Kumho 857s, pressure?

[Steve_B_]

Just put new Kumho 857s on my trailer, 205 14 Wondering what tire pressure other folks are running them at. Thanks.

[Steve_B_]

First, I did find a plate on the trailer with the tire size (the size I bought) and pressure - 35psi.
After reading all of the comments from all of you, I can't say I'm much more clear about what to do. I may go with one poster and go to about 45psi. Tire Rack did say to go with whatever the trailer manufacturer recommended, even though the max is 65psi. That seems mighty high to me so I don't think I will go to the max. Thanks for all of your input! As long as I get to Maine and back in September, I'll be happy.

[JIMNLIN]

EcoBullet wrote:

JIMNLIN wrote:
Unless you over tired the trailers axle rating and the wheels pressure capacity its advised to run the tires max sidewall pressure.

Please educate me. Where does this come from? Is it just a trailer tire thing? Sidewall on my truck tires say 44 lbs MAXIMUM, but door jamb sticker says 35 lbs.

What Larry says.
IMO tireman9 brings up a good point also in his rvtiresafety.com blog
In part;
"The manufacturers do not take into consideration the side to side unbalance, as to do so would require them to provide larger (more expensive) tires. The other thing RV industry does not take into consideration is the forces to the tire structure due to running close axle spacing. Engineering analysis shows that when turning corners the forces trying to tear the tire apart can be over 20% higher in multi-axle applications than with tires at the corners of the vehicle.
The only options for the trailer owner are to up-size the tires (if there is room) or up-rate and increase inflation (if a higher Load Range tire and stronger wheels are available). Lacking the above being sure to run the tire at the inflation shown on the sidewall (i.e. max) will slightly decrease but not eliminate the overload forces."

Wheel pressure can be a placard or indentation on the front back or in the wheel well which requires the tire to be taken off the wheel.

[EcoBullet]

Thanks folks! Next question: Is there an easy way to determine max pressure rating of wheels? Mine are aluminum. 65 isn't a huge jump from 50, but still, I don't want to ruin a wheel because of my stupidity.

[LarryJM]

EcoBullet wrote:

LarryJM wrote:
On a trailer you don't have to worry so much about 100% max road contact nor are dealing with steerable tires or the normal vehicle NVH issues where overpressure can have a negative impact on those.
Larry

Thanks Larry! What are NVH issues?

Assuming you have upgraded tires for more reserve capacity and you have overinflated for the load, won't you start wearing out the center of the tread? As an example: Lets say I put tires on my trailer that have a stated capacity of 2094 lbs each single, 1984 dual, at 65 psi and my trailer only weighs 5,500 pounds.

Perhaps this isn't a big issue for most of us since our tires will need replacement because of age before the tread wears out?

NVH is Noise, Vibration and Harshness which comprise ride quality in vehicles. It really is not applicable to trailers since they are not normally manned when in motion. I know a lot say you should have shocks and even balance TT tires, but unless things are WAY, WAY out of whack who cares if the trailer ride as we would describe it to be ROUGH. My take is that the simple springs or rubber in torflex type axles along with the tires provide all the ride quality needed in a TT and even balancing is again IMO of questionable benefit.

Your comment about the wear while has merit at first glance is again not that important in TT tires because of the lack of the type of reserve capacity in TT tires normally vs. what one might see in passenger type tires along with the normal life expectency of TT tires being time due to deterioration and not to mileage makes this concern basically mute.

As I mentioned in my first post TT tires, especially ST tires should be run at a much higher inflation than those maybe on a passenger type vehicle, because of scrubbing during turns and even curbing and other road hazards. Finally, a loaded TT can have a much higher delta wt. wise than a typical passenger vehicle because you have to account for the varying levels of extra liquids that can approach 120 to 200 gal and that is over a 10% variance approaching 20% on a 10K GVWR trailer. Thus the tires need to be inflated to account for supporting that extra often unknown exact weight.

Larry

[Heymon]

I don't think there is any reason why one should not run trailer tires at anything less than max pressure per the sidewall. Trailer tire problems are very often caused by under-inflated tires. My guess is that your rims can handle the pressure if they are the typical steel rims. My rims don't have a max pressure designation on them (that I can find) but I run at 65 psi so my tires last. I have not heard of too many problems from tires (or rims) run at max pressure.

[patperry2766]

I do 65 PSI on mine.

I know that there was shortage of the 205 75R 14 a couple of months ago, so I dont know if the stock is being replenished, but when I got mine in July, I personally called the Kuhmo customer service # and they said that there were only 8 tires in the entire country. My next call was to my tire store to get me two of them.

NVH is primarily an automotive term that stands for noise, vibration and harshness.

