Tire Question re 65 vs 80 lbs on E's

[thomas g. warner]

I have new Michelins and they are inflated to 80 PSI and will stay that way.
Why? Because test results completed by Cinnabar engineering and funded by
General Tire concluded that only all steel tires inflated to 80PSI would
adequately control the GMC suspension without failures. It really amazes me
that we seem to come back to this same topic time after time after time,
even though all of the data has been posted and hashed over. The MINIMUM
pressure for an all steel E rated tire is 80 PSI for them to properly
function on a GMC motorhome.

TIRE DEALERS DEAL IN GENERAL TIRE TERMS AND THEREFORE RECOMMEND TIRES BASED
ON THE WEIGHT OF THE MOTORHOME AND NOT ON ITS ENGINEERING SPECIFICATIONS.
THE GMC MOTORHOME IS SIGNIFICANTLY DIFFERENT, FRONT WHEEL DRIVE AND A UNIQUE
REAR AIR SUSPENSION.

During the tests drivers could not tell the difference between 65 and 80PSI.

Bottom line and the last time. If you have run your E rated tires at 65 PSI
you may already have damaged them. Read the report and see the data.
Everyone can spend their hard earned money and do what they want.

>The last thing I want is to get a lengthy discussion going on theory or
manufacture hype so this is a question aimed at facts gained by experience
only please.
>
>And it's not asking advice on what I "should be" doing , that may come
later.
>
>If you've been running tire pressures in the sixties and have gone to 80
lbs I'd very much appreciate your comments as to ride difference. Is it
harder/harsher?
>
>I'm currently running 65 on the new E's as was recommended by the tire
dealer. As he will get my complaints if he gave wrong advice I put
reasonable value to his advice, but....
>
>I've been runnning 65 since day 1, but on D's.
>
>The wear on the tires removed did not indicate under/over inflation.
>
>My E's are not squatting.
>
>I'm pondering the 80 lbs but it's one of those if it ain't broke I may want
to leave it alone.
>
>I'd especially like to hear if anyone has tried 80 and gone back. Don't be
shy ;-)
>
>Thanks
>
>Heinz
>Bakersfield, CA
>
>
>

 

[blank]

>
> It's nice to have the net to bounce things around...

And let's remember I'm the only one here with a license to be "Content Cop".

Strongly held and strongly stated beliefs don't bother me a bit, but when
you try to restrict the right to ask a question, that's another story.

'Nuf Said?
Patrick

 

[darren paget]

OK. The weight rating on your tires is based on full inflation as stamped on the tire. My 'E' rated tires are for 3250 #'s. I am running 65 psi which is very nice for me. I know I
am losing some weight rating but like the feel of 65 psi. Darren Good luck.

>
>
> If you've been running tire pressures in the sixties and have gone to 80 lbs I'd very much appreciate your comments as to ride difference. Is it harder/harsher?
>
> I'm currently running 65 on the new E's as was recommended by the tire dealer. As he will get my complaints if he gave wrong advice I put reasonable value to his advice, but....
>
> I've been runnning 65 since day 1, but on D's.
>
> My E's are not squatting.
>
> I'm pondering the 80 lbs but it's one of those if it ain't broke I may want to leave it alone.
>
> I'd especially like to hear if anyone has tried 80 and gone back. Don't be shy ;-)
>
> Thanks
>
> Heinz
> Bakersfield, CA

- --
Darren Paget
76 Experimental
Another Fab Day
paget
http://www.TZEplus.com

 

[thomas g. warner]

Heinz I could not disagree with you more strenuously. Its not the short
term performance of a tire that is important,even cheap tires may perform
well for a short time when new, or under less than strenuous conditions.
These D rated or E rated tires may even give good service for a long time.
It is the long term AVERAGE and DYNAMIC performance that is important. We
want these tires to perform well over their complete life cycle under all
conditions they may be exposed to.

