Home » Public Forums » GMCnet » Can someone explain the dogma against P tires ?
| Can someone explain the dogma against P tires ? [message #371025] |
Mon, 30 January 2023 07:09  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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This is not for the coach but for a Sprinter van, but i thought this is a good place to get the question answered.
You can buy an all season highway tire at 245/75/R16 with a load index 111T - that is 2400 lb per tire - 14,600 total load.
So why would it be a bad idea to put it on a GMC, or, a four ton Sprinter van. (four wheel 9600lb)
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Can someone explain the dogma against P tires ? [message #371028 is a reply to message #371025] |
Mon, 30 January 2023 17:08  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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How they engineer the tire. LT would almost always be a higher ply and heavier sidewall.
But from my experience from lots of fleet vehicles. We had “D rated”. And had flats here and there. We went to E rated and flats seemed a thing of the past. We
Were not overloading the D weight rating.
So would only buy E rated
Tires for gmc.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Can someone explain the dogma against P tires ? [message #371029 is a reply to message #371025] |
Mon, 30 January 2023 18:40 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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A 225 75R 16 LRE has a 2680# rating not 2000.
P is passenger car rated. Often improperly installed on Sprinters etc.
If you are on Facebook, go to “Tire Service, Elk Grove Village Illinois” and scroll way back to Sept 20, 2022 and you will see what happens in text and pictures what happens when P tires are used on commercial vehicles. You don’t want that with a MH and passengers.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Mon, 30 January 2023 20:06] Report message to a moderator |
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| Re: Can someone explain the dogma against P tires ? [message #371030 is a reply to message #371029] |
Mon, 30 January 2023 21:31 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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Ya'll are not answering the question. Where is Matt Collie when we need him?
Yes, LT tires have stiffer sides and whatnot and would be preferred for a lot of reasons, But there are P tires that will carry the weight, either four under a Sprinter or six under a GMC.
People do put P tires on a sprinter if the load is light and to reduce noise. And people say it's a bad idea. I want a better understanding of why.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Can someone explain the dogma against P tires ? [message #371031 is a reply to message #371025] |
Tue, 31 January 2023 06:58 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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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: Can someone explain the dogma against P tires ? [message #371032 is a reply to message #371025] |
Tue, 31 January 2023 07:03 |
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.
Just the way I do it.
Larry
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Can someone explain the dogma against P tires ? [message #371034 is a reply to message #371025] |
Tue, 31 January 2023 09:46 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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One of the very few inconveniences of being retired from the halls of Detroit is that I have lost contact with so many good sources of the factual information. This particularly true as much of my time in the OEs was warranty verification. (You might be surprised at what some people think should be covered by the warranty.) I was kind of hoping someone with more current experience might join in.
In an extended discussion with my Firestone friend (a now lost contact) when I was still an inexperienced coach owner, he suggested that our coach could well be fit with a P-metric tire except that I had not yet changed out the rims to 16. A lot of the discussion was actually about the future availability of 16.5 tires. (My real reason for the contact.) As it happens, they had recently taken one set of tooling out of line at one plant, but were going to keep up production at a lower rate for a very long time because that tire (specifically the 8.75) still had significant demand in the agricultural sector.
As usual, our conversation covered a lot of ground. He was aware of but not exceedingly familiar with GMCs and stated that there had been problems in multi-tire axles with P tires. In case of a dual (like a P30), not all dual mounts can accommodate the side wall shape of a P tire at load. P tires do have softer side walls, and in a dual configuration, the sidewall can contact each other and apparently this is a very bad situation. His description of the difficulties was extensive, but I really didn't retain it because it was not a case that interested me. He did say that tandems (what we have) also do not fair real well either as the scrubbing on short radius turns did could cause the tread belts to try to slip. This should not be an issue with a first quality tire.
