Milspec

I am having issues with shifting along the smallest gears of the cassette. It shifts smoothly on other gears, but once it reaches the smallest 3, it just jumps around and doesn't want to ride well. Sometimes it even jumps into another gear on it's own. It does it on all 3 of the chainrings so it doesn't seem to be an angle issue and I tried adjusting the derailleur, but no benefit.

The chain isn't stretched according to the park tool and there are no bent or missing teeth on the cogs. Am I looking at a worn out cassette or maybe a loose lock nut? The cassette doesn't show any movement along the axle either.

Where do I go here?

JanMM

I try to never use the 3 smallest cogs when on the smallest chainring.
Is the RD cable taut when on the smallest cog? Does the chain jump from smallest cog to next smallest cog or does it jump the other way or both ways? Is the cable and/or housing old? How old is the cassette?

cxwrench

To start, chains don't stretch, they do wear. I always make a point to use the proper terminology. How old are your cables/housing? While the derailleur hanger normally doesn't cause problems in the small cogs it's worth a check. Lock nut could be loose, can't your/haven't you checked that yourself? Have you recently installed a new chain? Wear issue between new chain/old cogs?

Germany_chris

Just about every time I've had this issue it's been a b screw too loose

cxwrench

Usually you notice that on the large cogs (pinching the chain between the upper pulley and big cog) not the small cogs.

Andrew R Stewart 

The first thing I think of is cable friction and/or a weak der parallelogram return spring. Andy

andrewclaus

It may be a cabling issue. How old is the bike? The last cabling loop at the RD often has excessive friction, from corrosion, dirt, or wear. The RD spring is at its lowest tension in those gears.

If you can't reliably shift from the lowest to second lowest cog and back again repeatedly, stop right there and fix the system before you go any farther.

Milspec

Jumps from the smallest to the next one and sometimes back again. The cassette is about 4 years old, but probably only has 400 miles on it....I wasn't riding much for a long while.

Milspec

No offense, but the Park tool literature called the tool used to check a chain for "wear / stretch", so maybe the terminology isn't so wrong. When Park changes their terminology, I will change mine.

I haven't checked the lock nut yet as the bike just went through a full servicing about 3 months ago and I don't see any side to side movement. I am still waiting for my lock nut tool to be delivered, so I didn't pop the wheel off yet.

Germany_chris

I'm not going to argue with you because your sample size is larger than mine but in my experience a chain jumping around on the smaller cogs is generally fixed by a turn or two on the b screw or a cable installed to tight.

Milspec

I will have to return to this later today, but I appreciate the suggestion. I tried to make a few adjustments, but got nowhere.

What is so strange is that it came up quickly. I had been riding all week and then one day it just was all over the place. I didn't change anything yet something was certainly wrong. I cleaned the cogs and chain, but don't see anything wrong. I checked cables, tried some adjustments on the derailleur but no dice...still slop.

Normally, I always had a shop in the next town take care of my bike, but I no longer have my van and the car doesn't have a hitch to run a carrier. So, the only way to get my bike to the shop 8 miles away is to ride it there. Not a big deal, but if it doesn't shift right, that becomes a bigger problem, so I have now become my own mechanic for awhile anyway.

holytrousers

Milspec : you have to be systematic. First loosen all tension by shifting to the highest gear, does the chain shift to the smallest sprocket ? is the cable loose then ? If not, then your cable might be too tight. Start troubleshooting from there.
If it happened suddenly maybe your bike fell on the ground and the derailleur hanger got bent...

Milspec

Bike has never been dropped, no impacts to the derailleur.

I will try that out after dinner, thanks for the help. I did decide to order a new cassette (will need one at some point anyway) if all else fails, but I just ran into another concern....not sure if they are related.

This started out as a Surly Long Haul Trucker, but then my needs changed and wanted something with a little more upper end to keep up with some local triathlons at the time. Not a good choice for a competition bike, but I was a marathon guy and not a tri-guy so I wasn't looking to be competitive, just wanted to give it a try. Anyway, a buddy of mine made the changes to turn it into more of a sport bike to make it lighter and a little quicker without losing all of it's lower gearing. Anyway, looking at things a little, I noticed that the front derailleur rubs a little at the extreme angles and no amount of adjustment seemed to remove it. Looking up the specs a little, I see why.

