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09-18-2018, 06:28 AM
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#221
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Rivet Master
2000 25' Safari
Davidson County
, NC Highlands County, FL
Join Date: Aug 2006
Posts: 4,493
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^^ maybe the best tire pressure/load/speed related post I ever read ^^
Excellent explanation.
Thank you!
__________________
Alan
2014 Silverado LTZ 1500 Crew Cab 5.3L maximum trailering package
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09-18-2018, 07:24 AM
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#222
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Aluminut
2004 25' Safari
.
, Illinois
Join Date: Feb 2003
Posts: 10,477
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Quote:
Originally Posted by gypsydad
Just drove from MT to Austin, TX thru Utah and New Mexico with my new Endurance tires. After looking at the tire pressure charts for these tires, as posted on the Forum, I lowered the pressures to 45lbs when cold, per weight of my 28'AS. No issues and very pleased with the performance.
I posted earlier that when I first had the new Endurance tires installed last month, Discount Tire guys had filled to max pressure of 70PSI; wrong!! I noticed a few screws on the floor along with a rivet, after a couple short trips last month running at 70PSI. I would not listen to the "experts" here, telling you to run Max pressure in any tire, without looking at manufacturer recommended load/pressure charts of your tires or talking with the tire manufacturer. My trip last week from MT to TX covered 2200+ miles and I had no screws or rivet issues. The AS tracked very nicely after adjusting pressures to recommended 45lbs.
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Your 28 footer has a GVWR of about 7600? At 45psi you are close to the max capacity, still within spec and even more within spec if you don't take every ounce of NCC. CapriRacer said it best though:
"And a word of explanation on my use of the words *speed capability* as opposed to the words *speed rating*. Speed rating is the result of a test. That may or may not be the speed capability of the tire under real world circumstances - hence the distinction"
Tires are tested under lab conditions and results can an usually will vary based on a lot of unforeseen factors a person might encounter and those capabilities may have a fudge factor included.
One thing to note is that as tires age, they loose capacity, so although you might be able to do this this year, and maybe next, the problem as I see it is as these tires age, that 45psi rating won't be entirely accurate and you might find that past year 2 or 3, you have misjudged the situation far more gravely than just a few popped rivets. I'm not advocating you pressurized them to 80psi, but......
If you really plan on running at 45psi from now on, I would suggest you increase the tire pressure at least 5-6 psi each year beyond the year you bought them to keep a margin of error wider. Normally between 3-5 years the tires should be replaced anyway, and you will still be well under the max pressure rating by the time replacement is necc, but also not upside down as the tire ages and looses capacity.
Just my .02
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09-18-2018, 10:56 AM
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#223
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Rivet Master
Commercial Member
Ravenna
, Ohio
Join Date: Apr 2012
Posts: 1,344
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Yup to what CapriRacer said ^^^
I would add that Interply Shear is present in all radial tires. The question is can the tire tolerate those forces long enough to wear out.
In general in Passenger car use with daily driving the answer is yes for 99+% of the time. In LT service my guess is 98% of the time
RV service presents problems of not enough miles per year. You would need to drive 12 to 15,000 miles each year AND run a 15% to 25% load margin to wear out in a normal tire lifetime (4 to 5 years). CLass-A will need to drive 25, to 50,000 a year.
Trailer service is a different issue because the tires are being dragged arounudevery turn. Even gentel turning forces extra "slip". I did not have the opportunity to test hundreds of variables but I would guess that IPS is 15 to 40% higher in trailer service depending on a variety of factors.
Given that high loads, high speeds (faster than 65) for ST type tires coupled with poor maintenance and infrequent use the suggestions of replacing tires at 3 to 5 years sounds reasonable with shorter life on heavy trailers. Possible 2 to 3 years on 3 axle 5th wheels.
You cannot eliminate IPS.
Only the owner can balance "rough ride" vs inflation. Maybe a better design suspension that didn't depend on tires so much and used shocks, bushings and springs better designed for the job would be a good plan.
__________________
Retired tire engineer (50 years). Write a blog on RV Tire Safety Net. Give seminars for FMCA across the US. Tucson AZ in Mar 2024 is next.
