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Old 09-03-2013, 11:46 PM   #29
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I think the likelihood of overcoming the coefficient of friction between the ground and the jack plate is extremely unlikely unless you are parking in San Francisco.
X2!
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Old 09-04-2013, 07:26 AM   #30
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I don't think the danger of lifting the rears off the ground is of sliding down the hill. I think the danger is of bending the jacks, which does happen. The jacks are not meant to withstand lateral movement, and tires on the ground are all that prevents lateral movement.

If you bend your jacks and they won't retract, you are stuck wherever you are until you can remove the bent jacks from your coach.
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Old 09-04-2013, 08:06 AM   #31
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x2 on shifting of coach not the issue, but the bending of the jack cylinders/rams. A bent ram will ruin your day when you go to leave and the jack will not retract so that you can drive the unit.
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Old 09-04-2013, 11:24 AM   #32
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Thanks for all the different advice. Never thought about using wood under BOTH rear tires.
I'll carry some 2x10 pieces to use under each tire. And the same for each jack. I'll move to another site if the front tires need to be off the ground.
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Old 09-04-2013, 12:04 PM   #33
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Thanks for all the different advice. Never thought about using wood under BOTH rear tires.
I'll carry some 2x10 pieces to use under each tire. And the same for each jack. I'll move to another site if the front tires need to be off the ground.
Front tires can be off the ground, the rears need to be grounded because they are the ones with the parking brakes.
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Old 09-04-2013, 12:35 PM   #34
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Front tires can be off the ground, the rears need to be grounded because they are the ones with the parking brakes.
Ramblin not picking on you but here is where the confusion gets into this thread for me. Some people are saying that the issue is not sliding but the jacks being bent because of lateral stress. You seem to be saying the issue is of the jacks sliding. (otherwise parking brake not an issue)

I agree with the other poster. Unless you are on a very severe angle like maybe downtown San Fransisco I cannot imagine gravity pulling the rig down hill based on the rear tires being off of the ground. I also cannot imagine a wheel chock with smaller surface area than a jack stand helping that much.

Lateral movement bending the jacks themselves. Again I ask has anyone had that happen to them or is that something that seems could happen and a lot of stories about it but never actually happen to anyone that is posting about it. I can see if you have one down and try to drive off. A lot of power in those big diesel engines. I have on occasion rented a backhoe to dig ditches on my farm. With a backhoe you lift the wheels off of the ground with jacks that depending on the backhoe are sometimes smaller than my MH jacks. I then entend and lower a boom force that into the ground and pull it back ripping big rocks and earth out of the ground. So if I understand what some folds are saying. Ripping big rocks out of the ground with a backhoe puts less lateral stress on jacks than a couple of people walking around in the coach ?

I am not trying to be an expert here at all just curious about some of the reasoning behind posts
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Old 09-04-2013, 01:34 PM   #35
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Originally Posted by gemini5362 View Post
Ramblin not picking on you but here is where the confusion gets into this thread for me. Some people are saying that the issue is not sliding but the jacks being bent because of lateral stress. You seem to be saying the issue is of the jacks sliding. (otherwise parking brake not an issue)

I agree with the other poster. Unless you are on a very severe angle like maybe downtown San Fransisco I cannot imagine gravity pulling the rig down hill based on the rear tires being off of the ground. I also cannot imagine a wheel chock with smaller surface area than a jack stand helping that much.

Lateral movement bending the jacks themselves. Again I ask has anyone had that happen to them or is that something that seems could happen and a lot of stories about it but never actually happen to anyone that is posting about it. I can see if you have one down and try to drive off. A lot of power in those big diesel engines. I have on occasion rented a backhoe to dig ditches on my farm. With a backhoe you lift the wheels off of the ground with jacks that depending on the backhoe are sometimes smaller than my MH jacks. I then entend and lower a boom force that into the ground and pull it back ripping big rocks and earth out of the ground. So if I understand what some folds are saying. Ripping big rocks out of the ground with a backhoe puts less lateral stress on jacks than a couple of people walking around in the coach ?

I am not trying to be an expert here at all just curious about some of the reasoning behind posts
I own a backhoe. The jacks on it are engineered for the stresses that the backhoe will exert on them. On mine, the hydraulic rams are not part of the stressed components when the jacks are down, other than the downward linear force needed to keep the jacks from retracting. There is a heavy steel structure to the jack that takes all the lateral force. The linear force is handled by the relatively delicate hydraulic rams. In fact, there is no component to my backhoe that allows lateral stress to the rams, because they are not very strong laterally.

