tire pressure, am I doing it correctly

[I-RV]

Bill Of Material

[kohersh]

Originally Posted by I-RV

Bill Of Material

I-RV, that's great advice, thankfully Phil gave me the same advice a few weeks ago when I posed the initial question of tire pressure. He also told me to speak to Randy who straightened me out. I was bound for Gaffney anyhow so now I'm riding around on the 12k axles after the bag swap and the 275/80s I referenced earlier...SO....I've got the beefed up 390 also. And my question today it was really get around how to air up the new setup, and it came from the disbelief in my tire guys eyes today when I told him I wanted 85 pounds. I have the us charts, it was the euro chart in wanted to look at that the other poster referenced. What I want to know more than anything is what level of belief the mainstream has that the US specs are purposefully low

I think for those who have had these mods done we should unofficially change their designation to a 390-50!

[5456Mich]

Originally Posted by kohersh

They did the same for me, except I upgraded wheels seeing the new tires as a winfall on a 4 year old used coach. Terrific service, Randy is the man

Kohersh if you don't mind me asking , how much was the upgrade to purchase the alum. wheels ? Thanks.

[5456Mich]

Well sent off an e-mail to Randy and received a reply within 20 mins. He is requesting a weigh in for the coach but stated that they could do the mods in S.C. Yippy-KI-Yay !

[I-RV]

Great to hear that Joe. That is how mine was done at the Gaffney Freightliner Oasis. They have nice over-night camp sites with electric and potable water nearby. Freightliner does the work, but is covered by FR.

[kohersh]

Joe, I am working on a write up for my aluminum wheel swap over, to explain it all ion detail because there is not enough on here about it. Freightliner is going to tell you its 3k....that is plain and simple what it is for them to do the work and a large part of it is the labor and the accessories needed to finish off the installation. Expect to wait weeks to months for the wheels to arrive. I went a different route, it was less money and looks nice. It was $1,985 for everything I needed and FR footed the mount and balance as part of the GVWR increase.

[accumack]

We've been waiting since June for Forest River to find a location near Southern California where we are staying to have this upgrade done.

[boowho]

Originally Posted by accumack

We've been waiting since June for Forest River to find a location near Southern California where we are staying to have this upgrade done.

FR HIGHLY prefers to have the upgrade done at either Gaffney, SC OR their own plant in Elkhart. This is because, those two locations know of this over weight issue and are better prepared to fix it.

At least that's the story. Maybe it's just cheaper for FR if they use one of those two locations?

I took mine to Elkhart from AZ and I spent $500 on fuel for the whole trip. Still, for 6 new tires (the existing ones were three years old) I think I came out OK.

Boowho??

[accumack]

We don't want to ride across country in an overweight coach. We grew up on the East coast and have no desire to go back. Also lately we have seen a couple of RV's stopped at portable spot truck inspection / weigh points here in Southern California and don't want to push our luck. We were back to the factory in late 2012 for issues that a dealer didn't fix and don't want to do it again.

[I-RV]

Originally Posted by 5456Mich

Well sent off an e-mail to Randy and received a reply within 20 mins. He is requesting a weigh in for the coach but stated that they could do the mods in S.C. Yippy-KI-Yay !

Joe; I cannot guide you for aluminum wheels; I will stick with the steel ones. However, it would be in your best interest to have the aluminum wheels put on at the same time as your new tires. It will save you $$$

[5456Mich]

Originally Posted by kohersh

Joe, I am working on a write up for my aluminum wheel swap over, to explain it all ion detail because there is not enough on here about it. Freightliner is going to tell you its 3k....that is plain and simple what it is for them to do the work and a large part of it is the labor and the accessories needed to finish off the installation. Expect to wait weeks to months for the wheels to arrive. I went a different route, it was less money and looks nice. It was $1,985 for everything I needed and FR footed the mount and balance as part of the GVWR increase.

Kohersh,

Can you answer a couple of questions while I look up wheels and dream.

Were the stock studs sufficient in length?
RATED AT 7400 LBS PER WHEEL,,, 45LBS PER WHEEL
Number of Bolts: 10

Bolt Pattern: 10 ON 285MM HUB PILOTED

Hub Bore: 220MMDoes the info directly above look right to fit our coaches ?
Thanks

[kohersh]

Hang on i never specified that I bought Alcoa Dura Brite treated wheels, which are more expensive than polished wheels, so that added to by bottom line.

