stuttering caster wheel

[Justin S]

When my chair picks up speed, like going down a ramp or something, one of my caster wheels starts making a stuttering sound. It jerks left and right really fast while the other caster rolls along normally. Does this mean that the bearings are bad and need to be replaced?

If they do need to be replaced, how many bearings are there in each of caster and what size do I need? I have a Quickie TI and the diameter of the caster rim is 4 inches. The caster rim plus rubber tire has a 5 inch diameter.

-Justin

[bob clark]

Hi Justin,

Try giving the caster axle bolt/nut a tiny tightening. It may be just a little loose. When I adjust mine I tighten it up until it rolls kinda slow..... doesn't keep spinning for very long. Then I back the nut off just a little bit... just enough until it starts to spin very easily and freely. You could also remove the axle bolt and nut totally and give 'em a spray of WD-40 as a maintenance procedure.

If that doesn't fix it then try doing the same thing with the fork stem. It could be a little loose too.

I doubt the bearings are going bad... but ya never know. I just switched back to my old rims (24 inch rear wheels) because one bearing did go bad in my new rims. I kept spraying WD-40 on the axle to get rid of a squeak but that remedy only lasted a day or two before the annoying squeak came back. I looked at the bearing very closely and it had totally siezed-up... wasn't spinning at all. It was running on the axle and not the bearing.

It was easier for me just to switch to my spare rims than to try and get that bearing out of the hub. I'll give it a try when I get around to it but they can be tough to remove. I'll probably take the pair of wheels to a bicycle shop.... after I order a new bearing and have the rims/spokes adjusted too. Maybe put some new tires and tubes on/in while they're in the shop. Keep the old ones as spares. It may be best to order the bearings by the pair... but they can be a little pricey. It depends on how "demanding" you are of performance.

A bicycle shop will probably know how to "true up" a rim better than a wheelchair repair shop. They have more experience because they have those fussy bike riders (those people who wear those funny-lookin' helmets!) who they need to service and satisfy. Call them up first and see if they sell wheelchair tires or the type of tire that you like.

[smokey]

I agree with Bob Clark....tighten the caster bolt a little. But also, check to see if your chair frame isn't bent with one caster wheel a fraction higher than the other...that would cause fluttering too.

[Rbrauer]

is it the caster or the fork that moves? If its the caster, I'm going with bad bearings.. might tighten just a smidge, or have bearings repacked.

or .. is it the fork that holds it flipping? I tighten mine so they do not move on their own, but will with just slight resistance.

the key though, is just tighten it up a smidge.

[russ1]

If it's the fork this will happen when one of your wheels is either higher or the fork is at a different angle to the other or if the castors as a pair are set up wrong. Many castors (all on adjustable chairs) should have an adjustment for angle and if yours are out (especially if it's just one of them) then that is most likely to be the cause.

You need to loosen them off and realign them - there's usually a flat edge on the fork which needs to be at exactly 90 dgerees to the floor. On the Quickie Ti it's a PITA to do - you have to take the castor wheel off, then there is a torx screw in the fork leg that you can only see once the castor is off that has to be released - you then need to get the straight edge at the bottom of the fork where the castor axle goes in at 90 deg to the floor (use a set square or a book) and retighten. Then repeat on the other side. You have to do one side at a time. Hope that explains it. The procedure is set out in your owners manual which is available on the web if you've lost it.

Unless you've really been mistreating your bearings it's highly unlikely that they'll be shot and even more unlikely that they''d cause the symptoms you describe if they were IMO. You can soon tell as the castors would feel loose on the axle - if they don't then I'm pretty sure they just need adjusting as described above

Bob - dont know how your castor axles work but mine (on all 3 of my chairs don't work in the way you describe. The screws holding the axle in shouldn't clamp down on the bearings, the screws just clamp the axle into the forks and should be tight but if you take it apart the axle is bigger than the screw holes in the fork such that the fork can only ever be closed to the width of the castor axle. The castor wheels sit on the axle with a couple of spacers allowing the smallest amount of play. With modern sealed bearings this is how wheels work (and why you dont need to clamp in the rear wheels which work on a quick release axle pin. Older cup and cone bearings as used on some bikes (and possibly older / cheap wheelchair??) do however work by being clamped up. However Justins Quickie ti definately has the newer system that I describe.

