|
04-13-2007, 03:42 PM
|
#1
|
Member
Forest River Owners Club
Join Date: Jun 2004
Location: Out West Somewhere
Posts: 54
|
Yes, it's another "age old" question about tire pressure.
I just had my new HR Endeavor weighed - I could not get a "4 corner" weight, but I did get the front axle and total weight. Anyway, the tires are the "new" Michelin XZA3 275/80R/22.5 Load Range H. I had 9840 pounds on the front axle and 19,540 on the rear axle with 7/8 fuel, full LP, and 1/2 tank water. Adjusting for additional load due to DW, clothes and food, and comparing the axle weight to Michelin's web site, Michelin recommends 90 psi front and 85 psi rear. HR recommends 115 psi front and 90 psi rear.
Can anyone tell me why such a difference between Michelin and HR on the front axle? And, assuming my figures are correct, which one would you go by? Also, any thoughts on why the actual rear axle weight is only 460 pounds less than the Rear Gross Axle Rating? That 400 hp Cummins ISL engine must weigh a lot!
__________________
Wayne
2016 Forest River Sunseeker 3050DS Class C | Ford E450
|
|
|
|
Join the #1 RV Forum Today - It's Totally Free!
iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!
You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!
|
04-13-2007, 03:42 PM
|
#2
|
Member
Forest River Owners Club
Join Date: Jun 2004
Location: Out West Somewhere
Posts: 54
|
Yes, it's another "age old" question about tire pressure.
I just had my new HR Endeavor weighed - I could not get a "4 corner" weight, but I did get the front axle and total weight. Anyway, the tires are the "new" Michelin XZA3 275/80R/22.5 Load Range H. I had 9840 pounds on the front axle and 19,540 on the rear axle with 7/8 fuel, full LP, and 1/2 tank water. Adjusting for additional load due to DW, clothes and food, and comparing the axle weight to Michelin's web site, Michelin recommends 90 psi front and 85 psi rear. HR recommends 115 psi front and 90 psi rear.
Can anyone tell me why such a difference between Michelin and HR on the front axle? And, assuming my figures are correct, which one would you go by? Also, any thoughts on why the actual rear axle weight is only 460 pounds less than the Rear Gross Axle Rating? That 400 hp Cummins ISL engine must weigh a lot!
__________________
Wayne
2016 Forest River Sunseeker 3050DS Class C | Ford E450
|
|
|
04-13-2007, 05:29 PM
|
#3
|
Senior Member
Monaco Owners Club Holiday Rambler Owners Club
Join Date: Dec 2006
Posts: 1,723
|
It's very hard to understand why both the factory and tire company are so far apart, but after working in the auto industry for 38 years I know why. It's safety from HR on a new coach that a new customer might overload. And early tire whare from the tire company, so they sell more tires. The best result can be found right here on this forum. My guess is to pic something in the middle and work from there.
__________________
Mike & Sharon and our Pup Frankie
2008 HR Endeavor 40PDQ
|
|
|
04-13-2007, 09:38 PM
|
#4
|
Senior Member
Alpine Owners Club
Join Date: Jun 2004
Posts: 2,554
|
Manufacturers make those inflation charts so that the tire at the correct psi for weight will flex at the proper point in the sidewall, and be able to absorb impacts more readily. It also assures a proper footprint for even tire wear.
On my rig I error on the higher side of recommended PSI by 5-10 pounds psi.
Try to find a scale on a Sunday that has room for you to put only the rt or left front tire on the scale. That way you can determine the different weights side to side. Always have the tires at the proper psi for the heaviest corner.
Here is a site with pdf's that you can download about weighing your coach.
http://www.bridgestonetrucktires.com...g/rv/index.asp
__________________
Tom, Patty, Hannah "The Big Dog" and Abby Kat, Indianapolis, Indiana 2000 Alpine 36' FDS 72232, 2005 Blue Bird M450 LXI Our Photos
"We live out in our old van. Travel all across this land. Drive until the city lights dissolve into a country sky, just me and you - hand in hand." Zac Brown Band
|
|
|
04-14-2007, 03:15 PM
|
#5
|
Senior Member
Monaco Owners Club
Join Date: Apr 2002
Location: On top of Windy Hill - Florida
Posts: 141
|
Wayne,
I think the difference may be simple. Your Endevor should be on the same chassis as an '07 36PDQ Diplomat. If so, the front axle is rated for 13,000 lbs. GAWR.