I am not willing to sacrifice my life or my families on one persons real
life experiences. GM did the study, it was paid for by General tire and the
conclusion was that only Michelin produced a tire that could meet all of the
engineering conditions. No one else could!

If it had been biased wounldn't it have been slanted towards General?

> >
> >Bottom line and the last time. If you have run your E rated tires at
65 PSI
> >you may already have damaged them. Read the report and see the data.
> >Everyone can spend their hard earned money and do what they want.
> >
>
>[Tongue in cheek]
>
>....but can you believe what you read ? ;-)
>
>Reports are funny things, they sometimes come out white and sometimes
black, no matter how much money was spent on them.
>A report substantiated by experience is the truly valuable one.
>
>It's nice to have the net to bounce things around...
>
>Thanks again
>
>Heinz
>
>
>
>

 

[thomas g. warner]

what was the purpose of this post? Are you supporting ones right to yell
fire in a crowded theatre?

>In a message dated 9/20/99 2:48:31 PM Central Daylight Time,

>
>>
>> Strongly held and strongly stated beliefs don't bother me a bit, but when
>> you try to restrict the right to ask a question, that's another story.
>>
>Patrick
>
>Thanks.
>
>Take Care
>Arch 76 GB IL
>
>

 

[mike finnicum]

Heintz

Now have over 32,000 miles on same set of "E" Goodyear Workhorses (a $99
tire). And have pondered the same question you have.

When I bought them the Goodyear Dealer (Naples, FL) he just automatically
set them to 75# when he installed them. I didn't ask any questions. The
Goodyear Dealer was a "TRUCK" only tire dealer. The same dealer also has 3
"AUTO" dealerships in our town.

After tires, I had to take it to one of his auto stores for shocks and
brakes. They said I should have 65 Remember - this is the same company.

So I called the owner (a friend) and asked him. He asked how many wheels,
type of vehicle and gross weight. He then responded with 75-77# (which would
become 80# at full temp). Said a recommendation from one of his "AUTO"
stores for 65# would be typical for a lighter vehicle. They do cars not big
trucks (or motorhomes).

I stayed at 75# and was a happy camper for many, many miles. Then came the
GMCnet and many were recommending the 65# range for a softer ride. So I
tried that for a while (about the last 5,000 mi). Last trip I lost a valve
stem in Nashville, TN. The Nashville Goodyear Tire Dealer fixed it for free
(nice man ) and then proceeded to put 75# in the tire. I asked him why -
he said that is recommended for the weight of my coach. So I had him set
them all back to 75

My conclusion (for me - not scientific):

I personally could not tell the difference in the ride (maybe some can). I
also have airbag lifters so my ride is a little softer. After going back to
the 75# it felt exactly the same to me.

My coach was more responsive (handling).

My tires ran noticeably cooler at 75

While I can't prove it, I believe my tires wore more at the lower setting of
65

I went back to 75# cold (which becomes 78-80# Hot).

I now have 32,000+ miles on a set of Goodyear Workhorses. On 4 rear tires I
have over 1/2 the tread left. My front wheels have about 1/3 left.

For me, I will stay with the recommendation of a Goodyear Truck center.

Like I have said, none of this is scientific. It's all "seat of the pants"
opinion. But I do have over 200,000 behind the wheel of 3 different GMCs.

AND . . . My dealer likes the 75-80# so that seems to make sense to me - but
then again - they are YOUR tires . . . and your seat ...

FYI

Mike Finnicum

 

[richard waters]

About 3,000 miles ago I went to 80 lbs from 60-65 lbs on my
Goodyear G159's mounted on steel wheels. I have not noticed
any difference in ride.

After riding with me for 2,000 miles I asked my wife and kids if
they noticed anything different about the ride. No difference they told
me. Admittedly, we are still new to the GMC (only about 10,000 miles
under our belts) and so we don't really know any better

Every time I stop I have been making it a habit to do a walk
around and feel the temperature of the tires and wheels with my hands.
It may be my imagination, but I think they are running a little cooler.

