Should the jockey wheels be in line?

[steve_sordy]

After breaking my Shimano SLX mech in half I got its replacement out of the box. The first thing I noticed was that when I squinted down the length of the lower mech arm, the jockey wheels were not in line with each other. The upper was where I expected it to be, parallel to the body, but the lower jockey was at a slight angle to the upper jockey, as though the mech arm was twisted. There wasn't much in it, maybe I'm just over picky! The box it came in was undamaged and I started to wonder if Shimano had a cunning plan to make the shifting even better. Previously, when I saw out of line jockeys, I assumed that I had done it and fixed them! My assumption to date has been that all jockey wheels should be in line and parallel to each other. Why shouldn't they be?

Anyway, I was in the LBS this morning and I asked the guy in there. He looked a bit puzzled as though it was not something he had ever considered before, but then produced a brand new in box XT mech. He removed it from the packaging and sure enough the jockey wheels were slightly out of line in the same way as mine had been.

An XT mech from my LBS and an SLX mech from High0nBikes, both with the same alignment. Is that evidence that the alignment is deliberate, or a manufacturing fault (that just happens to be on the XT as well as the SLX)?

If there are two out there from different sources, then there are probably many thousands, or is it all of them?

Any comment?

 

[Pyr0]

It's normal for shimano 12 speed to have a slight twist to the cage

 

[Mikerb]

I suspect it is done to try to compensate for the fairly extreme chainline on a 12 speed .......to better match the chainline return from the chainwheel in the highest gear. Probably adds a bit of noise when in the middle of the cassette though. Sram use a narrow/wide tooth profile on the lower jockey wheel probably to help with the same issue

 

[Mikerb]

I suspect it is done to try to compensate for the fairly extreme chainline on a 12 speed .......to better match the chainline return from the chainwheel in the highest gear. Probably adds a bit of noise when in the middle of the cassette though. Sram use a narrow/wide tooth profile on the lower jockey wheel probably to help with the same issue

Personally I never use the highest or lowest cog on a 12 speed.

 

[Stihldog]

I personally avoid the 6th cog on a 12speed cassette. It’s almost impossible but if you hold your breath and close your eyes while you pass thru the “forbidden zone” it can be done.
Besides that, what happens if your jockey wheel cage is carbon? Can it be aligned/straightened?

 

[Dax]

You probably know this already, but if you snapped your mech, you should also replace your mech hanger, it probably got bent in the process

 

[Zimmerframe]

You probably know this already, but if you snapped your mech, you should also replace your mech hanger, it probably got bent in the process

Most manufacturer's now suggest you buy a new bike if you damage your mech.

Or if it needs a chain. Or tyres.. or if it's 12 months old and no longer has the latest standard like Ultimate Final Hyper Super Boost.

 

[Hobo Mikey]

Most manufacturer's now suggest you buy a new bike if you damage your mech.

Or if it needs a chain. Or tyres.. or if it's 12 months old and no longer has the latest standard like Ultimate Final Hyper Super Boost.

Or if it’s dirty, what ever comes first.

 

[steve_sordy]

You probably know this already, but if you snapped your mech, you should also replace your mech hanger, it probably got bent in the process

Yep, good call. That was the first thing I did when I removed the stump of the old mech. The hanger was absolutely spot on, well within the 4mm that Parktool's instructions say that no further adjustment is required.

Incidentally, I learned something last week about mech hangers. I had always assumed (maybe I was told a long time ago) that mech hangers were there to protect the expensive mech from breakage when it got a bang. I had been whinging about two Shimano mechs breaking in half when I was told that the mech hanger is there to protect the frame and NOT the mech. Fancy that! Maybe that is why the latest Shimano mechs snap well before any impact on the hanger; the hangers are too strong.

 

[steve_sordy]

It's normal for shimano 12 speed to have a slight twist to the cage

Excellent choice of a video to explain what I observed. That would account for why all the previous mechs I have used had parallel and in-line jockey wheels and why on 12-speed they are not.