nexus 8 - requires cable retensioning all the time

[CroWizCom]

i have a problem with adjusting gear shifting on nexus 8.
while slowly breaking in for some 1000km and speed and ease of shifting
increased from initial 'lazy' shifting.

however, i am not happy yet.

i use adjustment barrel to line the lines in 4th gear.
if i check after while (15km) i notice that they are no longer
aligned.
i retension the cable with adjustment barrel, making sure that lines
are aligned and that cable is stretched. after a while i can no longer
shift to eight gear because cable is 'too short' and i have to readjust
tesion / realign the lines.

there does not appear to be any problem with cable movement and it
moves with ease.

its a new cable and new gripshift as provided with the wheel.

z

 

[jtaylor]

"CroWizCom" <[email protected]> wrote in message
news:[email protected]...
> i have a problem with adjusting gear shifting on nexus 8.
> while slowly breaking in for some 1000km and speed and ease of shifting
> increased from initial 'lazy' shifting.
>
> however, i am not happy yet.
>
> i use adjustment barrel to line the lines in 4th gear.
> if i check after while (15km) i notice that they are no longer
> aligned.
> i retension the cable with adjustment barrel, making sure that lines
> are aligned and that cable is stretched. after a while i can no longer
> shift to eight gear because cable is 'too short' and i have to readjust
> tesion / realign the lines.
>
> there does not appear to be any problem with cable movement and it
> moves with ease.
>
> its a new cable and new gripshift as provided with the wheel.
>

Check that

a) the cable end is securely fastened; and/or

b) if there are any guides or pulleys over which the cable runs, that they
are not insecure and so moving on the frame and reducing the cable run.

 

[CroWizCom]

it appears that yellow lines (was red dots) align in 5th gear. if i
realign them back to 4th gear, after a while they are aligned in 3rd.
so i am screwing adjustment barrel like crazy.

preety clueless so far. none of potential 'playing' places on cable
route generate entire gear slip.

my most recent suspicion is that end bracket is moving up and down

huh

 

[[email protected]]

CroWizCom wrote:
> it appears that yellow lines (was red dots) align in 5th gear. if i
> realign them back to 4th gear, after a while they are aligned in 3rd.
> so i am screwing adjustment barrel like crazy.
>
> preety clueless so far. none of potential 'playing' places on cable
> route generate entire gear slip.
>
> my most recent suspicion is that end bracket is moving up and down

Check that the rear axle isn't moving around under load / braking
(check brake arm if drum-brake). Check length on your axle locks in
the drop-outs, and tightness. If out, try using a thick grease or
low-stength locktight? They do vibrate out of alignment (my experience
from nexus7 in rear horizontal dropouts of a load bike).

Also check that your headset isn't loose and changing tension.

yours,
Sam R.

 

[CroWizCom]

i could understand that axle could rotate forward a little tightening
the cable but i dont understand how would it move back? its not loose.
i have v-brakes.

 

[Mike Reed]

CroWizCom wrote:
> i could understand that axle could rotate forward a little tightening
> the cable but i dont understand how would it move back? its not loose.
> i have v-brakes.

Braking puts significant force on the axle. If you draw a tangent
backwards off the rim from the center of your brake pads, that's the
direction of the force on the axel generated by braking. The force on
the axle is close in magnitude to the force on the brakes. With fairly
steep seat stays, and pad offset from the stays, they can center nearly
on top of the axle, which means the force would be nearly perfectly
rearward.

An axle allowed to move backwards will do so under braking.

This is one fact that has made me nervous about my friend's Klein with
rear/down facing dropouts. Plus the fact that it's impossible to remove
the wheel without touching the chain is just plain lame.

-Mike

 

[CroWizCom]

hmm it looks like i switched left and right side anti rotation washers
because my bike has been upside down when i was applying them. (or was
i looking at the wheel from the front?)

they should mark them 'sprocket side' and 'other side'

Mike: during the proces i have found the means of 'removing the wheel
without touching the chain'. you have to use the chain tensioner

z