People ask a lot about shimming their hydraulics to increase loader lifting capacity. It has become a trend over the last few year’s now everyone wants to do it. In some cases with these newer models I understand as a lot of dealerships are not doing final inspections properly and many tractors are sold with pressures to low. In those cases there is nothing wrong with shimming the relief valve to what kubota states factory pressure should be.
Most importantly before you do anything get a hydraulic guage. Without an accurate reading of where you actually are you are doing nothing but guessing and you can end up damaging your tractor or worse hurt yourself.
If you dont have a good understanding of how hydraulics work in the B and BX tractors then please read my other article “Kubota B and BX Hydraulic Systems”.
So what is shimming your hydraulics? The relief valve is responsible for limiting the hydraulic pressure to a specific setting. There is a spring and a poppet. When it reaches a certain pressure the poppet opens to allow excessive pressure to escape. Adding a shim effectively increases the spring tension which then increases the pressure it takes to open it.
So should you shim your relief valve? It depends. If you have a case of a newer tractor that the pressure is below spec then there is no reason not to. Otherwise read some more to understand better at whats involved.
Kubota as well as every other manufacturer out there spends a lot of money and time on research and devolepment to give you the best product. There are many aspects that go into how much the loader on each model is capable of lifting safely. When I say safely it means safe for the tractor and safe for you. Everyone uses their tractor differently and for different applications. 750lbs may be fine for a guy lifting and moving a pallet on level surface from point a to point b but may be dangerous or put undo stress on the tractor components for the next guy carrying it in off camber situations such as uneven ground, ruts, hills, etc. No two situations are the same and kubota has to recognize this and develop a product thats generally safe in most conditions.
As stated above there are many components involved in the lift capacity of a loader. Some of them being how much the axle can safely hold without damage, the center of gravity, how much the 3 point system can hold as a ballast, etc. Every inch you raise that loader off the ground changes the center of gravity and additional weight contributes to it.
Another thing to consider is what causes pressure to drop over time. Worn valves and hoses, leaks, junk in the system are all things that affect pressure. Worn and weak relief valve springs can affect pressure. Even old degraded fluid can lower pressure as much as 200-300 psi.
When considering to shim your hydraulics first thing you should do is check your pressure to see where your at. How long has it been since you changed the fluid and filter and cleaned the pickup screen? Do you have any leaks? Are your valves and hoses in good shape? If you answer no to any of that then you need to address those items and check your pressure again.
For those that just want to lift more than the rated capacity of the loader just remember this. Your going outside of what kubota recommends and may have consequences. It may be fine short term but it will cause problems at some point. Your buddy may have done it 5 years ago with no issues and you may break the axle the first time you lift something outside of its designed capacity. Its a gamble
Hopefully this article helps you have a better understanding. Any questions feel free to use the contact us button and send us a message. Thank you