Blown tire update. - Page 3 - Montana Owners Club

sreigle · 06-19-2005, 11:13 AM

Stiles, I'm not sure if I mentioned this before or not... I learned the hard way that mixing load ranges on the same axle can and will in a short time throw an axle out of alignment. So now I am reluctant not only about mixing load ranges but mixing anything else, including tread pattern. So if I move to another brand it will be at least two tires, not just one. I perhaps am overcautious on this but having spent $150 to get the axles realigned once is enough.

bob n pam · 06-19-2005, 03:02 PM

All of us thank you, Stiles, for the time you spent studying the matter. Your shared information has helped us all.

stiles watson · 06-19-2005, 05:28 PM

Good insight, Steve. My sources have also encouraged matching tires on an axle, i.e., same brand, same size, etc. I could have taken the two intact 10-ply tires to put on one axle and just put two new ones on the other. Since I had already lost the two LT (light truck) tires, I became uneasy with that arrangement.

I forgot about the spare. Next time I go to the "home sight", I will call my tire man and get the spare changed too.

Gary n Linda · 06-21-2005, 02:07 AM

Hi Steve,
In response to your question about where the wheels are marked. Most are on the outside surface usually on the back. I have not been able to find anything on my wheels though. I've done a little more reseach and they do amke a load range F tire. Carlisle makes it in a ST235/85R16. Sorry about the delay in responding I've been away from my computer for a few days.

sreigle · 06-21-2005, 11:59 AM

Thanks for the reply. I guess I need to once again crawl under the Montana and check the ratings on ours. I'd bet ours will handle the 80 psi of the E range even though ours came with LR D. Almost all got E's, we just hit a time when they were using D's but I want to make sure the rims can handle the pressure before I go and buy new E's someday.

As for the LR F, not having seen an F before I figured it was a psychological thing and they skipped F. Apparently that's not the case. Thanks again.

cargary · 06-24-2005, 05:18 PM

When discussing the load the tires will carry at a certain psi and knowing what your 5er weighs, are you folks subtracting any of the weight that is being carried by the truck or better known as "pin weight", when determining what tire is most suitable for your 5er's?

We have the Tacoma tires with the LT235/85R16 and with "E" load range which are rated at a little better than 3000 lbs @ 80 psi. Now if the 5er weighs 14,620 loaded and the pin weight is 2,320, then 14,600 minus 2,320 equals 12,300 lbs. Now 4 tires @ 3042 ea. equals 12,168 lbs., this is what we are rated to carry safely - right? Are we correct in our figuring to arrive at what we should be able to safely carry with our current tires or have we figured wrong? Asuming that we have figured correctly, then with our current load, we are 132 lbs over weight. Is there a cushion built into the tire manufactors on the load range? We certainly hope so or we are headed for trouble. Any and all comments are greatly appreciated. Thanks in advance for your feedback.
Gary & Carole

Montana_2785 · 06-24-2005, 10:21 PM

Gary & Carol,

Even if you went to the usual trucker scales that give you the "axle" weights of the trailer, that won't account for differences in the side-to-side imbalance we can have. Also, the truck scales will likely weigh both trailer axles at once. The mechanical equalizer between the axles doesn't do as good a job as you might think. It is really important to have a trailer as level as possible while towing because of this.

Bottom line, unless you weigh each [i]>>TIRE

Illini Trekker · 06-25-2005, 02:53 AM

Another thing we should watch for is to high PSI in tires along with to low PSI. I only air my trailer tires to 72.5 PSI, with the heat of the road surface along with the increasing temperature threw the day tires will gain pressure. Yesterday we left the camp ground it was 68 out, 190 miles later with a temp of 95 outside, the trailer tires gained near 5 PSI. Here is a link to TireRack with some useful info on tires http://www.tirerack.com/tires/tirete...currentpage=38

stiles watson · 06-25-2005, 05:09 AM

When the tire manufacturer states that the rating is based on a cold tire pressure, the fact that the tire pressure rises during use is being taken into account. Under inflated tires reduces the life of the tire and increases the heat factor by increasing the amount of flex in the sidewall. As for me, I will inflate my tires cold to the pressure indicated by the manufacturer for the weight carried. It is my opinion that the atricle in the indicated URL supports my decision.

sreigle · 06-25-2005, 05:23 AM

Cargary, we use the weight on the axles. Our Montana was weighed on a CAT scale about a month ago. Total weight is 14,360. Pinweight is 3300. Weight on the axles is 11,060. I just wish I'd had each axle weighed separately so I'd know neither is overweight. Our axles are rated at 6,000 lbs. Actually I'd like to have each wheel weighed separately.