There was an abrupt halt in the discussion at that point as he apparently accessed another mental file and had to shift gears to get things aligned. Side Walls? I had told him I did not have duals, but instead had a tandem rear axle. This was the speed bump in the discussion. He asked very specifically if we hit curbs with the rear tires. I allowed as this only happened when we turned corners. (This was actually not accurate but more on this later.) The actual issue here was that the LT tires do have heavier and stiffer side walls and are designed to tolerate a "curb hit" (he had an inside term for this) and the P tires are not there at all. This is why the ride is much softer and the lateral slip is less. I personally have never drifted the coach and do not intend to, but I cannot make this claim for my passcars.
As to rolling resistance, yes, a P tire of same size at same load will be lower than the LT. He was not specific as to how much lower. He allowed that an OE had recently been accused of doing the tests for CAFE for light trucks with P tires to get better numbers. I did not collect specifics, but I do believe that the case could exist. While at Jeep/Truck in the late 90s, we were told by the EPA that our recommended lubricants were "too low a friction" to be accepted for standard tests. In durability, we didn't change anything, but I know that the certification people did.
At the tail of all this, he injected something about the ag tires having better UV resistance and other things to improve the calendar life. I could not grasp how much effect this might really have.
That is pretty much what I know about the subject. So, I will end the technical part of this here. Maybe we can get Roger Marble to an international some year. He has been to several FMCA events.
I have also had great success with the two at a time rotation plan. When I discovered how much trouble I was really in, I bought a full set for the coach and that was a big bite to maintenance budget. I am glad I am not throwing away 22.5s. If you look at my coach pictures, you can notice that some times there is a mix of wheel colors. The white ones are 16 and those in gray prime are the 16.5s.
Oh, the side wall non-turning issue was that I used to regularly take Chaumière over a steel grate bridge that had high steel curbs and 9' wide lanes. If I was not real careful, those right side read rims could hit the high steel curb. I don't do that trip anymore with the powder coated white rims.
A specific aside for Dave (the OP), if you are still planning a bonsai run, P tires might get you a little more tank range and thus get a little longer between stops.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Can someone explain the dogma against P tires ? [message #371035 is a reply to message #371025] |
Tue, 31 January 2023 10:29 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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To go back in time, and this is all documented, there were issues with the OE General Jumbo tires failing. I believe Wes from Cinnabar was brought in as a consultant. Long story short he decreed that the only acceptable tire was the Michelin XPS Rib, an all steel carcass, steel belted tire. Reasoning had to do with unique side loading our coaches presented to the tires. Not an MS tire and not a gentile riding tire. As time passed, tire tech changed and I went with LTX MS load range E, poly carcass, steel belted though Cinnabar did not bless this tire. These served with zero issues and no rebalance for over 12 years (yes past recommended but indoor climate controlled storage). I then bought Cooper HT3s E rated about 4 years ago and again zero issues to date. I would buy them again due to better value, hoping that new ones have not been changed since the Goodyear aquisition of Cooper. All comments from memory. As a CDL driver I’d never put sub capable tires on a TZE.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Tue, 31 January 2023 10:35] Report message to a moderator |
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| Re: Can someone explain the dogma against P tires ? [message #371039 is a reply to message #371035] |
Tue, 31 January 2023 16:47 |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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JohnL455 wrote on Tue, 31 January 2023 11:29To go back in time, and this is all documented, there were issues with the OE General Jumbo tires failing. I believe Wes from Cinnabar was brought in as a consultant. Long story short he decreed that the only acceptable tire was the Michelin XPS Rib, an all steel carcass, steel belted tire. Reasoning had to do with unique side loading our coaches presented to the tires. Not an MS tire and not a gentile riding tire. As time passed, tire tech changed and I went with LTX MS load range E, poly carcass, steel belted though Cinnabar did not bless this tire. These served with zero issues and no rebalance for over 12 years (yes past recommended but indoor climate controlled storage). I then bought Cooper HT3s E rated about 4 years ago and again zero issues to date. I would buy them again due to better value, hoping that new ones have not been changed since the Goodyear aquisition of Cooper. All comments from memory. As a CDL driver I’d never put sub capable tires on a TZE.
Wes also was firm in his belief that the XPS RIB tires had to be inflated to 80PSI. Early on (1998) I followed his advice as did the PO. The ride was quite rough and and steering was worse.
