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I got a new Giant propel Pro with an Ultegra groupset back in April, but I am having a lot of trouble getting the gears set up correctly. It is now at a point where I feel they need adjusting after every use or clean, and the worst thing is that I have had to sacrifice the option of using the big ring at the back to let the other gears run smoothly. I know I shouldn't use this gear and the big ring, but it is nice to have the option in the middle of a race.

I have replaced the new cable to try and improve things, but it didn't seem to do much.

I have heard something similar had happened to someone I know, and they were unable to find a fix, but any advice or solutions would be great.

25 comments

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Bobbinogs [338 posts] 1 month ago
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It could be that you are trying to get something working that shouldn't really work without some kind of rub.  Running big/big on most mechnical setups is going to cause an issue as the front derailieur will probably rub at some point (either small/big or big/big) depending on which of the 2 options you have done the setup for.  If you check the angle of the chain when running big/big you will see why the chain, jockey wheels and everything else is having a problem running it.

Why not have a look at the range you are running and see whether there is a better option, albeit at the loss of a close ratio at some point, e.g. if currently running 11-25 try an 11-27 or maybe a 12-27, etc.  

Just as an aside, is it worth checknig that you are using any trim options if you have them?  Most groupsets have a trim option for the FD, puzzling my Potenza has 3 trim options for the small ring but none for the big, whereas my Shimano setups (4700/5800) have trim for big and small rings.

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Bobbinogs [338 posts] 1 month ago
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Oh, just reread and cannot think why you need to be re-indexing as such.  That should be a once off for new equipment setup...and then a minor adjustment after a little while.  The rear index function doesn't really care about what happens at the front.

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Jgdane [7 posts] 1 month ago
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Hi thanks for your comment, but My problem is all on the back derailleur, and there is as you said rub on the front derailleur, but no more than what would be expected. Sometimes I could have my gears set up and working fine, and then the next time I go out there would be clicking from the rear cassette and I would have to jump up 2 gears and down 1 to get the gear I want in the middle of the groupset. So I have to check the indexing regularly and unfortunately I am a bit new to this, but even when i bring it to a friend that has done this for years, he seems to have trouble with this.

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srchar [1540 posts] 1 month ago
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I'd check the rear mech cable routing at the clamp bolt. It's quite hard to get wrong on R8000, but always a possibility. Also check that all cable ends/ferrules are properly seated against their stops.

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jaysa [153 posts] 1 month ago
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Is your dropout properly aligned ? They're made of relatively soft metal, so dropping the bike bends the dropout rather than breaking the frame. You can't really tell by eye.

Our family has 9 bikes (don't ask ...) so I used the Park Tool aligner on them and 4 needed adjustment ...

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mike the bike [1253 posts] 1 month ago
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I know you've changed the rear derailleur cable but have you checked its smooth running through the cable guide under the BB?  

When my gears were all over the place recently it took me an hour to suss that my inner cable had jumped out of its channel.  

Best of luck.

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Jimmy Ray Will [1029 posts] 1 month ago
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So, is the problem going up the gears (so lets say to bigger sized cogs) or coming back down towards the smaller cogs? 

And if you correct the indexing, which way will the indexing go off?

Is it effectively losing cable tension, so you are always winding on tension, or is it more a case of you having to compromise between having enough tension in the cable to go up the gear, without limiting the run back down the gears? 

Generally speaking, gears that are dicks are either because your hanger is mal-aligned, or there is fundamentally too much resistance somewhere in the cable routing. For instance, you may have your inners crossed in the frame, or the run isn't smooth somewhere... maybe a snagging liner. 

Giant bikes are, in my experience, a little more senstive than others as the chainstays are typically short. This shortens the gap between the cassette and chainrings, which puts more pressure on chainlines and set up. 

Let us know the answer to the above and we can provide more pointers maybe? 

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Jgdane [7 posts] 1 month ago
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Yes I am having to compromise between having enough tension in the cable to go up the gear, without limiting the run back down the gears. But as a consequence of allowing the gears to run up and down correctly, I loose the big easy gear.

