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Open Roads Forum  >  Travel Trailers  >  General Q&A

 > Jacking For Tire Change

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JRscooby

Indepmo

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Posted: 08/05/22 01:24pm Link  |  Quote  |  Print  |  Notify Moderator

B-n-B wrote:



Actually it has a swivel saddle with a "scissored" lift arm and doesn't roll. Or, if it did I didn't notice enough to matter. I have actually used this jack twice without issue, so I'm not speaking hypothetically about its effectiveness. Once in a parking lot (on my car hauler) and once in sand (on my camper) at the CG. The 1x6 worked like a charm with the jack in the sand.
I don't know how I lived to tell about it.


Gdetrailer wrote:


Thin board UNDER the floor or trolley jack just like you SHOULD use under ANY jack solves your objection.

Was taught many yrs ago to never use any jack directly on ground as that ground can give way unevenly resulting in the jack tipping over.

Something else to consider, with a floor or trolley jack, the arc is small, maybe 1/4" inch in total travel for the entire lift. The vehicle also moves with that arc, your assuming the vehicle stays put and never moves which is not true. Trailers and vehicles are on wheels, the brakes, drive line have slop in them which allows the vehicle to move back and forth.



I don't know where you guys get the magic floor jacks that don't move. Just for snots and grins I just put a tape on 1 of mine (standard 7000 lb capacity that I load if I know I'm going to need a jack, or grab if I need to lift a car in the drive) I put the wheels against the wall and measured to center of pad. 5 inches. Jacked to top, 13 inches.
Junking cars around others junking cars, I have seen more than 1 slip off the jack because the little steel wheels would not roll on soft wood, or because the jack rolled off the end of the board.

Gdetrailer

PA

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Posted: 08/05/22 01:56pm Link  |  Quote  |  Print  |  Notify Moderator

JRscooby wrote:

B-n-B wrote:



Actually it has a swivel saddle with a "scissored" lift arm and doesn't roll. Or, if it did I didn't notice enough to matter. I have actually used this jack twice without issue, so I'm not speaking hypothetically about its effectiveness. Once in a parking lot (on my car hauler) and once in sand (on my camper) at the CG. The 1x6 worked like a charm with the jack in the sand.
I don't know how I lived to tell about it.


Gdetrailer wrote:


Thin board UNDER the floor or trolley jack just like you SHOULD use under ANY jack solves your objection.

Was taught many yrs ago to never use any jack directly on ground as that ground can give way unevenly resulting in the jack tipping over.

Something else to consider, with a floor or trolley jack, the arc is small, maybe 1/4" inch in total travel for the entire lift. The vehicle also moves with that arc, your assuming the vehicle stays put and never moves which is not true. Trailers and vehicles are on wheels, the brakes, drive line have slop in them which allows the vehicle to move back and forth.



I don't know where you guys get the magic floor jacks that don't move. Just for snots and grins I just put a tape on 1 of mine (standard 7000 lb capacity that I load if I know I'm going to need a jack, or grab if I need to lift a car in the drive) I put the wheels against the wall and measured to center of pad. 5 inches. Jacked to top, 13 inches.
Junking cars around others junking cars, I have seen more than 1 slip off the jack because the little steel wheels would not roll on soft wood, or because the jack rolled off the end of the board.


I have been using a 3.5 ton floor jack for well over 30 yrs on a concrete floor to lift my pickup trucks. I have not once ever seen the wheels on that jack or trucks move even 1mm.. That floor jack I have also has a contact point which looks like a castle and is 5" in diameter. Never had it offer to slide on that contact point either.

I think you have a piece of junk floor jack if it moves that much distance, you need better floor jacks.

Not ALL floor jacks have a large arc swing, junky cheapos and 50 yr old ones perhaps but not all.

On edit..

I do want to add that I figure that you are considering that one would have to use the FULL lift height of a floor jack.. You are also wrong on that assumption.

So, for the heck of it, I measured my floor jack.

At lowest part of the range, it is six inches tall, I put the jack against a wall and measured the contact plate edge as 3.5".

That jack just fits under my trailer axle at 6" with fully inflated tire.

If you jack directly under the axle you would only need to lift the tire about 1".

Now if you had a flat, my tire sidewalls are about 6".

Basically to change a tire you only need the jack to lift 6".

I measured my jack at 12" (6" min height + 6" lift).

The result?

the contact plate was now 3 5/8"..

The difference, 1/8"..

The reality is very few people will ever need to use the entire lift of a floor jack to change a trailer tire. Basically only using a small fraction of the arc and that fraction is statistically insignificant.

Now my floor jack tops at 18" lift and at that top the plate moves back about 2".. At that height would be stupid to consider to be usable.

But one could say the exact same for using any jack once you get past a couple of inches worth of lift, they all get unstable. Bottle jacks, scissor jacks since they have very small base foot prints get scary unstable the higher amount of lift you go.

Floor jacks and even smaller cousin the trolley jack both have a large base foot print over a much greater area making them by far more stable and less likely to tip over provided you only use the absolute minimum lift needed.

If one ever needed full lift height offered by a floor jack, one might wish to rethink the approach which reduces the amount of lift required..