It also may be my imagination, but I think my gas mileage has improved
slightly. It's hard for me to figure the gas mileage accurately because
of having to factor in the use of the genset and the dash air.

However, before I went to 80 lbs I am pretty confident that I was only
getting about 7.8 MPG. Now it is up to about 8.5. Again, I don't know
for sure.

I will be keeping my tires at 80 lbs from now on, until I can be convinced
that I should go down.

Richard Waters '76 PB (with 6 tires at 80 lbs), Troy, MI

 

[dave1]

>If you've been running tire pressures in the sixties and
>have gone to 80 lbs I'd very much appreciate your comments
>as to ride difference. Is it harder/harsher?

I was running my Michelin XPS-RIB E's at 65 until I read Wes's article in
the Cinnabar newsletter. Then I raised them up to 75 (I think that is the
max rated pressure on my tires). No, I don't think I can feel the
difference in ride quality.

I am not sure why the pressure difference make that big a difference in
reliability. But they (Cinnabar) did the design review and I don't see any
downside to the higher tire pressures so I am going to trust their judgment
and run at the full rated pressure. I guess only time will tell.

But I still keep a close eye on my tires while I am on the road. Experience
tells me that tires don't just pop. They come apart slowly and then they
pop. So at each rest stop, while things are still warm from the road, I do
a quick walk around. I look and touch the tires and wheels. I look for heat
or bulges in the sidewalls and tread. I have never had a blow-out on the
road but I did catch two tires before they failed (yes, they where D rated)
and a stuck caliper (caused by a plugged brake line). In all three cases I
was able to discover the problem and fix it before things got ugly. So my
advice is to be vigilant. Its no guarantee but it sure helps...

Dave
Ann Arbor, MI.
73 Sequoia (26'/455/EFI/HEI)

 

[dave1]

>BUT what about those of us so stupid (or poor) to
>still be running "D" range tires ???
>What pressure should we be running on steel wheels
>with oversize 9.50's X 16.5??

My suggestion would be to run them at their maximum rated pressure, keep a
very close eye on them and replace them with full steel E rated tires as
soon as practical.

There have been a lot of reports of failures on D rated tires, GM recalled
the D's and replaced them with E's. I have not heard of any failures of
full steel E rated tires (I am sure there must be some, but none that I
have heard of). For all of the above reasons, I dumped my D rated tires in
favor of full steel E rated tires after my second D rated tire failure.

Dave
Ann Arbor, MI.
73 Sequoia (26'/455/EFI/HEI)

 

[blank]

>
> There have been a lot of reports of failures on D rated
> tires, GM recalled the D's and replaced them with E's.

I don't disagree with the need for E rated tires. What gets me is all the
people that are running D rated tires, and there are a bunch of them out
there, and not seeing the failures. My father runs D rated General radials
that are severely underinflated(IMO) against my advice and admonition(he's
an adult and makes his own choices). Logically, he should be destroying
front tires on a regular basis. In 35,000 miles, he has never had a front
tire fail and has never had a General radial fail. The only failures that
he's experienced were with some Dunlops(two failed and he made the tire
store replace the whole lot with Generals) and those failures occurred on
the front bogie. He does however experience what I consider to be short
tread life. I've told him so, but it doesn't seem to bother him.

I'm not advocating that anyone use less than L/R E tires properly inflated,
but, if the problem is as bad as Cinnabar and GM make it out to be, why
aren't we seeing more failures? If it's that bad and that dangerous, then
it should be a very quick Darwinian process, leaving only those intelligent
enough to use L/R E tires(tongue firmly in cheek).

I have no desire to "argue with the experts". I'd just like to know why
their dire predictions don't come to pass.

My family rides on E rated tires,
Patrick

 

[travis martin]

>What gets me is all the
> people that are running D rated tires, and there are a bunch of them out
> there, and not seeing the failures.

