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What's going on with 3500 lb axles?

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Printed Date: 28 Apr 2024 at 10:59pm
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Topic: What's going on with 3500 lb axles?
Posted By: Happy Tripping
Subject: What's going on with 3500 lb axles?
Date Posted: 20 Jul 2017 at 10:15am
From what I can see, R-Pods and their clones/competitors all use 3500 lb axles. My 171 has a bent axle, I don't know when this happened, but it seems to be a fairly common occurrence.

With the 171/2, the unloaded wt (2342#) + cargo capacity (900#) leaves a 'cushion' of ruffly 250#, but with the other models, as has been pointed out by others, the unloaded weight plus cargo capacity exceeds 3500 pounds on all of them -  http://www.forestriverinc.com/product-details.aspx?LineID=173&Image=5054&ShowParent=1.

This doesn't seem to be a good situation. Someone, please explain to me what I'm missing.



Replies:
Posted By: CharlieM
Date Posted: 20 Jul 2017 at 2:40pm

You have to have the secret decoder ring to understand manufacturers’ spec sheets. For the Pod FR lists the unloaded total weight (UVW), the unloaded hitch weight (HW)  and the cargo carrying capacity (CCC). The sum of UVW and CCC equals axle capacity plus HW. IOW, the total fully loaded weight includes a fully loaded axel (3500#) and the unloaded hitch weight. Using the RPOD 179 as an example: HW=292, UVW=2756, CCC=1036. UVW+CCC=3792 which is exactly 292# more than the axel rating of 3500#. This is a bit fictional since it is unlikely that any weight added to the unloaded trailer will have no effect on hitch weight. Looking at the unloaded numbers: 292/2756=10.6% which is marginal but OK. If any additional weight is added exactly over the axle the tongue weight ratio would be 292/(2756+1036)=7.7% which is dangerously low. A trailer load this way will be very prone to swaying. The bottom line is added weight should and will be shared between the axle and the tongue and will result in a hitch weight significantly higher than the advertised HW number.  Many new owners do not discover this until they weight the tongue and find it much higher than expected. Loading cargo behind the axle in an attempt to minimize tongue weight is a recipe for disaster.



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Charlie
Northern Colorado
OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD
PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD


Posted By: fwunder
Date Posted: 20 Jul 2017 at 3:15pm
Charlie! I bet you are great with a slide rule! Just kidding. Fortran? Key punch? Thermo? Actually, I really like your approach to these problems. Math rules!

And, although I have never had a serious sway or control problem, I definitely have noticed a difference when carefully loading trailer and moving heavier cargo forward of the axle.

fred


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2014 RPod 178 => https://goo.gl/CV446f - MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6
Yes, those are wild ponies dining on grass while dumping tanks!


Posted By: Leo B
Date Posted: 20 Jul 2017 at 3:50pm
Ying Yangjust taking it all in!!

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Leo & Melissa Bachand
2017 Ford F150
2021 Vista Cruiser 19 csk
Previously owned
2015 Rpod 179
2010 Rpod 171


Posted By: mcarter
Date Posted: 20 Jul 2017 at 5:01pm
+1 to Charlie - Spot On.

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Mike Carter
2015 178
" I had the right to remain silent, I just didn't have the ability."


Posted By: CharlieM
Date Posted: 20 Jul 2017 at 6:19pm
Originally posted by fwunder

Charlie! I bet you are great with a slide rule! Just kidding. Fortran? Key punch? Thermo? Actually, I really like your approach to these problems. Math rules!
And, although I have never had a serious sway or control problem, I definitely have noticed a difference when carefully loading trailer and moving heavier cargo forward of the axle.
fred

Naw. I retired my slipstick and I'm now learning a four function calculator. đź‘Ťđź‘Ť

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Charlie
Northern Colorado
OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD
PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD


Posted By: birderdiane526
Date Posted: 20 Jul 2017 at 7:28pm
Feel like I just took a math class! Wow, Charlie!!

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Diane and Michael
2016 179 "PIP" (PODDING IN PARADISE)
2007 Toyota Tundra
BLOG:Podding in Paradise,
birderdiane526.blogspot.com


Posted By: ToolmanJohn
Date Posted: 20 Jul 2017 at 7:52pm
 Tongue weight of the trailer is carried by the tow vehicle rear axle. So the tongue weight is subtracted from the R-Pod loaded weight. That would make the (trailer gross weight minus the actual tongue weight=actual trailer axle weight) trailer see "less" on the trailer axle.

 For example my trailer is rated at 7700 pounds gross capacity at 100% everything. But it has two 3500 pound torsion axles. That's 7000 pounds of rating. It's expected the tongue weight would be at least 10% (770 pounds) making it just within the axle ratings.

I do wish they installed slightly higher rated axles, for a little overhead.


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2017 ATC 7X20 Custom Toy Hauler
2013 R-Pod 177 (SOLD)
2013 VW Touareg TDI


Posted By: Jpntime
Date Posted: 20 Jul 2017 at 9:21pm
 I look at my axle on my 2014 171 and it has a sticker on it that says it's a 3100 pound axle 

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Love to camp
2014 171


Posted By: TheBum
Date Posted: 21 Jul 2017 at 10:08am
Originally posted by ToolmanJohn


 Tongue weight of the trailer is carried by the tow vehicle rear axle. So the tongue weight is subtracted from the R-Pod loaded weight. That would make the (trailer gross weight minus the actual tongue weight=actual trailer axle weight) trailer see "less" on the trailer axle.
 For example my trailer is rated at 7700 pounds gross capacity at 100% everything. But it has two 3500 pound torsion axles. That's 7000 pounds of rating. It's expected the tongue weight would be at least 10% (770 pounds) making it just within the axle ratings.
I do wish they installed slightly higher rated axles, for a little overhead.