I am not a fan of placing boards or ramps under one tire to change the other nor the other gadgets that you must drive up on.. You have to lift the good tire very high in order to lift the blown tire high enough to get the new tire on.. Do that on the shoulder of the road (which isn't flat) on the high side and you risk toppling the trailer over..

* This post was edited 08/05/22 02:58pm by Gdetrailer *

Grit dog

Black Diamond, WA

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Posted: 08/05/22 03:17pm Link  |  Quote  |  Print  |  Notify Moderator

JRscooby wrote:




I don't know where you guys get the magic floor jacks that don't move. Just for snots and grins I just put a tape on 1 of mine (standard 7000 lb capacity that I load if I know I'm going to need a jack, or grab if I need to lift a car in the drive) I put the wheels against the wall and measured to center of pad. 5 inches. Jacked to top, 13 inches.


I'm with Scooby here. GDE, I am genuinely interested in seeing a pic of your rolling floor jack that doesn't just have a single pivot on the arm, which by default as the angle changes, the jacking point gets closer to the rear part of the jack.
Hard to believe 5 pages about changing a flat tire, but I guess that happens when people have magic floor jacks!


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Grit dog

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Posted: 08/05/22 03:23pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:


Now my floor jack tops at 18" lift and at that top the plate moves back about 2".. At that height would be stupid to consider to be usable.

But one could say the exact same for using any jack once you get past a couple of inches worth of lift, they all get unstable. Bottle jacks, scissor jacks since they have very small base foot prints get scary unstable the higher amount of lift you go.



If one ever needed full lift height offered by a floor jack, one might wish to rethink the approach which reduces the amount of lift required..



Lol, jack up something that isn't a pavement pounder and you'll use that travel. Heck, I have to put a wood block on top of my (not junky, whatever you called them) floor jacks fairly often.

I know you're trying real hard here to be right, but maybe time to pump the brakes a bit.

That, and I'm not familiar with a scissor arm floor jack.

Tvov

CT

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Posted: 08/06/22 06:36am Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:


....
If you jack directly under the axle you would only need to lift the tire about 1".

Now if you had a flat, my tire sidewalls are about 6".

Basically to change a tire you only need the jack to lift 6".

I measured my jack at 12" (6" min height + 6" lift).

The result?

the contact plate was now 3 5/8"..

The difference, 1/8"..
....


Ok, I understand with a large rolling floor jack only lifting 6" you will have minimal movement. Especially if it is not near the maximum lift height. As you point out, 1/8" of movement.

But go from all the way down to all the way up, every rolling floor jack I've seen (with a single pivot at the rear) will move on its wheels while jacking on a solid floor.

I think we are all talking about the same thing except in different ways.


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JRscooby

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Posted: 08/06/22 09:02am Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:


I have been using a 3.5 ton floor jack for well over 30 yrs on a concrete floor to lift my pickup trucks. I have not once ever seen the wheels on that jack or trucks move even 1mm..


Seen, that is the issue. The fact that many people do not realize the jack wants to move points out to me there is a risk. The beauty of a floor jack is you roll it in place on hard surface, stroke it up to contact, check that it is right, then jack the vehicle up without watching it. You might be surprised if you marked at start.


Quote:

That floor jack I have also has a contact point which looks like a castle and is 5" in diameter. Never had it offer to slide on that contact point either.


But when using the jack on a hard surface, like a concrete driveway, there is very little side force applied because the wheels roll. On the side of the road, wheels sunk into asphalt, there is a good chance of slip. (I have seen a little trolley jack lift it's rear wheels, wedged against bottom of car, when it rolled off 2X10)

Quote:

I think you have a piece of junk floor jack if it moves that much distance, you need better floor jacks.

Not ALL floor jacks have a large arc swing, junky cheapos and 50 yr old ones perhaps but not all.


Well, my Walker is pretty old, but I have had several. All seam to work pretty much same way. I think how much the carriage moves could be calculated by somebody that paid attention in math class, knew length of arms, (Radius) and how much lift

You make a good point about only using part of the travel. This is best no matter what style of jack you use. That is why I suggest pulling the flat up ramp to get center of hub normal height before jacking. Little lift, pull ramp out, got all room needed


Quote:

Floor jacks and even smaller cousin the trolley jack both have a large base foot print over a much greater area making them by far more stable and less likely to tip over provided you only use the absolute minimum lift needed.


Large contact area? Compared to what? All mine, even the 10 ton capacity I don't use anymore, each have 4 little bitty steel wheels that contact the floor. Now the contacts are spread out over a large area, are stable on hard surface. But the wheels will sink into asphalt sooner than the same weight on even the smallest bottle jack. Yes, the carriage will bottom out, spread the load, but not stable.

Sjm9911

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Posted: 08/06/22 03:33pm Link  |  Quote  |  Print  |  Notify Moderator

I use the floor jack at home and have 2 bottle jacks for on the road, I take extra cribbing incase I need it for stability. Either way works. Use whats comfortable for you. If you dont like floor jacks dont use them, same for the bottle jacks. But learn to use something safely.


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