What you are rated to carry is subject to the lowest rating in the system. Your coach GVWR is one. Axle ratings are another. Tires yet another. If your tires are rated for 3042 at 80, then you should not exceed that on any one tire. Two tires together allow 6084 but if your axles are rated at 6000 then 6000 per axle is the max. You could go more than 3000 on a tire, up to 3042, so long as the two tires on that axle do not exceed 6000.

Likewise, you can have up to 12,000 on the two axles together so long as neither is over 6,000 (assuming 6,000 lbs axles) and no one tire over its rating.

I wondered if there is a limit on the pinbox so went out and checked. It says 15,500 so it will handle the overall coach weight just fine. What I don't know is the vertical rating for the pinbox and the upper area frame, including stress ratings. But this discussion is about tires and overall ratings.

cargary · 06-25-2005, 06:35 AM

With regards to tire pressure, I do, like the tire specifications point out and Stiles has indicated, that is check and make adjustments to the pressure when it is cold. Usually this is in the Morning before the sun shines on the tires and heats them up. I strictly adhere to this process unless a slow leak or loss of pressure occurs. After making sure that the pressure is set at the correct psi cold, I rely on the tire co's to have done their homework in engineering of the tires and don't make changes in the pressure during the course of the day at stops when a check shows the pressure higher than it was set at. If it was lower, I would, but not higher because this is due to the use and the normal increase in temperature during the day.

Steve, you made a good point about wanting to know what the weight is on each axle of the trailer is and better yet, on each tire. Having it weighed for each axle shouldn't be a problem, we just have to make it a point to remember and request this at the time of weighing. We have ours weighed at a flying J facility near Lansing, Mich. We haven't the foggiest idea if they are very accurate or not. However, we would hope so though, as they advertise to the truckers, if they are inaccurate and they are fined by the State police, Flying J will pay their (the truckers) fine. Having the trailer weighed for each wheel would be much more difficult and finding some place able to handle this request could be difficult.

Refering back to our original post, is the way we calculated our weight distibution to arrive at the aprox. actual weight carried on the 2 trailer axles of our unit correct? Incidentally, our axles are rated at 6000 lbs also, as it is posted on a label near the propane tank storage dept. on the street side of the trailer.

Once again, thanks for the comments all of you have made. This has been a eye opener topic for us and we are learning as we discuss this issue. Stiles started up a good one with his unfortunate blow out incident.

Gary & Carole

sreigle · 06-26-2005, 06:30 AM

Gary, I think you said you take loaded trailer weight less pinweight to equal axle weight and that would be correct. I'm not sure how you arrived at pinweight but assume that was total truck with Montana attached then subract total truck without Montana to arrive at pinweight.

cargary · 06-27-2005, 02:22 PM

Steve:
No actually, to determine the pin weight, I weighed in at different times. Let me explain the process I did.
First I weighed the truck with Carole and myself and no hitch in.

Then I weighed the truck with both of us and the new superglide installed. Incidentally, for those that would like to know this weight, the superglide 16k hitch weighs 260 lbs.

Then weighed the truck with both of us with the fifth wheel attached and empty, no water or supplies. Had the bottle gas tanks full though.

Finally, weighed it all, with supplies and 2/3 tank of fresh water.

To arrive at the pin weight - I knew the weight of the rear axle of the truck when I had the 5er attached empty and then I knew the final weight of the rear axle of the truck with the 5er attached loaded, so I subtracted the two weights and that gave me what I think is the actual pin weight of our unit loaded. Is this how you folks figure it or did I miss something?

Thanks for the reply.
Gary & Carole

sreigle · 06-29-2005, 03:07 PM

Gary, maybe I'm missing something in your procedure. If you take the difference in axle weight with FW loaded and FW unloaded, but attached to the truck both times, then that should only tell you how much the gear you loaded added to pinweight. Maybe I misunderstand what you're saying.

There are probably more than two ways to arrive at pinweight but I can only think of two:

1. TOTAL truck weight (not just rear axle) with FW attached minus total truck weight without the FW. Using rear axle weight will give you a rough idea but when you add the pin to the bed it drops the rear of the truck and that results in a transfer of weight from or to the front axle. so you have to use the weight of the total truck to find how much weight you added to the truck when you dropped the pin on it.

2. If you have the total weight of the trailer without the truck and you know the weight on the trailer axles when hitched to the truck, then the difference between those numbers is the pinweight.

