Montana Tires - Montana Owners Club

adelmoll · 04-29-2006, 05:11 AM

Yesterday we had the pro's at the Escapades weigh our truck and Montana. We were well within the weight limits on the truck but 250 lbs over on the Montana. We had a full tank of water as we had been dry camping for five days and we do not usually carry that much so we don't feel it is much of a problem but the pro's told us that the tires on the Montana were not adequate for the Montana even if we don't have the extra 250 lbs. and we should replace them as soon as possible. Why would Keystone use tires that are not big enough to carry the load they are putting on it?

Helen

stiles watson · 04-29-2006, 05:27 AM

I can't answer for Keystone, but I chose to put F-rated tires on mine. I know there has been a lot of discussion pro and con on this. I did my own study and research and I agree with your pros.

steves · 04-29-2006, 07:41 AM

Stiles, what air pressure do you run your F rated tires? Did you mount the F tires on the original Montana wheels?

patodonn · 04-29-2006, 07:46 AM

"Why would Keystone use tires that are not big enough to carry the load they are putting on it?"

IMHO, they don't. It certainly isn't designed that way!!

The combination of axles and tires must be within their individual ratings at max allowable weight of the RV once you deduct the pin weight (or weight supported by the front struts). There may be uneven weight distribution problems which could cause one or the other axle or one or the other tires to carry a load in excess of max rated. That's not a good thing. If your rig is at max allowable weight, and the weight is distributed evenly, front to back, side to side, the tires and axles should be OK...not necessarily more than OK, but "adequate" "by the numbers".

Just how did those folks come up with their opinion? What is their definition of "adequate"? Either the numbers are OK, or they aren't. What were the numbers?

Ran across this while looking up some ratngs:

Quote: As per FMVSS 120-Section 5.1: the sum of the maximum load ratings of the tires and rims fitted to an axle shall not be less than the GAWR specified on the Certification Label.

The 235-85-R-16-E range tire, which has become the tire of choice for most of the trailer models effected by this rule, has a load rating of 3042 lb. at 80 PSI each, thus giving a total rating of 6084 lb. per axle. The axle itself has a rating of 7000 lb., as always, but cannot be stated as such on the certification label. The 7000 lb. GAWR can be accomplished with the same 7000 lb. axle, by up-grading to the 235-85-R-16-G range tire which has a load rating of 3750 lb. each, at 110 PSI. This meets and exceeds the axle rating allowing the full axle capacity to be stated on the certification label. End Quote (My point here is about the tires, not the axles, so don't focus on the axle info.)

Going to "F" tires certainly would be an improvement...greater load capability....but are the "E"s "adequate". Probably yes. Would some other rating provide an even greater overload capability? "G"s? Probably "yes". Just how much "extra" capability do you want and are willing to pay for?

Did I have too much time on my hands this morning? Absolutley "yes".

JMHO

steves · 04-29-2006, 07:54 AM

Patodonn, read my post on "actual weighing of a 3400" my left rear tire was overloaded by about 76 #'s.

JH Sechelt · 04-29-2006, 08:50 AM

Good post JP,

And should be noted that if you want to up grade the tires to a "F" or "G" series, you would probably need
to up grade the rims to. So you are right, just how much do you want to spend $$$$$ ?
Must be raining down where you are this morning for such a long post.

J & D

rvivey · 04-29-2006, 12:02 PM

Hi Bill and Helen,
First we miss you guys! Hope we see you down the road.
Second, Patodonn is right on with his quote "The 235-85-R-16-E range tire, which has become the tire of choice for most of the trailer models effected by this rule, has a load rating of 3042 lb. at 80 PSI each, thus giving a total rating of 6084 lb. per axle. The axle itself has a rating of 7000 lb., as always, but cannot be stated as such on the certification label. The 7000 lb. GAWR can be accomplished with the same 7000 lb. axle, by up-grading to the 235-85-R-16-G range tire which has a load rating of 3750 lb. each, at 110 PSI. This meets and exceeds the axle rating allowing the full axle capacity to be stated on the certification label. End Quote (My point here is about the tires, not the axles, so don't focus on the axle info.)"
Your axles are 6000 lbs axles and thus the tires capacity at 80 lbs is greater than that of the axles (6084 vs 6000). So the statement from the "Pro's" is not correct. Although I am not an expert on this issue, I have spent a considerable amount of time researching weight capacity of RV's and tires for my software. To put it simply, if you increased the load range of your tires your axles could not legally carry the tires capacity.
Travel safe and slow down a bit. You're putting way too many miles on for your first year.

