I know people are tired of this issue but it becomes curiouser and
curiouser to me:
I just talked to Bridgestone. This is what they told me. Believe it if
you like or dispute it if you must, but phone Bridgestone to complain.
Not me. I am running Bridgestone 173 steel Radials. E rated.
Weight rating 3345 # at 80 psi
I have 65 psi. What does that do to my weight rating?
It will reduce the rated capacity to 3000#/tire
Conclusion
Unless I am planning to load my GM to 6000# per axle I am ok.
For each 5# reduction in pressure reduce the capacity by 100#, within
reason of course. This was a good answer for me. You may make your own
decisions.. Over and out.
> I haven't seen any sign of info about the GMC/Cinnabar study of tires.
Here ya go, Vic, this is pasted from Billy Massey's site:
The pasting had a summary of Wes Coughlin's work for GMC in 1981. The part
of particular interest to me was:
However, this suspension
throws weight around when the vehicle goes down the road dynamically.
Individual wheel loads can exceed 2,500 pounds, and can go as high as 2,900
pounds under extreme situations.
Keep in mind that Load Range E tires have to be kept inflated to Load Range
E inflation pressures, otherwise their 2,680 pounds of load-carrying
capacity is lost. Load Range E tires have a minimum inflation pressure
requirement of 75 or 80 psi cold depending on the manufacturer. That seems
high and harsh to many GMC Motorhome owners, particularly considering that
Load Range D tires are only inflated to 65 psi cold, but they will only
carry 2,350 pounds.
Justin wrote;
Total 7,500 lbs
Total maximum weight at ground 11,700 lbs
Note: GM's definition of Curb weight is the maximum weight of the vehicle
without driver, passengers, or cargo, and empty fresh water, LP, and
holding tanks, but does include fuel and coolant. Now for some grade school
type arithmetic.....4,200 divided by 2 = 2,100 lbs. load per front tire at
GM recommended maximum wt. 7,500 divided by 4 = 1,875 lbs. weight on rear
tires at GM recommended max. wt.
Between these three postings I am led to the following conclusions:
1. Between manufacturers, load E tires of the same (or similar) size can
have very different weight ratings.
2. Michelin has a relatively low Load E rating compared to the Bridgestone
tire: 3345# Vs Michelin at 2680
3. Steel belted tires are the critical issue on GMC's not the load range
Which leads me ask a couple of questions:
1. Is the sidewall the same on a load D and a load E tire? Is the sidewall
belt count an issue at all?
2. Is weight rating really the only critical issue?
3. Would a Bridgestone Load D be equivalent to a Michelin Load E?
I would really appreciate some of you "engineering types" to give me an
absolute answer to this one because I would really like to put it to bed.
Vic Marks
Vancouver BC
75 transmode
curiouser to me:
I just talked to Bridgestone. This is what they told me. Believe it if
you like or dispute it if you must, but phone Bridgestone to complain.
Not me. I am running Bridgestone 173 steel Radials. E rated.
Weight rating 3345 # at 80 psi
I have 65 psi. What does that do to my weight rating?
It will reduce the rated capacity to 3000#/tire
Conclusion
Unless I am planning to load my GM to 6000# per axle I am ok.
For each 5# reduction in pressure reduce the capacity by 100#, within
reason of course. This was a good answer for me. You may make your own
decisions.. Over and out.
> I haven't seen any sign of info about the GMC/Cinnabar study of tires.
Here ya go, Vic, this is pasted from Billy Massey's site:
The pasting had a summary of Wes Coughlin's work for GMC in 1981. The part
of particular interest to me was:
However, this suspension
throws weight around when the vehicle goes down the road dynamically.
Individual wheel loads can exceed 2,500 pounds, and can go as high as 2,900
pounds under extreme situations.
Keep in mind that Load Range E tires have to be kept inflated to Load Range
E inflation pressures, otherwise their 2,680 pounds of load-carrying
capacity is lost. Load Range E tires have a minimum inflation pressure
requirement of 75 or 80 psi cold depending on the manufacturer. That seems
high and harsh to many GMC Motorhome owners, particularly considering that
Load Range D tires are only inflated to 65 psi cold, but they will only
carry 2,350 pounds.
Justin wrote;
Total 7,500 lbs
Total maximum weight at ground 11,700 lbs
Note: GM's definition of Curb weight is the maximum weight of the vehicle
without driver, passengers, or cargo, and empty fresh water, LP, and
holding tanks, but does include fuel and coolant. Now for some grade school
type arithmetic.....4,200 divided by 2 = 2,100 lbs. load per front tire at
GM recommended maximum wt. 7,500 divided by 4 = 1,875 lbs. weight on rear
tires at GM recommended max. wt.
Between these three postings I am led to the following conclusions:
1. Between manufacturers, load E tires of the same (or similar) size can
have very different weight ratings.
2. Michelin has a relatively low Load E rating compared to the Bridgestone
tire: 3345# Vs Michelin at 2680
3. Steel belted tires are the critical issue on GMC's not the load range
Which leads me ask a couple of questions:
1. Is the sidewall the same on a load D and a load E tire? Is the sidewall
belt count an issue at all?
2. Is weight rating really the only critical issue?
3. Would a Bridgestone Load D be equivalent to a Michelin Load E?
I would really appreciate some of you "engineering types" to give me an
absolute answer to this one because I would really like to put it to bed.
Vic Marks
Vancouver BC
75 transmode
