FO5 tyres are pneumatic - but that's the last thing to consider.
Firstly is the slab lifting boom design such that the slab is a swinging load? If so then for safety reasons the capacity must be reduced by 20% to 10800 lb or the equivalent load at the laod distance,
Secondly, at the point where the steer tyres lift off these forklifts will be overloaded by around 50% where the load is not a swinging load (or around 80% if the load is swinging).
Thirdly only the manufacturer knows if the forklift is limited by forward or side tipover. If its limited by side tipover then the capacity cannot be increased by adding weight to the steer tyres.
Fourthly any addition of weight at the counterbalance reduces side stability because the centre of mass moves backwards and is then closer to the edge of the stability triangle - so even if the forklift in its supplied form is limited by forward tipover adding weight to the counterbalance may result in side stability being the limit.
Finally forklifts are a dangerous item of plant which are associated with too many deaths and serious injuries - any suggestion that they can safely be "modified" without professional advice from the manaucturer dispays a lack of appreciation of the respect with which forklift operations must be given.
As for tyre ballast if approved - for 825-15-14pr tyres, they can only be 80% filled, and with calcium chloride at a specific gravity of 1.3, a wheelbase of around 2250 mm, and a load distance of around 620 mm, the maximum increase in capacity would be around 5%.

Fixitandy,

My first question to you is - are the tires on the machine air tires (w/valve stem) or solid molded (no air valve stem)? I am assuming they are air tires based on your commends about introducting a liquid into the tires but never like to AssUme anything so I give you 3 persepectives and advise.

If the tires are air type then your options would be:

1. Install a solid molded tire meaning there is no air cavity beyond the tread. This would give some added weight to the rear of the machine plus no worry of flat tires. You may need to change the rims - check with your local dealer if necessary. This is a manufacturers approved option I am sure. There are two types of solid tires one with a soft center to improve road shock absorption (names like Super Soft, Super Elastic, etc) but will tend to be a bit more bouncy and probably weigh less. The other is a standard solid tire it provides a harder ride and is made with more dense material (more weight) but it is tougher on the machine if operating surfaces are uneven.

2. The other option for an air tire is to do what you said add the liquid you are referring to the rear tires. That liquid is called calcium chloride and as you say it is commonly added to farm tractors and to rough terrain forklifts (a.k.a. turned around farm tractors) for operation around job sites (uneven surfaces). However, the tires will still compress and "baby buggy) as the liquid will compress as air is used to give proper inflation pressures. I am familiar with this approach, grew up on a farm and sold rough terrain forklifts.

3. If the unit already has solid tires then the advice that Edward T suggested to add plates to the rear is a possibility. I have seen this done on Nissan and other makes but first get the approval of the manufacturer (or authorized representative of the manufacturer a.k.a. dealer). They may have limits to how much weight can be added, where it is to be placed and sometimes the steering tires and rims may need to be changed (increased in size) to handle the increased in load when the unit is running empty. About 60% of the machines total weight is supported by the steering tires/rims when it is does not have a load on the front end (forks).

Hope this helps.

I know business is hard to come by at the moment but if your customer is not going to get the right truck for the job I would let someone else look after it, as you could be brought into any legal action depending on what you did / advised or the nature of the accident.

The only "person" who can advise on a capacity upgrade is the manufacturer as only he knows the ultimate strength and design capabilities of the truck and components. If he says "yes" do "XYZ", as long as you do "XYZ" you are in the clear. If he says no then no it is. It is highly probable that you could add ballast to the truck and all will be fine and dandy till something goes wrong, but its too late then.

not to disagree, but I have seen MANY forklifts that use the same frame for 5 and 6 k trucks, where the only real differences had to do with the counterweight, and have seen factory approved added plates to the counterweight, in order to change the rated capacity.
BUT there are far more parts of the truck that get "beefed up" than just the counterweight when you move up in weight capacity of a truck, and the brake shoe arc's diameter is one that comes to mind as pretty important.
you may find you do much better with a wider drive axle footprint (extra wide drive tires, or dual wheel if pneumatic frame) as a method of safely increasing the stability.

Andy Prentice is correct.

Tell your customer to get real !!!!!!!!!!!!!!!!!!

If he continues with this practice and there is a serious accident then he deserves all the grief that he will surely get.

Employers that won't wake up to their responsibilities have no [place in modern business, ( even under the present difficult Times )

Hello Andy,
To put it simply your customer needs the proper truck to lift the capacity with the longer load centers. My understanding its a big health and safety violation to change the truck weight on the rated load capacity plate.
I know allot of places do it........but they are not suppose to

seriously, no one has any input on this issue?