What Are The Spacer Tubes For?

[Dave]

This may be a dumb question, but I'll ask it anyway. With my rear hub kit there are two stubby little steel tubes that fit around the axle and inside the outside edge of the hub. (It's the coppery-looking thing on the axle in the photo.) There's one on each side of the hub, and I can't quite figure out what they are there for. They don't appear to have a purpose there at all because they don't fit tight against anything and don't appear to be needed to lock the wheel to the frame/fork. If the dropout has on one side the shoulder of the bolt where the flats end, and the bolts/washers on the other side, the spacers will just be sliding back & forth.

So, anybody know what are they there for?

[myelectricbike]

Looks like the factory used a threadless cover with an axle designed for a threaded cover but fitted with a short spacer. The "tube" is a spacer needed to compress and lock the inner bearing race against the axle seat. A longer spacer or even two spacers or multiple washers can be used to move the contact point with the dropouts to a location that will accommodate the flats. Either that or grind the flats back past the point where the spacer extends, being sure to remember that the axle is hollow on this side of the wheel. Be sure to use a washer between the spacer and the dropouts, preferably one that is slotted.

[Dave]

Looks like the factory used a threadless cover with an axle designed for a threaded cover but fitted with a short spacer. The "tube" is a spacer needed to compress and lock the inner bearing race against the axle seat. A longer spacer or even two spacers or multiple washers can be used to move the contact point with the dropouts to a location that will accommodate the flats. Either that or grind the flats back past the point where the spacer extends, being sure to remember that the axle is hollow on this side of the wheel. Be sure to use a washer between the spacer and the dropouts, preferably one that is slotted.

That explains much that had me puzzled. I was thinking that the dropout was held between a washer pressed up against the shoulder on the axle at the end of the flats, but that would leave that spacer drifting around loose between the washer and the bearing...  So instead the spacers need to be up against the dropout, with the nut & washers on the other side holding it tight? That means I'll need longer spacers on both sides, as the spacer on the gear side isn't long enough to reach past the freewheel. And there's still the grinding that needs doing.

Any chance there's a diagram somewhere that shows the proper setup?

Thanks!

[ahend]

I had similar issues with my front wheel kit. One spacer looked about right, but the other was about 25% shorter and not even protruding from the hub cover face. It was also made from different stock as the diameters were a bit different, along with the surface finish. They were both rusty and nasty looking so I turned some up out of stainless steel. I made sure the bearings were seated on the axle and in the hub covers, and then used the "good" spacer and a height gage to find the stackup width between the bearing thrust faces. I subtracted that from the dropout span and split the difference.

[myelectricbike]

Philip replaced the old dimensioned blueprint drawings with the pictographs that are there now and I have not yet found the copy of the old stuff I had downloaded. I'm still looking.

The drawings are not cut-away and show none of the innards... sorry.

Basically the compression forces derived from tightening the axle nuts are what keep the inner races from slipping on the axle while the flats keep the axle from spinning in the dropouts. The spacers must be extended out past the shoulder at the flats so they can transfer the compression from the axle nut through the washers and through the dropouts and through the inner washer and through the spacer to the inner race and finally to the axle seat which would not be the case if the spacer did not extend past the shoulder of the flats. Don't grind the flats back unless you need to in order to match the rear triangle spacing but instead use longer spacers.

 

[al]

I never got any spacer tubes I assumed you tightend the wheel against the washers with the tab hench having a tight wheel and an axel that wont slip. am I underestimating the torque here, would I have to cut the wires if I did go for spacers.

[myelectricbike]

You should have two slotted washers per side with the outer washer on each side also having a tab. The inner washer then butts the spacer which transfers the compression of the axle nuts to the inner races.

[Dave]

I never got any spacer tubes I assumed you tightend the wheel against the washers with the tab hench having a tight wheel and an axel that wont slip. am I underestimating the torque here, would I have to cut the wires if I did go for spacers.

You don't necessarily need to cut the wires; the individual connectors for each wire can be pulled out of the plastic housings by using a very small screwdriver or pick to push in a metal tab. Then the metal tab just pulls out through the back. Be sure to make a diagram of which wire went where before you pull any out because putting them back in the wrong order would be a Very Bad Thing.

Also, I'm guessing that the spacers need to be cut very carefully so that the ends are square with each other and with the axle. One end presses against the dropout and the other against the bearing; having the ends out of kilter might cause bearing or axle problems. I don't have access to a lathe, but I took some galvanized pipe that was the same size as the spacers to a local machine shop and they spun out the pieces I needed in a very short time for just a couple of $. Never hurts to have a friend in a machine shop!

[emzed]

Be sure to use a washer between the spacer and the dropouts, preferably one that is slotted.

Is the washer between the space and the dropouts important? Why? I was going to just have the spacers up against the dropout and have the washer with the tab on the outside.

[myelectricbike]

Very much so. That washer prevents the spacer from acting as a wedge and spreading the sides of the dropouts apart as the result of the dropout being open while the washer, on the other hand, is closed. Write Philip and ask that he send you a slotted washer to fit in this position to help assure that the axle will not turn in the dropouts.

[Mordaz]

I have just received my first rear wheel hub motor (the previous ones I ordered were for front wheels).  It came with just one spacer on the sprocket side.  The opposite side has no spacer.  According to this topic's explanations, I really need tube spacers on both sides, right? 

[Dave]

You can buy sections of pipe from most any hardware store and cut spacers from it. Just take your sprocket-side spacer along when you go to the store & get one with the same inside & outside diameter.

The length you cut is very important though; how long each side is depends on where the rim is in relation to the center of the hub. The easiest way to figure it is to put the wheel in the frame, center the wheel between the seat stays, then measure the distance between the bearing and the dropout on each side.

But that leads to what could be another issue; if the rim is centered on the hub and you center the rim in the frame, you won't have enough room for the freewheel & sprockets between the dropout and the hub. If that's the case, you have two options; source a different freewheel with fewer sprockets on it, or have the wheel re-dished. I've tried to have mine re-dished, but the spokes were too short to get the wheel dished properly, so my rim is off center by about 3/8 inch, even with the 5-speed freewheel that came with the wheel.

I got to this point late in the fall of last year, and had only one short ride on it. It seemed to work ok, but... It was only a short ride. I'll know more as the weather warms and I have a chance to get a few more miles on it. If it works out ok, I'll just use it as is, but if not... The next step is to source some longer spokes and and rebuild it to center the wheel.

[Badbaz]

Sorry to be thick but can some one show a picture of these washers / spacers and the order they go in...


Thanks in advance for your help

[Bikemad]

Sorry to be thick but can some one show a picture of these washers / spacers and the order they go in...

This should help:


                             Click to enlarge

Alan
 

[Badbaz]

Alan

Thanks again for this info you should work for GM with you knowledge!!

Thanks


Baz