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"A 30302 bearing has a load rating of around 20kn. I can't pretend to know how you determine if that is sufficient, but I'm sure the engineers at Suzuki do."
My point exactly, the dynamic forces acting on the bearings are variable and depend on many things, as diverse as the terrain a Jimny traverses. In many instances these dynamic forces exceed the static force you have quoted by a large margin.
Checking the state of a kingpin bearing is no simple task making regular maintenance problematical,, symptoms of failure usually are observed first such as oil leaking from the seal,Wobble or noise when turning.
You would think after 40 years of customer complaints a fix would have been warranted a lot earlier?
How have you calculated that the dynamic forces exceed 20kn? Like I say, the typical failure mode is not from the bearings being overloaded.
Typically for me they last around 30,000 miles which is 4+ years driving for the typical Jimny owner. I doubt many are failing under warranty.
With a little experience, changing them is a 45 minute job. For comparison, it takes the same time to change the fuel filter on my Honda Civic and that has to be done every 6,250 mile.
Inspection would take almost the same time as replacement and the bearings and driveshaft seal are inexpensive so you might as well replace them while it's apart.
The Jimny is a budget 4x4. It's built on a budget and is full of compromises. The lack of waterproofing around the kingpins is certainly one of them.
Hi Busta
The static force of a hammer is its weight at rest, the dynamic force is its force on impact.
While my finger can bear the force of the weight of the hammer it would be shattered if the hammer struck my finger with force.
The weight of the Jimny acting on kingpin bearings is the same, at rest the static force is low compared to hitting a pothole at speed, emergency breaking or the forces generated by off road driving.
When talking of bearings, a dynamic force is dependent on the rpm. As there are no rpms on these bearings the static force is the only one that is possible to calculate and do any bearing life calculaton on. There is of course large variation in the static force but still these variations will not be considered dynamic and based on experience they have less of an impact that one would think except when there is too much play in the bearings. So again maintenance and lube.
SKF do rate these at 20kN static force but how much the load will vary when driving is anyones guess or a Suzuki engineer to think of. and the load will be distributed thru all four bearings but how much on each i do not know except we all see the bottom ones failing first wich is logical both considering load distribution and lube failing.
My guess based on my own design experience is that suzukis design is mostly based on their experience as this is well beyond the tools that SKF or other bearing supplier have.
Driving hard and going thru curves with sentripental forces will in my opinion give the most loads on these bearings, maybe more than the offroad and bumps and terrain strain on the car.
The longevity of the large load when driving is what will reduce bearing life and again lubrication or lack there of from contaminated grease.
Wadjela, I'm aware of how static and dynamic loads work. The question was how do you know the load is too high for the bearings? And if it that is the case, why do we not see evidence of this in how the bearings fail?
As I and Yakuza keep saying, the issue is one of lubrication and contamination, not of the bearings being overloaded. Every failed kingpin bearing I've seen has been rusty. Even the most over-sized bearing will fail if the precision surfaces are damaged by corrosion.
It's why I've stopped using Koyo or SKF bearings for the kingpins. The expensive bearings aren't any more resistant to corrosion than the cheap Chinese ones, so I fit the cheap ones.
Update on my Jimny's surgery:
My Jimny is back on the road and wobble free.
New kingpins and bearings,
0.7mm shim added to top left kingpin.
0.9mm shim added to top right kingpin.
New CV joint added to R side,
New swivel joint seals.
New diff seals.
Packed bearings and CV Joints with Nulon 4WD & Marine Multi-Purpose Grease.
Total cost $1300 including labour (thanks to my apprentice mechanic grandson).
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