Leveling Scissor Jacks

Chris, You would need to be mindful of a slide-out being near the side you are lifting and lift real easy.
I remember a guy who came into the shop with a cracked corner at the top rear drivers side of the slide-outs frame, including the filon.
He tried to level it on the drivers side rear just behind the rear axle . The entire top corner at the roof-line split. From the roof down to the slides top right corner as you’re looking at it.

I never liked the design of slide-outs in RVs, there is no headroom for a substantial header.
Imo, from what i have seen , the slide-out is a weak link in an RVs wall. Maybe not so much on a “million dollar plus” Prevost chassis where it would have more room to beef up the build , but not on an average class C. You would need to be careful to not tweak the frame.

jwcolby54 wrote:
My concern is that the jacks are typically mounted parallel to the bumper. Jack that thing up very far and if the RV does start to move in either direction, forward or backward, the jack itself would "roll" the RV the direction it is already traveling, and end up dropping the rv, ruining the jacks, and likely doing damage to the RV in the process.

Definitely a concern.

They are mounted parallel so that you can more easily access the bolt to do the raising/lowering. I completely agree with you that if the RV rolls (even just a few inches) it will likely bend the jack. I don't think it would necessarily cause any damage to the RV, but your jack would be "jacked" (aka bent/broken). Perhaps if I added these on the rear (as close to the axle as possible) it would be my protocol to ONLY have one rear actually lifted at any given time and make sure the other one is on the ground so that the RV cannot roll (because the brakes will hold the RV in place). So as far as leveling goes, they would only come in handy if just one of the rear sides needed to be lifted some. They could also be used for stabilization.

An added benefit of having, for example, one of these 9000lb scissor jacks mounted at the rear frame as close to the rear axle as possible is that it could be used to change a tire if needed. I've also had to jack up the rear to adjust valve stems, and add a flush system, and fix my black waste tank..... So it does seem to come up from time to time. :-)

I'd still like to know from those in the know if it is okay to lift the rear corner of a Class C RV from the frame I-beam as close to the rear axle as possible (maybe ~3' from the rear axle). Anyone know? From some video links I posted in a post above, it seems like this is where (seemingly) professionals have installed lifts, but I'm still interested in more feedback if some here have experience.

Happy Camping!
Chris

valhalla360 wrote:


You can use 20 ton jacks on all 4 corners to support a few hundred pounds but it's silly when they were engineered for multiple times the expected load in the first place.

Yes, most are going to be rated for at least a ton...simply because it's more complicated to design them for less.

The 12-ton bottle jack (not 20 ton) reference was only for when I'm lifting one rear axle (~4500lbs) to remove a tire/etc and if I'm going to be underneath the RV at all. And if I am, I also put some extra 3-ton jack stands just to be extra safe.

You have mentioned multiple times above "support a few hundred pounds"...I assume you are talking about just using a jack to do some stabilizing (not lifting). Sure, in that case using a jack that is rated for as little as 1-ton would be fine.

-Chris

My concern is that the jacks are typically mounted parallel to the bumper. Jack that thing up very far and if the RV does start to move in either direction, forward or backward, the jack itself would "roll" the RV the direction it is already traveling, and end up dropping the rv, ruining the jacks, and likely doing damage to the RV in the process.

Mounting the jack on the frame is problematic because (at least on the ford e450) the frame itself is narrow and not close to the edge of the RV. It would be a PITA to get at the jack to do the cranking. It just seems that all other things considered, using them as intended is best, while using the typical leveling blocks to get you close to level.

I have a small 19' 5th wheel Scamp. It has front landing gear actually designed to hold the weight. Even those, if I extend them too far, will "wobble" or flex, mostly side to side. That's my 2c.

SJ-Chris wrote:

valhalla360 wrote:


Any borderline competent engineer is already including a 2-3 time factor of safety when setting the load limits.

I agree that a responsible company who produces a jack with an advertised weight rating of 5000lbs (for example) probably designs it such that it can safely handle quite a bit more load just so that there is some buffer of protection for the company's liability (and the end user).

As a consumer/user, If I am looking for a jack to lift 5000lbs I want to be extra safe so I will add in my own buffer of 2-3x (or more) just so that I know whatever jack I am using is more than capable of performing the task. I usually use a 12-ton bottle jack (24,000lbs) when jacking up one rear side (~4500lbs) of one of my 30' RVs. (And if I'm going under my RV or removing tires, I will also put some 3-ton jack stands under the frame as backup)

I would never use (or recommend) a jack to lift a load that is more than what the jack is rated to lift.

valhalla360 wrote:


The typical "stabilizing" jacks are only intended to support a few hundred pounds to take some of the bounce out of the rig. If lifting, they should be much stronger.

I haven't seen any stabilizing jacks (usually scissor type) rated for less than 1-ton (2000lbs). But I agree that even those would be only to provide some minor stabilizing to take some of the bounce out of the rig as you mention. They do have scissor jacks rated at 9000lbs+ though and I believe those could lift up to their weight rating if used safely, and thus could under the right circumstances be used for leveling an RV.

-Chris

You can use 20 ton jacks on all 4 corners to support a few hundred pounds but it's silly when they were engineered for multiple times the expected load in the first place.

Yes, most are going to be rated for at least a ton...simply because it's more complicated to design them for less.

Yes, i would use wood under rubber then stabilize with the jacks.

bobndot wrote:
My .02 cents.

1- Installed jacks to the frame will take up 4” of ground clearance while retracted.
I guess depending where you install them , that may or may not be an issue.

Yes, this is true. I have found that on my Class C RVs there is plenty of room for this on the rears, but not really room for this on the fronts. I suspect most Class C RVs will have this issue.

bobndot wrote:
My .02 cents.

