In the stand vs under load
 

General question: anybody have any tips on how to diagnose and address shifting/derailleur problems that happen only under load, and can't be observed simply by turning the cranks when the bike is in the stand?

Specific symptoms: Cogs 4-10 (big/slow) are shifting smooth, riding smooth under load, no noise. Cogs 1-3 are shifting fine, ride ok under light pressure but when I push, there is either slipping teeth or spurious failed shifts (I can't tell which while riding, and can't see it in the stand) all the damn time.

Relevant details: Krampus 1x10, 11-50 11-42. Deore XT. Problem appeared suddenly after chain broke and was replaced by a new chain. The old chain was VERY worn (stretched).

Obvious solution: just replace the cassette you dumb cheap bastard!

Secondary general question: why is it that I am experiencing problems only in the small cogs? I am old and fat and lazy and slow, so I feel like all my hard work goes onto the big cogs, and those are the ones that should really be worn out, not the small cogs that I use left often and rarely push hard on. Is there something about how load is spread onto fewer teeth that makes smaller cogs wear faster?

Yeah fewer teeth so more wear per tooth per revolution.

also fewer teeth to hold the chain so for equal wear on every tooth, skips more easily.

You already have your answer. Seriously though, very worn chain that eventually broke indicates your cassette is also very worn, and your symptoms confirm this.

I misremembered, I said 11-50 in the original post, but it's just 11-42.

I wouldn't mind stepping up (down?) to a 11-46. Already to reach 42, I've got a wolf tooth RD extender, will the extra radius from 42T-->46T be a problem?

https://www.ebay.com/itm/353468870971

Actually, 46T means 4 extra inches of chain wrap, right? That new chain I got, I just cut 2 links/inches out of it.

The 4 extra teeth/inches of big cog, how does that cash out in terms of degrees of RD flex? Maybe I should just stick to 42

Cog teeth, like chain pivots, are 1/2" apart so 4 teeth difference is 2" of chain length.

What flex are you talking about? Andy

and since the extra links are on both the top and bottom chain runs... ONE extra inch of wrap.

​​​​​​​oh ok, thx for the correction.

The flex I'm talking about is the lower/long arm of the RD that gets stretched forward when the chain is on bigger cogs, or the spring retracts backwards to take up slack on smaller cogs.

Already in the big cog the RD arm is pulled forward of vertical. Will another 4 teeth and the same chain pull it too far forward? What even is "too far"? As long as the chain doesn't actually bind is it ok?

hmmm. so +4 teeth sounds like not really a big deal and 11-46 should work?

that is up to the derailleur, your abilities, and your judgement.

the radius increase/decrease becomes less, per tooth change, as the gears' diameters get bigger.
the teeth are just fancy traction devices, that lock nicely into the chain, and are easy to count.
the "gearing" is really about the radial leverage ratio.

Checked the derailleur hangar alignment?
'Specially with the Road Link adapter.

https://cimg2.ibsrv.net/gimg/bikefor...c94444dc1.jpeg

Here's my 11-42, including Wolf Tooth extender.

I guess there's room for the RD to stretch a little more, but is there enough clearance to the upper jockey wheel?

Did you check the B-gap screw (although it looks already at the max?) to add some clearance?

Also it seems that with this extender/hanger combination you could gain some margin by rotating it slightly downwards? of course you'd need to have everything perfectly aligned, if that's even doable...

I haven't checked the b-screw, but IIRC, both the wolf tooth extender and the RD attached to the bottom of it, are not free to rotate, they just have to be where they be

Sounds like I should stick to the status quo and just order another 11-42

what derailleur is that?
and why is the hanger extension positioned so far to the rear of the bike?
(mystery solved: it's a Wolf Tooth GOATLINK... like a b-screw from hell, with a bit of drop too. i'm too used to seeing the WT RoadLinks, and their numerous clones :rolleyes:...)

clean that lower pulley too, ok? :D

correct, my memory of when I put that goatlink on there in like 2018, was that there was no adjustment to worry about, it only fit on with one specific orientation.

The RD is Deore XT, you can see the grey plastic XT design just to the left of "SHIMANO" (and a clutch above).

Agreed, I need to clean that pulley! Believe it or not, this is after my wife kindly volunteered to wash my bike when she washed hers. And no shade to her, I am just super lazy about cleaning my bike (or really doing any maintenance -- I'm dealing with a lot of deferred maintenance on 2 bikes rn)

It looks like both the Goatlink & the standard B-link is being used. Normally, the Goatlink replaces the B-link. Not sure if WT recommends this set-up, probably since it introduces another pivot (& its inherit 'play').

Don't know if the extended rearward position and 'play' would effect shifting.

Depending on the RD model, it may handle a 42T without the B-link.

i was more asking the model Number... it can make a difference in how big a low gear it will work with.
the model number is on the inner side of the parallelograms
not a biggy, just curious.

I also guess the hanger alignment, or the adapter. It's close to correct line in middle gears but getting worse further out. This sounds exactly like the problem I fixed on my kid's SX Eagle bike. You might be one shift off, too. I've had good luck sighting it and not buying a gauge.

My last ghost-shifting problem turned out to be cracks in the chain. But it didn't feel like your description.

It does look like you are doubled up. Here's a shot from the WT site

https://cimg6.ibsrv.net/gimg/bikefor...7d8eeb7657.png

Hmmm, is doubled up bad, or exactly what I need for this derailleur to handle 42 teeth?

My problem is not good in the middle, bad 'further out', I'm rock solid on 6 big cogs, terrible on 3 tiny cogs and iffy on #4

Well, 'doubling up' does change it from how WT designed the GL and the guide pulley will be in a different position. Did you check if your RD is one of the proper models? The GL is sized to replace the B-link, so it is the correct thickness & has the 'tab' in a different position. (see the attached, the GL is similar to the DM, which also replaces the B-link).
https://cimg8.ibsrv.net/gimg/bikefor...ce64c7dac9.jpg
The B-link normally attaches to a standard RD hanger (left).


If you have one of the proper model RDs, it should fit the GL w/out the B-link and work with 42T.

If your RD is not one of the supported model, you can only mount it as you have, with the inherent possible issues.

I used a wet toothbrush to clean dirt off the back of the cage, and the stamp says "RD-M786 VIA".

Looking closer at the double-up, it's surprising to me that shifting even works given the double-up means pushing the RD double-thickness away from the frame.

But I have already ordered a replacement 11-42, and if that gives me 10 good speeds of shifting like I have 6 right now, I'll be happy.

And with the help of Google, I can report that it is the 90mm jockey-wheel distance that indicates long-cage SGS, not 75mm short-cage GS

That is the classic symptom of running a new chain on worn sprockets.

Yes, smaller tooth count sprockets concentrate the wear onto fewer teeth, so they wear faster than the larger tooth count sprockets.