The EZ-Speedster Minimalist Chain Tube

(-NOTE: this bicycle was purchased in April 2004, current models may differ somewhat-)

(-UPDATE- This model was discontinued in early 2006, and all new bikes were closed out shortly after that time. Original prices were $800-$1300, closeout prices were about half that much- )

(UPDATE #2 - I sold this bike around June of 2007 )

This bike as it comes, has two chain tubes on the front-half. The image on the website does not show them, so they have been illustrated above (Fig. 1) in blue. The clamp that holds them in place is illustrated in violet.

The red arrows under the seat are pointing to the chain idler wheel (at the rear of the seat) and the seat skewers. For some reason this image shows three skewers (the chain idler wheel plus two seat skewers, the small black-in-white circles, the two right-most "forward" arrows) but the bike is supposed to come with only two seat skewers (one holds the idler wheel and one has a thumb nut); upon noticing this I verified it with Sun (as of 5/19/2005). The idler wheel fits onto one skewer, and the other is backed up by a thumb-nut. So the "rear" thumb-nut of the two in this image shouldn't be there. Also note that the idler wheel comes originally fastened under the rear edge of the seat.

...............

This bicycle must have at least one chain tube, because in many gear combinations the return-length of chain will contact the frame near the head tube (where the fork passes through the frame).

The long chain tubes cause at least two problems. The first is that they make it difficult to clean the chain without breaking and removing it or jacking up the rear of the bike off the ground as there's not enough exposed chain on the front-half of the chain run to attach a scrubber, and you cannot clean inside the tubes themselves when the chain is still inside them. The second problem is that they add a significant bit of friction to the drive system.

There are two quick-release seat skewers holding the seat on, one has a thumb-nut on it and the other has the chain idler wheel. If the idler wheel is left in its original (rear) position, with the chain tubes removed in lower gears the chain will be able to contact and grind on the other skewer's thumb-nut. The fix is as above in Fig 2.--switch the skewers' positions so that the chain idler wheel is mounted under the front edge of the seat, and the plain skewer is in the rear. This way there is much more chain clearance between the thumb-nut, and the seat still gets held on. Also make certain that the "return" run of chain is run on the outside groove of the idler wheel.

[edited Apr 12 2006]

Perhaps some clarification here is in order: I am quite tall, and need the seat moved all the way to the rear of the frame. With the seat all the way back, it's better to have the chain idler on the front end of the seat. If you were shorter and had the seat moved more than a few inches forward of the rear end of its travel, it might be better to leave the idler wheel on the rear end of the seat frame.

The "improved" chain tube is shown above in Fig. 3. This prevents the chain return run from rubbing on the head tube (where the fork passes through the frame). Another matter is that where the two directions of chains cross in front of the idler wheel, there is very little clearance between them, so the tube must extend back to prevent them from contacting each other as well. The tube has a lengthwise notch cut into it, which makes it much easier to remove for cleaning after the clamp on it has been undone. The arm is bent from coat-hanger wire, there are two small pieces bent into "U" shapes inserted into the clamps, and then the arm has small loops bent into its ends. This allows it to move left-right and up-down freely with the chain, but keeps the tube from moving fore-and-aft. The arm end loops are at a 90-degree angle to each other, and some adjusting is necessary to prevent the tube-clamp from hanging up on the frame.

This setup allows much easier chain cleaning and still has significantly less friction than the original long tubes and tube clamp.

The power/tension length of chain does not need a tube at all, it has free clearance between all the chainrings and cogs. When you are not pedalling, the chain will bounce down on bumps and contact the frame near the head tube, so perhaps a bit of protective tape there is in order. During pedalling that length of the chain is under tension, and will not do this.

In general, when you go over rolling bumps you will get some more chain noise from the front-half of the chain--but this is because the chain is no longer being forced into an unnatural position as before, by the long chain tubes and stiff clamp. During pedallling on flat pavement there will be slightly less noise than before.

Cutting the notch down the length of tubing took a bit of work, but it is the best way to make the tube easily removable. I tried cutting a piece of tubing totally in half and just allowing the clamp to hold the two halves together around the chain. This worked but was noisy, the ends curved slightly apart and it rattled a lot.

~~~~~~~