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| Tire pressure [message #363812] |
Tue, 04 May 2021 15:06  |
thigh19
Messages: 92
Registered: July 2019
Location: Vancouver Wa
Karma: 1
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Was reading online, cinnabar recommended 80psi tire pressure . My glovebox says 60psi. Have talked with another GMC’r and he says 65 front, 60 rear. What is the general thought process? By the way, Firestone says 80psi on the tire.
Thanx
Thom High
1973 Sequoia
Vancouver Washington
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| Re: Tire pressure [message #363816 is a reply to message #363812] |
Tue, 04 May 2021 16:23  |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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80psi is nuts, unless you're into loose fillings and a hard ride. All tire manufacturers have inflation charts for their tires on their websites. The correct tire pressure for a given tire is 95% dependent on the load on that particular tire.
I've assisted at GMCMI rallies where they weigh all 6 tires and check ride height. It's very illuminating. Without knowing the actual load and ride heights many people mistakenly believe that their handling and ride problems have to do with the steering box or linkage. We've seen coaches where the side to side weights were so far out of balance that I was surprised the things could drive straight in the parking lot. Over or under inflation affects the tire's contact patch and tread and sidewall stiffness. These are things that affect the safety of you and yours. Don't guess. Make it a point to get your coach weighed. There are a number of places to have it done.
Generally you won't go wrong with 65psi all the way around, but the rear 4 tires have less of a load than the front tires, so some will drop the rear tires by a couple or five psi. Again, the manufacturer's load tables rule. Know your weights.
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| [GMCnet] Re: Tire pressure [message #363819 is a reply to message #363813] |
Tue, 04 May 2021 19:16 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Thom,
What is on the glove box refers to Bias Belted tires, and were all using
Radials.
Lot depends on how much stuff your carrying inside the coach.
I run r65-70 in front
On Tue, May 4, 2021 at 1:26 PM James Hupy wrote:
> Firestone Number is MAXIMUM INFLATION PRESSURE. Not what you should run.
> Start with 65 psi all around. If that is a bit too harsh a ride, reduce by
> 5 psi at a time.
> Jim Hupy
> Salem, Oregon
>
> On Tue, May 4, 2021, 1:09 PM Thom High wrote:
>
>> Was reading online, cinnabar recommended 80psi tire pressure . My
> glovebox
>> says 60psi. Have talked with another GMC’r and he says 65 front, 60 rear.
>> What is the general thought process? By the way, Firestone says 80psi on
>> the tire.
>> Thanx
>> Thom High
>> 1973 Sequoia
>> Vancouver Washington
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| [GMCnet] Re: Tire pressure [message #363824 is a reply to message #363819] |
Wed, 05 May 2021 10:43 |
Norm Bowker
Messages: 6
Registered: August 2010
Karma: 0
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Also the pressure is for load range D tires, most are running E’s.
Sent from my iPad stormn
> On May 4, 2021, at 8:17 PM, Jim Kanomata wrote:
>
> Thom,
> What is on the glove box refers to Bias Belted tires, and were all using
> Radials.
> Lot depends on how much stuff your carrying inside the coach.
> I run r65-70 in front
>
>> On Tue, May 4, 2021 at 1:26 PM James Hupy wrote:
>>
>> Firestone Number is MAXIMUM INFLATION PRESSURE. Not what you should run.
>> Start with 65 psi all around. If that is a bit too harsh a ride, reduce by
>> 5 psi at a time.
>> Jim Hupy
>> Salem, Oregon
>>
>>> On Tue, May 4, 2021, 1:09 PM Thom High wrote:
>>>
>>> Was reading online, cinnabar recommended 80psi tire pressure . My
>> glovebox
>>> says 60psi. Have talked with another GMC’r and he says 65 front, 60 rear.
>>> What is the general thought process? By the way, Firestone says 80psi on
>>> the tire.
>>> Thanx
>>> Thom High
>>> 1973 Sequoia
>>> Vancouver Washington
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: Tire pressure [message #363845 is a reply to message #363812] |
Thu, 06 May 2021 09:40 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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This is a repost of something I wrote December 2019. Might be worth repeating.
I have put the coach on a 6 yr replacement plan. 2 tires every two years. Seems the front tires wear the fastest. Then is seems the mid axle wears next. and the rear axle is just along for the ride and wear the least. When the front wear to a point where traction may be compromised or reach 4 yrs old, I move them to mid axle. Mid axle rims get new tires and moved to the rear. Rear tires get moved to the front. Do this every two years, so I'm only laying out money for two at a time every two years. We also put on about 10 - 14 k miles every year. So by the time replace two 6yr old tires, they have between 30-42K miles on them. They have now timed out with as many miles as I can get out of them and still safely run them. This way, oldest tires are 6yrs, followed by 4 yrs and 2yrs. I've actually got one wheel...the passenger side mid axle that is slightly toed in and wears faster than all of the others. But it has become not worth the effort to correct the slight toe problem on that wheel, because the tire there times out before it is worn below the wear bars. This all works for me running Michelin LTX-MS tires. If the coach will stand still for more than a couple of weeks, I tire cover them as I do not have inside storage.
