Switch to 8K Axles?

[JimOMartin]

Hi -
Has anyone thought about making the switch to 8K axles from the current 7K ones? Would provide more buffer on the overall weights. Thanks.

[PNW Fireguy]

Switched to 8k IS for improved ride and to remove what I consider to be the Achilles heal the OEM suspension. Take note that none of these items changes the vehicle weight limit indicates on the sticker.

[DQDick]

We also went with 8K when we switched to IS.

[GrahamLock]

Originally Posted by PNW Fireguy

Switched to 8k IS for improved ride and to remove what I consider to be the Achilles heal the OEM suspension. Take note that none of these items changes the vehicle weight limit indicates on the sticker.

What does IS mean?

[GrahamLock]

What does IS mean?

[beeje]

Independent suspension= IS

[mazboy]

the updated 7K axles have been updated for 2021.


I did try and update my springs with 8K springs but I still had problems, but never with the axle it's self. Love my IS system


I'd look at going to IS rather than updating the axles.

[Texan]

I stayed with the 7k axles per Mor-Rydes suggestion after they weighed my rv. I had decided before i left for Mor-Ryde i would let them decide what was best for my rv as they are the professionals. Just because you have heavier axles does not mean you should carry more weight. Mobile Suites have the 8k axles but they also have 15'' frames where as we have 12'' frames on the Montana's. With the 8k axles you also have about 300 more pounds of weight and this subtracts from your carrying capacity. If your gross weight was 16,000# before the I.S. or what other mod you plan on doing then it is still 16,000# after. As for as ride, the 8k is suppose to ride a little stiffer than the 7k but as to how much different i really don't know. The I.S. i fell is the ultimate suspension improvement. If someone can afford the I.S. then i believe they would be well pleased.

[allenclme]

Originally Posted by Texan

I stayed with the 7k axles per Mor-Rydes suggestion after they weighed my rv. I had decided before i left for Mor-Ryde i would let them decide what was best for my rv as they are the professionals. Just because you have heavier axles does not mean you should carry more weight. Mobile Suites have the 8k axles but they also have 15'' frames where as we have 12'' frames on the Montana's. With the 8k axles you also have about 300 more pounds of weight and this subtracts from your carrying capacity. If your gross weight was 16,000# before the I.S. or what other mod you plan on doing then it is still 16,000# after. As for as ride, the 8k is suppose to ride a little stiffer than the 7k but as to how much different i really don't know. The I.S. i fell is the ultimate suspension improvement. If someone can afford the I.S. then i believe they would be well pleased.

I'm talking with MorRyde now to do an IS and Disc Brake upgrade. They have suggested sticking with the 7k axles as the 8k will stiffen the suspension as the weight of my 5er doesn't need it. They also mentioned that the brake size is the same between the 7k and 8k so no benefit in my mind to going with the heavier axles.

[kowbra]

Originally Posted by allenclme

I'm talking with MorRyde now to do an IS and Disc Brake upgrade. They have suggested sticking with the 7k axles as the 8k will stiffen the suspension as the weight of my 5er doesn't need it. They also mentioned that the brake size is the same between the 7k and 8k so no benefit in my mind to going with the heavier axles.

Interesting... if I have it correct, you have a ~16,800lb GVWR on your Montana? That would be much like the 3791RD floorplan we are looking to order. So, interesting that they do not recommend upgrading to the 8K axles from 7K...

I suspect that the disc brakes on the new Montana Legacy package / 7K axles will not be as robust as the ones MORryde is doing on their I.S. packages, but curious if you know that for sure?

Last, if you don't mind, what's the pricing for the 7K/disc/I.S. package, installed?

Thanks!
Brad

[allenclme]

$7500. They offer a seasonal discount if done in Dec-Feb but I don't know what that is. What was explained on another thread that 2800# of my GVW is on the pin, so with the two 7000# axles (14000#) that's how the total GWV was determined. Mine is about 168xx but it's at CW getting work done so I can't look to get the exact number. MorRyde didn't say I couldn't do the 8000# axles, just that it was not necessary and would make the suspension stiffer.

[Montana Man]

How can adding an 8k suspension improve ride? Would that not be like adding a 3500 suspension onto a 2500 truck? If you added a 10k suspension to a trailer does that make it even better than an 8k? Strength and smoothness are generally inverse given the same design.

