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Drivetrain problems

2K views 27 replies 13 participants last post by  jeffscott 
#1 ·
Went out yesterday and had some problems on the trail. My chain was coming off and getting suck in between the smallest gear and the frame when i would back pedal. I do this to position the pedal to clip in. This has never happened before. I rode mostly on the smallest front gear and would change the back as terrain changed.

Im not sure if this is related but the bike was shifting weird. The best way i can explain it is they were not smooth shifts (mainly going from small gear to big gears). The chain would drag a little before engaging on the next gear. By this i mean it seemed to make several rotations (or at least it sounded like it) before it would settle on the next gear. I could hear the chain dragging over the gear. Usually i cant even hear the shift except when going to the biggest gear so i feel like something must be wrong.

Drive train: Deore XT
Front: Shimano XT, 22/32/44 teeth
Rear: 9-speed, 11 - 34 teeth


I dont know if this is enough info for assistance but i would appreciate any feedback. thanks.
 
#2 ·
Went out yesterday and had some problems on the trail. My chain was coming off and getting suck in between the smallest gear and the frame when i would back pedal. I do this to position the pedal to clip in. This has never happened before. I rode mostly on the smallest front gear and would change the back as terrain changed.

Im not sure if this is related but the bike was shifting weird. The best way i can explain it is they were not smooth shifts (mainly going from small gear to big gears). The chain would drag a little before engaging on the next gear. By this i mean it seemed to make several rotations (or at least it sounded like it) before it would settle on the next gear. I could hear the chain dragging over the gear. Usually i cant even hear the shift except when going to the biggest gear so i feel like something must be wrong.

Drive train: Deore XT
Front: Shimano XT, 22/32/44 teeth
Rear: 9-speed, 11 - 34 teeth

I dont know if this is enough info for assistance but i would appreciate any feedback. thanks.
Time for a tune-up. Probably just a bit of derailleur adjustment. However if you've crashed recently you could have a bent derailleur hanger as well. Or could be gunked up or worn out cables too.

Good Dirt
 
#3 ·
#5 ·
Yup, I got the tools, and mechanics are not an issue. However, i need to know where to start in order for those abilities of mine to be useful. I will check out the docs and see if they can point me in the right directions. thanks.
 
#7 ·
Start with a good cleaning and re lubing.
When dirt accumulates on the drivetrain, it starts to make noise and stuff starts sticking. If your summer has been as dry and dusty as mine, that may be the entire problem. If not, at least you're starting your tuneup on a clean drivetrain.
 
#8 ·
On the pivot/hinges of the derailleurs? Yep, chain oil is fine.

As for getting started, it sounds like your RD is fine. If that's the case (and everything is properly aligned and shifting smoothly), then shift to the big cog on the rear and small ring up front. Unscrew the front cable, screw down the barrel adjuster on the left shifter and reattach cable.

Now, adjust the clearance between the chain FD. Too much clearance is what allows the chain to fall between the ring and frame. As for slow shifting, you might not have enough tension in the cable. So keep turning the barrel adjuster counterclockwise until the tension allows for smooth shifting.

Make sense?
 
#9 ·
I have been down a couple of times, but not hard. besides my falls always seem to be to the left now that i think about it so shouldn't have much effect on the drive-line.
Bike crashes are funny -- you can be in crashes that send you to the hospital and the bike is not affected. But you can also bend a derailler with the most minor of things.

I somehow got a stick in my rear wheel -- didn't crash or anything, and didn't damage the spokes even. But it wouldn't shift at all hardly. Just looking at it there was no evidence of damage. Fortunately it was a store group ride and one of their mechanic was riding with us, and saw that the rear derailler had bent a bit. He bent it back in the ballpark of where it is supposed to be and I finished the ride. When I got home I carefully alligned the derailler and reset everything -- the limiter screws and the barrel adjustmnet. As already said, adjusting your derailler is well documented and not difficult.
 
#10 ·
So I cleaned the driveline and that took took care of the chain coming off when back pedaling. I think it was getting stuck on gunk and the chain wasn't keeping up with the gears when they were spinning. As for the shifting problems still messing with it. its a little better but still noisy. Not knowing what it should sound like exactly i was hoping someone could tell me if any noise what should it sound like and how loud.
 
#11 ·
Sounds to me like you simply need to add some tension to your RD cable as it has most likely stretched as all will do over time. No tools needed, just use the barrel adjuster on the shifter or if the RD has one. Can't tell you which direction to turn it for the shifters, but if you're sitting on the bike, turn it "up" to you, if you're looking at the bars from the left hand side to the rear shifter, turn it anti clockwise - basically you want to push the housing out of the shifter, thereby giving the cable more tension. If the RD has a barrel adjuster, looking at the wheel from the side turn it up towards the wheel (anti clockwise).

Note, sometimes it can take as little as a 1/8th or 1/4 turn if you're vigilant on adjusting, other times it could take an entire turn or more. For clearer instructions visit the Park Tools web site.
 
#16 ·
Originally Posted by jeffscott View Post
If you back pedal with the chain cross chained....then it will be noisy and it might jam up...