2- keep in mind that the motorhome parking brake only locks the rears. Even blocking the fronts , don’t get too crazy lifting the rears.

THIS is the issue that occurred to me above as a potential problem, yet one that is never mentioned in the "Don't use scissor jacks to lift your RV" debate. I agree that you would want to block your front tires if raising the rear, and even then you need to be careful and use common sense. And as mentioned before, you REALLY need to take extra precaution any time you plan on physically going UNDER your RV.

One thing to be wary of...if you have the rear lifted by scissor jacks that are bolted to your frame...If your RV does roll forward or backwards it is going to bend your jacks and then you may have a problem. Because of this, I think if you were attaching scissor jacks to the rear of your RV for leveling it might be good practice to ONLY lift one side and to always make sure one side in the rear is on the ground or on leveling blocks. This restriction does limit their usability some, but I think they can still be very useful/handy. Then again, you can ALSO use them as stabilizers, so....

Happy Camping!
Chris

My .02 cents.

1- Installed jacks to the frame will take up 4” of ground clearance while retracted.
I guess depending where you install them , that may or may not be an issue.

2- keep in mind that the motorhome parking brake only locks the rears. Even blocking the fronts , don’t get too crazy lifting the rears.

You will probably need to carry wood blocks to place on the ground to prevent the jack from sinking in , why not just put wood under the tires where needed. Its less work.

I never use my hydraulic jacks since i installed a set if levels inside my cab. All i need to do is move my rig a few feet N-S-E-W to level it.

valhalla360 wrote:


Any borderline competent engineer is already including a 2-3 time factor of safety when setting the load limits.

I agree that a responsible company who produces a jack with an advertised weight rating of 5000lbs (for example) probably designs it such that it can safely handle quite a bit more load just so that there is some buffer of protection for the company's liability (and the end user).

As a consumer/user, If I am looking for a jack to lift 5000lbs I want to be extra safe so I will add in my own buffer of 2-3x (or more) just so that I know whatever jack I am using is more than capable of performing the task. I usually use a 12-ton bottle jack (24,000lbs) when jacking up one rear side (~4500lbs) of one of my 30' RVs. (And if I'm going under my RV or removing tires, I will also put some 3-ton jack stands under the frame as backup)

I would never use (or recommend) a jack to lift a load that is more than what the jack is rated to lift.

valhalla360 wrote:


The typical "stabilizing" jacks are only intended to support a few hundred pounds to take some of the bounce out of the rig. If lifting, they should be much stronger.

I haven't seen any stabilizing jacks (usually scissor type) rated for less than 1-ton (2000lbs). But I agree that even those would be only to provide some minor stabilizing to take some of the bounce out of the rig as you mention. They do have scissor jacks rated at 9000lbs+ though and I believe those could lift up to their weight rating if used safely, and thus could under the right circumstances be used for leveling an RV.

-Chris

valhalla360 wrote:
One thing to consider is the leveling systems I'm familiar with run 2 jacks at the same time (both front, both side or both rear). This causes the whole rig to rotate with the frame not twisting.

If you are doing it manually, one jack at a time, that can introduce a lot of twisting in the frame. Not a big deal for the frame as it's unlikely to fail but the house is bolted to the frame and not very strong...you might be opening up the seams in the roof as it all twists or loosening the screws holding the cabinets.

It is actually kind of amazing that RVs stay together at all when you consider they are twisting and flexing and turning and bouncing for 1000s and 1000s of miles as you drive down the road, over bumps and potholes, etc.

When leveling an RV, I believe you will either need to adjust 0, 1, 2, or 3 tires ("corners") to make them higher in order to get your RV level. I would contend that leveling your RV from a correct jack point (or like most people, just putting blocks under their tires) does absolutely zero damage and adds zero stress to the structural integrity of your RV. In fact, it ALLEVIATES stress/twisting/etc. The fact that your RV is unlevel implies it is being stressed or twisted as long as it is unlevel. Here is an exaggerated example to illustrate my point... Imagine you pull into a campsite and your front 2 tires and your rear driver side tire are all perfectly level but your passenger side rear tire is 12 inches too low. You are parked there. The rear passenger side of your RV is causing your entire RV to be wildly unlevel. If you try walking in your RV it is sloping a tremendous amount. At that moment, the frame and everything attached to the frame is under much stress BECAUSE it is unlevel. It is designed to handle it, but it is under stress. If you now raise that passenger side rear corner (from a proper jack point and/or by putting something under that tire) you will NOT be stressing/twisting the frame but rather you will be de-stressing/un-twisting the frame and putting the RV back to level (...I suppose you could call it the RV's happy place...being level). Right?

Or, another example...Assume you are parked perfectly level. I think we can all agree that when level and parked the RV and its frame and everything attached to it are in their happy place and they are not experiencing extra structural stress. Now imagine if you start putting blocks under just one tire (or jacking up just one corner from a proper jack location). You raise that tire/corner 3 inches, then 6 inches, then 9 inches, then 12 inches. As you are doing this, it is ADDING stress to the overall frame/structure/integrity of your RV. Right? Well, as you start removing this added height and you are dropping it back down to being level once again it is removing all that added stress. Making the RV level puts it in a state of the least amount of structural stress.

If the above is true, then any time you are leveling your RV, and you are doing so with items designed to support the load (either blocks under the tires, or jacks of any kind designed to hold the proper amount of weight) from a location designed for that purpose (ie. under the tire, or at a proper jack point), then you are actually REMOVING stress/twisting to the structural foundation of your RV.

-Chris