On an RV, the RAMS are the ONLY stressed components to the jacks. These are hollow steel tubes. Very, very strong lineally, but not so strong laterally.

Imagine a brick sitting on a tabletop balanced on 4 short soda straws. You could probably place another brick (or two) on top without collapsing the straws, however if you give it a little nudge from the side or the end, the whole thing comes down.

Now imagine the brick has wheels, and the wheels are in contact with the surface and two of them are locked and won't turn, it eliminates lots of lateral stress on the straws (people moving around in the coach, high wind, someone backing their RV into yours, earthquakes, etc)

I do not believe an RV could possibly slide down a hill on its jacks, but I DO believe you can bend them such that they won't retract by lifting all your wheels off the ground. And I further believe that by leaving at least the back wheels on the ground you mitigate the problem substantially enough to warrant the advice.

A search of this forum will almost certainly give you some real world examples of this actually happening.
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Old 09-04-2013, 02:43 PM   #36
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I do not believe an RV could possibly slide down a hill on its jacks, but I DO believe you can bend them such that they won't retract by lifting all your wheels off the ground. And I further believe that by leaving at least the back wheels on the ground you mitigate the problem substantially enough to warrant the advice.

A search of this forum will almost certainly give you some real world examples of this actually happening.
It happened to a friend last year, who was parked on a site where the back was lower than the front. Their electric jack controller went crazy, and over-extended the rear jacks, lifting the rear wheels completely off of the ground. When they went to reset and lower the jacks, three retracted, but one rear jack had too much side force on it and wouldn't retract. With the one corner up in the air like that, and the others down, the chassis was tweaked to the point that the windshield developed several long cracks radiating out from the corner.

At this point, they were stuck, and had to call around for help late on a Friday night. Several RV service departments were closed, a mobile RV technician couldn't help. Finally got ahold of a towing company that had a large enough jack to raise the back axle off of the ground high enough to take the weight off of the extended leveling jack. At that point, the jack could finally be retracted.

End result was five hours and a $300 towing company charge, plus a new windshield (and the time it took to get that replaced.) That was enough to confirm to me that you really don't want to lift the wheels (especially rear) off of the ground.

I usually put wood pads under the jacks, except on concrete or really well packed gravel. But if the site is so unlevel that a tire is close to being lifted off of the ground, then I will drive the low tire(s) up on blocks so all tires are fully supported. Less than a third of my camping trips are at RV parks, mostly I'm in the middle of a field at a dog show - and those fields are rarely flat and level.

I carry nine 18" x 18" x 1.5" plywood pads. I basically diced up a sheet of 3/4 pressure treated plywood into 18" squares. I then took pairs of squares and used construction adhesive to glue them face-to-face into double thick blocks, and used 1 1/4" screws to hold them together. This has handled 98% of my needs. The thick plywood will sometimes get pushed into a mushroom cap shape on soft ground, but they haven't split in 7 years.

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Get into place on the site. Then put wood under the jacks first. Raise the coach so the tires are off the ground on back or front, then slide the boards under the tires. Lower and then do the opposite end. Then lower and re level. I find that easier than backing unto the boards first.

Just my opinion
I don't like that opinion. Even though you aren't leaving it with the wheels in the air, you're still raising the rears off of the ground and could get into the situation described above. I feel it's worth the little bit of extra effort to drive up on the blocks if necessary. That's just my opinion.

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I recently had a site where I had my HWH levelers bring my rig level, ending with the rear curbside wheels, including tag, completely off the ground. The street side wheels were on the ground. Is this a problem?
Depends. Do you have air brakes where the parking brake sets the brakes on each rear wheel? In that case, raising one wheel set off of the ground lessens but doesn't eliminate your braking power. The load might still shift enough to put lateral strain on the jacks.

But if you have the type of parking brake that acts on the drive shaft (I think it's called AutoPark or something like that?) then once one side is lifted free of the ground, then the other side is free to rotate due to the differential. One side up completely knocks out the parking brake.

