LBS put a tie wrap on my rear derailleur to keep tension and told me I need a new one is this legit or are they trying to pull the wool over my eyes

[Traff]

 

[Drago]

Its really difficult to say without removing the rear mech and examining it.

They may be correct, or they may be trying to bend you over (although that seems rather unlikely given the relatively small profit in supplying and fitting a new one).

Can't tell for sure from afar, I'm afraid.

 

[Deleted member 26715]

Seems a bit strange that, not sure what the tie wrap achieves unless it's the adjuster that's broken & this allows the cable to be presented at the right angle. But as above without getting greasy mitts on it, it's difficult to say.

 

[Boopop]

I'm not really sure what this zip tie is accomplishing. Either it is so tight that it is clamping down on the inner cable and impairing the function of the mech, or it's not and it's not doing anything at all. Maybe it's to keep it tidier than to have the cable not tied down, but that's not really necessary either.

 

[Milkfloat]

To me it looks like it is making the cable path worse. You could always clip it off and see how your shifting changes. Worse case put one back on.

 

[yello]

I reckon the tie is for cable routing purposes (as @Phaeton suggests), to ensure the mech functions (or functions within a limited range) What might be wrong with the mech though, dunno. I'd need a hands on to see.

Have you any reason to doubt the LBS?

 

[Arrowfoot]

It cannot be the cable or barrel adjuster as these are easy and cheap fixes. Though strapping the cable to the mech adds to the mystery. The mech screw looks like it has been taken in and out a few times. If the thread is worn out and it becomes unsteady, it will no longer be smooth when changing gears as the spring action is compromised

 

[Ian H]

The idea is that the stiff outer cable acts as a helper spring to pull the derailleur back.

 

[Gixxerman]

The idea is that the stiff outer cable acts as a helper spring to pull the derailleur back.

I was just about to say something along those lines.
I had a similar issue on my folder. I fitted a new chain and the length was slightly too long due to where I broke it to get the quick-link in.
I'd normally adjust the deraileur tension with the B screw to adjust for chain length, but alas my folder doesn't have one.
So I used the shifter cable routing to tension the deraileur back a bit to get the chain tension right to stop the jockey wheels from juddering due to too close proximtery to the cassette.
It looks a bit Heath Robinson but it works. Better known to us engineers as "emperical engineering".

All this lends the question as to why the LBS could not use the B screw to adjust the tension. Maybe the B screw is at it's limit due to the tension spring being on its last legs?

 

[Big John]

I work for a bike charity and we've tried all sorts of non conventional fixes for things but this one takes the biscuit. Take a good look at how they've fitted the zip tie then snip it and take it off. That should give you a nice smooth curve on the cable and under normal circumstances your shifting, after proper indexing, should be good (assuming the hanger is straight). I'm always willing to learn new miracle cures and maybe this is one to use in an emergency but I honestly can't see what it achieves. However, if once it's removed it screws things up then fit a new one back on and sort yourself a replacement mech in the meantime.

 

[Ajax Bay]

@Traff
"LBS put a tie wrap on my rear derailleur to keep tension and told me I need a new one; is this legit?"

The idea is that the stiff outer cable acts as a helper spring to pull the derailleur back.

Except that pushing (and tying) the RD cable outer run down (below the QR nut) doesn't "pull the derailleur back" it pushes it forward, against the spring. Antagonistic little helper! Will also increase cable friction because of the small radius, which can only be a 'bad thing'.
I would trust your LBS. They have assessed your RD's 'B-axle' spring (1, below) - the one which twists the body, not the one in the paralleogram nor the one which provides cage tension - is ineffective (broken?) and to hold the RD in roughly the correct angle temporarily they've used this bodge to keep you going. B screw adjustment might do that too, but that only applies one 'limit'.
Think about this before following John's advice. The small angle of movement about this axis allows the guide jockey wheel to keep, across the cassette, at a minimum distance from the sprocket, which optimises shifting efficiency. Sacrificing this (by ziptie) will allow the rider to shift, but sub-optimally (but better than if the mech is just left 'hanging').
See https://si.shimano.com/pdfs/ev/EV-RD-5700-3042A.pdf
May be worth discussing with your LBS whether (1) Part No. Y5XH98010 B-Axle Assembly might be worth replacing rather than the whole mech. (check model 5700/5800 etc).
https://www.sjscycles.co.uk/gear-spares/shimano-105-rd5800-baxle-assembly-y5ye98010/
Page 20 of this may give you further ideas: https://si.shimano.com/pdfs/dm/DM-RD0003-09-ENG.pdf

 

[Traff]

I reckon the tie is for cable routing purposes (as @Phaeton suggests), to ensure the mech functions (or functions within a limited range) What might be wrong with the mech though, dunno. I'd need a hands on to see.

Have you any reason to doubt the LBS?

No reason to doubt the LBS except lad who put tie wrap on did out of ear shot of the gaffer also when I went out on the bike it won't shift into big ring at the front

 

[Traff]

What were the symptoms before they did this? Have they gone away?

Have they messed you around before? If so perhaps time to find a new LBS.

It was 2nd visit after new wheel set and new cables (said I'd have to come back for adjustments due to cable stretch) won't shift into big chain now

 

[Ajax Bay]

Not shifting up to the large ring is ZERO to do with the ziptie.
You sound as if you have 'trust issues' with the LBS. I'm sure they have other work to do.
Cables don't stretch, btw, beyond the amount you'd expect given Hooke's Law (ie elastic, consistent/predictable and (practically) negligible).

 

[Traff]

Not shifting up to the large ring is ZERO to do with the ziptie.
You sound as if you have 'trust issues' with the LBS. I'm sure they have other work to do.
Cables don't stretch, btw, beyond the amount you'd expect given Hooke's Law (ie elastic, consistent/predictable and (practically) negligible).

Yeah they probably do😂
First bike to go out with my pals and they're all twittering in my "never heard that before, does he know what's he's talking about" etc etc