[bob clark]

Bob - dont know how your castor axles work but mine (on all 3 of my chairs don't work in the way you describe. The screws holding the axle in shouldn't clamp down on the bearings, the screws just clamp the axle into the forks and should be tight but if you take it apart the axle is bigger than the screw holes in the fork such that the fork can only ever be closed to the width of the castor axle. The castor wheels sit on the axle with a couple of spacers allowing the smallest amount of play. With modern sealed bearings this is how wheels work (and why you dont need to clamp in the rear wheels which work on a quick release axle pin. Older cup and cone bearings as used on some bikes (and possibly older / cheap wheelchair??) do however work by being clamped up. However Justins Quickie ti definately has the newer system that I describe.

Hi Russ,

I thought my Quickie GPV was 7-9 years old but just found out it's only 5. So it isn't very old. But I don't believe the caster axles have changed since I bought my first Quickie Foldable 22? years ago.

There are two sets of holes drilled in the fork. One set for 5 inch casters and the other for 8 inch casters.

The bolt (which IS the axle) has one of those nuts on the end with plastic that acts as a locking or friction tightening feature. The bolt goes through the fork hole, then through a 3/8 inch spacer, then through the sealed bearing and hub and back out the other sealed bearing, through another 3/8 inch spacer and through the other fork hole. Simple as that. You then just screw on the nut (with the plastic locking or friction tightening feature) and tighten it up. If you tighten too much the wheel won't even spin. So you need to back off the nut until you get the caster to spin fast and free. If it's too tight the caster will be inhibited from spinning freely and if it's too loose it will wobble. You play with the tension until it spins freely but is still as tight as possible.

Maybe they've changed in the past few years, I don't know. As soon as I get my new GPV (whenever that might be?) I'll check it out and see if Quickie has improved or changed the design. IMO, the design, as it is on my chair's forks, is somewhat "unsophisticated" but seems to work okay. I've never had an axle nut come loose.... the plastic on the nut appears to do it's job of keeping the nut from loosening or tighening on its own.

you then need to get the straight edge at the bottom of the fork where the castor axle goes in at 90 deg to the floor (use a set square or a book) and retighten.

I use a plumb bob (monofilament and a weight... usually a nut) to get the fork bearing holder perpendicular to the floor. Since I just drilled an extra set of holes in my frame to increase the dump I had to re-adjust the front fork angle. It's strange how the fork angle is adjusted on my chair. There's a bolt with a head that's off-centered with a hole punched on the end of it to indicate what position it's in. It's a hexagonal bolt head so there's six positions to choose from. Actually there's twelve (??) since there are two of these bolts that "swivel" around a pin that goes through lower horizontal frame member. It's important to have the fork bearing-holder perpendicular to the floor or it makes turning the chair very awkward to do. It had me cursing a little more than usual until I adjusted it properly! What effect it has when going fast I can't say as I haven't test driven mine fast on a flat, smooth surface yet.

The new GPVs look indentical to mine.. Except for the folding back... mine is completely rigid... the hinges on the backrest tend to break after awhile.... and they aren't covered under the lifetime warranty as part of the "frame" and are quite expensive to replace. You can see the two holes in the forks in this picture and the two fork angle off-centered adjustment bolts and frame-pin in this picture.

I see they've designed the Quickie Ti's forks much differently than those on it's lowly cousin, the GPV. So you'll be "go to" guy for this model. But the casters definitely shouldn't wobble like on an old beat up shopping cart from the "Shop & Go"!

[Shaun]

The 'highspeed wobble'...anytime its happend to me its been the bearings.When you grab your fork does it wiggle? Is there any play in it? If there isnt then it maybe something else,this has always accompanied my wobble.

[Spadfan]

When my chair picks up speed, like going down a ramp or something, one of my caster wheels starts making a stuttering sound. It jerks left and right really fast while the other caster rolls along normally. Does this mean that the bearings are bad and need to be replaced?

If they do need to be replaced, how many bearings are there in each of caster and what size do I need? I have a Quickie TI and the diameter of the caster rim is 4 inches. The caster rim plus rubber tire has a 5 inch diameter.

