length & axles

[tom41]

I hear alot about frame flexing and broken welds on some montanas as well as SOB's. My monty is a 2980 which is only 33 ft in length with a pin weight (dry) of 2375. I havent had any frame problems as of yet (keeping my fingers crossed) But keystone along with some other manufactures are building longer and longer trailers, with only two axles, like 37 to 40 ft. If you look at Newmar, Travel Supreme,Teton, and other high end trailers, they all seem to install 3 axles on any trailer over 35 ft. Makes me wonder if this has a bearing on frame flexing and breaking welds. Anyone have any ideas on this or thoughts? just something to ponder on. And I never hear of triple axle trailers having these problems.

[ggranch]

The frame flex problems usually happen in the "goose neck" area rather than in the axel area. It is a by-product of weight and leverage. By going to a triple axel set-up, the mfg can use a lighter weight (cheaper) axel and tire combination. The longer trailers also tend to have I-beam frames while the shorter ones mostly have C-channel frames. I-beams are more costly but flex less.
Your 33' Monty has approx. 400# more pin weight than my 38' SOB. I believe your rig also has the C-channel frame where mine is an I-beam. Both are from Lippert. The mfg's order what they want for each brand/model they build. Hopefully, the "old world craftsmen" build the right rig on the frame they have in front of them. Bob

[tom41]

thats good information Bob. I just figured with a longer frame and two axles, that while towing, with all the bouncing and rough roads, that was the cause of frame flexing in the "goose neck" area. I knew the axle area wasnt the culprit because the axles was holding the weight at that point. I know back when HR was putting tag axles under their motor coaches it was because of lighter frames. But I figured Teton, Travel Supreme and some others had the heavier frames, with the weight they are and all. Anyways I'm glad to know now. Thanks Bob for your information!

[BB_TX]

I was surprised that my 3075RL weighs from 800 to 1400 pounds less than the various 37'-38' models. But it has a pin weight 200 to 400 pounds more.

[sreigle]

I'd have to crawl under but I think the Montana frame is an I-beam, isn't it? I seem to recall it is when I installed the scissor jacks behind the rear wheels on our 2003 3295RK and this 3400RL.

I, for one, would not buy a triple axle simply because they have their own problems, especially the stresses of turning all three axles. That's just my opinion, though. If I needed more capacity back there I'd go with one of the dual wheel axles like some rigs have. As for the Montanas, the axles are sufficient for the weight they support so I'm not sure there's a need for more. Again, my opinion, not based on any engineering expertise.

[ggranch]

Steve, you may be right about the Montana frame. As you know I bought the SOB but was basing my statement on what I remembered from shopping the Mountaineer. If I am wrong, I am sorry for mis-leading statements. Bob

[awaywego]

I read somewhere that they thought the frame flex was partly from the length of the pinbox. I thought Montana shortened the pinbox on the new units to help this.
I may have dreamed this so don't take it as the truth.
The Montana has a I beam and it was an 8 inch and they had problems and changed to a 10 inch in 2000 or 2001.

[HamRad]

I'm with Steve on the I beam. We have a 2002 3295RK and it has the ten inch I beams. If the C beams flex more than the I beams then I wouldn't want to be pulling that rig!

Tom41,

Just keep an eye on the areas that tend to have the flex problems and get it looked at as soon as anything might show up. For the most part Keystone seems to step up and take care of any flex problems.

Travel safely and Happy Holidays.

Dennis

[bsmeaton]

Awaywego,

I believe you are right. All the problems I have seen reported regarding frame flex have to do with the front as a result of flex on the upper frame resulting in broken side welds holding the walls. I don't recall ever seeing problems with the main I-beams, even though they did upgrade to 10" way back in 2003 or so.

[sreigle]

That's, my understanding, too, that the flex was due to the leverage effect of the longer extended pinbox causing twist in the overhang frame which then popped some welds. When they fixed our 2003 they added triangular corner gusseting and also put wood into some hollow square tube framing so the screws would get a better bite. I don't think those tubes were load bearing, though.