So far many have posted information on the inflation pressures and types of
tires various netters use on their coaches. It is obvious that the choice of
tires for the GMC motorhome is a complex issue and it is complicated by the
fact that most of us think we are experts because we have used tires for so
many years on our automobiles. However if we take that attitude with the GMC
we are going to get into trouble fast. You cannot compare car tires to ones
used for an RV and especially not the GMC. The GMCmotorhome uses TRUCK TIRES.
I am a perfect example of the ignorance that surrounded this issue, before
this forum and our discussions. I bought a 1976 palmbeach March 1998, tires
looked good(Michelins), much bigger and heavier than my car tires, they were
the proper tires for the vehicle (glovebox sticker told me that)and fat dumb
and happy I started to drive it. I told myself that the tires could be
changed later during the winter.
After several thousand miles of driving, first tire went and than a
catastrophic failure on the second causing over a $1000 damage to the coach
(generator door, skirt, air bag and paint). Thats when I started looking for
information. If you have never had a really bad blow out you haven't lived.
It sounded like a bomb going off in the rear of the coach, complete with
fire and smoke. Fire later determined to be from the steel belts hitting on
the bogie suspension and producing lots of sparks. wonder what that would
have been like on the propane tank side if the tank had been turned on and
additionally had a leak? Maybe break the LSR?
Some things I found out:
1. Auto tires have a RECOMMENDED and MAXIMUM cold pressure rating, and
TRUCK TIRES have a MINIMUM cold pressure rating to carry MAXIMUM loads. Big
difference, and very critical. If you mix up these two concepts you are
asking for trouble.
2. On radial truck tires(ours for the GMC motorhome) the number of plies
has no meaning! Load range and inflation pressure are the determining
factors. In other words the GMC needs E rated tires but if you inflate them
incorrectly you only have a D range or less tire.
3. A load range E tire is only a load range E tire if it is inflated to the
correct pressure for the load. And that is critical also. Truck tires
typically are inflated to carry the present load and this can vary day to
day in commercial operations by knowedgable people.
4. GMC rims need Schrader TR570 metal stems and metal sealing caps to hold
the correct pressure long term. Alcoa rims come with them mounted.
5. During separate East and West coast GMC motorhome rallys some time ago,
86% of the motorhomes tested had underinflated tires and could not carry the
measured weight safely. At those same rallys 61% of the coaches were
exceeding their gross vehicle weight. I will make a bet with all of you. If
you check your pressures right now ( many of you can't since your hubcaps
are in the way and you have to remove them to check), at least one and
probably all of your pressures are incorrect for the tires.
6. Highest tire loading appears to be on the right front tire and can reach
3000# if the air suspension is malfunctioning or as some have said they
dirve in hold! That greatly exceeds the load carrying capacity of all D
rated tires.
7. In the case of the GMC motorhome, the tires load is constantly changing
because of the independent front and rear suspension. If you don't want to
exceed the recommended tire loads, than the system must be working properly.
I am still learning and as I find out more will post.
Anyone find out anymore facts?
>In a message dated 5/14/99 9:07:19 PM Central Daylight Time,
>
>>
>> My coach came with load range "E" Goodyear G159 which I maintain at
>> 65 lbs front and rear. I do that because the previous owner said that was
>> what he did and he had the coach for 18 years.
>
>The previous owner of my coach installed "D" load rated 2 + 2 ply Kelly
>radial tires with 30 PSI mounted on non-radial wheels. He's the same one who
>insured me they were all radial wheels, the one who installed the 16 ga wire
>toting 6 volts to the HEI, and the one who didn't know the water pipe going
>to the commode had burst from freezing 2 years earlier........Ad Nauseum
>Infinitum.
>He's the reason I'm going to "E"'s and 65 PSI, and Scott Shean is the
>reason I have radial wheels to put them on.