I'm not a statistician, don't even play one on TV, but isn't this what they
call "anecdotal evidence?" That is, we all know people who have driven home
drunk and not been caught nor in an accident, but we intuitively know that
this is dangerous practice and odds are much better for the sober driver.
And the penalty for being wrong is pretty stiff. The risk/reward ratio is
deplorable.

The exceptions, your father for example, certainly exist, but the data
apparently favors the all steel E rated tires at 80 PSI cold...

My brother, who still smokes, always tells anyone who admonishes him to stop
"They haven't killed me yet."

Best regards,

Travis

 

[patrick flowers]

>
> >What gets me is all the
> > people that are running D rated tires, and there are a bunch of them out
> > there, and not seeing the failures.
>
> I'm not a statistician, don't even play one on TV, but isn't this what they
> call "anecdotal evidence?"

Hmm... One statistician's anecdotal evidence is another's data.

> That is, we all know people who have driven home
> drunk and not been caught nor in an accident, but we intuitively know that
> this is dangerous practice and odds are much better for the sober driver.
> And the penalty for being wrong is pretty stiff. The risk/reward ratio is
> deplorable.

Agreed, but dragging the illustration out to the extreme - my father
puts over 10,000 miles annually on his coach with tires that I agree are
dangerously underinflated. He's the equivalent of the fifth-a-day
drinker, not the social type. The last time we did this little
dance-around-the-tires ditty, more than a few GMCnetters fessed up that
they are still using D rated radials - I doubt they will open themselves
to such ridicule again. Go to a rally and try a random survey, I doubt
I need to tell you what you'll find.

> The exceptions, your father for example, certainly exist, but the data
> apparently favors the all steel E rated tires at 80 PSI cold...

This isn't going where I planned, nor even where I want it to, but here
goes anyway... What data? All I've seen is an engineering opinion from
Cinnabar/GM. Where's the data regarding failures? I doubt anyone
besides GM ever kept any and I'm sure they've tossed it by now. If Wes
was here, maybe he could share whatever Cinnabar has in their files, but
he probably wouldn't since we're "clueless".

> My brother, who still smokes, always tells anyone who admonishes him to stop
> "They haven't killed me yet."

I guess you missed the part where I said I don't condone my father's
actions, eh? I'm not trying to justify what he does - I want to know
why he hasn't paid for that mistake.

Patrick
- --
Patrick Flowers
Mailtoatrick

The GMC Motorhome Page
http://www.gmcmotorhome.com

 

[travis martin]

> I guess you missed the part where I said I don't condone my father's
> actions, eh? I'm not trying to justify what he does - I want to know
> why he hasn't paid for that mistake.

No, I didn't miss that part, I understood that you believed in the E rated
tires enough to run them yourself. And I really don't have any idea why he
gets away with it and some others apparently have not. Perhaps he doesn't
drive as fast or as heavily loaded.

My father-in-law is one of the finest people I've ever met, but we have
essentially the same disagreement on tires, albeit passenger car tires. I
have been married to his daughter for a bit over 21 years; in that time,
we've both bought a fair number of tires. He insists on buying the absolute
cheapest tire he can find. When he was younger the family went to South
Padre Island every summer, pulling a travel trailer behind a pickup. Every
summer he'd have at least one and usually two blowouts. This cost him a fair
amount of down time and often he paid 'way too much for some fillin'-station
brand tire to get going again. Once he had a blowout on his trailer that
took out a lot of floor and destroyed his refrigerator. But he still buys
the bargain tires to this day.

Me, I have a much better idea. I buy premium tires, then trade off the car.
I've done it several times. I'm a great guy to buy a car from.

Travis

 

[patrick flowers]

>
> > I guess you missed the part where I said I don't condone my father's
> > actions, eh? I'm not trying to justify what he does - I want to know
> > why he hasn't paid for that mistake.
>
> No, I didn't miss that part, I understood that you believed in the E rated
> tires enough to run them yourself. And I really don't have any idea why he
> gets away with it and some others apparently have not. Perhaps he doesn't
> drive as fast or as heavily loaded.