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09-18-2018, 05:44 PM
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#224
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Rivet Master
2012 27' Flying Cloud
W
, New England
Join Date: Oct 2012
Posts: 7,402
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Thanks to our resident TEs. Very educational as always!
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09-19-2018, 05:53 AM
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#225
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Rivet Master
2013 31' Classic
billings
, Montana
Join Date: Feb 2010
Posts: 3,576
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The tire problems in the early 2000’s I believe was caused by running them tires on low air pressure to get a better ride....it don’t work....In the middle 1960’s I worked at an Oldsmobile dealer servicing new cars...checking out everything....was told to air the tires to 24 lbs, and add 5 gallons of premium gasoline....was told their customers wanted a soft , smooth ride...they didn’t care about the tire wear...it was all about the ride....
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09-19-2018, 06:04 AM
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#226
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3 Rivet Member
2013 25' FB International
Liberty Corner
, New Jersey
Join Date: Mar 2014
Posts: 209
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Tireman9 highlighted the big issue:
...Maybe a better design suspension that didn't depend on tires so much and used shocks, bushings and springs better designed for the job would be a good plan.....
AS needs to upgrade from the standard design of the last century. Time for a real suspension and larger tire sizes that are required for today's overloaded trailers traveling at silly speeds over poorly maintained roads and in our trailers that seem to have weaker rivets.
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09-20-2018, 04:07 AM
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#227
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2020 Globetrotter 25 FBT
2020 25' Globetrotter
Wildwood
, Missouri
Join Date: Aug 2009
Posts: 2,589
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Any idea how the tire psi effects mpg? I remember a past president telling us we all needed to run higher psi in our vehicle tires to save gas. Does it effect mpg as much with a trailer? Our last trip out west (last month) I seemed to be getting better mileage from a tank of gas. I was running the GYEs at close to 70 psi. Before I had been running 14” GYMs at much lower psi.
__________________
2020 25GT FBT
2012 Toyota Tundra Dbl Cab, 5.7 4x4
Previous AS trailers: (04) 19’ Bambi, and (11) FC 23FB
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09-20-2018, 05:46 AM
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#228
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CapriRacer
I'm in the
, US
Join Date: Sep 2012
Posts: 990
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Quote:
Originally Posted by GettinAway
Any idea how the tire psi effects mpg? I remember a past president telling us we all needed to run higher psi in our vehicle tires to save gas. Does it effect mpg as much with a trailer? Our last trip out west (last month) I seemed to be getting better mileage from a tank of gas. I was running the GYEs at close to 70 psi. Before I had been running 14” GYMs at much lower psi.
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That's for passenger car tires, but you get the drift!
__________________
CapriRacer
Want to learn about tires? Please visit my website: Barry's Tire Tech New content every month!
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09-20-2018, 09:10 AM
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#229
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Rivet Master
2017 28' Flying Cloud
2014 25' FB Flying Cloud
2008 25' Safari FB SE
Georgetown (winter)Thayne (summer)
, Texas & Wyoming
Join Date: Jan 2007
Posts: 6,621
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Quote:
Originally Posted by Silvertwinkie
Your 28 footer has a GVWR of about 7600? At 45psi you are close to the max capacity, still within spec and even more within spec if you don't take every ounce of NCC. CapriRacer said it best though:
"And a word of explanation on my use of the words *speed capability* as opposed to the words *speed rating*. Speed rating is the result of a test. That may or may not be the speed capability of the tire under real world circumstances - hence the distinction"
Tires are tested under lab conditions and results can an usually will vary based on a lot of unforeseen factors a person might encounter and those capabilities may have a fudge factor included.
One thing to note is that as tires age, they loose capacity, so although you might be able to do this this year, and maybe next, the problem as I see it is as these tires age, that 45psi rating won't be entirely accurate and you might find that past year 2 or 3, you have misjudged the situation far more gravely than just a few popped rivets. I'm not advocating you pressurized them to 80psi, but......
If you really plan on running at 45psi from now on, I would suggest you increase the tire pressure at least 5-6 psi each year beyond the year you bought them to keep a margin of error wider. Normally between 3-5 years the tires should be replaced anyway, and you will still be well under the max pressure rating by the time replacement is necc, but also not upside down as the tire ages and looses capacity.
