yusiy

Hello guys. I have this strange problem.

I'm running a 10 speed Sram Red on 2013 Crux. And the shifting is only really poor/hesitant when going from 6th largest cog to the 7th largest cog. Going from 7th to 6th is fine. And everything else is very smooth as well. I've taken the bike to the shop, and they replaced the chain, straightened the RD hanger, and did the best cable tension adjustment they could. But we have not solved the problem yet. Also, the cassette is a relatively new Sram cassette without any visual damage.

According to previous threads, a bent hanger is usually the cause. But unfortunate it didn't fixed the issue. I really hope it's not caused by the shifter itself. What do you guys think?

Thanks so much for the help!


- Richard

Bike tinker man

Only my humble points,

So assume its a double on the crank, & this only happens when you are in the smaller chain ring ? there re no issues with the FD ? & obviously the cassette ring is not in any way slightly bent, I don't know Sram one assumes you looked at the teeth profile closely ?
If you take the chain off, does it index through the range on the shifter smoothly.
When you say it its hesitant ? does it ride up onto the 7th then drop back i.e. not going far enough over ?

Andrew R Stewart 

Often shifting sluggishness in one direction but not the other is a cable friction cause. We've seen inner cable kinks right at a frame stop before, usually due to poor auto carrier contact location. Not saying that this is your problem but has been others'. Andy

yusiy

Hi. Thanks for your reply. To answer your questions:

1. chain ring: It happens for both small and large chain ring.
2. FD. FD is not an issue. No rubbing as long as it's not cross chained.
3. teeth profile: They look okay. We didn't see any damage or missing tooth. But swapping to another cassette may be something we would try next.
4. index through the range on the shifter: Not tested yet.
5. hesitant: It does not go far enough. Once it goes over with a little extra cable pull or pushing the RD with finger, then the chain stays on 7th cog quietly.

yusiy

Hi Andy. Thanks for your suggest. I think replacing the cable is what we are going to try next. Maybe the internal cable routing made things worse.

Phil_gretz

Akin to Andy's diagnosis, friction in the rear upshift can also result from grit in the rear derailleur. This movement is relying on the tension of the derailleur spring to move outward toward the derailleur's neutral or relaxed position. If you're going to replace the derailleur cable and housing, then it's an opportunity to break the chain (quick release link? or press pin type), and then remove the rear derailleur.

If you have an ultrasonic cleaner, then this would be best. Ask around, maybe you have a friend who does. Otherwise, next best would be to take an old mayonnaise jar filled half way with a light solvent like mineral spirits. Agitate by hand and see what results. Re-lubricate with light machine oil, 3-in-1 or Tri-Flo or somesuch. Move the derailleur action by hand repeatedly to work the lube into all movable joints. Wipe down and then re-install everything.

Along with new cables, this may get you over the hump. Good luck. PG

cxwrench

If it's a bent hanger it would definitely not only happen on 1 cog. It would start at some point (depending on how bent the hanger is) and get worse as you shift to bigger cogs...if the hanger is bent 'in'. Shifting problems like this are nearly always cable/housing related. If the housing has been on the bike for a year or more replace it as well as the cable.

yusiy

Hi Phil, thanks for your advice.

yusiy

Thanks for your advice. The current housing and cable has been on the bike for 7 years. Namely, never replaced because they look pretty clean. So definitely could be the cause.

Andrew R Stewart 

Duh!!! Besides the increased corners and curves the cable goes through, being run internally, the cable is now far less serviceable too. For the 99.8% of us internal routing is a marketing solution. Andy

yusiy

Hi guys. Here is an update of things.

For some reason, changing a new cassette (a 10 speed 105) solves the transition issue of going from 6th to 7th. However, I felt the shifting is still not perfect. For example, when the chain is on the small cogs, I would want to tighten the cable a little more. When the chain is on the bigger cogs, I would want to loosen the cable a little more. Basically, it's not easy to keep all gears quite. I'm sure Sram Red is better than this haha.Therefore I'm still going to change the cable and housing.

Thanks!

Troul 

you might be trying to create a solution to a problem that doesn't exist.

cxwrench

Are the cables crossed/twisted internally? Keep a really close eye on the rear derailleur and shift the front...see if the rear moves.

oldbobcat

To me that bend the cable has to negotiate just before it exits the dropout, on all Specialized road bikes with internal routing, is suspect. It's angled upward to let the dirt and water in, and it's a source of friction that can't be replaced when it gets worn.