We are 285.75mm bolt spacing. It is hub piloted 10 lug 22.5 x 8.25 as I understand it these are pretty much standard truck wheels. Yes the studs are plenty long, that confused me too there is not much info on it but in a nutshell the extra stuff FL sells you is to attach their pretty shiny hub covers to the hub. Most of the aftermarket covers wont fit, because of the studs...but, i bought the alcoa covers which are held in place in between the nut covers...so no need to worry about brackets or any of that. Main difference I see between these is the stylizing around the holes, I think the Accurides that FL buys have this stylized triangular-ovally opening, whereas these are simple round holes. They all look awesome compared to the simulators

I bought mine from Buy Truck Wheels | Accuride & Alcoa Wheels Buy Truck Wheels
You can chat online or call, the guys name is Paul and he is really helpful.
your stealing my thunder here i'll elaborate on another thread

[Tireman9]

Some general comments.

To my knowledge there are only two actual tire engineers on the various RV forums out there and the other one hasn't posted on this thread.

Some FACTS
- The Load Inflation tables only give you the MINIMUM inflation needed to carry the stated load on a tire.

- Load is seldom split 50/50 side to side so getting the individual "corner" loads or at least doing the calculations is important to establish the MINIMUM inflation needed.

- So you don't have to chase your tail when the ambient temperature changes it is suggested that a margin on +10% be used above that minimum inflation. Remember pressure changes 2% for a 10F change in temperature.

- Inflation pressures are the "cold" pressure i.e. when the tires have not been driven on got the previous 2 hours and the tire has not been in direct sunlight for the last 2 hours.

- In testing of pressure gauges at various RV events 10% to 15% of gauges are off by more than 5 psi.

- 30,000+ RV weighings show that more than half have one or more tire and/or axle in overload

- Using a TPMS can provide warning of impending failure due to air leak and a system can pay for itself with a single such warning.

[boowho]

Originally Posted by accumack

We don't want to ride across country in an overweight coach. We grew up on the East coast and have no desire to go back.

X2. I'm a real Western USA bigot!!

Hope you get it fixed close to home.

Boowho??

[jadatis]

Originally Posted by kohersh

Could you attach a link to these Euro tires load pressure chart that your referencing., this is interesting stuff.

Was a search to find European list.
But found it and searched your tyres.
Tire and Retread Selector | Michelin Truck
EDIT: tried it out and you have to push the "loads & Pressure"button to give the pressure /loadcapacity list in KG and LBS and kPa and PSI ( 100 kpa =1 bar=14.5 psi)
From this you can search all the other tires .
I hope.
But checked the calculation and came out to the European calculation.
Compare this to American give lists .

[Phil57]

The list I go by is published by Michelin and gives specific tire model and size.
Why would I go by a European chart to determine tire pressure? If I read this correctly the European chart is telling me I need 120 lbs in my steer Axel. This so much different than the chart I go by.
Someone please explain why we would or should go by this European chart rather than the Michelin chart we have used forever.

[jadatis]

@ Phill

I gave the European site to show Kohearch that the calculation is done different in Europe and in America for the same tire.
Here even exact same kind of Michelin tire.
And because laws of nature are the same in America and Europe , it must show that the charts lists in America are not to laws of nature and European lists are closer to them.

[Phil57]

Why are they closer to "laws of nature ". What are you basing that on. I am fairly certain that I don't need 120 psi in my steer Axel. I guess I will keep doing what I'm doing and ignore this info unless a better explanation that a dummy like me can understand.

[kohersh]

I only wanted it to look over it for comparitve purposes.
Unless I'm seeing something different then the rest of the you 275/80/22.5G tires look identical here, the only differnce I spotted was the numbers on the michellintruck.com website that jatadis provided me are loads per axle whereas the micehllinrv.com website shows it as load per axle end. So the loads are doubles on the non rv specific website.

Don't know what to say here guys I am at peace with how I am running them now and I'll keep an eye on them through the TPMS

[Tireman9]

Different markets have different needs, primarily due to different roads & speed limits. Tire companies may publish slightly different tables for different applications to address these identified differences.

Just as i would not follow GM specs for an engine rebuild of a Ford I would not follow US specs for a tire application in Brazil or Germany which may be different for some specific tires.