Well, that's at least part of it. He's close to 70 and doesn't like to
drive the GMC much over 60mph.

> My father-in-law is one of the finest people I've ever met, but we have
> essentially the same disagreement on tires, albeit passenger car tires. I
> have been married to his daughter for a bit over 21 years; in that time,
> we've both bought a fair number of tires. He insists on buying the absolute
> cheapest tire he can find. When he was younger the family went to South
> Padre Island every summer, pulling a travel trailer behind a pickup. Every
> summer he'd have at least one and usually two blowouts. This cost him a fair
> amount of down time and often he paid 'way too much for some fillin'-station
> brand tire to get going again. Once he had a blowout on his trailer that
> took out a lot of floor and destroyed his refrigerator. But he still buys
> the bargain tires to this day.

Hmm... His last name's not Flowers is it? )

Patrick
- --
Patrick Flowers
Mailtoatrick

The GMC Motorhome Page
http://www.gmcmotorhome.com

 

[gary miller]

Emery
Now I see why you know what you are talking about. I taught physics lab at
Dartmouth in the mid 50's -- maybe you were one of my students.
Gary
North Bend, Oregon Coast

Yes, I am an "engineering type" but I also have an MBA from Dartmouth
College

> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[ron & gina]

Hi Heinz, As you might know I am new to RVing, and the great GMC! But when
I got my Pumpkin-Rose P.O. said tires should be at 80# cold(or for here as
cold as can be > ), Tho for first trip when I got to Antioch tire
pressure was at 67#, Increased all to 80#, During return trip to AZ. I did
not notice any real difference in the ride. I for one believe that most if
not all GMC's are close to there limit on weight during travel (info from
this great net site and the few that I had the great opportunity to see, So
the extra security of knowing that the tires can take its max. load being
set at 80# far outweighs the small difference in ride change that I notice.
I know there's alot of different variables to tire problems and taking one
of them away eases my thoughts for my little brain >. It could have
always been OK, But sometimes it only takes that one time and it could be
the last one!!!! Hope not!!!!And again as I have see here Thats just me and
what I do!!!!!! > Have a safe drive!!!!!!!!!!

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave, AZ.

- -----Original Message -----
From:
To:
Sent: Monday, September 20, 1999 11:06 AM
Subject: GMC: Tire Question re 65 vs 80 lbs on E's

> The last thing I want is to get a lengthy discussion going on theory or
manufacture hype so this is a question aimed at facts gained by experience
only please.
>
> And it's not asking advice on what I "should be" doing , that may come
later.
>
> If you've been running tire pressures in the sixties and have gone to 80
lbs I'd very much appreciate your comments as to ride difference. Is it
harder/harsher?
>
> I'm currently running 65 on the new E's as was recommended by the tire
dealer. As he will get my complaints if he gave wrong advice I put
reasonable value to his advice, but....
>
> I've been runnning 65 since day 1, but on D's.
>
> The wear on the tires removed did not indicate under/over inflation.
>
> My E's are not squatting.
>
> I'm pondering the 80 lbs but it's one of those if it ain't broke I may
want to leave it alone.
>
> I'd especially like to hear if anyone has tried 80 and gone back. Don't be
shy ;-)
>
> Thanks
>
> Heinz
> Bakersfield, CA
>

 

[bdub]

Gene

Hey! It's no big deal! Don't have a coronary, just exercise your delete
key. The subject is clearly marked and if you don't want to read it, you
don't have to.

This is merely a few growing pains of the list. It'll go away shortly but
will undoubtedly return again and again. Like Patrick pointed out, there
are new subscribers signing on all the time and need this 'new to them'
information. As an old hand, you'll just have to learn to put up with it
or suffer not having access to all the rest of the excellent information
that comes with it.

Hang in there Gene. It won't last long.

bdub
(You addressed Patrick, but you posted to the list so I guess it's ok for
me to respond.)