Both 1 and 2 should derive to the same number.

Gary, an example. On my F250, without the FW attached, the weight on the FRONT axle is 4980. That's with 100% full fuel and Vicki and I onboard along with our normal traveling gear. The front axle weight with FW attached (same scales, same day, same fuel and gear load) is 4860. That's 120 lbs LESS weight on the front axle with FW attached. That weight had to go somewhere. It's now on the rear axle. So, when I compare rear axle weights with and without FW attached, I get a difference of 3,420. But 120 of that is truck weight transferred off the front axle. So subtract the 120 from 3420 and we come up with our pinweight of 3,300. Does that make any sense?

If you also have truck weight without the FW then you have the numbers to come up with actual pinweight, truck with the fw less truck without.

Gary, if I misunderstand your process, I apologize. It's really hard to tell from a post whether I am missing something. Don't hesitate to say so.

RMccord · 06-30-2005, 05:01 AM

I just looked at which tires I have on my 2005 335rlbs. Mine are Mission ST225-75R15. Rated at 2540 lbs @ 65psi with a load rating of D. Summing up the capacity of all four tires that would eguate to a total capacity of 10160 lbs. My trailers GVWR is 11100 with a tongue rating of 1000. THis would seem to be just enough to meet minimum requirements.
Has anyone had issues with the Mission tires. Mine have about 350 miles on them.
I am going to add the Doran tire monitoring system to them next week.
I think I will attempt to use them for a year about 7-10,000 miles of travel and then up grade to the highest rated 15" tires I can and that my rims will support. I will mention that we do not travel at the max weight. We run at about 9500-9700 lbs. remove about 900 from that for tongue weight and we are within these tires load rating by about 1360 lbs. or 13.5% of max rating.
Are most of the tire problems on the Montana 5th wheel units or both their 5er's and TT's.

Any other suggestions or recomendations would be appreciated.

cargary · 06-30-2005, 11:31 AM

Steve:
Sorry if I have made this confusing. To start, I had the truck weighed with the superglide installed. When doing this, I had the truck weighed to show what the weight was on each axle. The front axle weighed 4340 lbs and the rear weighed in at 3180 lbs. This gave me what the weight is on the rear axle of the truck.
Then, as I said previously, I had the truck attached to the 5er weighed empty and subtracting the trucks unattached rear axle weight from the new weight on this axle with the 5er attached. This gave me the pin weight with the 5er attached empty. I wanted to know this so when I weighed the 5er full, I would have an idea of how much weight I was adding and would be able to make adjustments if needed to bring the weight in to the specifications recommended.
Finally, to get the pin weight loaded, I knew what the trucks rear axle weighed without the 5er attached and then we loaded the 5er and weighed it. I subtracted the trucks rear axle weight from the weight with the 5er loaded to get the new pin weight. I think this is right, but I could be wrong. Hope this clears up how I arrived at the pin weight.
Thanks again for the feedback. It is appreciated.
Gary & Carole

sreigle · 06-30-2005, 01:37 PM

Gary, that sounds like you did it correctly except it doesn't account for differences in front axle weight, hitched and unhitched. If you have the front axle weights, if they are not the same then the difference needs to be added or subtracted from the pinweight. If they're the same then obviously there was no impact on the front axle. Sorry if I confused things. Thanks for the explanation.

Anyone know who makes Mission Tires? All I could find with a brief search is that they are made in Taiwan.

richfaa · 06-30-2005, 02:12 PM

I am dually impressed by the technical knowledge exibited here in regard to weights, tire size, axles and the associated relationshipss......What does it all mean?????

RMccord · 06-30-2005, 03:06 PM

I am starting to believe they are made by Maxxis? Hope I am wrong.

Montana_2957 · 06-30-2005, 04:23 PM

Bob, I just upgraded to Denman 225/75R15 10 ply load E rated at 2830 lbs/ tire @80 psi for my 315RLS after 10,500 miles on Maxxis load D tires that gave me no trouble at all. I ran most of the time at about 9200-9300 lbs total trailer weight. My trailer GVWR is 9520 lbs. The maxxis were starting to wear on the inside of all 4 tires which implies to my novice mind that the weight may be too great for the axles. Axle tags on my trailer are only rated 4400 lbs each minus weight of wheels and tires. The Denman E tires certainly look much stonger that the Maxxis D and will give me at little more peace of mind on the road. The axles do not give me too much confidence however. I would be interested to know what the axle rating is on your 335RLBS - if you ever get the chance to check. I also use Doran pressure monitoring and have had no problems.

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