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Caster flutter on a Permobil M5-DME supplier cannot seem to fix

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    I need to correct my statement about Permobil F casters not being adjustable. Well, somewhat.

    Short (as possible) story: F3, right caster wheel bearing developed a squeak/squeal, like a dry bearing. Jacked up rear to discover right and left caster pivot/swivel had a lot of resistance and a very noisy squeal in right. Wheel brg felt good with no load so I addressed the obvious first, right swivel noise. Removed plastic cover then caster Allen bolt. Caster falls out/down. From underside of the hole I punched the top washer/cover out. WOW, 13 thin/shim wave washers, 2 were broken probably due to them being totally dry. Removed broken pieces, red grease on wave washers, reassembled. By hand, caster would swivel 1 1./2 turns. Removed left caster to find dry wave washers and 1 was broken. Removed broken wave, red greased them, reinstalled. By hand it would swivel about 3/4 turn. Now both casters are swiveling with some but much less resistance. Test drive showed extreme caster flutter above 3 MPH. Right started first causing left to join in on the flutter. Day is done so I rode chair in house. In my many tight spots I noticed near no caster jerk (about the same as old C series).

    Next day back in the shop: I measured wave washer thickness as .012". Since I'd lost .024" from 2 broken wave/shims on right side, I went to my shim stash. .030 was as close as I had. OD was good, had to open up ID to fit. Installed new shim on top cover washer (it insured new shim alignment) and remaining 11 wave washers. Test by hand showed some resistance to swivel, about 1/2 turn. Test drive had no flutter from either caster. Also caster jerk is better than before this experiment. I'll soon re-test on a 3 mile run on varying pavements.

    Note; if shim thickness is too little, Allen bolt will turn, top washer won't when swiveling (this is wrong). Top washer and Allen should rotate in sync with caster swivel. If shim stack is too thick, swivel resistance will be increased. I could have done detail measurements of the ideal wave/shim stack but my shoulders had had enough.

    Advise: If you have or get a new F series (and probably M), remove casters and red grease wave/shims. There are 2 top washers. Top, shims, lower top washer. If this comes out as an assembly, remove any broken shims, pack w/red grease and reinstall as an assembly. My right shim stack came apart, the left when removed came out as an assembly (I couldn't separate but still allowed packing grease into it). My experiment so far has shown it might be OK with 1 wave/shim removed but 2 removed will cause flutter after it's greased. Since the lower wave/shim moves with caster swivel and it contacts stationary caster arm, they WILL wear/break. I doubt factory techs are aware of this.

    Note: Excessive grease is not needed. Just enough to pack a little in, wipe excess from outer diameter.

    BTW: my right wheel (not caster pivot) still squeals when under load. For another day after shoulder rest.

    All the above are my experiments, experience and suggestions that suits me and my situation and it not to be interpreted as a fix all or safe for all. Use any advise or input from me AT YOUR OWN RISK. No need to sue me, I'm so broke I can't pay attention.
    Attack life, it's going to kill you anyway
    Steve Mcqueen (Mr Cool)


      Sorry for just getting back. I've been out of town for 2 months and took my backup chair, because I don't like flying with the newer chair. If they're going to break something, I would rather it be my backup. I got to give it one quick run before I left and it is better, still flutters above 6-ish, but not nearly as bad. He just replace the wheels and all the hardware that went with that. Think the problem was being made worse because my left caster was already worn down quite a bit further than the right one. He said most of that was due to flutter. There was no specific fix involved, and I've spent so much time messing with them that I just want to leave the new ones alone for a while and see how they settle in. It seems like they get worse when I have them play around with them. So, going to roll with them as is for a while. But again, other than all new hardware and wheels, nothing terribly specific.
      Thanks for all the info and advice.