The sources of noise in a vehicle are many, including the engine, driveline, tire contact patch and road surface, brakes, and wind. Noise from cooling fans, or the HVAC, alternator, and other engine accessories is also fairly common. Many problems are generated as either vibration or noise, transmitted via a variety of paths, and then radiated acoustically into the cabin. These are classified as "structure-borne" noise. Others are generated acoustically and propagated by airborne paths. Structure-borne noise is attenuated by isolation, while airborne noise is reduced by absorption or through the use of barrier materials. Vibrations are sensed at the steering wheel, the seat, armrests, or the floor and pedals. Some problems are sensed visually - such as the vibration of the rear-view mirror or header rail on open-topped cars.(Wikipedia)

[pasusan]

When we bought our Kumhos there was a chart on Tire Rack that showed different pressures for different rated tires by weight carried.

I'm sorry, I haven't been able to find that chart this morning or I would link to it. Our tires max pressure is 65 lbs. The plate on the side of our trailer says 35 lbs. According to that above mentioned chart and as a sort of in-between point I put in 44.

Why put in less than on the sidewall? Because the ride is less bouncy and I'm not sure the rims will take that much pressure.

We have a TPMS and the trailer tires raise in temperature the same as the truck tires (which also are not aired to the max on the sidewall).

Hope this helps...

[EcoBullet]

LarryJM wrote:
On a trailer you don't have to worry so much about 100% max road contact nor are dealing with steerable tires or the normal vehicle NVH issues where overpressure can have a negative impact on those.
Larry

Thanks Larry! What are NVH issues?

Assuming you have upgraded tires for more reserve capacity and you have overinflated for the load, won't you start wearing out the center of the tread? As an example: Lets say I put tires on my trailer that have a stated capacity of 2094 lbs each single, 1984 dual, at 65 psi and my trailer only weighs 5,500 pounds.

Perhaps this isn't a big issue for most of us since our tires will need replacement because of age before the tread wears out?

[LarryJM]

EcoBullet wrote:

JIMNLIN wrote:
Unless you over tired the trailers axle rating and the wheels pressure capacity its advised to run the tires max sidewall pressure.

Please educate me. Where does this come from? Is it just a trailer tire thing? Sidewall on my truck tires say 44 lbs MAXIMUM, but door jamb sticker says 35 lbs.

Inflation information for vehicles is a COMPLETELY DIFFERENT scenario than trailers. Typically vehicle inflation pressures take into account the GAWR of the axle and closely match the tire inflation pressure load to that number. GENERALLY trailer tires, especially ST tires don't have hugh reserves unless you have upgraded the tires plus because of the unique stresses on TT tires running them at the max pressure on the trailer sidewall gives you the best service. On a trailer you don't have to worry so much about 100% max road contact nor are dealing with steerable tires or the normal vehicle NVH issues where overpressure can have a negative impact on those. There might be a few exception like some trailers that are in the high end weight and use 16" E rated truck tires where inflating those to the max sidewall would give one HUGE (like 4K and up excess capacity) reserves so a somewhat reduced inflation pressure might be called for.

Larry

[hddecker]

EcoBullet wrote:

JIMNLIN wrote:
Unless you over tired the trailers axle rating and the wheels pressure capacity its advised to run the tires max sidewall pressure.

Please educate me. Where does this come from? Is it just a trailer tire thing? Sidewall on my truck tires say 44 lbs MAXIMUM, but door jamb sticker says 35 lbs.

Ever since the tire issues Ford had back in the 90's with Firestone tires on the Explorer, I go with the tire sidewall.

Ford had a different pressure on the door sticker than Firestone had on the sidewall. Of course Firestone blamed Ford and Ford blamed Firestone for all of the tire failures that caused the wrecks.

The tire sidewall pressure gives you the maximum load capacity for the tire, a lower pressure reduces the load capacity.

[EcoBullet]

JIMNLIN wrote:
Unless you over tired the trailers axle rating and the wheels pressure capacity its advised to run the tires max sidewall pressure.

Please educate me. Where does this come from? Is it just a trailer tire thing? Sidewall on my truck tires say 44 lbs MAXIMUM, but door jamb sticker says 35 lbs.

[JIMNLIN]

Unless you over tired the trailers axle rating and the wheels pressure capacity its advised to run the tires max sidewall pressure.

[EcoBullet]

I was going to replace a couple of tires with the Kumho 857, but my local tire store said he couldn't get them. He did have the Hankook RA08 which has the same specs, having a higher speed rating and load capacity than the original tires. Sidewall says max pressure is 65, but I plan to run 60, since my trailer is several thousand pounds lighter than the total load these tires are rated for. Incidentally, the tires are not for the trailer in signature, they are for a boat trailer with the same size tire.

[rexlion]

Steve B., are you saying that Kumho is no longer making tires?

I would run them at max, which I believe is 44 psi. That is, unless your trailer weighs only about half of the max load rating for the tires, in which case I could see dropping the pressure.