Best way to drive washboard in a Fuso?

[kerry]

Took the truck into Chaco Canyon over the weekend. 16 miles of the worse washboard I've ever seen and I've driven on a fair amount of it. Chacoans were known as exacting road builders but they must have taken their road grader with them when they left in 1150 and nobody has bothered to take another one down there. Experimented with a couple of methods. 23+ mph was relatively smooth. I think the tires were only hitting the tops of the ridges since the speed was high enough that there wasn't time for the wheels to drop into the troughs. However there were two problems. 1. I think it was unsafe due to such little road contact between tire and road surface. 2.--this was the big one--if you had to slow down while on the washboard, once you dropped below about 21 mph, the shaking and hammering was horrific down to about 1 mph. The only way it would have been feasible was if you could hit the washboard at that speed and maintain that speed until you came off it onto smooth road. Not an option on this road due to tight turns and traffic. So, I ended up using the other option, granny low with the speed so slow it wasn't registering on the speedometer. It was like driving over a continuous serious of speed bumps about 18" apart.
The washboard is not like your typical dirt road with two ruts of washboard and smoother dirt outside the ruts. This washboard is uniform from berm to berm and frequently 4-6" tall. There were places where the road was clay and hard packed but most of it was loose dirt/sand and washboarded. There were a few places with about 1' of sand on the end of the washboard before the ditch of sand but in most of those places you could see where people were running with their right tires on that narrow lip and got sucked off into the sand ditch and stuck. The conditions are a result of very high traffic flow due to the popularity of the destination and the fact that the Native Americans own the road into the park and don't want to keep it useable since they don't like the fact that the park exists.
Are there techniques I didn't figure out. There are one or two houses on the road about halfway out. A local past us heading out as we were heading in. It sounded like every bolt and nut on his truck was rattling as he headed out.

 

[FusoFG]

We have the same problem on the Flag-Ashton Rd south of Yellowstone NP and the road to Polebridge, MT near Glacier NP in our 11,000 pound Fuso camper. We air down the front tires to 40-50 psi and the dual rear tires to 20-25 psi and drive 15-20 mph.

 

[pugslyyy]

The biggest danger to running at 'smooth' speed on washboard is the workout it gives your suspension. Shocks can overheat and fail in as little as a few minutes. Air down + go slow is the only safe (vehicle preserving) choice... unfortunately.

I've gone very fast on washboard, but on vehicles that were set up for it (at least dual shock, remote reservoir, etc)... and I was younger then.

 

[fluffyprinceton]

We have the same problem on the Flag-Ashton Rd south of Yellowstone NP and the road to Polebridge, MT near Glacier NP in our 11,000 pound Fuso camper. We air down the front tires to 40-50 psi and the dual rear tires to 20-25 psi and drive 15-20 mph.

that's the only "solution" I know of...

We got up to 20mph twice...mostly it was about 10mph on the Racetrack Rd. in Death Valley last trip - still rough & a very tedious drive but beautiful once you stop listening to your truck...

You know, I've wondered about your rough experiences with the FG's ride - then I trailered my 8700 lb(4000Kg) boat with a 400-500 lb (180kg-225Kg) tongue weight and got launched into the cab ceiling several times..What's your weight distribution front to rear? Mine's 50/50 yours looks rear heavy...just a thought. Moe

 

[kerry]

Here's a picture:

 

[kerry]

Can't remember my exact weight distribution at the moment. I have it written down somewhere. Our ride is vastly improved and I don't complain anymore now that I have the Aeon Rubber (Timbrens) graduated bump stops and new OE shocks.

 

[westyss]

That racetrack road is awefull! Airing down really is one of the best ways to make it a bit better but not great, I will go pretty low on the front, down in the 25psi range and around forty in the rears and that helps some.
If able, a low tire pressure and speed works great but if the frequency is wrong things can go pretty bad if the vibrations create an out of control state. Go slow and take your time is the best way, that way you can put it in gear and have a walk along side while under way for some excercise!

 

[Overland Hadley]

Here's a picture:

Yeah, that looks brutal. I hate washboard roads!

 

[FusoFG]

Can't remember my exact weight distribution at the moment. I have it written down somewhere. Our ride is vastly improved and I don't complain anymore now that I have the Aeon Rubber (Timbrens) graduated bump stops and new OE shocks.

If the bump stops and shocks don't improve the ride on washboard roads, what type roads do they improve the ride on?

 

[kerry]

They improve the ride on washboard roads and all roads. I can't imagine what it would have been like driving on that washboard without Aeons. I wouldn't have an fillings left in my mouth for sure.

 

[blackduck]

16 miles of the worse washboard I've ever seen and I've driven on a fair amount of it. .

Looks a lot like the road out to Mt Augustus in northern West Aus. except that one goes for about 600 miles
only way to tackle it, put up with the rough ride till you can stride over the top of the peaks
35+ miles an hour normally does it in my canter
bit hairy when you hit a washout though

 

[Tony LEE]

Looks a lot like the road out to Mt Augustus in northern West Aus. except that one goes for about 600 miles
only way to tackle it, put up with the rough ride till you can stride over the top of the peaks
35+ miles an hour normally does it in my canter
bit hairy when you hit a washout though

Crack Mercedes team thought they would try that method in being the first factory team to conquer the infamous Canning Stock Route. Didn't work and they blew the shocks on all the standard models.
At the other end of the spectrum, silly old fart Tony Lee and decrepit copilot - sans factory mechanics team, caterers and media contingent - driving a 20 year old OKA with no special preparation and no add on enhancements managed to tootle 2000km from one end to the other with the only problem being to replace a 20 year old pre-strainer from one of the fuel tanks.
We were passed by a pair of identical high end big 4x4s, each towing a high end KK camper and their jeering suggestion to my offer to trundle behind to pick up the pieces was "Oh, you just have to ride the tops of the corrugations and anyway, our campers have racing shocks Ha ha"

We caught up with them a few wells later and while we sat around sipping our wine, one of them spent all day reinforcing his camper. Every half hour there was a muffled curse as he broke yet another of his rapidly diminishing supply of hacksaw blades. I completely forgot I was carrying an angle grinder that might have made his job a lot easier.

