How fast could or should I go?

Lately I really got into hiking.
To reach the trailheads often I have to travel on forest service roads. Sometimes I cover 3 miles or 15 miles one way on these gravel roads with potholes. The quality of these roads fluctuates a lot. Obviously I am driving with a speed corresponding to the road conditions, but potholes have a tendency to pop up behind curves or in shady spots so it is difficult to impossible to spot them. My question is how much “abuse” a suspension and a frame can take on these roads? The vehicle in question is a 4x4 pickup truck.
Thank you for your insights!

Any idea how this could be measured? Speed alone isn’t useful as potholes come in all sizes. The worst can swallow your whole truck.

Go slowly,young fellow,speed is usually what creates the pot holes to start with or you could hike to the trailheads,by the time you get there you may already feel that you have had your hike. I used to have this discussion with a govt inspector on why the nice govt(taxpayer roads) were closed to everybody except timber cutters and hunters

Just like the “red line” on a tachometer, there really is no well defined speed where abuse suddenly starts. How long do you want your truck to last? What’s your definition of “worn out”?
It’s like defining where the atmosphere ends and space begins. The 62 mile Karman Line was based on Karman calculating that at this altitude, the stall speed of an aircraft begins to be higher than the velocity needed to be in orbit. NASA uses 76 miles as the altitude where a re-entering space shuttle can quit steering with thrusters and begin steering with control surfaces. For human survival without breathing pure oxygen, the altitude of Mt Everest is about the limit.

I feel that like the Karman line that defines where space begins, there is a speed where the cost of operating the vehicle is so high that driving no longer beats walking. By the time I could earn enough money to take a F-1 car around a race track for one lap, I could easily have walked that distance, many times over.
I think we need to call that speed the “B.L.E. Line”.

Test it and let us know.
You must realize that there’s absolutely no way we could even come close to guessing the answer to this without knowing the truck and the road.

+1 to mountainbike’s comment.
In order for us to make any recommendations, we really need the OP to tell us how often he is willing to replace his shock absorbers and how often he is willing to have his front end realigned.

If increased maintenance costs are not a problem for him, then…Have at it, mate!

Thanks for the replies.
Maybe I was not clear enough. I am in no hurry and I am not racing on these roads. But let us say part of the road is nice and smooth and it is okay to go maybe 20 mph. Now if I hit a pothole (that would be big for a passenger car) could the truck’s suspension is better suited, sturdier to withstand the impact? Are they designed for this or just for putting some stuff to haul around in the bed?


Let’s talk about this 4x4 truck . . .

If it’s got independent front suspension, I’d be a little more careful

What kind of transfer case?

You’re shifting into 4LO, yes?

A 4X4 pickup truck is designed to handle some potholes. Just take it easy and watch out for large stones or stumps that may have been washed down over the winter. I was raised on a farm located on a gravel road and that’s exactly what my dad told me. We got a good 10 years out of our trucks.

@db4690 it has a 4 lo setting but I did not have to use it. The front suspension is independent but I am not doing any off roading and if anything on the way that looks sketchy I just turn around. Not crawling over stumps or boulders or anything like that. Some hikers are driving regular cars on these roads but I just do not think that that is a good idea. On my very first hike I was driving my car and I was driving it very slowly. Since then I do a research before an outing and if the trail is not accessible from the main road, (gravel road is the way in) then i just drive my truck because it is better suited for the conditions.
@Docnick, good suggestion. I am driving slow but sometimes there is no way to avoid potholes.
Now with the snow in the mountains the only way to hike is to park on the main road and snowshoe in on the FSRs.

I can tell you that all manufacturers or cars and trucks drive them over roads that cause the vehicles to slam their compression and extension stops as well as hop the tires up and down many times between each crash-through.

Picture very badly installed cobblestones driven at 35-45 mph until the vehicle falls apart or finishes the cycle. Usually 10,000 miles with cool down stops every 20 minutes so the shock absorber fluid doesn’t burn the seals right out of the shock. (275 F or so). It is also so the drivers can take a break so they don’t urinate blood after the shift ends. This is designed to speed up durability testing and to test the worst case conditions.

So the bottom line is, if YOU can stand it, the truck can, too. But you will shorten the life of the chassis bits in the process. So, if it hurts, slow down.

Whatever kind of truck this is, and you haven’t told us, you might also do some research and see if it’ll take a wider rim with larger tires. More cushion can’t hurt.

If someone has to ask how fast to drive on unpaved roads maybe they should not drive on unpaved roads.

Driving on dirt roads with pot holes can be less harmful then driving on the interstate and hitting one at 70 mph. They are often less harmful with a truck like yours. It is no different then a city street with potholes which can be worse. The key is to drive at slower speeds. On rough roads with pot hole potential, my absolute top speed is twenty mph if you want to save a suspension, then drop from there. I tend to drive slow enough I can avoid them by steering without having to brake all the time. My advice is, mathmatically speaking, less then or equal to 20 mph. I have always had at least one vehicle designed for off road use with oversized tires and HD suspension. We drive very slowly off roads. But contrary to popular belief, they are not designed To hit potholes at high speeds unless the tires are really oversized and very low pressure. So Drive slowly as in any car. I don’t actually hit a pot hole higher then 10 mph if at all possible while traveling at 20 to avoid them over dirt roads.

Btw, we do a lot of hiking and I know the road types you mean. Flying rocks and debris is a big problem for other cars too as well as your own under carriage if you drive too fast.

Thank you for the replies.
@Mustangman now I know something about stress testing.
@the same mountainbike‌ you are right I should have mentioned the truck, it is a Dodge Dakota with factory tires rims P265/70 R16.
@dagosa‌ it is good to know that yes the suspension is tougher but still not designed for abuse.

These vehicles will “fool” you. They can seem to travel at much higher speeds more comfortably with the larger tires. But over time, tie rod and sway bar ends and other components start to rattle earlier, just like any other kind vehicle with the abuse.

Tirerack shows a number of different tire/wheel options for the Dakota depending on the cab type, model, year, and options. You might want to visit their site to see what your options are.

I think a good rule of thumb is, if it feels like you are abusing the truck, you probably are. Like I stated in an earlier post, there is no well defined line where abuse suddenly begins.

If someone has to ask how fast to drive on unpaved roads maybe they should not drive on unpaved roads.

That’s the answer I was waiting for.

it is a Dodge Dakota with factory tires rims P265/70 R16.

This truck should never be driven on anything other than glass smooth paved surfaces.

I think a good rule of thumb is, if it feels like you are abusing the truck, you probably are. Like I stated in an earlier post, there is no well defined line where abuse suddenly begins.

Best answer besides going back to the first quote.

@ PvtPublic thank you for repeating the quote from VolvoV70. If he would have bothered to read the whole discussion then he should have realized that this is not about speed racing on dirt tracks. Maybe I made a mistake with the title. I should have asked how slow should I go on gravel roads to ensure the longevity of my vehicle. As for your second quote please let this know every city, village and jurisdiction in all 50 states because you would be hard pressed to find the roads that you described.

Thank you for all the constructive ideas and advice, and no thank you for the less than useful ones.
@cdaquila please feel free to close this discussion. I have got the answers that I was looking for.
Thank you.