Major issues with gear cable on new TCR

scotthunter

I've had a new 2018 Giant TCR Advanced Pro 1 since last summer, with full mechanical Ultegra R8000 group set, and the bike has been constantly in and out of the bike shop due to gear issues.

The bike has only done 500 miles so there should be no component wear-out yet, and I would have thought the mileage already done is sufficient to rule out cable stretch related issues which you get with new bikes.

The bike has trouble shifting onto some of the middle sprockets, and shifting is generally very clunky. Sometimes it jumps a sprocket, other times you will change gear and nothing happens, it just rubs. The mechanic has replaced the U bend part of the cable sheath that goes around the back of the rear derailleur and indexed the derailleurs. Yesterday the mechanic did a quick adjustment to the rear derailleur barrel adjuster. This made it shift perfectly, at least for the ride home. But this morning during the morning commute, I noticed that it was still having trouble moving onto one of the middle sprockets.

There seems to be an issue with the rear derailleur cable loosing tension, which is causing the gears to require indexing about once a week. The mechanic suspects that there may be an issue with the internal routing of the cable through the frame, or perhaps the cable is too long? Something may be loose and causing the cable to slip down through the frame, thus loosing tension. They have already replaced the small section of derailleur cable housing that loops around the back of the derailleur to reduce friction, but the problem persists.

I think the next step is to go back to the bike shop where I brought it from and ask them to replace the gear cables all the way from the shifters to the derailleurs. Any thoughts?

Has anyone else got a TCR who has had similar gearing issues? It's incredibly frustrating especially this time of year when I want to get out and enjoy the bike.

Alejandrosdog

ahhhh there are loads of things to check including:

cable sticking. Shouldn't be an issue but if you change the outers as well as inners and are certain the routing is right you can eliminate this as an option.
cable damage in the shifter. often has inconsistent shifting experience as a symptom.
derailleur pivots have some stiction in the pivoting bit. especially if put away wet/dirty/salty at any point. Spray liberally with gt 85 and manually move back and forward
derailleur damaged. Have you banged it ever? had an off?
Hanger bent / slightly off. Check and adjust if necessary.
Cassette has some damage. (try with a different cassette if you have one if the problem stops thats your issue.) some wear and damage can be almost imperceptible on inspection, other times a little burr is visible on the cog that wont select. a mico file will sort it.

if all that fails.............. check frame alignment or hurl in frustration and anger against the garage wall, pick it up, look at it and smash it into the ground, then stamp on it twice and boot it out the door and up the drive. Leave it for 20 to 23 seconds then go and retrieve it hoping no one has seen. and if they have tell them to do one

keef66

No experience with a TCR or internal cables, sorry. The whole thing about losing the indexing in the middle of the cassette sounds odd though. If it was something as simple as losing cable tension it should affect indexing in all gears, no? The fact they can apparently fix it then it goes out of adjustment very quickly is also strange.

Is the outer cable loop at the derailleur a bit of plain old SP41, or the proper, more flexible OT-RS900 one recommended for R8000?

scotthunter

Alejandrosdog wrote:

ahhhh there are loads of things to check including:

cable sticking. Shouldn't be an issue but if you change the outers as well as inners and are certain the routing is right you can eliminate this as an option.
cable damage in the shifter. often has inconsistent shifting experience as a symptom.
derailleur pivots have some stiction in the pivoting bit. especially if put away wet/dirty/salty at any point. Spray liberally with gt 85 and manually move back and forward
derailleur damaged. Have you banged it ever? had an off?
Hanger bent / slightly off. Check and adjust if necessary.
Cassette has some damage. (try with a different cassette if you have one if the problem stops thats your issue.) some wear and damage can be almost imperceptible on inspection, other times a little burr is visible on the cog that wont select. a mico file will sort it.

if all that fails.............. check frame alignment or hurl in frustration and anger against the garage wall, pick it up, look at it and smash it into the ground, then stamp on it twice and boot it out the door and up the drive. Leave it for 20 to 23 seconds then go and retrieve it hoping no one has seen. and if they have tell them to do one

Thanks for the thorough very useful reply!

Good point about the lever. Yes, in fact I did have a crash last summer from skidding on a right hand bend, and the right shifter lever did take a knock where it hit the road. The insurance company refused to replace the right Ultegra shifter saying that it had only suffered cosmetic damage. The did replace the front and rear mech though, and the hanger is straight (I presume this was also replaced).

So I suspect it's either the cable routing or the lever. I might have a word with the insurance company about the lever and see if they can offer a cash settlement so I can get my LBS to replace it.

scotthunter

keef66 wrote:

Is the outer cable loop at the derailleur a bit of plain old SP41, or the proper, more flexible OT-RS900 one recommended for R8000?

Well the R8000 came with the bike from new so I would expect the cable loops to be designed for that specific groupset.

keef66

Have you peeled back the cover on the shifter to check the condition of the plastic body? I only ask because my son's bike had an innocent sideways fall in the house, but his RH shifter body was cracked through on both sides and he was aware of it feeling wobbly in his hand while riding.

We've supeglued and splinted it but I suspect he'll be needing a new shifter eventually.

keef66

scotthunter wrote:

keef66 wrote:

Is the outer cable loop at the derailleur a bit of plain old SP41, or the proper, more flexible OT-RS900 one recommended for R8000?

Well the R8000 came with the bike from new so I would expect the cable loops to be designed for that specific groupset.

From new, yes, but you've now said

"The mechanic has replaced the U bend part of the cable sheath that goes around the back of the rear derailleur"

and

"The insurance company..... did replace the front and rear mech though


Was it all 100% OK before your spill?

scotthunter

keef66 wrote:

scotthunter wrote:

keef66 wrote:

Is the outer cable loop at the derailleur a bit of plain old SP41, or the proper, more flexible OT-RS900 one recommended for R8000?

Well the R8000 came with the bike from new so I would expect the cable loops to be designed for that specific groupset.

From new, yes, but you've now said

"The mechanic has replaced the U bend part of the cable sheath that goes around the back of the rear derailleur"

Not sure if the replacement sheath made a difference tbh. The barrel adjustment on the end of the cable made the difference. So I suspect something is loose further up the cable through internal routing or the shifter.

and

"The insurance company..... did replace the front and rear mech though


Was it all 100% OK before your spill?

laurentian

scotthunter wrote:

Good point about the lever. Yes, in fact I did have a crash last summer from skidding on a right hand bend, and the right shifter lever did take a knock where it hit the road. The insurance company refused to replace the right Ultegra shifter saying that it had only suffered cosmetic damage. The did replace the front and rear mech though, and the hanger is straight (I presume this was also replaced).

So I suspect it's either the cable routing or the lever. I might have a word with the insurance company about the lever and see if they can offer a cash settlement so I can get my LBS to replace it.

As above, was it OK before your spill? - the right shifter may or may not be damaged and this is what controls your rear mech shifts, the rear mech was replaced, you presumably fell on the right side where cassette, shifter, hanger and mech are, the cables were obvioulsy played around with when changing the rear mech . . . I'd be looking at the inside of the shifter first as you only seem to be getting problems in the middle of your cassette and it was the only damaged part not replaced when you had your off . . .