and a lot on grades, both at preventing formation, and improving ride.
Tire Pressure:
I think this can be gathered by reading the preceding pages, but the pressure you will air down to depends HEAVILY on your vehicle, your tires, and your desired speeds. People citing any pressure without that info are well meaning, but their suggestions are pretty much useless.
For example, I have 255/85R16's on my 4k lb Jeep. I don't consider it "aired down" until I'm at or below 15psi. (Street pressure ~28psi by chalk test.) I've been down to 5psi at the dunes when it was really dry. At 15psi, washboard is liveable, but I don't have to worry about speed even on hard hard surfaces. At 10~12psi, washboard is non-existant, but I wouldn't run down a paved road for more than a few miles at lower speeds.
My GMC 2500 with camper runs the same size tire on a 17" wheel. It probably weighs ~9500 lbs, and airing down to 45psi has about the same effect as running the Jeep at 15psi. I've run it as "low" as 30psi, for heavy washboard and sand. I'd equate 30psi on the truck to ~10psi in the Jeep, as it makes washboard a non-issue, and tire bulge appears similar. For the truck, I would consider 15psi "emergency" pressure, for getting out of deep sand perhaps, and I would air up to at least 30psi immediately after I was free. At 5psi, the truck tires are still "flat", so this isn't even a workable pressure.
Aspect ratio:
Nobody much mentions this, but aspect ratio is VERY important. Anything less than about 60 is not well suited to offroad use. I would recommend staying above 70 for best performance. (IE, 265/70R17, 285/75R16, etc... NOT 265/60R20...)
With less sidewall, the tire will be less tolerant to airing down before overheating becomes an issue due to excessive flex. With a limit on how much you can air down, you're stuck with a tire that is often still too hard for the terrain, and you can't get much flotation if you can't air down. Even if you are OK with a LOT of sidewall flex, you still don't get much elongation in contact patch at lower pressures, which is the primary benefit to airing down in soft surfaces.
Shocks:
Valving is everything, and the same series or brand shock can be valved differently for different applications. This means a 5100 may be valved to your taste on a Tacoma, but not for a Jeep TJ. It all depends on the priority of the tuner, and what vehicle they used. (Ie, how heavily accessorized it was...)
Knowing the valving style for a particular shock is key, and if possible, valving the shocks to your specific vehicle and needs provides the best result. Read this article... It explains things pretty well...
In my experience with my TJ, Bilstein's 5100 series (Digressive valving) are meant for bombing around in the desert. Washboard performance was not a priority of the tuning, though with a loaded vehicle, it is somewhat tolerable. OME Nitrocharger Sport shocks also seem to me to be digressive. The old OME "comfort ride" Nitrochargers were likely linear, or progressive. They were AWESOME for washboard and cobbled trails, but a bit soft for high speed travel in the rough. (I still want a set of these!!!)
I would try a set of Fox shocks, but the ones for my application (~1.5" lift) severely limit droop travel...
Last edited:
rruff
Explorer
Thanks for your post!
It's a shame more companies don't publish data or even mention how their shocks are valved. It seems that most offroad aftermarket shocks go the digressive route to give more handling stability and bigger bump performance.
It's a shame more companies don't publish data or even mention how their shocks are valved. It seems that most offroad aftermarket shocks go the digressive route to give more handling stability and bigger bump performance.
comptiger5000
Adventurer
As a note, Bilstein 7100s are linear valving from everything I've seen. I love mine as an all-around DD, off-road, high speed stuff, etc. shock.
Also, stiff shocks and soft springs won't fix it. It'll make it worse. Shocks need to be well matched to the springs (stiffer springs = stiffer shocks). If the shocks are too stiff for the springs, the ride will be harsh and the suspension won't want to move fast enough. If the shocks are too soft, the ride will be floaty / mushy / bouncy.
Also, stiff shocks and soft springs won't fix it. It'll make it worse. Shocks need to be well matched to the springs (stiffer springs = stiffer shocks). If the shocks are too stiff for the springs, the ride will be harsh and the suspension won't want to move fast enough. If the shocks are too soft, the ride will be floaty / mushy / bouncy.
1stDeuce
Explorer
Since Pinz can't see it, perhaps it isn't as clear as I thought...
In summary, the most marked improvements to the vehicle for travel over washboard are:
1. Run tires with as much sidewall as possible, and LOWER TIRE PRESSURE. Lowering tire pressure makes more difference than anything else you can do...
2. Choose shocks that are linear or progressively valved for best ability to allow the suspension to follow terrain without jarring the vehicle.
3. Larger tires improve ride over rough surfaces in general, when run at appropriate pressures.
4. This sounds dumb, but fix all the rattles in your vehicle you can. Your seat-of-the-pants-ometer will tell you a quiet vehicle rides smoother than a rattle trap, even when the ride is 100% the same.
XJOverlander
Member
My Xj is setup very well for high speed. running 14" 7100's Sb front and rear. custom valve stacks with a 30%increase in high speed rebound ( helps with my air bumps) fronts were 255/100 and rear was some funky custom valving they did for my jeep 246/94. for washboards you will need a resi shock, everything else will over heat quickly. lots of sidewall and around 18 psi help out alot. havent over heated a tire. my street pressure is 24 psi.
Martinjmpr
Wiffleball Batter
.
I've never understood the "wagon wheel" trend that seems to be infecting even trucks and off-road vehicles.
.
For road-bound performance vehicles, I can understand wanting as little sidewall as possible. Less sidewall flex means better cornering at high speeds because the tire will not be able to flex as much. Of course, the downside is a much rougher ride but where performance and speed are paramount, ride quality can be compromised. I can also understand the value of bigger wheels on road bound vehicles in that it allows for a bigger disc brake and thus better braking force.
.
But for a vehicle that spends time off-road, the big wheel/small sidewall combo has always seemed stupid to me. And with modern trucks and SUVs having every larger and larger wheels, it just seems like this awful trend is getting worse. Some half ton trucks and SUVs now come standard with 20" wheels, meaning that on a 30" tire you're going to have 5" or less of sidewall - seems like a TERRIBLE idea to me!
.
When I got my Suburban one of the first changes I made was to get rid of the factory 17" wheels (because they looked like crap) and replaced them with factory 16" wheels. At the time I got the 16's because (a) they were in good condition and cheap and (b) because I could get a set of 33" tires for almost $200 cheaper by going with 16's over 17's. With 16" wheels running 33's (285/75/16) I have ~ 8.5" of sidewall. That gives me plenty of room for airing down.
.
Of course, anymore it seems like the big brakes on trucks are requiring 17" wheels minimum, which is a shame. Not that I don't appreciate the increase in braking but it's a shame to lose that extra half inch of sidewall to a bigger wheel - it effectively means you need to run bigger and bigger tires (with the weight penalty that brings) in order to get the same capability.
SoCal Tom
Explorer
My JKU Sahara came with 18 wheels. The first upgrade was to find a set of 17 Rubicon take offs. If it weren't my daily driver I would go smaller.
Tom
Betarocker
Adventurer
The Bro-dozer trend is retarded. Sema was full of 24x14 and 24x16 wheels with rubber bands stretched around them. There's a risk of damaging rims driving over a shadow.
38" tires on my 18" wheels.
pappawheely
Autonomous4X4
A shadow, ha ha ha ha! That's sad but true. Known as "no profile" tires.