Unable to shift to two largest cogs

Question

Just been out on a ride and beforehand it was shifting through all the gears fine but I think I hit a few bumps and heard some clunking and I could not shift into the two highest gears. I did just re-wrap my hand bars but I really doubt that has anything to do with it as I didn’t adjust anything and the cables were already taped down.

I’ve now managed to get my high gears back but lost the two lowest gears… I’ve set the H & L screws and the B screw and aligned the gears where I could and tightened the cable which seems in good condition. I’m really lost where to go now any more advice I’d be grateful.

Any help and tips would be greatly appreciated. Running a triban rc520 shimano 105.

Answer 1

As an update I have taken it to a mechanic and it turned out the cable was fried at the shifter end!

Thanks everyone for your help and advice, I now know a lot more about the derailleur etc.

Answer 2

There are two issues:

1. identifying the problem, and
2. solving the problem.

The latter is immediate once you identify what's wrong, and so I'll mainly address the first.

Gear-Cog mismatch

You may think that you are in Rear Shifter Gear 3, just because you see that you are on Rear Derailleur Cog 3.

That may not be the case. Your Rear-Shifter may already be on Gear 1, and you can no longer shift down). The shifter has no more "lift" left to pull the cable.

The cable is frayed

Your cable may have frayed. A cable becomes longer when it's frayed. After some elongation, the cable will be unable to hoist the derailleur to the larger cogs.

Two locations are possible. Inspecting under the Rear-Derailleur pinch bolt is easy. It's harder to inspect whether the cable is frayed at the shifter (the "brifter"). The ugly look of older Bowden cables, sticking out from the brifter towards the centerplane of the bike caused the cable to turn by only 90-degrees. All recent cables turn 180-degrees, which reduces their lifespan.

Your Front Derailleur cage prevents the shift

This should be easy to identify, as you would hear loud rubbing between chain and cage.

The Low bolt is inserted too far

That's unlikely, partly because you adjusted it, but also because you would at least be able to pull to the second-largest cog ("rear cog #2").

I would bet on the first. At the rear shifter, shift up all the way to the smallest cog (Gear #11), and re-attach the bolt while pulling firmly on the cable. Your barrel adjuster(s) may pull the cable enough without reattaching the cable. This should re-align Gear 11 with Cog 11. (Replace 11 with 12 if you have 12 gears). Peeking under the brifter cover will reveal the condition of your cable there. Once G11 is aligned with C11, G1 also will be aligned with C1.

Video tutorial

Calvin Jones @ Park Tool describes the procedure in detail. Give it a shot.

Answer 3

Unfortunately I can't comment yet so I'll try this way.

I would take of the chain (clean around the quick link before removing and later reusing it is anecdotally fine).

With the chain removed; shift all the way up and then count the clicks when shifting down. There should be 10 clicks for all 11 gears. If you only hear 8 clicks the issue is probably in your shifter. Try again by manually putting tension on the cable to rule out the derailleur spring and/or limit.

That could explain why you can manipulate which gears are used by playing with the cable tension.

With the chain removed I would also check if you can move the derailleur by hand over the full range of the cassette to rule out any limit screw issues, but since you can reach all the gears when manipulating the cable tension I expect this to be fine.

I guess removing the chain is not strictly necessary but does eliminate 1 more variable.

Edit: Unfortunately I'm unfamiliar with the exact details of the 105 shifter. For the SRAM rival shifter I know you can access the shifting ratchet, which if you do would probably explain why not all shifts are available. While looking for the 105 equivalent I did find this, which looks similar to your problem. Might be better to just take it to Decathlon.

Answer 4

Your bike is unsafe, don't ride it.

You have multiple issues to be corrected. I would trust any competent mechanic to fix them. If you are green I wouldn't try it, take it in

When I saw this, I thought for sure I was seeing things. I wasn't. What DID you do??

Answer 5

It seems like there's not quite enough information in your post to troubleshoot the exact cause of the problem. Because of that, I'm going to suggest how to troubleshoot what the issue is, and adjust correctly as you go.

If this derailleur-shifter-cassette combo worked previously, then it's not a problem of compatibility, so let's assume all the parts work together when correctly installed and adjusted. NB reading through all the comments on other posts, my bet is you have a combination of improperly adjusted limit screws and some issue with the cable and/or housing. However, I think it's good to rule other possibilities out!

Ensure the derailleur hanger is straight

This usually requires a special tool. But, if your shifting was working before, and you haven't crashed or smashed your derailleur on something, this is probably not the issue.

Make sure your rear wheel is mounted correctly and that the axle is straight and correctly tightened.

Check that your cassette spins freely forward and backward, and isn't loose on the freehub

Check the range of the derailleur

• Disconnect the cable entirely from the derailleur.
• Ensure the derailleur pivots freely back and forth around the mounting bolt.
• Turn the cranks forward until the chain settles on the highest gear. If the chain is NOT settled on the highest gear, or the pulley wheels aren't lined up with the highest gear, then your outer limit screw is not in the correct position. This bolt should allow the derailleur to "relax" to the highest cog, but not pass it. Once that's adjusted...
• Press the derailleur cage slowly in toward the hub while turning the cranks. The chain should change gears as you turn, and stop on the largest cog. TAKE CARE not to press the derailleur too far and push the chain over the big cog and into your spokes! Again, make sure the chain and pulleys are lined up with the correct (biggest) cog, and if not, adjust the inner limit screw until the chain can reach the lowest gear but not pass it (though, I usually find it needs to reach a small amount past to shift smoothly-- like, half a chain width or less.)

At this point, if all has gone well, then the problem is not likely in the derailleur.

Check the cable and housing, including the ferrules

Sometimes if your cable ferrules aren't seated correctly in the frame lugs, or the housing is kinked or dented, the cable will have unexpected slack in it, or catch when you try to shift. Checking all this might require unwrapping your bars, depending on where the ends of the housing are. It's possible there's exposed cable, or a gap between the housing and a ferrule underneath the wrap.

• The cable should slide freely in both directions in and out of the housing.

• If the cable doesn't slide freely, replace the cable and housing, and the ferrules if any of them are damaged or dirty.

Check the shifter

At this point, it might be the shifter. Shifter internals can fail, get dirty, or the cable could be catching or be bound inside the shifter body.

• Put gentle tension on the cable, and see if you have 11 "clicks" from the highest (cable furthest out) to the lowest positions. Listen and feel for any binding or skipping.

• You might want to disassemble, clean, and lube the shifter internals. It's easy to lose these parts and not so easy to reassemble some shifters, so it wouldn't be my first choice.

Reconnect the cable to the derailleur

• Tighten your adjustment barrel on the derailleur (and the shifter, if there is one) all the way down, and back it off a couple of full turns. This lets you adjust the cable tension in either direction and at either end if you need to later.

• Make sure the cable is pulled gently all the way out and the shifter is set to the highest gear.

• Make sure the cable is fed through the anchor point on the derailleur correctly. It's possible to attach this, but do it wrong, and affect the shifting.

• Snug down the binding bolt.

• Turning the cranks, test your shifting.

• You may need to add or remove tension using the barrel adjusters to get crisp shifts from one cog to the next.

Hopefully a methodical approach like this, checking one part of the system at a time, will help you identify where the problem is in the system.

Good luck!