Dual axle vs triple axle

[bluwtrman]

I've narrowed my purchase options down to 2 models of one brand. Either the Momentum 350M or 376TH. There's just over a foot of length difference between the two. A big difference to me is the 350 is dual axle and the 376 is triple. Understanding there's also a weight difference, how much consideration should I give to the extra axle. I'm thinking about additional maintenance/repair as well as extra wear & tear from simply turning the trailer on 6 wheels versus 4.
What are the group's thoughts and recommendations to a newbie?

[momentum_rv]

tinner12002 wrote:
Also, the 376 doesn't look very bike friendly to me as you would have to leave the bike outside in order to have access to the bed...not something I would want to do. Think about if your driving and want to pull over and rest...no bed unless you unload the bike. Get the unit with the bedroom in the front and power beds in the garage if you need extra sleeping space like the 399 or the 388M if you don't need the extra capacity.

In the 376 there are no moving parts in the garage/bedroom. The Bedroom is above the garage so everything can stay in place.

Edit: and the 388M does have triple axles and 18,500 GVWR. 350M is tandem at 16,500 GVWR.

[Lantley]

fj12ryder wrote:

tinner12002 wrote:
Triple axle everytime for me, spreads out the weight better and pulls easier in my opinion. I also prefer the extra carrying capacity provided by the triple axle vs tandem axle. Someones worried about the cost of 2 more tires....really... your spending 75-80K on an RV so don't be worried about the cost of two more tires!! If that's all that was concerning me with purchasing an RV as to whether I would have to purchase 4 or 6 tires down the road, then I think I would hang up my keys and stay in a bricks and sticks house, but that's just my opinion. Get the triple axle and have fun camping and spending that extra $500 in 5 years, you won't regret it!!

I'll have to admit if the cost of two more tires was the only expense then I'd have to agree.

But I, for one, would love to have disk brakes but those are substantially more with a triple axle, and suspension improvements are also around 50 percent more. I installed the EZ Flex components and wet bolts which costs more for the triple axle. If you have your wheel bearings done rather than doing it yourself, higher cost for a triple axle. If you do it yourself, you looking at more time and work with a triple axle. Want to add a TPMS? Higher cost for a triple axle. And higher tolls if you happen to hit a toll road. And the friction of 6 tires rather than 4 means a hit to your mpg. Not a big deal unless you put several thousand miles a year on it.

So there really is more than just the cost of an extra set of tires involved.

In theory it would seem all those additional components would provide for a better towing experience. Those that tow regularly for long distances would stand to benefit more from the improvements not less.
I would also think six tires carrying less weigh per tire would last longer than 4 tires carrying more weight per tire.

[fj12ryder]

tinner12002 wrote:
Triple axle everytime for me, spreads out the weight better and pulls easier in my opinion. I also prefer the extra carrying capacity provided by the triple axle vs tandem axle. Someones worried about the cost of 2 more tires....really... your spending 75-80K on an RV so don't be worried about the cost of two more tires!! If that's all that was concerning me with purchasing an RV as to whether I would have to purchase 4 or 6 tires down the road, then I think I would hang up my keys and stay in a bricks and sticks house, but that's just my opinion. Get the triple axle and have fun camping and spending that extra $500 in 5 years, you won't regret it!!

I'll have to admit if the cost of two more tires was the only expense then I'd have to agree.

But I, for one, would love to have disk brakes but those are substantially more with a triple axle, and suspension improvements are also around 50 percent more. I installed the EZ Flex components and wet bolts which costs more for the triple axle. If you have your wheel bearings done rather than doing it yourself, higher cost for a triple axle. If you do it yourself, you looking at more time and work with a triple axle. Want to add a TPMS? Higher cost for a triple axle. And higher tolls if you happen to hit a toll road. And the friction of 6 tires rather than 4 means a hit to your mpg. Not a big deal unless you put several thousand miles a year on it.

So there really is more than just the cost of an extra set of tires involved.

[tinner12002]

Haven't driven by the 350M yet but looked at and ad for one for sale and its showing 2 axles so maybe the site I had postmarked was outdated or something...still going to do a drive by anyway. Also, the 376 doesn't look very bike friendly to me as you would have to leave the bike outside in order to have access to the bed...not something I would want to do. Think about if your driving and want to pull over and rest...no bed unless you unload the bike. Get the unit with the bedroom in the front and power beds in the garage if you need extra sleeping space like the 399 or the 388M if you don't need the extra capacity.

[tinner12002]

momentum rv wrote:
Just one example of a brand new 5ers.
2017 Grand Design 350m
GVWR
16500 lbs
Length**
38' 9"
Height
13' 5"
Axle Rating
2 x 7000

I think they've redesigned either their website or their RVs or both. The site I had saved listed the 350M/388M with a triple axle and a GVWR of 18000lbs. I now cannot open their website and people are listing the GVWR of 16500lbs so something has changed there. In fact there is a 350M parked a couple miles from me so I'm going to do a drive by today because I'm pretty sure it has 3 axles and an 18K GVWR.