The other issue with a dangling wheel is that the suspension components are designed to hold a lot of compression weight on the axles. When a wheel is dangling, there is no weight on it, instead there is tension in the suspension system. That can cause the suspension components to be over extended and could put strain on them over time. It may not hurt the suspension, but it can't be good for it, and I avoid it whenever possible. (After leveling, I check the tires, and if any aren't making firm contact with the ground I will start over again, putting blocks under the tires this time.)

It's just the way I do it. Maybe you won't have any trouble holding a wheel in the air, but after seeing what my friend went through, it just confirms in my mind that it's not a good thing to do.
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Old 09-04-2013, 03:31 PM   #37
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Thanks for the input. My air brakes lock up the wheels, so I am not concerned about movement, just the suspension.


Thanks again.
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Old 09-05-2013, 07:49 AM   #38
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I might not have not camped as many years in a DP as others, but I can think of nothing good that would come from raising an axle/wheels off the ground on a DP for leveling at a campsite. As mentioned above, the jacks are some what tolerant of lateral adjustment while raising and lowering the motor home. I have had several DP's and none of the jacks have had any tolerance for fore aft movement. Think of the geometry when the frame os off level fore/aft. The jacks will not initially contact the ground at a perpendicular angle, hence it forces the body in a fore/aft direction as they extendable then retract. If the brakes are locked that is even more strain in the jacking system. You can help some by driving the low axle)s) on lumber to get the unit as level as possible before jacking, but again a lumber yard is needed, especially if a tag is involved. I consider limited leveling capability as a fact on my motor home and choose campsites/campgrounds based on that fact. I carry enough wood to raise the low axle maybe 3 inches and to block the jacks. Again, nothing good can come from raising a wheel or axle off the ground.

Also, my air brake motor homes have only had parking brakes on the rear axle. I would not recommend raising even one wheel, let along both rears off of the ground on a slope. Find another more level campsite or trade for a 5er.
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Old 09-05-2013, 08:06 AM   #39
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I own a backhoe. The jacks on it are engineered for the stresses that the backhoe will exert on them. On mine, the hydraulic rams are not part of the stressed components when the jacks are down, other than the downward linear force needed to keep the jacks from retracting. There is a heavy steel structure to the jack that takes all the lateral force. The linear force is handled by the relatively delicate hydraulic rams. In fact, there is no component to my backhoe that allows lateral stress to the rams, because they are not very strong laterally.

On an RV, the RAMS are the ONLY stressed components to the jacks. These are hollow steel tubes. Very, very strong lineally, but not so strong laterally.

Imagine a brick sitting on a tabletop balanced on 4 short soda straws. You could probably place another brick (or two) on top without collapsing the straws, however if you give it a little nudge from the side or the end, the whole thing comes down.

Now imagine the brick has wheels, and the wheels are in contact with the surface and two of them are locked and won't turn, it eliminates lots of lateral stress on the straws (people moving around in the coach, high wind, someone backing their RV into yours, earthquakes, etc)

I do not believe an RV could possibly slide down a hill on its jacks, but I DO believe you can bend them such that they won't retract by lifting all your wheels off the ground. And I further believe that by leaving at least the back wheels on the ground you mitigate the problem substantially enough to warrant the advice.

A search of this forum will almost certainly give you some real world examples of this actually happening.
I am trying to visualize your explanation. The hydraulic ram is actually the part of the jack that moves. in a motor home or a backhoe it is attached to a plate that sits on the ground. When I used a backhoe and the ones I have seen used the jacks are extended to the point where the tires are off of the ground. What I dont understand is how a heavy steel frame would affect the actual rams themselves. They are still extended. They are holding the backhoe off of the ground. Any movement in any direction is going to be transmitted to those rams. If I understand the workings correctly one of the reasons you use the jacks to get the frame off of the ground is to anchor the backhoe. If I remember correctly I tried using the backhoe without getting the frame off of the ground just sitting on the tires and when I tried to dig the bucket just pulled the tractor to it. I had to get the jacks down and the frame off of the ground to be able to dig. That would indicate to me that all of the stress of the digging is placed on the jacks. Am I missing something here ?
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Old 09-05-2013, 08:19 AM   #40
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It happened to a friend last year, who was parked on a site where the back was lower than the front. Their electric jack controller went crazy, and over-extended the rear jacks, lifting the rear wheels completely off of the ground. When they went to reset and lower the jacks, three retracted, but one rear jack had too much side force on it and wouldn't retract. With the one corner up in the air like that, and the others down, the chassis was tweaked to the point that the windshield developed several long cracks radiating out from the corner.

