revan114

On a seemingly new Mountain Bike, my gears have stopped changing correctly.

I will be on the 7th gear(The smallest cog on the cassette), then change to the 6th only for it to not do anything. I can however, change to gear 5, then it will change to 6... I can go to gear 1 just fine.

Any advise?

I've also noted that changing from the biggest cog to lower doesn't have that many problems, but once I go to 6 it will slip down to 7 if this helps.

FBinNY 

Most likely it's a simple trim (cable tension) adjustment. Basically you want to turn the adjuster where the cable meets the derailleur upward slightly (usually less than 1/2 turn) to move the RD inboard a hair. You can search the net for tutorials on Adjusting rear derailleur, and find a bunch, both text and photo, and video. Watch/read one or two then give it a shot.

OTOH- it may be some other adjustments, so start with the simple and if that doesn't resolve it quickly, take the time to check all the adjustments or othet possibilities, such as a misaligned hanger.

cyccommute 

It's a new bike and it's a cable issue. Your cables stretch with use when new but eventually bed in. Most bike shops offer a tune up on new bikes and it's to fix this problem. Take it back to the shop you bought it from.

If that is inconvenient, you can adjust it yourself. Shift to the highest gear (smallest cog) and pull on the cable. Properly adjusted, the cable should be taut but not tight. If the cable is slack, turn the barrel adjuster on the shifter or on the rear derailer until the cable is again taut. Takes about 30 seconds.

RonH

No one mentioned which direction to turn the barrel adjuster.
When facing the bike from the rear, turn the adjuster 1/2 turn counterclockwise (CCW). Then try shifting. If it still hesitates, turn it another 1/2 turn CCW.

revan114

Holy crap, thanks!
I honestly don't know much about the mechanics of bikes, I only just got this one as my very first mountain bike, and at first I was thinking it was a Derailieur problem, for the past few weeks I have had a chain slip problem, the gear problem only just appearing.

So, I went ahead and adjusted the derailieur h and l screws, and that fixed the chain slip problem instantly, but not the gear change issue.

I came back, refreshed and saw your post, and wen't back to my garage and followed the instructions as you said, and now it is shifting without a problem! Thanks!

blinky

RonH is spot on !! also, here's a tip that I picked up from a friend and bike mechanic : as the derailleur cable loosens over time , I re-set it as follows (1) loosen the cable anchor screw/bolt so that the cable is not under tension (2) following Ron's advise turn that same adjuster CW all the way & then CCW a full turn (3) pull the cable taut with plyers & re-anchor using the other hand.

As the cable stretches over time again, that full turn in (2) above gives you the ability to tighten the cable .

PS : RonH , I have an '03 Tuscany - my only road bike - love it - our bikes are all USA made - a rarity these days & it's too bad that Litespeed was swooped up by I think American Bicycle Group several years ago .

cny-bikeman

Actually the CCW turn allows one the leeway to slightly relax the tension if needed. You really need to do the above only if you are starting to run out of threads on the adjustment barrel, though that may happen quickly on a new bike if the assembly did not include solid seating of the cable housing.

blinky

actually cny-bikeman my original comment and rationale were correct - standing at the position labeled "rear derailleur" in RonH's diagram , a CW turning of the barrel is the direction to tighten the cable & then you back off a turn in the CCW direction - all this being done with anchor loosened & a slack cable - this is done because the cable's natural tendency is to loosen & you want to be able to have enough of a tightening turn left in the barrel adjuster.

FBinNY 

IME- a derailleur cables total stretch over it's useful life should be less than a turn or two of the adjuster. If the cable as originally installed by the method outlined, there should be no need to reset at the anchor, since the barrel has more than enough travel.

OTOH- if after a long service life the cable begins stretching anew, it's an early warning sign of fraying and imminent failure up at the lever.

migrantwing

Simple way to remember which way to turn a barrel adjuster: Turn the adjuster the way you want the direction of travel. If the chain is hesitating to jump to a larger cog, turn the adjuster towards the larger cog, if it hesitates to drop to a smaller cog, turn the adjuster towards the smaller cog.

cny-bikeman

It's poor practice to describe moving a bolt or other threaded object from the perspective of the "bottom" looking toward the top. The convention "righty-tighty" lefty-loosy" no longer works, and as you just showed it can confuse the audience. It is for that reason that when I taught a mechanic's course I always told students to turn spokes only when looking from the tire toward the hub.