Just my .02
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So, your suggesting 50-55psi? I see the running pressure at around 54-58psi this past trip, 2500miles~. Pressures as registered with the TPMS did not change much the whole trip from MT at times, 8k feet, to close to sea level here in Austin. I will increase to 50psi cold and monitor. I do think the original pressures put in by dealer where I bought them was too high at 70PSI...that's why I found some hardware on the floor after couple short trips.
__________________
Empty Nesters; Gypsies on the road! 2017 28' Twin Flying Cloud
2017 F250 King Ranch, 4X4, 6.7L, Blue-Ox WDH
Summer-Star Valley Ranch RV Resort (Thayne, WY); Winter-Sun City (Georgetown,TX)
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09-21-2018, 05:08 AM
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#230
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2020 Globetrotter 25 FBT
2020 25' Globetrotter
Wildwood
, Missouri
Join Date: Aug 2009
Posts: 2,589
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Quote:
Originally Posted by CapriRacer
That's for passenger car tires, but you get the drift!
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Interesting. More of an impact than I thought. I know I’m way too high on the pressures, but I didn’t have any issues the last 2,500 miles. Must still be hard on the trailer. I think I’ll drop the pressures some.
Thx
__________________
2020 25GT FBT
2012 Toyota Tundra Dbl Cab, 5.7 4x4
Previous AS trailers: (04) 19’ Bambi, and (11) FC 23FB
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09-21-2018, 08:12 AM
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#231
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4 Rivet Member
2017 30' International
Lincolnwood
, Illinois
Join Date: Apr 2016
Posts: 312
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I believe if you following the charts the profile of the tire remains the same at a given pressure for the weight of the TT. The higher the weight of the TT the higher the tire pressure. If the tire is over inflated by 10 psi for a given weight according to the charts,
you the slightly change the profile of the tire decreasing rolling resistance. But, remember that you are sacrificing a softer ride for your trailer to gain a miniscule amount of mpg.Maybe increasing the jarring from a 4.5 to a 5.5 on the richter scale. Not a good trade-off in IMHO. The stiffer the ride the more things tend to pop and loosen inside the trailer. I will experiment with lower tire pressures on my next trip, based on the weight at the CAT scale and
post my findings on this forum. I have been running the GYE,s at 75 psi and will try the recommended psi according to the inflation chart next trip. Add maybe 10 % based on weight of TT for a margin of safety not knowing the exact weight at each tire position.
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09-21-2018, 08:56 AM
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#232
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Rivet Master
2017 28' Flying Cloud
2014 25' FB Flying Cloud
2008 25' Safari FB SE
Georgetown (winter)Thayne (summer)
, Texas & Wyoming
Join Date: Jan 2007
Posts: 6,621
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Quote:
Originally Posted by Milo1952
I believe if you following the charts the profile of the tire remains the same at a given pressure for the weight of the TT. The higher the weight of the TT the higher the tire pressure. If the tire is over inflated by 10 psi for a given weight according to the charts,
you the slightly change the profile of the tire decreasing rolling resistance. But, remember that you are sacrificing a softer ride for your trailer to gain a miniscule amount of mpg.Maybe increasing the jarring from a 4.5 to a 5.5 on the richter scale. Not a good trade-off in IMHO. The stiffer the ride the more things tend to pop and loosen inside the trailer. I will experiment with lower tire pressures on my next trip, based on the weight at the CAT scale and
post my findings on this forum. I have been running the GYE,s at 75 psi and will try the recommended psi according to the inflation chart next trip. Add maybe 10 % based on weight of TT for a margin of safety not knowing the exact weight at each tire position.
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I am with ya...my gut says 45-50 was too low, but I did not notice any sag in the sidewall with these tires when I adjusted down from 70psi dealer put in. I remember seeing the sidewall movement when I added air on my Michelins on my earlier AS's; likely these ST extra ply sidewalls are a lot stiffer. Intuition says if 80PSI is max running pressure on the GYE's, 45-50psi would be too low, until you see the tire chart and weigh your AS...like I said above, this past trip 2500~ miles from MT to TX over the Tetons and Capital Reef, I had plenty altitude, off road boondocking, and freeway...I had them cold filled prior to leaving MT at 45-48psi; they seemed to perform fine registering ~52-58psi recorded on my TPMS the whole way home after warm up...time will tell.