Sorry, not really relevant to this forum because I know how rough a ride you blokes have just driving along smooth freeways so corrugations must be spine-fracturing:smiley_drive:

 

[gait]

35 years ago I regularly drove a clapped out MkII Jaguar at speed on heavily corrugated all weather laterite roads in central Africa. The roads are heavily cambered for the wet which made negotiating corners at speed possible. There was though a distinct sense of not quite being in control. On at least one occasion an oncoming vehicle left us driving through a right hand bend on the right hand side with full power and full left lock. Apart from the rear cantilever springs falling out of their chassis mounts a few times and the contacts breaking on a voltage regulator there were no problems. There was also enough power to drag the front wheels out of ditches if resting on the chassis. My MGA sports car with rock hard suspension was a different, back breaking, proposition.

These days, I plod along in the Canter. Doesn't seem to matter how long it takes me. I seem to get there ok. The parabolics help. I try to attain more comfort than higher speed. I can't imagine trying to cruise over the top of corrugations with our 4.5 tonne for long distances. I'm also mindful that I'm 30,000km from home and support.

As well as tyre pressure 4wd helps a bit. My analysis is it drives the front wheels over the corrugations rather than pushing the wheels into them. Similarly, for intermittent corrugations I find it easier to drive through them rather than trying to slow in the middle of them. Braking is bad news - just as well I don't drive on the brakes anyway. The exhaust retarder is my friend.

For us there's usually a "right" speed for regular corrugations (like those in the pictures) which is relatively slow. The nature of the corrugations (height, frequency, hardness) and thus the speed depends on the other traffic is (trucks, buses, consumer 4wds, etc) and on the underlying road bed (sand, laterite, gravel, etc) as well as straightness / hilliness. Something about the relative height / frequency of the corrugations in the photo suggest to me they would be uncomfortable at any speed and destructive at high speed.

For hilly / twisty roads the worst corrugations usually occur where other vehicles are under power, going up hill or accelerating out of corners. As well as when they brake. I usually manage to drive so I'm not surprised by the changes and enter them at about the right speed. "Out of phase" with other drivers I guess.

Time of day helps as the sun can highlight or hide changes in corrugations. We tend to be more cautious when we have difficulty reading the road.

FWIW the most uncomfortable roads for us seem to have been concrete roads with tarmac on top. Long frequency undulations with a bump at every join plus potholes with hard edges. It was a German Autobahn that finished off one of our original rear leaves. Strangely, the culverts (drains under roads) on some Swedish roads slowed us, they'd subsided and occurred roughly every 100m. Hardly worth accelerating to slow down for the next one. How rough was unpredictable. Worse than those half round speed bumps. Unfinished Mongolian roads with 3" sharp stones were diabolical but usually had old tracks alongside them.

I'm the proud owner of one hacksaw blade which has been used many times in the last couple of years and should see us home - not to suggest we haven't had problems but its generally all about technique whether its hacksaw or driving.

 

[fluffyprinceton]

As well as tyre pressure 4wd helps a bit. My analysis is it drives the front wheels over the corrugations rather than pushing the wheels into them. Similarly, for intermittent corrugations I find it easier to drive through them rather than trying to slow in the middle of them.

That's a new one I'll try...thanks for the idea. Excellent post on a difficult subject - you have the right attitude which I think is 90% of the solution. For me - I asked for it - those miserable roads are what I have an FG for and it's harder for me than for the truck so...all is right in the world ( but then again I don't have 2000km of it smiling at me), really appreciate you Aussies perspective, you guys are the real deal. Moe

 

[Amesz00]

gait
As well as tyre pressure 4wd helps a bit. My analysis is it drives the front wheels over the corrugations rather than pushing the wheels into them. Similarly, for intermittent corrugations I find it easier to drive through them rather than trying to slow in the middle of them.

the man speaks the truth.
i found with my 649 FG, if i tried to drive over them in RWD, the back end would just skip and jump around. as well as being rougher, it seemed to shock the drivetrain more, and was far too 'tail-happy' (and i suspect used alot more fuel). it would often not go above 40 or 50, you could feel all the drive just getting lost thru the rear axle skipping around. then go 4wd, much smoother, more control etc. could get up to whatever speed was required much more easily and safely.
tyre diametre plays a huge part. my old 649 had 1100r16s @38" dia, and on stock suspension handled badly currugated tracks better than a mates 80 series cruiser with coils, but 32" tyres.
tyres pressures do play a massive part. ive seen a MAN 4x4 (which are renown for having very strong front axles, compared to jap trucks) in the kimberley region of northern WA, which is very corrugated and lots of shelf rocks, with a snapped front axle. the guy didnt have a clue and hadnt lowered his tyres at all, they were at 70 or 80psi...
i have likewise found on most roads there is a speed you can get up to that smoothes the ride mostly, except on the canning stock route. the ridges were so randomly spaced that the only thing to do was go soft tyres, and about 20km/h..