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Old 03-09-2018, 11:56 AM   #1
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Please review my weight numbers

I blew out a 2014 Goodyear 245/70/19.5 inside drivers side dual Sunday, driving 60mph, temps in the mid-70's, cold tire pressure 85psi and pretty sure I didn't hit anything. I am replacing all 6 with Toyo M143's that seem so popular on this site. Not willing to take a chance that the other Goodyear tires are ok, since they have the same date code and we are headed to Utah in late April. The G670's were put on by the PO and they don't seem to have a very good reputation.

Thought it would be a good idea to review the numbers again and still come up with 85 psi being the right pressure for these weights.

Here are the numbers I based using 85psi on:
20,500# GVWR 2006 F-53
7,000# Front GAWR
13,500# Rear GAWR

Scale weights loaded for a 2 week trip, full fuel, 1/4 water and empty holding tanks:
6.570# Front
12,580# Rear
19,330# Total
( I can't find my notes for 4 corner weights, but they were fine, very close side to side)

Goodyear and Toyo tire charts are the same for this size:
85PSI
3740# single x 2 = ,7480# front
3515# duals x 4 = 14,060# rear
Total 21,540#

19,330# x 105% ( 5% safety margin)= 20,296#
19,330# x 110% (10% safety margin)= 21,263#

National's sticker specified 80 psi = 3460# single + 3415# dual for a total of 20,940#. I thought that did not have enough safety margin, so went with 85 psi.

90 psi = 3890# single + 3655# dual for a total of 22,400#.

I tried 90 psi, but thought it rode significantly rougher, went back to 85.

Anyway, if you made it this far, I would appreciate your opinions on where my psi should be.

Thanks, Steve
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Old 03-09-2018, 12:46 PM   #2
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Your pressures and weights sound fine.

You may have hit something that you just didn't see or maybe the tire had a defect.

I don't think there was anything you could have done different to avoid the blow out.

Do you have a tire pressure monitoring system (TPMS)? If not, that is one device that I would recommend. It won't help in a sudden blowout, but it will let you know if you have a slow leak that could result in a blowout over time - so in that case you could pullover and deal with the situation before it becomes a blowout.

Was there any vehicle damage?
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Old 03-09-2018, 12:49 PM   #3
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So Goodyear is having problems with tires... search and read the blogs..

As per your tire pressure request... I suggest you go to the Toyo Truck tire web site which will give you suggested tire pressure at a given weight... However after driving a large rig for years I'm wondering if your 85 lbs isn't too light, allowing for too much side wall flex and the heat related to side wall flex... Seems like closer to 100 lbs makes more sense to me.... but that's what I'd do...

BTW truck tires are marked with suggested tire pressure at a specific load, see the side wall, this differs from automotive tires which are rated at MAX load and tire pressure....
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Old 03-09-2018, 12:56 PM   #4
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Quote:
Originally Posted by StephenW View Post
I blew out a 2014 Goodyear 245/70/19.5 inside drivers side dual Sunday, driving 60mph, temps in the mid-70's, cold tire pressure 85psi and pretty sure I didn't hit anything. I am replacing all 6 with Toyo M143's that seem so popular on this site. Not willing to take a chance that the other Goodyear tires are ok, since they have the same date code and we are headed to Utah in late April. The G670's were put on by the PO and they don't seem to have a very good reputation.
Thought it would be a good idea to review the numbers again and still come up with 85 psi being the right pressure for these weights.

Here are the numbers I based using 85psi on:
20,500# GVWR 2006 F-53
7,000# Front GAWR
13,500# Rear GAWR

Scale weights loaded for a 2 week trip, full fuel, 1/4 water and empty holding tanks:
6.570# Front
12,580# Rear
19,330# Total
( I can't find my notes for 4 corner weights, but they were fine, very close side to side)

Goodyear and Toyo tire charts are the same for this size:
85PSI
3740# single x 2 = ,7480# front
3515# duals x 4 = 14,060# rear
Total 21,540#

19,330# x 105% ( 5% safety margin)= 20,296#
19,330# x 110% (10% safety margin)= 21,263#

National's sticker specified 80 psi = 3460# single + 3415# dual for a total of 20,940#. I thought that did not have enough safety margin, so went with 85 psi.

90 psi = 3890# single + 3655# dual for a total of 22,400#.

I tried 90 psi, but thought it rode significantly rougher, went back to 85.

Anyway, if you made it this far, I would appreciate your opinions on where my psi should be.

Thanks, Steve


I dont believe you stated what max pressure was stated on the side of the tire. I have a similar F 53 that you outlined and my tires state max pressure of 110 psi. I would never ride on the tires on my rig with pressures that low. I suspect your tires will ask for a similar max pressure.

I am also surprised you dont have seven or eight million replies by now as tire pressure is a hot topic on rv forums.

If I am in the ball park then your tire might have failed because there was not enough pressure. Remember JMHO and worth exactly what you paid for it.

Good luck and keep us posted.
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Old 03-09-2018, 01:28 PM   #5
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Steve-

Could you please provide a copy of, or a link to an online source for, the Toyo inflation charts you used in your calculations? The one I looked at was at this link. I'd like to look at the same tire data you are.
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Old 03-09-2018, 02:08 PM   #6
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Hey Steve,

Sitting here eating lunch and read your post.

Getting all this weight stuff squared away so you're confident your good to go is a PIA isn't. It was hard for me in the beginning.