At this point, they were stuck, and had to call around for help late on a Friday night. Several RV service departments were closed, a mobile RV technician couldn't help. Finally got ahold of a towing company that had a large enough jack to raise the back axle off of the ground high enough to take the weight off of the extended leveling jack. At that point, the jack could finally be retracted.

End result was five hours and a $300 towing company charge, plus a new windshield (and the time it took to get that replaced.) That was enough to confirm to me that you really don't want to lift the wheels (especially rear) off of the ground.

I usually put wood pads under the jacks, except on concrete or really well packed gravel. But if the site is so unlevel that a tire is close to being lifted off of the ground, then I will drive the low tire(s) up on blocks so all tires are fully supported. Less than a third of my camping trips are at RV parks, mostly I'm in the middle of a field at a dog show - and those fields are rarely flat and level.

I carry nine 18" x 18" x 1.5" plywood pads. I basically diced up a sheet of 3/4 pressure treated plywood into 18" squares. I then took pairs of squares and used construction adhesive to glue them face-to-face into double thick blocks, and used 1 1/4" screws to hold them together. This has handled 98% of my needs. The thick plywood will sometimes get pushed into a mushroom cap shape on soft ground, but they haven't split in 7 years.



I don't like that opinion. Even though you aren't leaving it with the wheels in the air, you're still raising the rears off of the ground and could get into the situation described above. I feel it's worth the little bit of extra effort to drive up on the blocks if necessary. That's just my opinion.



Depends. Do you have air brakes where the parking brake sets the brakes on each rear wheel? In that case, raising one wheel set off of the ground lessens but doesn't eliminate your braking power. The load might still shift enough to put lateral strain on the jacks.

But if you have the type of parking brake that acts on the drive shaft (I think it's called AutoPark or something like that?) then once one side is lifted free of the ground, then the other side is free to rotate due to the differential. One side up completely knocks out the parking brake.

The other issue with a dangling wheel is that the suspension components are designed to hold a lot of compression weight on the axles. When a wheel is dangling, there is no weight on it, instead there is tension in the suspension system. That can cause the suspension components to be over extended and could put strain on them over time. It may not hurt the suspension, but it can't be good for it, and I avoid it whenever possible. (After leveling, I check the tires, and if any aren't making firm contact with the ground I will start over again, putting blocks under the tires this time.)

It's just the way I do it. Maybe you won't have any trouble holding a wheel in the air, but after seeing what my friend went through, it just confirms in my mind that it's not a good thing to do.
That is a problem with a controller that has run amok. Your friends controller actually did what everything I have read says not to do lift one corner by itself. Not sure that the issue would apply to having the jacks operated normally. I still have not heard where someone has had a problem with having tires off the ground in a normal level condition. Carrying wood around is a good idea and I am sure it would give me peace of mind to have something besides air under the tires the very few times I have had one of them jacked off the ground but how much wood can you carry and what do you leave behind to do that. I carry a half a dozen short pieces of 2x6 boards. I have them in case I run into a campground that is so out of level that i can not get the jacks raised high enough to level the camper. If I had another option I would not carry them. I sure do not want to carry a bunch of 4 foot long 2x whatever to make sure the wheels are on something solid. I agree with one of the other posters that RV parks should just make the sites solid. Arkansas has some very nice state parks. The facilities are great. My favorite park is called Petit Jean Mountain state park. Is on a small lake and has some of my favorite hiking trails. Several of the sites on it are fairly unlevel. It is one of the few places I have to put wood under a jack and have a tire off of the ground when level. Evidently I am not alone about staying there even though the sites are not level. The 50 amp section is almost always full on weekends.
I probably will continue to have a tire off of the ground occasionally when I park. I hope to not have both back tires off of the ground and on the one or two times I can remember where that would have happened I actually turned the MH around and leveled it where the front tires would be off of the ground.
I do not have a valid reason for this in my opinion. The back jacks are twice as big as the front jacks so they can handle more weight. I just do not feel comfortable with the part of the coach having the most weight off of the ground.
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Old 09-05-2013, 10:17 AM   #41
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I can think of nothing good that would come from raising an axle/wheels off the ground on a DP for leveling at a campsite.
Short and sweet - A very good summary!