__________________
Empty Nesters; Gypsies on the road! 2017 28' Twin Flying Cloud
2017 F250 King Ranch, 4X4, 6.7L, Blue-Ox WDH
Summer-Star Valley Ranch RV Resort (Thayne, WY); Winter-Sun City (Georgetown,TX)
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09-21-2018, 09:14 AM
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#233
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Aluminut
2004 25' Safari
.
, Illinois
Join Date: Feb 2003
Posts: 10,477
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Quote:
Originally Posted by gypsydad
So, your suggesting 50-55psi? I see the running pressure at around 54-58psi this past trip, 2500miles~. Pressures as registered with the TPMS did not change much the whole trip from MT at times, 8k feet, to close to sea level here in Austin. I will increase to 50psi cold and monitor. I do think the original pressures put in by dealer where I bought them was too high at 70PSI...that's why I found some hardware on the floor after couple short trips.
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What I'm saying is that I think you need to take into account that as the tire ages, tire carrying capacity is lost. If tire carrying capacity is "x" at 45psi, then as the tire ages, the carrying capacity at "x" may be decreased at any psi. To offset that, I'm suggesting that if you decide to run lower than average pressures, that you add some PSI every year until you replace the tires in roughly 4 years. For example if year one 45psi more than covers your rig, great, not what I'd do, but the numbers don't lie. Next year, I'd make sure I'm around 50psi, the next year around 55psi and so on and so on.
I run mine between 68-70psi. More than the 65psi the "D" rated tires required when I had them, but about 10psi from max on the "E" rated tires I've used the past 13 years.
There is nothing wrong with the axles Airstream puts on the trailers as I read here somewhere. Besides tire pressures, tow vehicle and hitching (over hitched or not), one of the things that make for a harsh ride is an out of balance wheel hub. Sure they can get balanced with weights on the rim, but here too as the tire ages and wears, those weights can become less than effective.
In addition to looking closely at the tires, I have 100lb weight distribution bars, I have centramatics on all 4 hubs and I run an air safe hitch connecting the 3/4 ton truck to the trailer that puts an airbag in between the hitch and the trailer connection. IMHO, I can't think of a softer ride for an Airstream connected to a 3/4 ton truck. Been running this setup for over 12 years over 10s of thousands of problem free miles.
Your results can and will vary. Don't use my info a law, but take it under consideration as you make your own decision.
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09-21-2018, 09:49 AM
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#234
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3 Rivet Member
2005 34' Classic
tucson
, Arizona
Join Date: Mar 2017
Posts: 160
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1 year...so far so good
After a disastrous attempt to get through Phoenix in June of 2017 where 2 tires (out of 6) blew at 8:00 pm...I put on 6 (ouch!$$) of the new Endurance tires the next morning at Discount Tire.
Since then we've done a few thousand miles at 65 psi all the while watching with the also new TPMS monitor.
https://eezrvproduct.com/products/ti...6-flow-through
Pressures have held really well and temps stay about 10 degrees above ambient. Much of our travel have been in the southwest when temps have been 100 to 110. A year ago I was lamenting not bumping up to the larger Michelins but so far my experience has been a good one.
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09-22-2018, 09:44 AM
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#235
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Rivet Master
2017 28' Flying Cloud
2014 25' FB Flying Cloud
2008 25' Safari FB SE
Georgetown (winter)Thayne (summer)
, Texas & Wyoming
Join Date: Jan 2007
Posts: 6,621
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Quote:
Originally Posted by dvgofaz
After a disastrous attempt to get through Phoenix in June of 2017 where 2 tires (out of 6) blew at 8:00 pm...I put on 6 (ouch!$$) of the new Endurance tires the next morning at Discount Tire.
Since then we've done a few thousand miles at 65 psi all the while watching with the also new TPMS monitor.
https://eezrvproduct.com/products/ti...6-flow-through
Pressures have held really well and temps stay about 10 degrees above ambient. Much of our travel have been in the southwest when temps have been 100 to 110. A year ago I was lamenting not bumping up to the larger Michelins but so far my experience has been a good one.
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Which tires "blew"? (what rand and age were they?)