Also, the cable does not have a natural tendency to loosen. If the adjustment loosens a great degree it's because the original assembler did not seat in the housings (the cable does not actually stretch), a housing stop stretched or a front derailleur slipped down.

cny-bikeman

Unless of course one has a rapid-rise derailleur, or an in-line adjuster, or the adjustment is at the shift lever.

Although that could be a handy hint for the situation here, it's always best to understand why a certain adjustment has a particular effect rather than to just attempt to memorize what to do in what circumstance.

blinky

I think the experience of FBinNY regards cable stretch ( which does occur along with chain stretch ) supports my suggestion of a one turn backoff , i.e. the cable will only stretch not compress & Migrantwing's method for memory assist is good & works all the time as far as I know - not sure what a rapid-rise derailleur is ? .

My original tip was more aimed at someone replacing the derailleur cable which the OP might want to do at some point - my reference for the barrel turn was from the anchor looking toward the barrel but it could just as easily been switched in which case it would have been CCW all the way down and a back-off one turn CW - it's a little different than our everyday experience in that when you're at the barrel looking toward the anchor it's CCW to tighten .

cyccommute 

DON'T MESS WITH THE LIMIT SCREWS!!!!!!!!!!! The limit screws do nothing outside of limiting the high and low travel of the derailer. If your derailer is shifting into the spokes or off onto the frame, you can adjust the limit screws. Otherwise DON'T TOUCH THEM! Have I made myself clear?

This is a cable issue which is fairly easy to deal with. By adjusting the limit screws, you've introduced a whole new problem which isn't that hard to fix if you have the knowledge of how to fix it. Unfortunately, you lack that knowledge. You should probably take your bike back to the shop and tell them what you have "adjusted". Depending on how you adjusted the limit screws, you may not be able to shift into high or low gear or you may end up throwing the chain onto the frame (minor annoyance) or into the wheel (major damage).

Get thee to a bike shoppe!

cny-bikeman

FB referred to stretch over a cable's lifetime. The amount of stretch in even a year is negligible. What people call stretch is almost entirely seating in of the cable housing to the stops, or slight give of bolt-on cable stops.

I acknowledged that Migrant's hint would work in this case. My point was a more general one, addressed to the fact that many who are new to repair tend to follow rote procedures rather than pay attention to the why and how of what they are doing. A rapid rise rear derailleur moves in the opposite direction to that of a normal derailleur.

I never disagreed with backing the adjustment barrel off 1 turn. It is OK to do so on a new cable, but that's not what we were discussing. Again my point was the more general one of adopting a consistent method of describing how to turn a threaded item.

wrk101

+1,000,000 those screws are limits, which keep you from shifting into the spokes (bad idea), or the chain stay. They are not adjustments for shifting.

Read the Park Tool site tutorial on adjusting rear derailleur. It is excellent.

blinky

well it appears that Revan114's original issue was resolved early on in these threads - good continuing discussion , solid info from all !!!!!

migrantwing

Just be glad it's not the FD. They are a complete PITA compared to an RD.

reddog3

??? FDs need only to shift the chain between two rings (maybe three). For the most part the shifters aren't indexed. FDs have a couple of adjustment differences- height and alignment) but if shifted fine at one time, those adjustmens won't change. Look at the cables.

migrantwing

I wholeheartedly agree. I was just stating that, for such a simple device, an FD is, in my finding, a whole lot more fiddly than an RD when it comes to correct height/position on the seat-tube, and in relation to the front chainrings. An RD is a little more 'forgiving' regards initial setup and alignment.

digibud

If you played with the stops I'd do some more viewing of video tutorials and learn how to exactly and precisely set those correctly again. If they were set correctly before and you "adjusted" them you have a problem. You will either NOT be able to shift all the way to a fully low gear, or your high gear OR you run the risk of shifting into your spokes or out of your high gear and both are a potentially huge or dangerous problems. Your stops have NO effect on gear changing other than to prevent over shifting and it's very easy to have a stop set incorrectly and have that problem "hidden" by the tension on the cable for a long period of time only to crop up when you double shift to your lowest gear under load with a dirty chain and end up locking up your rear wheel beyond your ability to pull the chain out by hand. If your cable is tensioned such that it just gets to the low gear (big cog), you can entirely remove the stop and it won't seem to make any difference -most- of the time. Hence the need to get those stops set perfectly and properly. A similar thing can happen with the high gear.