-Justin

I believe from your description, the caster stem bearing pre-load is not adjusted correctly. The caster stem is the shaft the caster fork pivots on. There are usually two bearings carrying this stem with a nut on top and the fork on the bottom. The diagram is for a Quickie manual chair of some model, probably not your type. I just picked one that shows the parts. The items I have arrowed are adjustment nut (3) and the bearings (4). Unless this has been a problem for a long time the bearings are probably still OK and the nut just needs to be adjusted to pre-load the bearings.

To do this take the dust cap off and have someone tighten the nut, while you are out of the chair. A deep well socket of the proper size and a ratchet handle works fine. Have them tighten it until the fork just starts to be hard to pivot, then back it off until the point is found where it spins freely again. That should do it. Leave the dust cap off and take it for a spin while your handy adjuster person is still around. That way he/she can make finer adjustments if necessary.

I the worst spill I ever took was caused by a wobbling caster. One evening leaving work, I was going down a ramp and I just let’er roll. A caster started shimming and like a dumb ass I leaned over to see what was going on while I was still on this steep ramp. The chair tipped forward, the foot plates caught and I pitched out forward and landed at the bottom of the ramp. A little road rash was all that happened, fortunately.

[Patonb]

FOR THE LOVE OF GOD......... DO NOT DO NOT DO NOT USE WD-40. It will ruin ur bearings as it will leave a sticky film, it gets sucked into the metal and destroy them. Use a light oil like 4 in 1 or sewing machine oil.

[Spadfan]

After doing a little more looking at the Quickie parts manual seems my earlier post does not apply to the Quickie Ti chair at all. It does work for any chair that has caster stems of the type in my earlier post. The Ti chair is a completly different animal. I didn't do any searching for the maintenance manual and without it I personally don't have a clue as what the adjustment procedure would be. Ole Spad is stuck in the dark ages.

[russ1]

Spadfan wrote;

The Ti chair is a completly different animal. I didn't do any searching for the maintenance manual and without it I personally don't have a clue as what the adjustment procedure would be

The adjustment procedure is as I explained in my post above, However you can't overtighten the adjustment mechanism of an Quickie Ti - you just need to make sure it's aligned properly and fully tightened up.

Bob Clark wrote;
The bolt (which IS the axle) has one of those nuts on the end with plastic that acts as a locking or friction tightening feature. The bolt goes through the fork hole, then through a 3/8 inch spacer, then through the sealed bearing and hub and back out the other sealed bearing, through another 3/8 inch spacer and through the other fork hole. Simple as that. You then just screw on the nut (with the plastic locking or friction tightening feature) and tighten it up. If you tighten too much the wheel won't even spin. So you need to back off the nut until you get the caster to spin fast and free. If it's too tight the caster will be inhibited from spinning freely and if it's too loose it will wobble. You play with the tension until it spins freely but is still as tight as possible.

I've left it a while to reply as I wanted to go do some investigation before replying. You're right about the axle going all the way through and your description of the set up with the spacers is spot on but you're absolutely mistaken about the fact that tightening up the nut stopping the wheel spinning. The way a sealed bearing works is that the inner ring can (and possibly should) be fixed in the axle by the spacers and the bearing will then spin around it. If you take the castor off you'll see that you can hold the inner ring of the bearing and the castor will spin (or at least it should do). I've just been through all three of my chairs and tightened up all the bolts / nuts on the castor axles as tight as they will go and none of the castors has been in the slightest affected in the way they spin round.

If you can tighten the axle to stop the castor wheel spinning that's a good indication that the whole bearing needs to spin on the axle and shows that the bearing itself is shot / seized. I do know what I'm talking about with bearings as up until three years ago I was one of those fussy cyclists. I've taken bearings out of hubs (it can be a real pig) and I've even rebuilt sealed bearings when I was too late to get a replacement and had a race next day. Bearings themselves aren't that expensive if you go to a bearing shop rather than a wheelchair or cycle supplier, they're all pretty standard.

FOR THE LOVE OF GOD......... DO NOT DO NOT DO NOT USE WD-40. It will ruin ur bearings as it will leave a sticky film, it gets sucked into the metal and destroy them. Use a light oil like 4 in 1 or sewing machine oil.