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Originally Posted by gemini5362 View Post
I am trying to visualize your explanation. The hydraulic ram is actually the part of the jack that moves. in a motor home or a backhoe it is attached to a plate that sits on the ground. When I used a backhoe and the ones I have seen used the jacks are extended to the point where the tires are off of the ground. What I dont understand is how a heavy steel frame would affect the actual rams themselves. They are still extended. They are holding the backhoe off of the ground. Any movement in any direction is going to be transmitted to those rams. If I understand the workings correctly one of the reasons you use the jacks to get the frame off of the ground is to anchor the backhoe.
There are a few subtle differences, so one can't really say that it's not a problem to lift a motorhome off of the ground just because a backhoe does that.

The motorhome has a hydraulic ram with a smooth plate attached to it, and is primarily designed to have only compressive (no lateral) forces. On the other hand, a backhoe has a large steel arm that is hinged to the backhoe frame. It is this arm and hinge that is intended to take most of the lateral forces. The hydraulic ram angles between the backhoe frame and the pad on the heavy steel arm, and mostly supports the weight of the backhoe, while most of the lateral forces are absorbed by the arm and hinge.

Furthermore, on the backhoe, the pad that contacts the ground is not smooth, but has a "tooth" on it that sinks into the ground to help stabilize the backhoe and prevent the pad from slipping, the motorhome doesn't have this.

So while both have hydraulic rams that supports the weight, the details are quite different. One is designed to lift the equipment, stabilize it from movement in all directions, and prevent slipping; while the other is much less robust and designed only to support vertical weight. You cannot make assumptions that the motorhome jack will safely do everything that the backhoe jack is designed to do.

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That is a problem with a controller that has run amok. Your friends controller actually did what everything I have read says not to do lift one corner by itself. Not sure that the issue would apply to having the jacks operated normally.
Only partially true, I left out some details. Everything started out normally, and after the initial leveling attempt the rig was nice and level, but one of the rear wheels was raised up into the air. It was while trying to lower the rig from this stance (so that he could put boards by that wheel and drive up on them) that things went horribly wrong. It's not clear whether the jack jammed first and that triggered the controller to go haywire, or if the controller went haywire first and jammed the jack. Or perhaps the jack jammed and the operator pressed too many buttons too fast trying to un-jam the jack and that confused the controller? (The husband was at the controls that day, and he has limited experience with that relatively new coach. The wife usually goes to dog shows alone for 90% of the trips. I think this was only the second or third trip in this coach for the husband.)

Whatever the sequence of events, raising the wheel off of the ground may or may not have caused the event, but once it happened it certainly made the situation worse.

It sounds like you don't want to believe that the experiences of others will have any impact on you, and you would like to continue to occasionally raise your axle in the air. If that's what you want to do, please feel free to do so. I truly hope you never run into trouble with it. But prudence would seem to dictate that it would be better to avoid the situation if possible, as that's the best way to prevent it happening to you.

Good luck! (And I really mean that, I'm not being sarcastic.)
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Old 09-05-2013, 01:29 PM   #42
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I am trying to visualize your explanation. The hydraulic ram is actually the part of the jack that moves. in a motor home or a backhoe it is attached to a plate that sits on the ground. When I used a backhoe and the ones I have seen used the jacks are extended to the point where the tires are off of the ground. What I dont understand is how a heavy steel frame would affect the actual rams themselves. They are still extended. They are holding the backhoe off of the ground. Any movement in any direction is going to be transmitted to those rams. If I understand the workings correctly one of the reasons you use the jacks to get the frame off of the ground is to anchor the backhoe. If I remember correctly I tried using the backhoe without getting the frame off of the ground just sitting on the tires and when I tried to dig the bucket just pulled the tractor to it. I had to get the jacks down and the frame off of the ground to be able to dig. That would indicate to me that all of the stress of the digging is placed on the jacks. Am I missing something here ?
Consider this image of a typical backhoe stabilizer. Notice the small ram as compared to the massive leg structure. The LEG isolates the ram from ANY lateral movement. The ONLY stress on the ram is linear.

On an RV, the RAM is the ONLY STRESSED MEMBER, and IS NOT ISOLATED from lateral movement, except to the extent that tires on the ground isolate it. I contend that lateral movement can, and has, caused RV jacks to bend and become unusable because they are not designed to withstand much lateral stress.

Hope this clears things up.

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