Looking at your weights you seem look fine to me without looking at the charts themselves.

You're just a tad heavier than me in the front and a little more in the back. I run 80psi - 82psi CP all the way around. I have Mich's in front and Toyo's (H) rated in the back. See my signature.

I know my weights are perfect because I went to Escapees and had an exact 4 corner weigh which has a scale under each tire. This was my first preliminary weigh to see where I was at. After this weigh, I came back to home base, shifted some weight, and now am adding the last bit of items on our list to get ready to travel FT, first long trip in May to Maine. Right before we leave, I'm going to Escapees one more time to get a final 4 corner weigh.

So with all being said, I built me a drawing model of our rig with all the data and notes, along with both tire charts at the bottom. It makes it real easy for me to keep track of where I am and insures me that I'm within spec and then some.

I've attached my drawing just so you can see how I do this, and compare with your numbers.

And yes I also have TPMS on coach & toad. You betcha. I cover them too while parked. I watch my tires like a hawk.

You were smart in changing out ALL your tires.

Good luck and stay safe.
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Old 03-09-2018, 04:59 PM   #7
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Quote:
Originally Posted by jelag View Post
So Goodyear is having problems with tires... search and read the blogs..

As per your tire pressure request... I suggest you go to the Toyo Truck tire web site which will give you suggested tire pressure at a given weight... However after driving a large rig for years I'm wondering if your 85 lbs isn't too light, allowing for too much side wall flex and the heat related to side wall flex... Seems like closer to 100 lbs makes more sense to me.... but that's what I'd do...

BTW truck tires are marked with suggested tire pressure at a specific load, see the side wall, this differs from automotive tires which are rated at MAX load and tire pressure....

X 2
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Old 03-09-2018, 05:48 PM   #8
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Additional info

The 2014 Goodyear's have a G load rating and I used the weight numbers from their weight tables. Previous owner owned this MH 9 years and recommended 85 psi, same as I came up with using their info. Max sidewall pressure is 110psi. He traveled several times from GA to UT and Wyoming with no tire issues.Always stored indoors when not on the road.

The new Toyos have an H load rating at 120 psi and I used their weight tables for this posting. This is a pretty lightweight class A, especially when compared to my neighbors 40k# Newmar.

Clearly, I want to safe, but don't want to beat the RV to death with too much pressure. I may try 90psi in the new Toyos to see how the ride compares to the Goodyear's at that psi.Thanks for all the comments!
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Old 03-09-2018, 06:04 PM   #9
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Your pressures are good. We ran the same tires and pressures four years on the previous coach; weights almost identical to yours. I use an infrared thermometer to monitor tire temps.
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Old 03-09-2018, 06:19 PM   #10
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Just in case you don't have a TPMS system, here's what I posted earlier today:

Hey Folks! Today eBay has a 20% off coupon so I finally bought a TPMS, saved over $80!

It’s the Tire Minder A1A-6 and with the coupon got it for $343!

I think this is the link(if not, just go to eBay): http://www.ebay.com/itm/263523972878
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Old 03-09-2018, 08:05 PM   #11
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Your weights vs. pressures are just fine. Your math appears to be sound.

The only problem I see is that you really don't know what pressure the tire had in it just before the failure. It's possible a valve failed, an valve stem extension failed, you ran over something or any one of dozens of other events could have reduced the pressure in that tire resulting a blow out due to sidewall flexing or over loading. Although in the picture it doesn't appear the sidewall failed.

At any rate, it's very difficult to determine what the cause of a blow out is due to all the damage caused post blow out. About all you can do is put on the new tires, blow them up to the appropriate pressure, cross your fingers and hope for the best.

TPMS might help but in all the blowout reports I've seen nobody seems to have any indication prior to the boom even with TPMS.

Just a side note, in tires of the same size and load range, the inflation tables will be the same regardless of the tire manufacturer.
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Old 03-10-2018, 08:36 AM   #12
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update from OP w/pics

Pics attached of the 2014 Goodyear G670 245/70/19.5 that blew out. It's not shown in the pics, but the valve stem and braided extender were intact and looked good. Never had a leak issue and confirmed tires were at 85 psi just before we left. We had driven about 100 miles before it blew.

I'll report back what the tire dealer thinks caused this tire to blow when the new Toyos are mounted the end of next week. The PO told me the tires had 15 k miles on them when I bought the RV January 2017 and we've put another 5k on them, so 20k total. RV has 44,500 total miles, FWIW.

Thanks again for all the help.
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Old 03-10-2018, 06:56 PM   #13
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I always stop a few miles down the road each morning to do an additional check of things and a walk around. One time I checked my tire pressures before departure and all was well at 90# all around. About 5 miles down the road I pulled into a rest area for my second walk around.

I hit all the tires with a tire billy and one of them went thud. Took out the gauge and checked pressure and it was at like 5 pounds. Turns out when I checked the pressures prior to departure the valve stem stuck open and all the air leaked out while I drove the 5 miles to the rest area.

Moral of the story is that what the pressure was 5 minutes ago ain't necessarily the same as what the pressure is now.

Since then I've had TPMS for near real time tire pressure monitoring. Not saying your problem was due to low pressure or that TPMS would have helped. Just relating a real life story.
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Old 03-10-2018, 07:12 PM   #14
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3+ year old tires and you had a blowout? Yikes! Hope you get some info on the failure. And that you are done with tires for awhile!
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