Aroo

First of all I hope I've put this in the right place.
I am having trouble with my rear derailleur/cassette. When in the smallest cog it takes 2/3 shifts to move up one cog. What is likely to be the issue? Any help is appreciated.

Iride01 

Might just need the barrel adjuster turned to takes some slack out of the cable. Might be the cable slipped in the holdfast and doing what I first suggested will only be a temporary fix. Might be a housing end somewhere that isn't correctly in it's stop.

Did you mess with anything prior to this happening? More info about the bike and components will help. And if it's a new bike you got a few months ago....... take it back to the shop you bought it from. If it's only a simple adjustment, many will deal with it for free.

alcjphil

With so little information about the bike, all answers will be guesses. Even knowing the make, model, and year of production would be useful

Aroo

Thanks for the quick reply guys. It's a specialized allez, think 2013 with Shimano rear derailleur (that's the only identifying details I can find).
I have tried the barrel adjuster, it did no good I'm afraid.
It's not an issue I'm desperate to get fixed, just wondered if it was a common issue that might be easily resolved.

blamester

If it was all working fine before the first and easiest step is to spray with wd-40 or similar.
Where the cable enter and leave the outers and the shifter internals.
You can disconnect the pinch bolt to isolate the fault. Hold the cable end and shift the shifter up and down see is it operating smoothly

Bill Kapaun

IF it shifts "normally" after those first couple shifts, it would indicate there is too much slack in the cable.

IF the shifter goes to the highest gear indicated, but the cassette is still a couple shifts short of the largest cog, that would reinforce the above.
There should be no slack in the cable when on the smallest cog/highest gear.

Did this problem suddenly occur or??

Iride01 

I might not rule out that the cable is almost completely frayed up in the shifter. Though usually this shows up going from say 7th gear to 8, 9 and 10. It is Tiagra 10 speed rear?

If you aren't a DIY type and not wanting to get the knowledge, then check with a bike shop. Many won't be as expensive to look and fix this as you think. Some, like many auto shops will determine the issue and give you a free estimate before they do anything.

Aroo

What you describe is what is happening and it was my initial thought but there doesn't appear to be any slack in the cable.
The bike has been sitting in the back of a garage for a couple of years so couldn't tell you if it suddenly occurred or not, it's been like that since I took it out the garage a few days ago.

Aroo

Its only 8 speed. Cable seems in good enough condition. No visible fraying

Bill Kapaun

As a stop gap attempt try-
Turning barrel adjust CCW to "lengthen" the housing. That basically shortens the cable.
If it shifts 1 or 2 gears closer to where it should be, that's the path to pursue.

IF still some problems, I'd try dousing the shifter mech with WD-40 or similar to dissolve what may be hardened grease, preventing proper pawl engagement.

And make sure the housing ends are properly seated in the stops.

Chuckles1

Shift to smallest cog. Give shifter a couple more clicks to make sure shifter has released as much cable as its going to. Screw barrel adjuster in all the way and back out a half turn or so. Loosen cable clamp, pull on cable end with pliars, manually push derailleur body so it is a bit inboard from smallest cog, and with your third hand, while maintaining pull on cable end, tighten the cable clamp. Try shifting and adjust barrel adjuster to get smooth indexing.

if that fails, take it to LBS. Good luck.

Litespud

sounds like a slack cable. Even when on the smallest sprocket, the RD cable should be tight. Otherwise, the first couple of clicks are simply taking up the slack before the RD starts to move. When the shifter is clicked down to the smallest sprocket (and the TD is on the smallest sprocket), how tight is the RD cable at the down tube (the longest “open” cable run)? If you push it at the mid point with your finger, it shouldn’t deflect more than a mm or two