Decent advice and a thin oil can extend the life of a seized bearing a little as will WD40 to a much lesser extent but both will eventually flush out the grease that the bearing is packed with (Good if the grease is old and seized up - Bad if the grease is new and working properly). The proper way to do it is to get access to the bearing, remove the cover, flush out old gease and then repack with a proper bearing lubricant. It's a proper PITA to do and not really worth it but be advised that once you start oiling your bearings it's the beginning of the end. Bearings shouldn't be oiled unless there's actually a problem with them as it'll shorten their life.

[bob clark]

Hi Russ,

I gotta get ready for a doctor appointment. Grrrrr.... But she's the one doing the paperwork for my new chair so I can't miss this appointment! Then buy another (just bought one 2 weeks ago) new battery for this freakin PITA Asus A8N-SLI Deluxe motherboard. There must be a short somewhere eating up my batteries! "CMOS checksum error" and once in awhile a "CMOS battery failed" warning. Among other errors and warnings. I'm lucky to still have this computer booting up and able to get online. Always have a backup computer.

But when I get back I'll remove a caster and spin it between my fingers and make sure the bearings aren't seized. I don't believe they are because I remember moving them around just the other day when I was changing their position. And they behave the same way on my other chairs. If I tighten up the axle bolt I can make them totally freeze up. So I need to back off the nut until I find the perfect spot. Hmmmmmm. I now need to have them in the lower holes (the 8 inch caster holes) in order to lower the front end of the chair so I can get under my kitchen sink and the bathroom vanity without bruising my knees and wearing holes in my pants! I have 3/4 inch fork extenders on this chair. On my last chair I had a 1 & 1/2 inch extenders. Maybe my kitchen and bathroom sinks are slowly collapsing because I didn't have this problem before. I'm gonna remove the fork extenders from my first Quickie (normal length) and see if they still fit on the newer chairs. Then I can put the casters back in the 5 inch caster fork holes. After I borrow a socket set from my neighbor. My "toolbox" is very limited. It's always something!!

I'll letja know.

[Patonb]

For proper bearing maintance, check any skateboard site. But Russ is right...... the work versus cost isn't worth it. You can get bearings just as good but cheaper.

[Spadfan]

The way a sealed bearing works is that the inner ring can (and possibly should) be fixed in the axle by the spacers and the bearing will then spin around it.

I agree with this part of your post.

. . . edited text. . . but your absolutely mistaken about the fact that tightening up the nut stopping the wheel spinning.

I don't agree with this statement. Take a look at the attachment. It is easy to see that the axial force being applied to the bearing inner race can be increased so that all the bearing free play is taken up (properly adjusted preload) and going beyond that point will start to cause the balls to bind with the outer race and not turn freely. Enough force will completely lock the bearings up. In any of the chairs I've had this was the case with the main wheel bearings, the caster wheel bearings and the caster stem bearings. Your chair must have a stop of some sort that limits the load being applied.

[russ1]

That's clearly the way some bearings in very demanding applications are supposed to work but I'm entirely unconvinced that that's the way they're supposed to work in a chair. With machinery designed to work at many 10's of thousands of rpm tolerance in a bearing of micro inch levels may be desirable and achievable - in chairs it's just not necessary and I don't believe it's the way they're designed to work.

What's the mechanism in the main rear wheels that applies preload - certainly not the quick release axle and there's nothing else in there that could do it.

My castors have a spacer between the two bearings which is presumably in there to stop the inner bearing race having an axial load applied to it. However the axle on my castors on at least my Quickie ti and my Ti Lite is of such a length that its clearly matched to the combined length of the bearing races, spacers (between bearings and betwen bearings and forks) and the fork width such that it's impossible to overtighten it. This indicates clearly that preload isn't being applied. Maybe chair manufacturers have worked out that allowing users to apply preload is shortening the life of the bearings and have designed it out. The only thing I'm absolutely clear about is that I cant apply a preload to the castor bearings on my chairs and nor would I want to.

It's interesting to read the skateboard forums about preload where they maintain that unless manufactured to exceptional levels of tolerance the preload doesn't preload as the description above but applies a skew load to the bearing which is entirely counter productive - eg here http://www.slalomskateboarder.com/ph...34c3624e7b66c6 - Wheelchairs will be the same.

Anyway - back to the OP's problem. Castor flutter is covered on page 37 of the folowing Quickie Ti user manual troubleshooting guide and highlights castor housing adjustment (page 33) as I recommended above. rhttp://www.sunrisemedical.co.uk/medi...=1141382919968