The Front Derailleur is a Shimano Sora for a triple chain ring. The chain rings on this bike are 52-42-30 and the literature at Shimano says that max for this derailleur is 50. I think this bike was set with the stops to make it work, but not across all gears due to the limitation. My riding needs changed with the hilly courses that I now take and maybe that is just too much for the system to handle smoothly?

So maybe I need to replace that front derailleur as well?

holytrousers

when tinkering with the derailleurs, follow these guides from the park tool website for the rear and the front.
Not sure anything new will fix your problems unless you understand precisely what's wrong with the current setup.
Cheers !

Atlas Shrugged

Hey don't ruin a good scold with facts. There is a reason bike shops put some mechanics in the back behind closed doors or in the basement so they toil away in solitude.

cxwrench

Park Tool is most definitely not the end-all be-all when it comes to anything bicycle related. Chains obviously elongate due to wear but if there was any part of a chain that could stretch what would it be? If you answered the plates you'd be correct. But...if they actually stretched then the holes would get bigger and all the pins would fall out. The pins wear and the inside of the rollers wear as well as the bushing on the plate. Result: a longer chain but no 'stretch'.

cxwrench

I 'toil' right up front, mine is the first stand you come to in the service area.

Andrew R Stewart 

In all seriousness there are other reasons why a work bench out of sight (and earshot) from the customers is a good thing. Stuff like using hammers and poor music choices. Andy

KerryIrons

They use the term stretch because so many people incorrectly use it. They put wear first, and that is what is happening. No stretching involved. Why would you want to use an incorrect term?

Andrew R Stewart 

[QUOTE=KerryIrons;22564694]They use the term stretch because so many people incorrectly use it. They put wear first, and that is what is happening. No stretching involved. Why would you want to use an incorrect term?[/QUOTE]

Because that term is what one "grows up" with. After the first "term correction" following posts are just piling on. Andy

Milspec

Language is not that structured, I used that term because as you pointed out so many use it and understand it. I come from a family of auto mechanics and my entire life, the same was said for timing chains....stretched. As you noted, the chain doesn't actually stretch, it becomes elongated by the wear, but the end result is the same....the chain no longer rides tight to the teeth and is loose. It may not be technically correct to use the term "stretched", but everyone understands it so as far as language goes, it is effective.

Every industry has such terms. In firearms, people are always mixing up terms such as "clip" instead of "magazine" or "bullet" vs "cartridge". In the food industry, people say Ketchup when referring to the condiment, but that is actually a brand name and not the product, yet we accept it's usage because it is commonly understood. Using the term "stretched" has the same result, you knew what it meant and so did everyone else who read it. Monkey wrench or Adjustable wrench..... the list is endless.

This is a forum for discussion, it isn't sitting for an oral board where the exact term is vital. Language only requires understanding and we all understood what the term was referring to. I appreciate the corrections as bike repair is not my strength, but I think pushing the issue is not very helpful in such a loose discussion as a forum.

andrewclaus

Going along with the drift, I was recently corrected by a retired professor about the right name for a semicircle. I volunteer on a trail crew, and we sometimes dig a drain in that shape. The crew leader calls it a "half moon." But that's not technically correct. The shape we associate with a semicircle is actually either the first or last quarter moon. But nobody's pedantic enough to care--we know what to do and it's just moving dirt and rocks.

Iride01 

My thoughts initially from the title and description in the first post seemed like this will be the friction on downtube shifters needing to be tightened. However I don't know if this is an old bike with downtube shifters.

More info about the bike and the history of the parts involved might help. Has the chain ever been replaced? You said the cassette was replaced a short while back. Was the chain replaced then too? Mountain bike with shift levers or a road bike with STI's?

When a chain checker tools shows a chain as bad, you still need to measure the chain with a steel tape or scale to check how far the chain pin is from 12" out from another pin. There is a certain type of wear that will fool a chain checker tool into flagging a chain as bad when it's not.

Frayed cable inside the STI's or shift levers? Chain not sized properly and too long but just showing up now for other reasons?

ClydeClydeson

Mentioned above, might be an issue with cable friction when the derailleur gets down to the smallest gears where its return spring is least stretched and the amount of force it can generate to counteract cable friction is least.

cxwrench

And on firearms forums they get ruthlessly corrected. I'm not aware of any condiment forums but they surely exist.