The hard part is getting into that replacement management scheme. You may have to replace a set a year or two earlier or later to get the rotation right. I was able to do it when I bought an off-brand set of tires that tread separated. Two of them at two years use and another two at 4 years. Just worked out for me. The problem with off-brand tires is that they were regionally available, so when they went bad while traveling south, I was not able to get to a shop that carried the brand to make the adjustment. The one time I could get to a shop that carried them, it was far enough out of the way that it would have cost me more in gas to get there than the cost of the replacement tire. JMHO, but now I use only Michelin LTXMS, and have never had a problem with them. To me, the peace of mind is worth the extra money for the Brand Name.
I also take the best of the two 6 yr old tires and move it to the spare. Requires having same size rim on spare as the other 6 on the coach. That way the spare is never more than 8 yrs old.
FWIW, some time when you have time, take your GMCMH to a empty part of a parking lot. Stop somewhere out of the way. Then, turning the steering wheel, crank the wheel all of the way either left or right. Put coach in gear and go forward 1/4 to 1/2 of a circle. Stop, put it in park and get out and look at the 4 rear wheel/tires. It is shocking how much those bogie arms and tires bend/squirm to accommodate a turn. / | \ Front tires don't react nearly as extreme as rears. So, every time you turn a corner, you are really working those sidewalls. IMO, with that kind of squirm, this is why most blow-outs occur on the rear as those sidewalls are consistantly being bent/streatched to their limits. So, I think we need to be running a well made/engineered tire that is capable of handling this abuse. When I park my coach for the night or for that matter, any period of time, if I had just turned the wheel a little, I will point the wheels straight forward, then pull forward and back 2-3 times just to take the bend/squirm out of the tires. Just what I do. (JWID)
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Tire pressure [message #363852 is a reply to message #363812] |
Thu, 06 May 2021 18:21 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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80 is the maximum allowed inflation for load range E, AND the pressure required to carry the max load molded into the tire sidewall. I run 65 fronts and 63 rears. 65 spare. If I ever get 4 corner weights I will adjust accordingly, probably lower I’m guessing.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Tire pressure [message #363853 is a reply to message #363852] |
Fri, 07 May 2021 01:23 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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John,
That is exactly where I run my coach based on the weights measured on each tire. If you are ever coming through NW Indiana with your coach, call me and we will have you stop by the airport in Valparaiso, Indiana. We can weigh your coach at each wheel. The portable scales are hanging on the wall in my hangar there.
We also usually weigh coaches at most GMCMI rallys if I attend. We will probably weigh coaches next fall at the GMCMI rally in Wisconsin.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Tire pressure [message #363854 is a reply to message #363812] |
Fri, 07 May 2021 07:36 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Hope to get it weighed there in Wi this fall Ken. Thanks.
Remember the driver education classes for spouses and such at the rally’s? Might be interesting to have a couple good driving and bad driving coaches for owners to compare if the fairgrounds had a paved area parking lot at one of the rallies someday. I remember how they drove back in the 70’s.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Tire pressure [message #363855 is a reply to message #363854] |
Fri, 07 May 2021 08:50 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Senior Member |
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John, yes! This. I've asked a number of GMC owners how many GMCs they've driven - a very common answer being one. It's hard to compare when your data set is one.
Alex Ferrara related a story about how he was, as usual, spending his time at a GMCMI convention fixing peoples' coaches to drive straight. He was talking to a long time GMCer, with decades of automotive knowledge and business experience, and Alex asked to take a look at the guy's steering setup. Guy's like no, no need it's fine. Alex says humor me. Yep, the steering box was mis-clocked. Alex does his thing, fifteen minutes later says take it for a drive. Guy comes back with a huge smile exclaiming that he had always thought that that was how they were supposed to drive and just got used to it!
I'm willing to assist in this any way I can.
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| Re: Tire pressure [message #363856 is a reply to message #363852] |
Fri, 07 May 2021 08:53 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Senior Member |
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I've weighed my coach several times and it's pretty heavy. I use almost the exact same tire pressures as you do, John.
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| Re: Tire pressure [message #363867 is a reply to message #363812] |
Sat, 08 May 2021 08:41 |
MikeB
Messages: 133
Registered: December 2018
Location: South Bama
Karma: 1
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Senior Member |
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Thom
I have Firestone Transforce tires and there tire chart recommended 60 psi front (4190 weight) 55 back tires (6260 rear axle weight.) I did not weigh each tire. I just weighed the front and divide by two and rear divide by four. I think it should get you in the ballpark. Too much pressure keeps tires cooler but higher risk of impact damage. To low of pressure moves towards more heat but less chance of impact damage and better tread patch on road. Hope this helps.
M Beam
75’ Avion
TBI EBL , 3.70 LSD and other stuff
Zuki Sidekick,
Dozier Al
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| Re: [GMCnet] Re: Tire pressure [message #363889 is a reply to message #363888] |
Sat, 08 May 2021 21:46 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Yes, he read it right off of the side of any LRE tire of that size but failed to read, or understand, the weight molded in the tire next to it. Then he passed that information on to us GMC dummies.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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