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Those questions, and more, answered right here, in the most comprehensive guide to eccentric bottom brackets around. And if you still have questions after feasting on this, be sure to let us know in the comments section below. Off-center is definitely one way you could put it.

There are two types of eccentric BB. The first type is those that accept a threaded bottom bracket. This model does not contain any sealed bearings. You insert the eccentric bottom bracket into the BB shell then tighten it into the shell. They are closer to an adapter than a fully-functioning bottom bracket. The bolts either. The specific bottom bracket you intend to use then screws into the eccentric bottom bracket unit. The eccentric effect chain tensioning or BB height comes through loosening the bolts, then rotating the unit containing the bottom bracket as a whole.

The second type house bearings and directly accept an integrated spindle—they are complete bottom Fm domestic discipline spanking in themselves. The mode is press fit: t ighten the bolts to Position of bottom bracket. Then you install your 24mm integrated spindle crank, adjust the fit—you may need spacers depending on what crank you have—tighten all bolts to within the correct torque tolerance.

Getting an answer to that involved looking at what they are designed to do and then what they actually do. Eccentric BBs Position of bottom bracket two functions:. When you rotate an eccentric bb there is both horizontal and vertical movement since Position of bottom bracket unit moves in an arc.

On a single speed we take advantage of this horizontal or forward and aft movement. You loosen the Position of bottom bracket bolts built into the eccentric BB, easily rotate the unit until the chain or belt reaches the right tension.

Then tighten the bolts. The tension is maintained just as you like it. The added convenience factor is that you can do this anywhere with a minimum of fuss. No turning your bike upside down. On a mountain bike we take advantage of the vertical movement. With an eccentric bottom bracket you are able to quickly and easily adjust your bottom bracket height. What difference does it make? Any at all? On the subjective side of things, the answer is it depends on the rider.

Every rider also has a certain level of physical adaptation to the mountain biking discipline. Add to that again the trail conditions rocky, flat, or somewhere in between means there is no single definitive answer to the question.

If you are interested in the nuances, a wide ranging discussion Position of bottom bracket all the issues is available on this MTBR Forums thread. Check out the video for a detailed demonstration of how to remove your existing bottom bracket and install the model we examine in the rest of this post.

For the most comprehensive coverage on removal and installation of a square taper bottom bracket check out this article. The eccentric effect is achieved by offsetting the sealed bearings within a pentagonal structure. Unlike most other eccentric models, the bolts on this model are uniquely positioned. There are no bolts laterally installed across the unit. Three of these bolts are evenly distributed around the outside casing.

Each is easily accessible on the casing in Position of bottom bracket the chainring and BB shell. Achieving very light finger-tight fit is all you need.

First up you Position of bottom bracket to remove the existing bottom bracket. Our Square Taper Bottom Bracket article can help you remove that type if that is indeed what you have. Loosening the axle Position of bottom bracket releases the chain tension. I should note that this will be the last time you have to touch the wheel nuts if chain tension is the main reason you normally have to fiddle with them.

Having loosened the bolts, the chain Position of bottom bracket be slack enough to lift cleanly Position of bottom bracket and away from the crank and chainring. A procedural reminder: the chain will likely scratch the chainstay clear-coat and even chip the paint.

Protecting the chainstay is easy. Secure the chain around the chainstay whilst you install the eccentric BB. With the chainstay protected, dislodge the chain from the chainring. Protecting the seat stay is also important.

Remove the drive-side crank. Off with the left crank. Out with the Position of bottom bracket bracket. Give the BB shell a wipe—clear out the old grease. Apply a fresh coat of grease to the threads. This is because both sides need to be aligned for accurate spindle positioning. Whatever position the bearing casing is on one side, it must be in the opposite position on the opposite side.

Give the threads a good coating of grease. Always ensure the BB threads are seated exactly in the BB shell threads. If not, you can often proceed to tighten the cross-threaded bottom bracket, thinking the increasing resistance is simply due to a snug fit. You can repair the BB shell threads. However the bottom bracket cup will most likely be ruined. Returning it to a usable state will require the right die set and expertise.

Turn the bottom bracket cup to the right, rather than the left and to the left rather than the right on the non-drive side. The wrench supplied with this BB set hooks into any one of the three notches located in alternate succession to each casing bolt. The short handle means tightening to the limit will give you around 35nM of torque, which is sufficient.

The spindle in this image is Position of bottom bracket 5mm short of its final, ideal, position. The fix is simple. Before tightening the casing bolts, you need Position of bottom bracket rotate the outer casing on each side to where you want it, as long as you know the exact position.

Otherwise you can adjust the position with the Position of bottom bracket installed and the chain mounted. This design can certainly be produced in a press-fit model. The spacers that come with this unit allow you to adapt your crank to this eccentric BB. The key principle to keep in mind when adjusting the bottom bracket for. If one side jams up, you have to reverse that side, re-align it with the other, then continue the adjustment.

The purpose of an eccentric bottom bracket for a single speed is the greater convenience when increasing or decreasing chain tension. You achieve this by loosening the outer casing bolts—the casing is now free to rotate around the stem Position of bottom bracket the sealed bearing and thus the spindle with it. The single speed chain here has been refitted to the newly installed crank.

The job now is to get the right tension on the visibly slack chain. The casings can be rotated in either direction. Position of bottom bracket end result Position of bottom bracket the same. The easiest access is from the non-drive side. Left hand on the drive side BB casing; right hand on the non-drive side casing. A half to three-quarters rotation is all it takes to deliver the correct tension.

The final step is to tighten each of the 3 casing bolts on each BB. Note that the maximum torque is 2. One bolt can hold the casing in position by itself. An MTB eccentric bottom bracket is for bottom bracket height adjustment. The rig here is a 34T narrow-wide crank fitted with the new eccentric bottom bracket. If you were out on the trail, one without too many rocks or boulders, you could quickly lower your bottom bracket.

Or with the BB already lowered, you hit a rough patch raising the risk of a pedal strike. You stop for a few minutes, raise the BB to maximum height, then power off down Pima county adult detention center trail.

All you need to do is have that 2mm allen wrench handy. Loosen the Position of bottom bracket bolts on both sides. Rotate the Position of bottom bracket, altering the crank height to the correct level. Re-tighten each bolt just a bit. Final Thoughts. What place might an eccentric bottom bracket have in your cycling life? Skip to content. Johnson Li.

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