steves · 04-29-2006, 12:54 PM

Rvivey, I have to disagree with you. I had my unit weighed and the left rear was 3,100 and the right rear was 2,650 which puts an axle load of 5,750 which is under the 6,000 axle rating. My tires are only rated for 3,042 thus I am 68# over loaded at 80 PSI on my left tire. I would need to get higher rated E tires or move up to a F class tire but then I have the wheel issue of being able to handle the higher PSI. I think they are building too close to max and don't want to go with the higher tires and axles because of cost.

adelmoll · 04-29-2006, 02:47 PM

Oh boy, this could get interesting. I will be looking forward to what you all have to say. Mickey, we miss you and Patti too. Glad to see you had fun in Texas. We had a great time with Smokey and Pam at the Escapades. The hardest part about this traveling in having to say good-bye. Bill usually drives about 58-60 MPH where the ratings are at 75 MPH so we do run cooler than the specs.

Dick (Rlwit), our hitch weight was 3025 lbs on the 3475rl.

We should be getting a letter on the entire weighing process within a couple of weeks and I will let you know what they put in writing. The professional's that weighed us were from the Receation Vehicle Safety Education Foundation.

Helen

steves · 04-29-2006, 03:12 PM

RVSEF is who weigh me at Daytona.

rvivey · 04-29-2006, 06:11 PM

Steve, I assumed that Bill and Helen's axles were balanced and the tires would be fine. I understand your point about an out of balance condition where one side of the axle was over the tire load rating. I also assume that the axle manufacturer expects equal weight distribution on each side or the total of 1/2 half of the axle capacity not be exceeded on a given side. Using the logic that to compensate for the 68 lbs would be to increase the tires load range capacity would be difficult to understand if one side of the axle was 1000 lbs heavier than the other side. I realize that my 1000 lbs is a bit ridiculous but at what weight over 1/2 half the axle capacity would be allowable? I don’t know so I’ll continue to assume none.
I believe, as you do, the rating for the axles are a bit on the low side. I would like to see at least 7000 lb axles for my RV. As far as the tires go, if the axle capacity would go to 7000 then the load range should change. I can't find load range tables for the Mission tires so I don't know the correct PSI so I use 80 lbs regardless of the individual wheel weights.
Weights continue to be a confusing issue with me and most RVer’s. Just when I think I have a handle on it, something causes me to rethink the whole issue.

steves · 04-30-2006, 12:44 AM

If you look at the designs of most any 5th wheel There is generally a heavy side that has all the appliances, slides, and cabinets. Take my 3400 as a prime example, my left side has 3 slides, all kitchen appliances (refrig, stove, microwave) but most of that weight I think is on my front axle, but I would guess that some of that weight does impact the rear axle too.

Additionally, the fresh water tank is in the back of the unit favoring the left side as that's where the fill is located and all that weight would be placed on that left rear tire. My weighing was done after 6 days of dry camping, I started with full fresh water tanks and had about 1/3 left in the fresh water tank. My other holding tanks were in various levels of capacity with the used 2/3 of water. So, my weighing was done under extreme or full load capacity which is what they want
to correctly test your weight, axles, etc.

Running with no water I am well under all ratings (axles and tires). Based on most RV designs I don't think you will have balanced load on both sides of the axles. Understandable, when making estimates and predictions we do used that balaced concept for load ratings, etc.

stiles watson · 04-30-2006, 03:41 AM

After having two blowouts from properly inflated tires in three days, NOT caused by road hazards, on E-rated tires with less than 10,000 miles, with good tread all around, I began to investigate other causes. The cause was the tires. My loads were in the limits of the tire design, but at the upper end of those limits. That doesn't allow for the kind of safety margin that I want. Therefore, I decided on the F-rated tires.