>Patrick,
>A few months ago on this list I enjoyed all that I could stand on this tire
>thing. Now its going again I'm tired of it again! I'm not at all sure that
>most people are. I'll do what I want to with my tires and you do what you
>want with your tires. I get too much good info on hundreds of other things
>about the GMC Motorhome and I have all that I ever want on tires! If your
>list is going to continue this tire business then I will just get off. A
>number of people have helped me with alot of stuff and I really appreciate it
>too.
>Thanks,
>Gene

 

[ron & gina]

Hi Gene and all,
Now this is nothing towards you, But I for one am new to RVing and this net
site. So alot of old hard hashed out, not going to change me, I'll do what
ever I want (and all should/will, but KEEP info coming) post/replys are new
to me. So I believe Patrick in allowing this to go on is very valid and his
right, this is a fine info. site for the GMC for new and old owners. And
like you said there is alot of info to be had. Does not all web browsers
have a delete button? Don't restrict newbies as my self to the many good/bad
(but let me learn) GMC info on this web site new or old, which I'm sure you
have contributed too, So any removal of one's self from this site removes
good info for newbies like my self and others. Just delete them old darn
used up messages please I need all the help I can get. I do delete when I
believe I got the info I need to make my decision on what ever the topic is.
And as always I use but not my saying This is what I do, not what you
should do. BUT KEEP THE INFO FLOWING!!!!!!! YABGASHYH----> You All Be Good
and stay here You Hear >

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave,AZ. 105deg. IHHAI----> Its Hot Here Ain't It

- ----- Original Message -----
From:
To:
Sent: Tuesday, September 21, 1999 3:15 PM
Subject: Re: GMC: Tire Question re 65 vs 80 lbs on E's

> Patrick,
> A few months ago on this list I enjoyed all that I could stand on this
tire
> thing. Now its going again I'm tired of it again! I'm not at all sure that
> most people are. I'll do what I want to with my tires and you do what you
> want with your tires. I get too much good info on hundreds of other things
> about the GMC Motorhome and I have all that I ever want on tires! If your
> list is going to continue this tire business then I will just get off. A
> number of people have helped me with alot of stuff and I really appreciate
it
> too.
> Thanks,
> Gene

 

[rob teed]

Well,
I've been on this list long enough to know that most
everybody puts the " Subject " up for everyone so
you know what the content of the post is..If I see
a thread going round that I think is of no interest to
"ME" I just skip it!
Of course,
I may have have to post a question on that subject to
retreive information that I may have passed up the first
time. Like when I get ready to purchase new tires next
year..then I'll need the info thats already been hashed
over....You all forgive me if in the future I need this
info.....Anyway...If ya wait a week or so we will all
be debating something else.
Rob Teed 74 Painted Desert

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailtowner-gmcmotorhome]On Behalf Of Genehy
> Sent: Tuesday, September 21, 1999 6:15 PM
> To: gmcmotorhome
> Subject: Re: GMC: Tire Question re 65 vs 80 lbs on E's
>
>
> Patrick,
> A few months ago on this list I enjoyed all that I could stand on
> this tire
> thing. Now its going again I'm tired of it again! I'm not at all
> sure that
> most people are. I'll do what I want to with my tires and you do what you
> want with your tires. I get too much good info on hundreds of
> other things
> about the GMC Motorhome and I have all that I ever want on tires! If your
> list is going to continue this tire business then I will just get off. A
> number of people have helped me with alot of stuff and I really
> appreciate it
> too.
> Thanks,
> Gene
>

________________________________________________________
NetZero - We believe in a FREE Internet. Shouldn't you?
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html

 

[patrick flowers]

>
> Patrick,
> A few months ago on this list I enjoyed all that I could stand on this tire
> thing.

Now you fella's don't be tough on Gene! He's just expressing his
opinion too!

Patrick
- --
Patrick Flowers
Mailtoatrick

The GMC Motorhome Page
http://www.gmcmotorhome.com