Later on I was made aware of the benefits of going with less pressure and going away from all steel tires (I went with BF Goodrich Commercial T/A) and have been much happier with both ride and steering. I've have no problems with the Goodrich tires. Also, I never run my tires more than 6 years.
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
[Updated on: Tue, 31 January 2023 16:51] Report message to a moderator |
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| Re: Can someone explain the dogma against P tires ? [message #371042 is a reply to message #371040] |
Wed, 01 February 2023 09:40 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
Karma: 2
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I had a 1984 VW Vanagon and always used light truck tires usually D because they were only one or two dollars more.
I was recommended to use LT's because of front wheel loading under high speed braking.
Near the end of the vans life I needed snow tires for the last few years. The tire store salesman recommended a passenger snow tire.
Seeing it was the only one in stock I bought 2 and mounted them on the front temporarily. I was planning to put them on the back in a few weeks with the old snows on the front. Well driving to work before the swap, in the rain, I had to brake hard and blew out the right front tire. Used all 3 lanes,no traffic,did a 360 hit the right guard rail with the front right bumper,fender.Changed the tire in the hard rain. The next day I drove to the tire store told them my story. They were more than happy to give me 4 new tires on my choice.
Moral of the story: Don't be cheep with things that can kill you or others.
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
[Updated on: Sun, 05 February 2023 20:57] Report message to a moderator |
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| Re: Can someone explain the dogma against P tires ? [message #371043 is a reply to message #371034] |
Thu, 02 February 2023 12:27 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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Matt Colie wrote on Tue, 31 January 2023 09:46
A specific aside for Dave (the OP), if you are still planning a bonsai run, P tires might get you a little more tank range and thus get a little longer between stops.
Matt
Matt, thanks for all that. very informative as usual. I'm gonna sell the coach with the best tires i can put on it, probably Michelin LTX or something like that.
I was really wanting to get smart on this topics for my 2006 Sprinter- it is SO NOISY and i want to eliminate every bit of sound I can trim and I think P tires might help.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Can someone explain the dogma against P tires ? [message #371045 is a reply to message #371043] |
Fri, 03 February 2023 11:10 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
Karma: 2
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Check out the Nokian tires.
Cheaper than the Michelins and very good tires.
I have the Nokian Rotiiva HT All-Season Radial Tire - 225/75R16 112S on my GMC and couldn't be happier.
Quiet, good grip, long life. Also made with canola oil, so better for the environment.
There should be a version for your Sprinter.
From Amazon:
The Nokian Rotiva HT tire is a highway tire for SUVs with a new high modulus tread compound that grips and lasts a long time. The Nokian Rotiva HT tire has Nokian Tire's patented silent groove and silent sidewall technology. These technologies ensure that noise generated by the tire is minimized for a quiet, comfortable ride. This strong light truck tire is reinforced for heavy SUVs, and trucks with a tread design and tread pattern for excellent on-road wet and dry traction. The Nokian Rotiiva HT tire is also an tire that meets the strict European and North American standards for rolling resistance. This means better fuel economy and savings at the gas stations.
hertfordnc wrote on Thu, 02 February 2023 12:27Matt Colie wrote on Tue, 31 January 2023 09:46
A specific aside for Dave (the OP), if you are still planning a bonsai run, P tires might get you a little more tank range and thus get a little longer between stops.
Matt
Matt, thanks for all that. very informative as usual. I'm gonna sell the coach with the best tires i can put on it, probably Michelin LTX or something like that.
I was really wanting to get smart on this topics for my 2006 Sprinter- it is SO NOISY and i want to eliminate every bit of sound I can trim and I think P tires might help.
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
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| Re: Can someone explain the dogma against P tires ? [message #371047 is a reply to message #371025] |
Sat, 04 February 2023 09:43 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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LTX have been discontinued for several years. Agilis is the replacement. If you look at the tread pattern both center sets of blocks are angled the same way not alternating like the old LTX. In my mind this would tend to want to move you sideways with front drive under acceleration. I went with the HT3 Cooper as it almost copies the old LTX pattern. None of these tires have road noise issues.
John Lebetski
Woodstock, IL
77 Eleganza II
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