I am not a crusader. What others do is their business. We all have to make the best decisions we know how concerning our "home on wheels". While I might miss the mark, I don't make decisions based on rumor or the best popular advice. I do my own research and encourage other to do the same. Whatever I decide, I stand where I stand.

patodonn · 04-30-2006, 05:23 AM

Although the thrust of my earlier post was to look at the "Why would Keystone" question, I absolutely agree with Stiles' thoughts re the advantages of upgrading to "F" tires, in that, although "E"s may be "within limits", you certainly gain a safety margin by going the extra $$ for additional tire rating "protection". Just a matter of the amount of $$ needed for the investment in the tires AND rims for the "extra" margin of safety.

Re the "F"s using the "old" axle rating, you will still be right on the upper limit of the axle rating, to be sure, and the axles would become the "weakest link", Axles generally don't "fail" in as catastrophic manner as tires do, nor nearly as often. They aren't subjected to road hazards as tires are, plus, no "heat buildup" problems. I would feel a lot safer towing at max axle rating than towing at max tire rating...

Again, JMHO...

Best to all,

Searchers · 04-30-2006, 06:55 AM

I found that the axles on my Montana are rated at 5000 pounds each, but they're tagged at 4400 pounds. A comparison of the individual suspension componets against the parts list reveals that the spings are rated at 2200 pounds each, therefore the 4400 pound rating indicated on the axle tag and also the tag on the front of the unit. It's possible to upgrade all the componets to higher rated parts for saftey, but it won't legally raise the maufacturers rating.

rvivey · 04-30-2006, 07:20 AM

I do not wish to belabor the point about what is correct regarding tires and axles. I totally agree with Stiles about doing your own research and making your own decisions. My only point in this discussion was to assure Bill and Helen that Keystone had used the proper equipment for their RV and for the Pro’s to indicate otherwise was not correct.
I am including a passage from the Michelin RV Tire Guide that supports what I have posted earlier.

“Note: Even though the weight of the total axle may
be within the axle’s rating, it may be overloaded on
one side. This causes one wheel position to be overloaded.
Therefore, side-to-side weighing is required.
If there is a difference in the weights on one side of the
vehicle as compared to weights on the other side, components
(tires, wheels, brakes, springs, etc.) on the heavier
side could be overloaded, even though the total axle load is
within the G.A.W.R. It is important to redistribute the load
to avoid component failure, as well as to improve the
handling characteristics of the vehicle. With these actual
weights, it is now possible to compare them against the
G.A.W.R., G.V.W.R. and tire capacities. These actual weights
are also what should be used to help determine the
proper air pressure for the tires.”

RKassl · 05-01-2006, 12:15 PM

Just to throw more gas in the fire, I had the Monty out this weekend for the Spring shake-down. I have Goodyear G rated tires now.[http://www.goodyear.com/rv/products/g614rst.html].

They are on new high pressure wheels balanced at 110 PSI. I love them. It was a very windy day lots of cross winds and the very stiff sidewall construction helped me by reducing most of the sway.

Whay did I upgrade? Piece of mind! Did it cost me $$ yes, but I feel better that our Monty has the best shoes I can afford to protect her and my family.

stiles watson · 05-01-2006, 02:48 PM

After reflection, it was 14-ply, G-rated tires I switched ot rather than F-rated tires. I run at 105 psi.

Montana_5700 · 05-01-2006, 04:03 PM

Wow you guys spend more time than I care to discusing tires. lol
after reading all the post I to would like to upgrade to goodyear unisteel g rated 235/85r16 and after calling my local goodyear dealer hear in sunny Naples, Fl the tech I spoke with told me I could use my factory wheels as long as I used high presure stems, but I think he is incorrect.
what are your thoughts on this matter?
thank you

RKassl · 05-01-2006, 04:25 PM

I really think that is incorrect, heres why. The OEM rims on the Monty are rated for X## of pounds for the E rated tire at 80 PSI. The G rated tires are rated at 3750 lbs at 110. That means the rims must match the weight rating of the tires, or you are only good to the lesser of the two ratings. You must have high pressure screw in valve stems to. Bottom line, the weight rating of my new Goodyear's match the new rims at 110 lbs.

By the way, tires are everything, they are the only thing between the Monty and the road.

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