The pressure Monaco / HR gives will be based on a 13,000 lb. weight load; not a 9,849 lb. load. The manufacturer dosn't have a clue how we load our coaches, so they base everything on max load IAW the specs. Check your owner's manual for the GAWR and then check Michlein's load chart for that weight and pressure. That should account for the difference.
You are correct in weighing your coach. What you don't know is the weight difference from one side to the other on the same axle. My '01 Dip weighs 200 lbs more on the street side front vs the sidewalk side front. There are some coaches, out in the world, with over 1,000 lbs difference street side vs sidewalk side. You will need to adjust tire pressure based on the heavy side, of an axle. But, for what you know you seem to be doing well. Do a search for RV Safety Education Foundation (RVSEF). The do four corner weights and should be posting (on their website) what RV shows thwey will be working.
Green lights and soft breezes,
__________________
Roland, Diane & Katie - the furry 4-footed kid
'01 Diplomat - ISC330 - Allison MD3060 - Progressive Ind. EMS-50C - Hughes Autoformer - '06 Jeep Liberty CRD
|
|
|
04-14-2007, 06:15 PM
|
#6
|
Member
Forest River Owners Club
Join Date: Jun 2004
Location: Out West Somewhere
Posts: 54
|
Thanks to all for your replies..
Roland: Good insight, I do have that same chassis. So, I looked up on the Michelin site the requirements for a 13,000 pound axle and it is right inbetween 105 and 110 psi. At 105, the axle weight supported is 12,870 and at 110, the axle weight supported is 13,360. Don't know why HR would say 115 psi though
I use to carry an air compressor for my gasser Class A's. But with the air chuck available to tap into the Endeavor's air system could mean that I would not need to carry my air compressor. However, the max reading on my dash gage is 110 to 115 psi which could be problems with the 115 psi HR suggests for the front tires. So, if I really need 115 psi, I will have to continue to carry my compressor with me. If I can run at 110 psi, then the compressor can stay at home and I can save 50 pounds!
__________________
Wayne
2016 Forest River Sunseeker 3050DS Class C | Ford E450
|
|
|
04-14-2007, 07:48 PM
|
#7
|
Senior Member
Monaco Owners Club
Join Date: Apr 2002
Location: On top of Windy Hill - Florida
Posts: 141
|
Wayne,
If your coach had been shipped with Goodyear then the number would be 115 psi. But don't fret. The only time you need to be in the 110 - 115 psi range is if you are carring 13,000 lbs on the front axle. Based on your figures, I would consider running 95 psi all around. The extra allows for loss over time, changes in ambient temperature and occassional high speed use(over 65 mph).
As to the weight on the rear, in addition to the engine & trans, consider propane & fresh water just in ftont of the rear axle and batteries just behind the rear axle.
Green lights and soft breezes,
__________________
Roland, Diane & Katie - the furry 4-footed kid
'01 Diplomat - ISC330 - Allison MD3060 - Progressive Ind. EMS-50C - Hughes Autoformer - '06 Jeep Liberty CRD
|
|
|
04-14-2007, 09:06 PM
|
#8
|
Member
Forest River Owners Club
Join Date: Jun 2004
Location: Out West Somewhere
Posts: 54
|
Thanks for the answer and suggestion. I think I will take your suggestion and run 95 all around.
__________________
Wayne
2016 Forest River Sunseeker 3050DS Class C | Ford E450
|
|
|
04-15-2007, 12:24 PM
|
#9
|
"Formerly Diplomat Don"
Newmar Owners Club
Join Date: Apr 2005
Location: Moorpark, Ca.
Posts: 24,125
|
WayneLee....I have pretty much the same coach as you. My weights are almost identical to yours and my Goodyears called for 85psi rear and 90 psi front. I wanted to run as close to the recommended numbers as I could to make the ride as nice as possible.
After running the above pressure on a few trips I could always smell the slight odor of rubber after several hours of driving. I knew I was running a shade low on air. I bumped the fronts to 95psi and the rears to 90psi. We just finished a 1000 mile trip and this is the perfect setting for mine.
__________________
Don & Mary
2019 Newmar Dutch Star 4018 (Freightliner)
2019 Ford Raptor
|
|
|
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
» Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
|