Yet another tire pressure question.

vonkal wrote:
Thanks Dennis. Are you suggesting I use the 85 and 95 lbs pressure, as the chart shows, +5? I would love to do this as the coach rides a little stiff now. The tires are currently at 115 on the front and 100 on the rear.

I have already installed a TPMS, and it seems to be working fine.

The coach is already what I would call "camping ready" with food, fuel, propane clothes, some tools, etc. I will watch the weights and pressures carefully, but if you think I should start with the recommended pressures, +5, I will do that and see how it goes. The TPMS gives me some confidence that I am not running it too low, and should let me know if I am in the ballpark.

I have set the reserves to zero and used the tire specifications for the first goodyear tire wich you gave in first post, so to my opinion wrong, and even conversed maximum load to max speed of 100km/62m/h , then advice 93F and 81R. But this would bring it to the limits. A little unequall loading R/L and/or misreading of pressure , and/or more loading,and/or higher speed, brings it in the danger-zone.

An inside tire temp of about 112degrF/45degrC, when driving about 60m/h, is normal and this gives a pressure rising from cold pressure filled at 18degrC/65degrF of about 10 to 11% . So if your TMPS gives that its most likely save for the tire.

Because driver and co driver are sitting above the front axle, front pressure has most effect on comfort. So you can leave rear to higher pressure.
But to my opinion the comfort wont get much better at 95 psi then at 115 psi front, but mayby your experience after the trip can make me chanche my opinion. This is because the construction of the suspencion of the motorhome that is in fact a middle weight Truck.

But mind that you dont feel what you expect and want to feel, try to be objective.

Have a nice trip

Perfect! I am leaving on a small weekend trip in a few hours. Perfect testing distance. I will change the pressure right now, and report back when we return. Thanks!

Given that it's camper ready then I would go 5 over on the front... 100. There is no need to go 5 over on the rear because at 85 you are good for 4770 which is already 400 lbs more than what each tire needs to carry. The 85 psi is the minimum needed to keep the tire on the rim and not flex too much but if you adjust the table downward... 75 would be enough for your 4363 so at 85 you are already 10 psi over.

Thanks Dennis. Are you suggesting I use the 85 and 95 lbs pressure, as the chart shows, +5? I would love to do this as the coach rides a little stiff now. The tires are currently at 115 on the front and 100 on the rear.

I have already installed a TPMS, and it seems to be working fine.

The coach is already what I would call "camping ready" with food, fuel, propane clothes, some tools, etc. I will watch the weights and pressures carefully, but if you think I should start with the recommended pressures, +5, I will do that and see how it goes. The TPMS gives me some confidence that I am not running it too low, and should let me know if I am in the ballpark.

Vonkal, if you want to run 100/110 that's up to you...it's your coach. You may find your coach to be light on the front as far as steering goes and a little squirrelly in the rear due to over inflation. You could always do the flour test if you're unsure.

First question is whether your coach was camping ready when you weighed it? You mention full fuel and water. That's good, as most of us only travel with 1/2 tank/water or less unless we're boondocking. Water weighs 8#/gal so removing 50 gallons of water give you 400# of "stuff" to carry, usually groceries without changing the dynamics of your weight. That said, once you load your coach with your camping goodies your weights may change due to how and where you store your stuff. This is why I add 5# to the recommended weight charts.

IMHO, load your coach for camping, full fuel, then weigh. Consult the Goodyear chart for proper PSI, add 5# for moving stuff around and you're set.

Finally, get yourself a good TPMS and install it. We use the TST 507, external sensors replaceable batteries. Besides PSI it also shows the tire temp. A locked or hanging caliper or bad bearing can overheat a tire to the point of catching fire. The temp portion of the TMPS can alert you well before that point is reached.

Good luck....I know a lot of this stuff is confusing as many people have opinions as to what is best. I tend to follow the recommendations of the engineers that work with the mfgs of the tires. Afterall they are the ones that have the knowledge and have done the testing to provide us with the best information.....Dennis

Escapees does 4 corner weighing at their locations. It costs $45. We just had ours done and it was quick and easy. Once you get the 4 corners weighed, you take the heaviest side and multiple by 2 and use that weight to get the pressure. Then go 5 pounds over that measurement.

Thanks for all of this great info. Doing this exercise has given me a better understanding of tire loading. Starting with a basically unloaded coach, I will use 100 lbs for the rears, and 110 on the front. This should give me a cushion while starting to load our belongings into the coach.

I will re-weigh once I have loaded it up, and make adjustments. I will also do the four corners as soon as I can.

Thanks to all!

Reaction to last post.
Another reason to always use as much possible reserve .
If you weigh per wheel by driving over scale with only for instance l right side and besides it ( where the left wheels drive over) is lower placed ( or higher) then you dont stop and go somewhere else, you are happy then you found a scale.
You will then have to do with the inacuracy .
Lower besides scale means to low weight given and higher besides scale means to high weight given, and it depends on the hight of the gravity point of the vehicle, and the level difference .
You could get an idea of howmuch inacuracy, if you estimat the level difference and asume a Hight of total gravity point of about 3 feet for a motorhome.
Same happens though by the roadcurve , right side a bit lower then left side. ( in UK where left driving the other way around).

Once made a picture , dont mind the Dutch text, the picture will make it clear enaugh for you. Totaal zwaartepunt = total gravity point, and Rechts is Right and Links is Left.

If you do get a four corner weight make sure that it is done properly. The coach must be kept perfectly level for the weights to be accurate. If it is LEANING off to the side, with one set of wheels on the scale, the weight will be too light.

Also seached the tire sises and loadkind from Michelin.
Will give both pictures in this post and below that will give my idea what has been done here.

First the goodyear data



and now same sise from Michelin.



What to my opinion has been done by goodyear is that the tire was originaly calculated in maximum load for 9 bar wich is conversed to 130 psi.
this gives single 6940 lbs maxload = LI 148, wich is also given at Goodyear list list at top for 125 psi.
Later they realised that for 125 or 120 psi the maximum load has to be recalculated to lower.
The G159 list gives 6610 lbs maxload at 125 psi wich is Loadindex 146. If you look at Michelin list at 125 psi you see 13460 axle = 6730 a tire loadcapacity wich is yust below LI 147/6780 lbs so rounded down to LI 146.

So this strongens my opinion to use the lower maxload tire in the goodyear list.