Cross chaining is when you are in granny and the chain is on one of the littlest three rear sprockets.
hello

I am new at this forum and plan to buy my first xc bike (I am riding a Trek 7300fx, not adapted for xc...!).
I looked at a lot of bikes and decided to get a Giant Talon 0 (price + equipments + unrationnal parameters!). But I went to the shop to try it, I noticed something looking like what you are decribing and I don't know if it is normal or not (beginner...).
This bike is equiped 3x10 shimano (rear: xt, front: slx)
When the chain is at the same time on the front middle crank wheel and on the rear smallest crank wheel, if I back pedal, the chain touches the second smallest rear crank wheel and engages badly on the smallest rear crank wheel.
I know that using this configuration (middle front + smallest rear) is a little stupid (I should use the big front) but I thought that I should work better than it is. I thought that I should be able to access correctly all the rear crank wheels when using the middle front wheel.
I haven't yet bought this bike. I should go tomorrow. What is your opinion please:
- this is normal and I am a stupid beginner?
- this is a little known problem that can be solved by a correct tunning of the bike?
- this an error on this bike or a mismatch of the equipments?
Thank you!
:)

Daniel
 
#18 ·
Daniel77-

Chainrings are connected to the crank (front) and cogs are grouped in the cassette (rear).

As for the middle chainring and rear small cog rubbing, that would probably be fixed with a slight adjustment. Sounds like the rear derailer cable is too tight or the limit screw isn't adjusted correctly.

Keep in mind that shifting and derailuer performance is tuned for pedaling, not back pedaling. The deraileurs guide the chain in this direction. Back pedaling causes the chain to exit on the guide. Nothing is guiding it to the topside of the rear cassette or bottom of the chainrings. Because of this, chainlines at extreme angles can drop if pedaling backwards.
 
#19 ·
Thank you jetboy23 for your answer and vocabulary!

I totally agree on the fact that well-tuned deraileurs have no impact on the guidance of the chain on the topside of the rear cassette when back pedaling. The angle of the chain (on the topside) is imposed by the mechanical positions of the chainring and the rear cog. If this angle is too important (extreme), it is normal that the chain touches the next rear cog and may drop. This configuration would result in the degradation of the cog and the chain and should not be used.
I am wondering what are the combinations of cogs/chainring that are normally usable on a 3x10 and what are the ones that should not be used to preserve chain and cogs (in fact, I want to check if the bike I saw is "normal") ?
Does someone know the 2012 Giant Talon 0 and have an opinion?
Thanks again

Daniel
:)
 
#28 ·
Your gears won't work well if it is cross chained and it will wear the drivetrain out quicker.

On the other hand you should be able to shift and pedal forward in any gear combination, if cross chained it will make more noise.

If you pedal backward, and you are cross chained then the chain will likely come off.

I use my big chain ring and big rear sprocket (cross chained) when I go into a very steep gully....I have to pedal really fast down into it then grab all of the rear gears to manage to get out the other side.....No time for a front D change.
 
#22 ·
thank you for your answers!
Actually, I went back to the shop today and decided not to buy this bike.
Maybe my decision is badly justified but to me : bad feeling = I don't do it.
I will look at other bikes and try to learn a little more about bikes before making my choice.
I guess this forum will be a great source of information and hope I will soon be riding and sharing experience with you.
Thanks again

Daniel
 
#24 ·
One tip: When you adjust the stop screws, do it while the chain is on the middle ring. On the middle ring, there's no pressure on either stop screw.

If your chain doesn't drop on to the small ring, then you need to loosen the outer screw ... the one nearest the crank arm. Turn the screw one half turn counterclockwise and then shift down. Keep loosening the screw in half turns until it shifts.
 
#26 ·
I might have to claim defeat and just take it in. The combination of the derailer adjustments and cable adjustments seems to be to sensitive or something. Sometime the up and down derailer adjustment screws dont even move the derailer which i cant understand.
 
#27 ·
Sometime the up and down derailer adjustment screws dont even move the derailer which i cant understand.
That right there throws a red flag for me. The "adjustment screws" are limit screws. Their only function is to prevent the derailleur from going farther than the gears on the highest and lowest gears. Changing from gear to gear is adjusted through cable tension.

Have you checked out Park Tool's website? You should bookmark that homepage if you're going to be doing work on your bike: Park Tool Co. » ParkTool Blog » Rear Derailler Adjustments (derailleur)

Here is my basic procedure:
  1. Check to see if the hanger is straight. Either visually or with an expensive tool
  2. Shift the front derailleur to the middle chainring.
  3. Disconnect the cable from the derailleur
  4. Set the high limit (H)
  5. While pedaling the bike I will move the derailleur by hand up to the lowest gear and see if I can push it off the end. If I can I tighten the low (L) limit; if I can't I will move on to the next step
  6. Pedal the chain back to the highest gear, turn both (when applicable) of the barrel adjusters so they are 2 clicks in from fully tight, ensure shifter is in the highest gear (8,9 or 10) and attach the cable pulling it firmly but not so much that the derailleur is preloaded against the cable.
  7. Shift the bike using the shifter and see how it behaves.
  8. If it is slow going from high gears (8,9,10) to low gears (1,2,3) (for example, if it takes more than one click to move up a gear) then increase cable tension through the barrel adjuster on the rear. If no rear barrel adjuster, use the front.
  9. If it goes from high to low gears too quickly (skips gears) then reduce the cable tension using barrel adjuster(s).
  10. If you get to a point where you have turned the barrel adjuster more than half of the way it is threaded then you need to pull more slack out of the cable: return to step 4. I usually reset the tension if I need more than 3 full turns of the barrel adjuster to get the tension correct.
  11. If you can't get the tension set properly through this procedure then you either have a bent hanger (told you to check that, didn't I?) or you need to replace your cable and housing. Any additional friction in the cable and housing will usually manifest its self through difficulty going from low gears (large diameter) to high gears (small diameter).

Hope this helps.
 
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