[tinner12002]

Triple axle everytime for me, spreads out the weight better and pulls easier in my opinion. I also prefer the extra carrying capacity provided by the triple axle vs tandem axle. Someones worried about the cost of 2 more tires....really... your spending 75-80K on an RV so don't be worried about the cost of two more tires!! If that's all that was concerning me with purchasing an RV as to whether I would have to purchase 4 or 6 tires down the road, then I think I would hang up my keys and stay in a bricks and sticks house, but that's just my opinion. Get the triple axle and have fun camping and spending that extra $500 in 5 years, you won't regret it!!

[fj12ryder]

taken wrote:
By law the axle capacity needs to meet or exceed the GVWR of the RV. Yes, pin weight will prevent the full GVWR from ever being completely on the axles, but that's the way it is. (Some brands got burned and fined big time a few years back for not complying...) On mine, I have three 7k axles for my 21k GVWR. Dry weight on my RV was 16k so two 8k axles won't work or even come close to working.

Could you please cite a reference to that law. I'm just wondering how Mobile Suites can make 5th wheels that have a GVWR of 19,000 lbs. and have two axles. So you're saying they are breaking the law?

And I know I've seen people complaining about their 5th wheel having a GVWR of 14,000 lbs., but only having 6,000 lb. rated axles. Please explain what I'm missing.

I did find that there is some confusion about how GVWR and GAWR are figured into things. This is one: "The total of all axle loads plus the tongue weight must not exceed the GVWR. All of these ratings are found on the Federal Certification Sticker on the tongue of your trailer."

And I found this: "Even manufacturers have different interpretations of GVWR because the government leaves it up to each manufacturer to rate its trailers as they see fit."

[taken]

Yep, lots of them out there.

PS: Not trying to create a debate about this. Just sharing what I learned through personal experience with my recall on a Keystone product and a good friends with a FR RV. I'm also buddies with some of the guys from my current brand of RV who told me about fines they've seen and experienced in the past in their careers. To be honest though, I haven't heard about it being enforced in quite some time...

Back to to he regularly scheduled programming. OP, I have had TH's that are both double and triple axle. I find my current triple is much more stable than my past double. Sure it scrubs backing a hard corner into my driveway. That's the nature of a triple. Doesn't hurt anything though.

[momentum_rv]

Just one example of a brand new 5ers.
2017 Grand Design 350m
GVWR
16500 lbs
Length**
38' 9"
Height
13' 5"
Axle Rating
2 x 7000

[taken]

So your trailer is a fine waiting to happen for the manufacturer. Doesn't make what I said untrue. There is no legal way to determine pin weight at all times so the only legal way to have GVWR match axles is to have the GAWR meet or exceed the GVWR. It's a regularly abused rule for sure. If and when they get caught, there is a recall. I was involved in one. I have friends with different brands who were too. The RV industry is the wild west and something is generally only an issue if you get caught...

[momentum_rv]

taken wrote:
By law the axle capacity needs to meet or exceed the GVWR of the RV. Yes, pin weight will prevent the full GVWR from ever being completely on the axles, but that's the way it is. (Some brands got burned and fined big time a few years back for not complying...) On mine, I have three 7k axles for my 21k GVWR. Dry weight on my RV was 16k so two 8k axles won't work or even come close to working.

Sorry, this is simply not true. It would be nice if it was.

(The two axle version of my trailer is a 19,500 GVW with two 8,000 axles)

[RVbikers]

taken wrote:
By law the axle capacity needs to meet or exceed the GVWR of the RV. Yes, pin weight will prevent the full GVWR from ever being completely on the axles, but that's the way it is. (Some brands got burned and fined big time a few years back for not complying...) On mine, I have three 7k axles for my 21k GVWR. Dry weight on my RV was 16k so two 8k axles won't work or even come close to working.

We have been looking at pretty much every toy hauler in the past 6 months. I have seen some new double axles with gvwr over 14k with 7k axles. What you say makes perfect sense because when I saw them I thought to myself "how can they do that?".

[taken]

By law the axle capacity needs to meet or exceed the GVWR of the RV. Yes, pin weight will prevent the full GVWR from ever being completely on the axles, but that's the way it is. (Some brands got burned and fined big time a few years back for not complying...) On mine, I have three 7k axles for my 21k GVWR. Dry weight on my RV was 16k so two 8k axles won't work or even come close to working.

[fj12ryder]

Bumpyroad wrote:

fj12ryder wrote:
Ah, another reason to prefer duals over triples: higher tolls for that extra axle. Honestly I don't see the reason for a triple axle if the weight can be handled by two axles. You hardly see any heavy regular 5th wheels with triple axles anymore, most are two 8,000 lb. axles if they need the carrying capacity.

"Don't try and justify not doing it, extra axle helps in many ways." Please explain how an extra axle helps if two axles can carry the weight? I'm not referring to an over-40 foot trailer, just say, a 38 foot trailer.

I'm starting to get the same old feeling that ego enters in here, rather than necessity. Of course if you NEED the carrying capacity of 3 axles get them, if not why?
bumpy

I agree with the "if you NEED the carrying capacity" thought. I just haven't figured out when that occurs. I got curious and looked at the weight of the Mobile Suite brand. Most of their larger 5th wheels' GVWR run around 20,000-22,000 lbs. and all of them are double axles. Their toyhaulers are triple axles but the GVWR of those is 24,000 lbs.

I'm starting to think that maybe the builders use triple axles so they can get away with using frames that aren't as expensive to build, i.e. smaller beams for frame.