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Wardy74 [54 posts] 1 month ago
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How or where are you adding /reducing cable tension? If one of the adjusters (most likely at the rear mech) has been unscrewed past its thread, it can move about giving uneven adjustments when moving up and down the block. I'd definitely check the hanger alignment too.

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Jgdane [7 posts] 1 month ago
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I am adjusting at the rear derailleur, and I havent turned to so it has screwed past its tread.

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Jgdane [7 posts] 1 month ago
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mike the bike wrote:

 

I know you've changed the rear derailleur cable but have you checked its smooth running through the cable guide under the BB?  

When my gears were all over the place recently it took me an hour to suss that my inner cable had jumped out of its channel.  

Best of luck.

Yes I am sure that the cable is in its channel.

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gbzpto [133 posts] 1 month ago
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Is the cassette on the freehub correctly ?. Any excessive play ?

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Jgdane [7 posts] 1 month ago
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gbzpto wrote:

Is the cassette on the freehub correctly ?. Any excessive play ?

Yes it is now, but I found that it wasnt secured properly and there was some marking on the free hub. I thought that at that point it might have solved the problem but it is still happening.

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cyclesteffer [420 posts] 1 month ago
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Could be a twisted derailleur cage as well. Not just the hanger. 

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Jgdane [7 posts] 1 month ago
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The bike has never been dropped or crashed. Is it likely that the hanger and cage could be twisted from normal use.

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kil0ran [1647 posts] 1 month ago
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Jgdane wrote:

The bike has never been dropped or crashed. Is it likely that the hanger and cage could be twisted from normal use.

Yep - road debris snagging in a jockey wheel could do it. Or knocking it when you lean the bike against a wall. Hangers are designed to bend to protect the derailleur and frame.
Have a professional mechanic take a look, these things can be hard and time-consuming to track down. Ideally a Giant dealer just in case there's a warranty claim required.

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Drinfinity [247 posts] 1 month ago
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Definitely recommend a rear mech alignment tool, it sounds just like mine when the hanger is out. I wouldn’t even fiddle with indexing any more till I check alignment. 

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Butty [351 posts] 1 month ago
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Jgdane wrote:

The bike has never been dropped or crashed. Is it likely that the hanger and cage could be twisted from normal use.

I had the same issues on you on a new bike. The LBS kept on adjusting the gearing when I returned it on several occasions but they never cured it. When I borrowed a rear hanger check/adjuster tool I found the hanger to be out of alignment.

When readjusted the problem went away.

I have to presume that the hanger was shipped bent, was damaged at the LBS and they never checked it before I picked it up.

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Pyro Tim [12 posts] 1 month ago
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Does sound like the hanger is bent. I bent mine with an inoccuous knock on a door frame as I carried it outside. Was very gentle, and thought nothing of it at the time, but it was the only thing that happened to it that could explain the bend

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Jimmy Ray Will [1029 posts] 1 month ago
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Are you confident in the cable routing job done? 

Are all the outers cut flush and fitted correctly in the plugs etc? 

Otherwise, get the hanger checked. Mine was bent from new, which made the gears tricky to get right... 

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Jgdane [7 posts] 1 month ago
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Jimmy Ray Will wrote:

Are you confident in the cable routing job done? 

Are all the outers cut flush and fitted correctly in the plugs etc? 

Otherwise, get the hanger checked. Mine was bent from new, which made the gears tricky to get right... 

Hi yes I think they are cut flush and fitted correctly, but when you say" routing correctly" what so you mean?

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Crookie [4 posts] 1 month ago
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Would this have a bearing on the performance of the front mech as well?

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Crookie [4 posts] 1 month ago
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Would this have a bearing on the performance of the front mech as well?

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Crookie [4 posts] 1 month ago
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Would this have a bearing on the performance of the front mech as well?

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kil0ran [1647 posts] 1 month ago
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The R8000 front mech can be a bit fiddly to get the right base tension set. My LBS mechanic explained the best way to approach it was to over-tension slightly to get it set and then remove tension with the on-mech adjuster.