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RoverAl

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Reply with quote  #26 
Came out nice, really looks good. What's this about an online swap meet?
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EagleGrinder

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Reply with quote  #27 
Its an Facebook buy/sell/trade page. Got over 40k members. Got my crank and brakes there. 


Now, I have run into a bug with my drive train. Have it currently at the shop for evaluation since I am sick of messing with it. 

Took it out for 14 mile ride. Was going well until we hit the first hill. Naturally, I settle into the 42t cog in the back and the chain was skipping all over the place from going back to the next cog below and back and forth. I think it was a simple Hi/Lo adjustment issue. Tweak around with it and I think I have it. Now its intermittent. Does it on climbs, and it skips off the cog, but it stays on the 42t. I have messed with the Hi/Lo adjustment enough to throw in the towel and take it to the bike shop in Athens


My theory is the bike shop that installed the chain installed the chain way too tight on the rear 42t. They are good guys, I think they just got in a bind and needed to get it done quickly. 

For reference, here is the image below in the highest cog. What do you guys think? Sorry its a late night photo, but I think that thing is just stretched too much. It almost maxes out the lower pulley on the rear clutch (and SRAM 2.1 Clutches are strong) 
20170714_185857.jpg 

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knl2stl

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Reply with quote  #28 
That chain does not seem all that too short to me.  Perhaps a b screw adjustment.  That top pully seems a bit far away from the 42t.  Also, even hangers on new bikes can be off, so best to make sure that it is aligned with a good gauge.  
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EagleGrinder

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Reply with quote  #29 
I have messed around with the B screw all day and cant get the dang thing to commit to staying in the upper cog. Messed around with the low limit screw all day and no dice. It will shift crisp up and down the block, but after a couple of revolutions on the upper cog, the RD will tense up and the chain will pop off slightly. It will stay back on the cog, but not fully and under load up a long climb. If I pull the lower pulley to stretch out the RD, it will go up to its limit in a couple  (1-2) MM, but (I thought) after watching a few videos of 1x groups in the upper cog, I just think it could be the chain. 

I did think of the hanger being off a touch, hopefully the bike shop will think of that too. We will see what Georgia Cycle Sport and Concepts thinks tomorrow. 
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knl2stl

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Reply with quote  #30 
The hanger can be a tricky one, since just when you think you have it....the adjustments don't hold.  Drop out and frame alignment come into play more with more gears.  Let's hope that is not it.  One more thing to check is the friction of the cable in the housing.  A little drag can cause a lot of problems with Sram.  Easier to test when not running full housing....with no chain on just pull a little exposed cable somewhere and feel for drag.  Have to feel with shifter if full housing.

There is also a chain length equation.  I have only used it to double check my work, and it has always validated my own method.  I think that the Park Tool site might have a more exact formula.  Good luck.  

L = 2 (C) + (F/4 + R/4 + 1)

L = Chain length in inches. Round the final result to closest whole inch figure.
C = Chain stay length in inches, measure to closest 1/8".
F= Number of teeth on largest front chainring.
R= Number of teeth on largest rear cog.

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EagleGrinder

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Reply with quote  #31 
so update. 

Chain was too long and putting some bad tension on the pulleys. One of the causes. So new chain wasted and new chain put on. 

So get home and we have a real tough hill in our neighborhood, and I figure its time to see how it went. 

Dont even get to the hill...crunch crunch crunch. 


Sugar Honey Iced Tea! 

so, back to messing with the L-Screw, and I thought to myself, this has got to be a cable tension issue. Couple of quarter turns here and there and as of 4:23 EST it is holding true. Did all the hills in the neighborhood and so far so good. (knock on wood). Tomorrow I got a ride and I wasnt planning on taking her, but I think I am to make sure everything is a-ok

20170715_144021.jpg 
New chain and less tension on the pulleys. 

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oleritter

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Reply with quote  #32 
chain was too short?


Quote:
Originally Posted by EagleGrinder
so update. 

Chain was too long and putting some bad tension on the pulleys. One of the causes. So new chain wasted and new chain put on. 

So get home and we have a real tough hill in our neighborhood, and I figure its time to see how it went. 

Dont even get to the hill...crunch crunch crunch. 


Sugar Honey Iced Tea! 

so, back to messing with the L-Screw, and I thought to myself, this has got to be a cable tension issue. Couple of quarter turns here and there and as of 4:23 EST it is holding true. Did all the hills in the neighborhood and so far so good. (knock on wood). Tomorrow I got a ride and I wasnt planning on taking her, but I think I am to make sure everything is a-ok

20170715_144021.jpg 
New chain and less tension on the pulleys. 

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EagleGrinder

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Reply with quote  #33 
I meant too short. yeah it was super tight. Shes purring now. Wife calls the bike a cicada with all the noise the pawls make. 

On another note, people have been highly complementary of the wheelset. 
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BluesDawg

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Reply with quote  #34 
As a part time bike mechanic, I see bikes almost every day that are totally out of tune because their owner's first instinct was to mess with the limit screws to fix what was much more likely to have been a cable tension problem. What could have been a quick turn of a barrel adjuster turns into a total start from zero derailleur setup. Sometimes it can even turn into replacing spokes and even a derailleur if they botched it so badly that the derailleur shifts off the cassette and into the wheel.
When I'm showing someone the basics of bike adjustments, I usually explain what the limit screws do and then tell them not to touch them.

With your problem description, I would have checked (order may vary):
1- eyeball check of derailleur hanger alignment (sometimes this is an obvious problem)
2- cable tension (often a couple of clicks of tightening will fix a problem like this)
3- RD limit adjustment. (Before adjusting I would push the RD with my hand to see if it can move into position. If so it is more likely not a limit issue)
3- chain length (yours looks marginal, but not necessarily a problem)
4- gap from big cassette cog to derailleur pulley (to see if a B-tension screw adjustment was needed)
5- hanger alignment using the alignment tool (sometimes a less obvious misalignment is enough to cause a problem)

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