__________________
Empty Nesters; Gypsies on the road! 2017 28' Twin Flying Cloud
2017 F250 King Ranch, 4X4, 6.7L, Blue-Ox WDH
Summer-Star Valley Ranch RV Resort (Thayne, WY); Winter-Sun City (Georgetown,TX)
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09-22-2018, 10:14 AM
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#236
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Rivet Master
Commercial Member
Ravenna
, Ohio
Join Date: Apr 2012
Posts: 1,344
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Interesting comments on the hard ride on AS causing problems. Has anyone ever developed rubber or poly bushings for all the suspension mounting points?
What about alternate shocks or air bags or coil springs rather than leaf springs.
I know from personal experience that even something as "minor" as a design difference in some cast aluminum wheels on a full-size car can be felt almost immediately by an experienced ride evaluator.
IMO Increasing the IPS by lowering the inflation may not be the best trade-off.
__________________
Retired tire engineer (50 years). Write a blog on RV Tire Safety Net. Give seminars for FMCA across the US. Tucson AZ in Mar 2024 is next.
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09-22-2018, 11:04 AM
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#237
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Moderator dude
1966 26' Overlander
Phoenix
, Arizona
Join Date: Apr 2002
Posts: 7,501
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Quote:
Originally Posted by Tireman9
Interesting comments on the hard ride on AS causing problems. Has anyone ever developed rubber or poly bushings for all the suspension mounting points?
What about alternate shocks or air bags or coil springs rather than leaf springs.
I know from personal experience that even something as "minor" as a design difference in some cast aluminum wheels on a full-size car can be felt almost immediately by an experienced ride evaluator.
IMO Increasing the IPS by lowering the inflation may not be the best trade-off.
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The issue with Airstream rubber torsion axle is there are no bushings except the shock absorber bushnigs. And shocks are unique to Air Stream and only available at an Airstream source.
As to axle mounting, it is metal to metal bolted to the trailer. There are NO rubber mountings.
All of the rubber and cushoning is inside the axle tube. Not able to get there and non-serviceable.
>>>>>>>>>>>>Action
__________________
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!
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09-23-2018, 10:11 AM
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#238
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Rivet Master
Commercial Member
Ravenna
, Ohio
Join Date: Apr 2012
Posts: 1,344
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Quote:
Originally Posted by Action
The issue with Airstream rubber torsion axle is there are no bushings except the shock absorber bushnigs. And shocks are unique to Air Stream and only available at an Airstream source.
As to axle mounting, it is metal to metal bolted to the trailer. There are NO rubber mountings.
All of the rubber and cushoning is inside the axle tube. Not able to get there and non-serviceable.
>>>>>>>>>>>>Action
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Thanks for the info. Never got into the suspension design of AS.
So since you have little shock absorption components due to the AS design all that is left is the tires. To me, that would dictate lower inflation but to do that you would need physically larger tires.
Sounds like the complaints about poor shock control need to be directed to AS and not the tire companies.
__________________
Retired tire engineer (50 years). Write a blog on RV Tire Safety Net. Give seminars for FMCA across the US. Tucson AZ in Mar 2024 is next.
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09-23-2018, 10:51 AM
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#239
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Moderator dude
1966 26' Overlander
Phoenix
, Arizona
Join Date: Apr 2002
Posts: 7,501
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Air Stream usually specifies lower tire pressure for a softer ride.
I don't know for sure and the tire placard on newer Air Streams (My Air Stream experience is mostly with 1960s units) I would guess is at the lower end of most tire charts.
>>>>>>>>>>>>>Action
__________________
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!
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09-24-2018, 09:38 AM
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#240
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Rivet Master
Commercial Member
Ravenna
, Ohio
Join Date: Apr 2012
Posts: 1,344
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Quote:
Originally Posted by Action
Air Stream usually specifies lower tire pressure for a softer ride.
I don't know for sure and the tire placard on newer Air Streams (My Air Stream experience is mostly with 1960s units) I would guess is at the lower end of most tire charts.
>>>>>>>>>>>>>Action
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Yup lower tire pressure will give a softer ride. Now, what about AS standing behind their technical decision to suggest lower pressure and to warranty tires for 4 years?
__________________
Retired tire engineer (50 years). Write a blog on RV Tire Safety Net. Give seminars for FMCA across the US. Tucson AZ in Mar 2024 is next.
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