That's only for a simple hitch. A WDH will redistribute some of the tongue weight back onto the axle (as well as to the front axle of the TV).


Posted By: mcarter
Date Posted: 21 Jul 2017 at 5:24pm
JPNtime, Think you are correct 171s ad 172s do not have 3500 axle, the 3500 axles are used on the larger TTS.

-------------
Mike Carter
2015 178
" I had the right to remain silent, I just didn't have the ability."


Posted By: Happy Tripping
Date Posted: 28 Jul 2017 at 3:48pm
Originally posted by Jpntime

 I look at my axle on my 2014 171 and it has a sticker on it that says it's a 3100 pound axle 

I dislike 'rants', so I have waited a while to see if there are other responses to this topic.

first, I think the 172/172 is the ideal travel trailer for someone who wants a minimalist, go anywhere, 'home on wheels' complete with a/c and a minimal but adequate bathroom and really good tank capacity for its size. The components, a/c, refer, oven, etc are by manufacturers with good reputations and it's design is very sturdy, at least based on pics of one upside down after an accident and still intact. 

That said, I do have a constructive criticism. R-Pods generally appear to have axles that are too small for their weight - http://www.rpod-owners.com/forum_posts.asp?TID=5018&PN=1&title=179-axle-issues . Now, I checked, R-Pod competitors also use similar size axles, so this is not unique to FR, they'll have problems, too.

 After driving with our R-Pod a lot, including cross-country, but without unusual contact with bumps, curbs, etc, my axle is undeniably bent. I acknowledge that I may have hit something, altho I am not aware of it, however the basic question is - Is a 3000 pound capacity axle sufficient for an R-Pod 171?

 I did the math on my first post of this thread, the expected weight on the axle is right at the 3000# limit. If I were a bridge builder would I want my bridge to be right at the limit or would I want a little 'cushion'?

 Ok, maybe FR feels the cushion built into the Dexter or Lippert axle, generally acknowledged to be of good quality, is enuf. As seen above, past posts on this forum suggest otherwise. Again, why doesn't either FR or the axle manufacturer tell us exactly where to put a jack when changing a tire, to avoid damaging the axle? Changing a tire is not an unusual event, indeed it's to be expected, but the last time I checked, they were mum on this subject, I conclude because damage to the axle while changing a tire can be expected, sometimes, and they don't want to be blamed!

 Replacing my bent axle will cost somewhere around $600-$900, I'm just gonna replace the tires more frequently because over the life of the R-Pod it'll be cheaper to do that, but it is really unfortunate that the axle isn't a little heavier design to avoid the whole problem.

 I emphasize, I love our R-Pod.



Posted By: ToolmanJohn
Date Posted: 28 Jul 2017 at 4:25pm
Originally posted by TheBum

Originally posted by ToolmanJohn


 Tongue weight of the trailer is carried by the tow vehicle rear axle. So the tongue weight is subtracted from the R-Pod loaded weight. That would make the (trailer gross weight minus the actual tongue weight=actual trailer axle weight) trailer see "less" on the trailer axle.
 For example my trailer is rated at 7700 pounds gross capacity at 100% everything. But it has two 3500 pound torsion axles. That's 7000 pounds of rating. It's expected the tongue weight would be at least 10% (770 pounds) making it just within the axle ratings.
I do wish they installed slightly higher rated axles, for a little overhead.



That's only for a simple hitch. A WDH will redistribute some of the tongue weight back onto the axle (as well as to the front axle of the TV).

Actually, tongue weight is the tongue weight. 100% of the time.  If the trailer tongue is 350 pounds, that's what it always is, regardless of the hitch type. If your hitch rating is 500 pounds, with no other WD rating, it can only carry 500 pounds. Using a trailer with a 700 pound tongue weight and using a WD hitch to get that number closer to 500 does NOT make it safe. The hitch is now burdened by 700 pounds, PLUS the additional stresses of spring bars trying to torque the tow vehicle front end down. Big time failure. Many people ignore this and tow too heavy anyway. Always inspect the tow hitch regularly look for stress cracks, especially at welds and near bolted attachment points.

You're right that the WD hitch does distribute weight.

The weight distributing hitch removes weight from the tow vehicle REAR AXLE, and distributes it BETWEEN the front axle of the tow vehicle AND ALSO the towed trailer axle. The distributed weight does not ALL go the the tow vehicle front axle, a common misconception. You could theoretically completely un-weight the entire rear axle by using spring bars that are extremely stiff. The rear axle could be entirely lifted from the ground.Only the front axle of the tow vehicle and trailer axle(s) would touch the ground.


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2017 ATC 7X20 Custom Toy Hauler
2013 R-Pod 177 (SOLD)
2013 VW Touareg TDI


Posted By: ToolmanJohn
Date Posted: 28 Jul 2017 at 4:52pm
I'll add that WD hitches can be complicated too. They can make towing UNSAFE if improperly setup. You could set the tension too high and seriously impair rear axle control. Hard braking in a turn and it would be easy to get jack-knifed if the rear axle is unweighted too much. Always shoot for at least SOME sag of the tow vehicle rear end. Don't go for a perfectly level tow vehcle, it's not safe.

-------------
2017 ATC 7X20 Custom Toy Hauler
2013 R-Pod 177 (SOLD)
2013 VW Touareg TDI


Posted By: Happy Tripping
Date Posted: 28 Jul 2017 at 7:16pm
Originally posted by ToolmanJohn

I'll add that WD hitches can be complicated too.

Uhh... I don't know how to say this, but ..... Your contribution, faskinating (sic) as it is,  has no relevance to the topic of this thread.



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