Recently put the tt bike on the turbo and rear shifting is out. Basically it works fine shifting down the entire cassette, but going up it won’t shift into top 3 gears. I need to go up 2 then down 1 to land in certain cogs

It’s etap so sticky cables aren’t an issue. When I’ve tried reindexing basically the issue just reverses itself and I can’t shift down on a few cogs.

I’m assuming it’s the hanger that is bent (don’t have a tool to check) as the mech cage isn’t hanging at 90 degrees to the ground. Should it? The thing that makes me question this diagnosis however is that bike has only done 20 miles outdoors, and never dropped. I also seem to remember the shifting working fine when I used it outside

The other thing im thinking is are the sliding dropouts causing the issue? As they are adjustable is there a chance that they are misaligned?

Any ideas as I usually find rear mech relatively easy to set up?

as the mech cage isn’t hanging at 90 degrees to the ground. Should it?

How have you evaluated that? By eye is seemingly not enough given the prevalence of tools to do it for you, but maybe more for dinner plate MTB cassettes.

Yes it should. Pic?

Is the mech hanger bolt tight and is the cassette on tight?

Bent mech hanger should be the first port of call with any mis-shifting issues.

Agreed. Get an alignment tool, and those impossible-to-index-out shifting problems are gone. I wasted so much time and frustration  before I got one.

Well I haven’t yet got my alignment tool yet, however to add to the mystery, shifting is fine at back when I’m in the small ring up front. The issue only occurs when I’m in the large ring.

Chain length looks fine. It’s an oval ring up front but I’d have thought that would only affect shifting up front, not at back.

Does it shift ok on the road but not on the trainer? That’s a crucial thing in diagnosing this.

A) it’s probably the hanger

B) because Sram 🤷‍♂️

Poopscoop..

I’ve not used it on road in 6 months but it did shift fine then yes. The issue only appears to have materialised since putting on trainer.

I’ll need to dig out a rear wheel for it and I’ll ride it up and down the road to confirm

As you tighten the qr/ axle I suspect the mech hanger angle is moving inwards. My qr axle bike does this on my Core. So rides fine irl but hanger angle is out once on the turbo.

So effectively it throws the mech hanger angle out.

If you are only using the bike on the turbo for an extended time, you might be able to align the hanger whilst fitted to the turbo. That’s what I’ve done as the bike is only used on the turbo.

A thread on here a few days ago was similar and there was discussion of using a shim on the turbo to space it out. That didn’t work for me though.

Poopscoop..I’m confused. Why would tightening the qr on the turbo be any different than when tightening with normal wheel?

It very well may be thats the issue, especially if it works when outside but I can’t understand the mechanism for why this would occur.

Ta

Poopscoop..I’m confused. Why would tightening the qr on the turbo be any different than when tightening with normal wheel?

It very well may be thats the issue, especially if it works when outside but I can’t understand the mechanism for why this would occur.

The thread on here related to that contained the crucial detail that the freehub on the turbo (an Elite IIRC) was slightly too short and this was throwing everything out.

On my setup the axle length on the turbo is very slightly different to the wheel so when tightened the hanger bends in slightly.

I’ll try and find the other thread as the op has a similar issue. Brb.😁

Here we go. Bloody hell, I still haven’t figured out the search function on here.

Elite Smart Trainers 1 mm off freehub to flange? spacing = poor indexing

Interesting!

I’ll take bike off turbo first and see if shifting works. If it does it must be a turbo issue and I’ll see if a shim will work

Mine is a taco neo. I’ve never used the tt bike on it before now, but my normal turbo bike didn’t have an issue, but then again it used the 135mm spacer, and the tt bike used a 130

It’s odd for sure. Some (most) frames seem fine, not mine unfortunately. It did the same on the Neo 2T I had for a while so it’s definitely a “feature” of the frame. Just an oldish Arkose btw.

Took me ages to figure out but I can physically see the hanger/ mech rotate in a few degrees when I torque up the qr when I look from the back of the bike/turbo.

Fortunately with a stick and bluetack I could use my hanger tool on the Core treating the pully wheel as a normal wheel. Not an issue once done as it only used on the turbo now.