[JimOMartin]

Hi -
I agree with what you guys are saying. My question is geared towards regular axles not IS. With the increase in axle load you should gain additional cargo capacity. True the tag won’t reflect it and there would be a limitation to how much the frame would handle but I would think that a switch from 7k to 8k axles (and springs) would safely gain you at least 1000lbs of extra cargo vs. the 2000lb increase in actual capacity gained. I’ve been looking at the 3791RD and the rated cargo capacity is2481 but I’ve seen tags stating 1700 of capacity, which isn’t much hence my question around the upgrade.

[kowbra]

Originally Posted by JimOMartin

Hi -
I agree with what you guys are saying. My question is geared towards regular axles not IS. With the increase in axle load you should gain additional cargo capacity. True the tag won’t reflect it and there would be a limitation to how much the frame would handle but I would think that a switch from 7k to 8k axles (and springs) would safely gain you at least 1000lbs of extra cargo vs. the 2000lb increase in actual capacity gained. I’ve been looking at the 3791RD and the rated cargo capacity is2481 but I’ve seen tags stating 1700 of capacity, which isn’t much hence my question around the upgrade.

As you know, Montana does not offer a factory installed 8k axle option.
However, we also considered the Solitude in an RD floor plan, and they do offer a factory 8k axle with disc brakes and 17.5" H rated tire upgrade. AND, when you order that, the GVWR goes up from 16,800 to 18,000. Even with the extra weight of the suspension, the payload gain is right around the extra 1000 lbs of payload as you've suggested.

We ruled out the Solitude due to differences on the floorplan, decor, bathroom storage, closet storage, etc, but I think it was interesting that upgraded suspension and tires was enough to increase GVWR on the Solitude -in other words, they are using the same 12" lippert frame (not changed with the updated suspension and like the Montana's), yet they chose to upgrade GVWR without upgrading the frame...

So, as noted, only the manufacturer can change the sticker with the increased GVWR... but I think you are on the right track that in practical terms about 1000lbs of increased payload with the existing frame is a reasonable assumption. Whether that is a risk one is willing to take is TBD by each person, of course...

HtH!
Brad

[BiggarView]

Originally Posted by Montana Man

How can adding an 8k suspension improve ride? Would that not be like adding a 3500 suspension onto a 2500 truck? If you added a 10k suspension to a trailer does that make it even better than an 8k? Strength and smoothness are generally inverse given the same design.

It not as simple as adding 8k vs staying with 7k. For non FTers weight is rarely an issue. But for FTers, a loaded out trailer with 7k axles could be over the 7k axle rating by being 3900 on one side but only 3100 on the other. In that scenario, going to 8k axles makes a difference. At 3900lbs in the example the tire position is likely to be overloaded as well. The axle bearings on that side will experience much higher wear. Get the 8K axles in that case. Not everybody will need 8k, it depends.

[CalandLinda]

Individual axle certifications with a higher load capacity than the OE axles do not change the trailer’s GVWR or GAWRs. Only the trailer manufacturer or a certified vehicle modifier has the authority to do that.

There’s only one way to say it when you exceed vehicle certified GVWR…YOU’RE OVERWEIGHT!

[McRod]

Originally Posted by CalandLinda

...
There’s only one way to say it when you exceed vehicle certified GVWR…YOU’RE OVERWEIGHT!

That's true. The upgrade is to prevent breakdowns, not too concerned about the logic of GVWR.

You can request from the manufacturer a revised GVWR plate. Some will provide it and some won't.

[prndl]

It is more than just the rating of the axles. The entire frame, spring, axle and load positioning is engineered into your trailer. If you need to carry more than you are rated for you should buy something that is engineered to carry that weight. It is foolish to just add axle capacity to a structure that is not designed to carry it.

[JimOMartin]

Good points. So what happens when other manufacturers offer axle upgrades? The fundamental structure of the trailer doesn’t change, right? Not arguing, just wondering.

[beeje]

Originally Posted by JimOMartin

Good points. So what happens when other manufacturers offer axle upgrades? The fundamental structure of the trailer doesn’t change, right? Not arguing, just wondering.

IMHO you should put your hard earned $$ towards the IS and be done with the horse and buggy suspension. The difference is night and day.