>(and LSU taking out KY is the reason my Diamond Dawgs are going to the SEC
>tournament next week, 'cause MSU let Ole Miss get away last night - ain't
>won but 1Friday game all year)
>
>Lanier
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
"The beautiful Mohawk Vally"
tires various netters use on their coaches. It is obvious that the choice of
tires for the GMC motorhome is a complex issue and it is complicated by the
fact that most of us think we are experts because we have used tires for so
many years on our automobiles. However if we take that attitude with the GMC
we are going to get into trouble fast. You cannot compare car tires to ones
used for an RV and especially not the GMC. The GMCmotorhome uses TRUCK TIRES.
I am a perfect example of the ignorance that surrounded this issue, before
this forum and our discussions. I bought a 1976 palmbeach March 1998, tires
looked good(Michelins), much bigger and heavier than my car tires, they were
the proper tires for the vehicle (glovebox sticker told me that)and fat dumb
and happy I started to drive it. I told myself that the tires could be
changed later during the winter.
After several thousand miles of driving, first tire went and than a
catastrophic failure on the second causing over a $1000 damage to the coach
(generator door, skirt, air bag and paint). Thats when I started looking for
information. If you have never had a really bad blow out you haven't lived.
It sounded like a bomb going off in the rear of the coach, complete with
fire and smoke. Fire later determined to be from the steel belts hitting on
the bogie suspension and producing lots of sparks. wonder what that would
have been like on the propane tank side if the tank had been turned on and
additionally had a leak? Maybe break the LSR?
Some things I found out:
1. Auto tires have a RECOMMENDED and MAXIMUM cold pressure rating, and
TRUCK TIRES have a MINIMUM cold pressure rating to carry MAXIMUM loads. Big
difference, and very critical. If you mix up these two concepts you are
asking for trouble.
2. On radial truck tires(ours for the GMC motorhome) the number of plies
has no meaning! Load range and inflation pressure are the determining
factors. In other words the GMC needs E rated tires but if you inflate them
incorrectly you only have a D range or less tire.
3. A load range E tire is only a load range E tire if it is inflated to the
correct pressure for the load. And that is critical also. Truck tires
typically are inflated to carry the present load and this can vary day to
day in commercial operations by knowedgable people.
4. GMC rims need Schrader TR570 metal stems and metal sealing caps to hold
the correct pressure long term. Alcoa rims come with them mounted.
5. During separate East and West coast GMC motorhome rallys some time ago,
86% of the motorhomes tested had underinflated tires and could not carry the
measured weight safely. At those same rallys 61% of the coaches were
exceeding their gross vehicle weight. I will make a bet with all of you. If
you check your pressures right now ( many of you can't since your hubcaps
are in the way and you have to remove them to check), at least one and
probably all of your pressures are incorrect for the tires.
6. Highest tire loading appears to be on the right front tire and can reach
3000# if the air suspension is malfunctioning or as some have said they
dirve in hold! That greatly exceeds the load carrying capacity of all D
rated tires.
7. In the case of the GMC motorhome, the tires load is constantly changing
because of the independent front and rear suspension. If you don't want to
exceed the recommended tire loads, than the system must be working properly.
I am still learning and as I find out more will post.
Anyone find out anymore facts?
>In a message dated 5/14/99 9:07:19 PM Central Daylight Time,
>
>>
>> My coach came with load range "E" Goodyear G159 which I maintain at
>> 65 lbs front and rear. I do that because the previous owner said that was
>> what he did and he had the coach for 18 years.
>
>The previous owner of my coach installed "D" load rated 2 + 2 ply Kelly
>radial tires with 30 PSI mounted on non-radial wheels. He's the same one who
>insured me they were all radial wheels, the one who installed the 16 ga wire
>toting 6 volts to the HEI, and the one who didn't know the water pipe going
>to the commode had burst from freezing 2 years earlier........Ad Nauseum
>Infinitum.
>He's the reason I'm going to "E"'s and 65 PSI, and Scott Shean is the
>reason I have radial wheels to put them on.
>(and LSU taking out KY is the reason my Diamond Dawgs are going to the SEC
>tournament next week, 'cause MSU let Ole Miss get away last night - ain't
>won but 1Friday game all year)
>
>Lanier
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
"The beautiful Mohawk Vally"
