Washboard Roads

[Topgun514]

Hey guys, I may want to post this in a more general area but I was wondering if there is any way to make or help my 88 Cherokee along washboards. I think the most viable option is airing down but what PSI is best and I would love to hear some ideas.

I just got back from a 1000 mile trip around Utah and Hole in the Rock outside of Escalante almost did me in. My muffler rattled off, a sway bar link popped, and my rear view mirror screw backed out. I know jeeps ride the exact opposite of Cadillac's but I preferred the hard offroading with 4Lo ANYDAY over a straight section of washboard now. The rattling and noise and nervousness was the worst.

Thanks!

 

[Martyn]

Airing down is good both for the ride, the vehicle and the tires themselves. The exact tire pressure needed to produce the best effect is a little bit of trial and error and depends on the vehicle and tires.

My Ford F250 normally runs 60-65 psi, on wash board I reduce the pressure to 30 psi to soften the ride. So for me it's a reduction of approx. 50%

 

[goodtimes]

Martyn is dead on.

In my Wrangler, I ran 33psi on the street, 9 - 10psi in the dirt.

In my Dodge (w/camper), I run 55 - 65 on the street (loaded), and 35 - 40 in the dirt.

 

[alexfm]

I run about 25psi on the street and about the same on the dirt (don't have a working air compressor right now), and I do ok on washboard roads. If possible/allowable go a little faster. Around 30mph you just coast on top of the ridges, and it rattles a lot less.

For the record, I've a 95 XJ, and I certainly know all about the rattling.

 

[Black Dog]

The best way I've found is to slow down. If you drive hard things are going to fall off.

 

[Martyn]

The best way I've found is to slow down. If you drive hard things are going to fall off.

Slowing down can be a good approach, the case for speeding up can also be argued.

No matter what speed you decide on going, lowering tire pressure off road reduces the potential for internal tire damage.

 

[HumphreyBear]

That's the reason washboards confuse a lot of people - there is no correct, cookie-cutter approach because they are pretty much different every time for every vehicle. The washboards vary depending on what created them.I find the widely spaced, deeper ribbing made by road trains much harder to judge/deal with than the shorter interval, shallower ribbing of small car/4WD washboard. I guess what I'm saying is you have to experiment to find the perfect balance based on your tyres, your wheelbase, your suspension, your weight and the specific washboard you're travelling.

Martin's nailed the best approach:
- let your tyres down enough that you get some extra suspension to pad out the vibration, but not so much you start to heat the tyre up. You are not 'off-road' and usually travelling relatively fast so watch you don't cook your tyres by letting out too much air;
- counter intuitively speeding up is often the best response, especially in short interval, shallow washboard made by the small tyres of a 4WD. The theory (or at least a theory) is that you 'float' from peak to peak. Your traction is often reduced during this so beware camber and bends whilst travelling at somewhat higher speeds.
- if you regularly do a lot of washboard then choose big full oil dampened shocks with large oil reservoirs of the absolute best brand you can find. Don't skimp as the end result of vibration damage or a new kidney will be more expensive.

If anyone can tell me how to navigate the road train washboards without losing a filling then I'm happy to hear suggestions! Maybe buy a Unimog with 46" tyres?

 

[Mel.Specs]

Slowing down can be a good approach, the case for speeding up can also be argued.

No matter what speed you decide on going, lowering tire pressure off road reduces the potential for internal tire damage.

And if damage does occur, you can always stitch it with dental floss.

 

[Hill Bill E.]

When running a lot of wash board or rough dirt roads, I usually ran my XJ w/33's around 16-18 psi, and the same for my TJ w/35's.

It helps a lot.

But, the best improvement I did for the ride, was installing a set of Bilstein 7100 shocks with remote reservoirs.

The Bilsteins are a great shock, add in the extra oil of the remote res', and they get better. Toss in the fact that the 7100's are rebuildable, and can be valved to fit your needs, and they are pure awesomeness!!

Been out to Moab, UT every spring for the last 5 years. We always have a 'mini Baja' run across the valley floor by 'Gooney Bird Rock' on our way out of Gemini Bridges road.

This was the first year that I made that run, and didn't loose any fillings! Nor did I loose/break any shock mounts, have any shock fade, or blown shocks.

They made a world of difference for the trip up to the 'Top of the World' trail, which is very rough.

As HumphreyBear said, get the best shock you can afford, one with a reservoir, or lots of oil. That and dropping some PSI will help out greatly with the ride.

 

[mizedog]

I agree. Lowing the tire pressure is the first step, then speed up within the limits of the road (watch for drifting sideways at speed). I did two weeks down the Baja penninsula in a 3/4 ton Chevy with about 500-800 pounds of water in the back (for our group of ten vehicles). We never lowered the psi due to the weight we carried. Boy did that really hurt. Taller tires and lower psi would have helped. Although I'm not convinced of the completeness of their method, Mythbusters did a show on this very subject. They first came up with some common, but wrong assumptions. Eventually, they agreed. High enough velocity that wil mean the tire hits the next peak sooner than the rebound of the shock/tire/spring combo gets you floating on the top.

 

[HillbillyfromAL]

What shocks do you have? If one is bad you can rattle to death. I don't find it necessary to lower tire pressure, but I check patterns instead of filing it up to what's on the sidewall. I'd bet that your shocks are either not charged, or just not up to the task of handling the abuse that washouts can give them. Get something heavy duty, and charged at a minimum. I like OME for vehicle/load specific, and the adjustable Rancho's if I'm running at different weights, like an empty/loaded truck bed. If you've already got the right shocks then I'd be looking into the springs as the problem. If they are too stif then the shocks won't be able to do much, too light and the truck will pick up a swaying rocking motion that can make you lose control. Good luck

 

[Martyn]

And if damage does occur, you can always stitch it with dental floss.

I'm still trying to decide if "Mint" or "Waxed" is best for tire repair