Tire pressure

Grenadiers

Adventurer
I have Continental HCS 14 R20 tires on our Saurer 6dm. The PSI rating on the sidewall is 120 psi. The tires currently have 95 psi in them since I bought the truck. The treadwear is not good. The center tread is wearing out faster than the outer tread. Under inflated tires, it’s usually the opposite. What is wrong here? Thanks!
 

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DiploStrat

Expedition Leader
120 PSI is the maximum pressure for maximum load. You need your load, by axle and the inflation chart for your tire. FWIW - My 917 at about 18,000 lb. runs in the neighborhood o 50-60 PSI and the wear is even. But run the numbers for yourself.
 

Grenadiers

Adventurer
We’re at 28,000 pounds, will do some research. Have the German language manual to look at. Wife reads and speaks German. She’ll be ‘excited’ I’m sure!
 

Grenadiers

Adventurer
I’m most concerned when it’s time to buy a new set; 6000 or so for four new ones! Have ‘tread time’ left to figure it out.
 
You are lucky you’re overinflated rather than under. Under inflated tires that big tend to explode long before they wear out. Weigh each axle separately. I suspect 60 psi will be enough for the front, 95 for the rear.
 

Grenadiers

Adventurer
Not sure of the unsprung weight, I’m sure it’s a lot, the axles are massive. The bare cabin unloaded is 2000 pounds. I’ll have to get it weighed.
 

Neil

Observer
I have often wondered how much increase in pressure is applied when going to altitude. If we are at 5 bar at sea level , how much at 5000m. Would people be adjusting their pressures as the ascend and decend. I dont but sometimes think i should

Neil.
 

DiploStrat

Expedition Leader
Neil,

When I lived at altitude, I would not bother to adjust for brief descents, and vice versa.


So when I lived in Guayaquil and drove to La Paz for about six weeks and did nothing. In any case, we often went up and down each day and over pressure is safer than under.

In your case, depends on how long you will stay up or down - more than a week or so I would adjust at sea level and altitude. Just grab your gauge and set appropriately for weight. Probably more important to adjust pressure when you descent than ascend.
 

mog

Explorer
MB 1017AF with 395/85-20 XZLs on Atlas MRAP rims, 13,940 lbs (Flatbed) to 16,660 (Camper), 55 psi front and rear has been working great.
 

Verkstad

Raggarkung
You might have to play with chalk or printing your tyres.
It was a lot of trial and error to get my Unimog tyres pattern looking good.

Btw, Cool truck. Extreme heavyduty,
One might think its a quarry truck just to look at its framerails and axels !
 

Joe917

Explorer
Completely wrong.
Our tires 315 80 22.5
Our weight 4700KG per axle
Continental recommended pressure 87 psi
 

Explorerinil

Observer
I put a line of chalk across the tire, drive down the street and see what part wore, I readjust the pressure until the entire line is gone within ruffly the same driving distance each time.... I hope that makes sense, lol it does to me at least.
 
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