mjbike

Hi,
yesterday I got a new full suss. It is a Trek Fuel EX 9.8 GX. Overall a great bike. Normally it would come with Eagle GX but the bike shop upgraded it to GX AXS for me.
It is brand new.
Overall the GX AXS shifting is super smooth, accurate and fast.
There is only one problem with the smallest sprockets. It feels as if the chain is jumping a bit on the 11th and 12th gear (the smallest sprockets).
I added a bit of chain lube and this mostly solved it for the 11th gear but the 12th gear (the one with only 10 teeth) is still a problem. After about every 100m it makes a noise and it feels as if the chain has trouble really grabbing the sprocket. For about half a second it seems to let go of the sprocket and then grabbing it again with a loud noise.
This does not only happen under extreme load but also when paddling lightly on a flat road.
It doesn't try to shift up to the 11th gear nor does it fall off to the right and off the cassette. Shifting up/down between the 11th and 12th gear is smooth. Only riding the 12 year is not that much fun.

I hope my description of the problem is clear.

Thanks for any help

SpedFast

Since all parts are new it would appear to need a little "fine" tuning with the barrel adjuster.

bboy314

May also need a small adjustment of the high limit screw or b screw. I would take it to the shop that sold it to fine tune it if it’s convenient.

mjbike

Thanks for the quick reply.
I will bring it back to the bike shop, hope they can fix it. They are quite competent, so I am optimistic.

Rolla

You do realize that the OP is talking about an electronic shifter, right?

SpedFast

No. I didn't realize that. My bad. Thanks

cxwrench

Another thing worth checking is the connecting link. There is always the chance it's upside down. Sounds more like a limit screw issue. Barrel adjuster...how do I know you either didn't read the whole thread and/or the title...or you just think you know more than you do?

mjbike

Went to the bike shop today. They spent about an hour adjusting the drive train and both they and I did some several test rides. Now it work really well.

Iride01

Don't hesitate to go back to the shop for any issues you have with the new bike. Especially if it's in the mid to high price tier. But even the lowest price tier bike should go back when things don't work right in the first 3 to 6 months. Maybe more.

It's great if you want to do your own DIY, but on brand new bikes, you should limit that until it gets to the point the shop starts charging you for every little thing, or you wear out your welcome there.

When shops do something free for me, I usually buy a pair of gloves, socks or something else I can put to good use.

mjbike

I fully agree. This is a new shop for me (my first bike from Trek) and I am very happy with them. I am sure to have a great relationship with them in the coming years.
And I did buy something. I needed another lock (Abus) and they had the one I wanted.