Kontact

It sounds like you have a defective derailleur, as Shimano derailleurs of this type adjust easily and obviously when you turn the screw. Contact the seller or a Shimano dealer.

Iride01 

On my son's Trek Emonda with Tiagra, it shifts fast and very well to all the gears. 11-32 with a 52/36 up front. And the jockey wheel was very close to the cogs. I am sort of wondering if that hanger is putting the RD too far down. But it's not much if it is.

All the shops in my area would have the mechanic come out and look at any problems I took to them. Their advice is free. Maybe your shops are the same. But if it is a bad RD, their word will go a long way with whomever you bought this from. And possibly they could do an exchange since they are probably a Shimano authorized dealer or service provider.

Redbullet

The hanger is around 25mm, so, within requested limits.I bet mine would also work nice with 11-32. Finally, B screw does adjust the pulley up, but not more than total 3-4 mm (therefore, I did not observe at the beginning). But 3-4 mm is not enough to cover the interval of large cogs (25 to 34 teeth) for which Tiagra was designed. Thus, it was optimized for upper range (30-34 teeth) on a standard hanger. Once you go toward cassettes with the large cog of 25, B screw can not compensate and shifting starts to deteriorate. I think this is rather a poor B adjustment design than a malfunction.
SRAM solution is way, way better: I regularly switch between wheels with 11-26 and 11-32 cassettes and all I must do is to rotate B screw +/- 8 complete rounds to adjust upper pulley position, then shifting is crisp with selected wheel. And I still have “B adjustment” unused.
With Tiagra I must re-optimize around my big cog of 26. But since “B adjustment” is not enough, I must find another hanger (around 1.5 cm height instead of recommended 2.4-2.6), so the upper pulley will be closer to the cassette. I do not even know whether such hanger exists…

Kontact

Sounds like you finally came around to believing what I have been telling you.

You are not going to find a different hanger. Trek doesn't work like that. Neither do aftermarket hanger makers.

You could try a different derailleur. The 11 speed Shimano ones will work. The 105 R7000 works like a SRAM B screw, and has a medium cage version.
You could use a larger cassette.
You could modify your hanger by filing the B stop so the derailleur rotates further forward and up (counter clockwise). If it doesn't work, new hangers are available.

oldbobcat

I can see that you're getting plenty of chain wrap, but any way you cut it, the jockey pulley is way too far forward of the axle to get close enough to the cogs for crisp shifting. I think this might be due to the shape of the hanger. Normally, on a triple I'd discount using the small ring with the fast end of the cassette (the smallest 2 or 3 cogs), but the positioning is still too far forward on the largest cog. That would suggest that the chain is too long. But your big-big photo shows the chain pretty much at its limit. Shimano specs the unit for a 20-tooth spread on triple chainrings, but we can see this pushes it close to the limit.

I've worked with 4700 plenty of times and never had issues with it. In fact, that's what's on the Trek Emonda 3 that I bought my daughter a few years ago. But that was with double chainrings.

As a penultimate to the last resort measure I'd take the derailleur to a shop and ask if there is anything wrong with it. As a last resort, I'd try removing one more link-pair from your chain. I believe it will still be long enough. You can test before cutting by folding over a pair of links on the slack side. I used to be doubtful, having cut my chains slightly loose for years, until I tried shortening one for some reason that I can't remember. It was on my own SRAM Force 10-speed. And presto, the rear shifts were noticeably crisper because the jockey pulley was was in better line with the cogs.

Kontact

There is nothing wrong with the bike or the parts - they just don't work well together because the cassette is small.

Removing links is going to make the problem worse, not better, because the upper pulley will rotate further down.


Personally, I would use a short cage derailleur and leave the chain long enough that the small/small is slack. That's how we ran short cage Deore XT derailleurs with triples on MTBs in the early '90s. It won't break anything and the small/small with a granny is easy to avoid.

Redbullet

Larger cassette is out of scope, and I would like to avoid further investment in 105.
I already filed a large portion of the hanger (red line in the picture). It improved shifting up to a certain level of chain stretch. I cannot go further, otherwise I will make the hanger fully circular.

Maybe I can find a 15 mm height hanger? It is not Trek, it is an older, inexpensive aluminum bike for trainer. Hanger picture is attached (it can be seen, although it has the same color as the frame).

Kontact

As I said, hangers don't come in variable lengths. You are lucky if you can find the original hanger on most bikes. The hanger length and angle were spec'd by the frame manufacturer and there is no market for shorter ones. Most people are looking for ways to make them longer.


I looked at the specs, and the gearing you have for both crank and cassette meets Tiagra GS minimums, so you might consider going to a Shimano dealer and starting a warranty inquiry. But the answer may be "don't cross chain" or other suggestions as to when the derailleur can be expected to function correctly and when it will not.

And, of course, getting a mechanic to look at it might also be valuable in case you have missed something. Usually getting 10 speed to shift isn't difficult at all, even with a big pulley gap. The HG cassettes require very little to hook the chain up to the next cog.

Redbullet

Although it is advertised as working with cassettes with largest cog between 25 and 34 teeth (on triple), it looks that Tiagra GS design can only shift crisp with cassettes with largest cog around 30-34. With smaller cassettes, shifting progressively deteriorates because B adjustment can not compensate the increased distance between upper pulley and cassette.
I use SRAM Force 22 for years and I have almost 100% crisp shifts with 2 cassettes: 11-26 and 11-32, because B adjustment is very effective. I obtained similar 100% crisp performance with low end Microshift 8 speed, 12-25. But Tiagra 4700 hesitates around 30% of shifts with 12-26 cassette. I would say it is simply a design flaw where B screw cannot compensate for smaller cassette, although the manual says it should work (in fact it works by shifting all the range, but with very low / hesitating performance).

Kontact

BTW, the section you file away should have a flat that points at the center of B pivot, like the original did. What you illustrated in red has the flat where the B screw contacts parallel to the old flat, but it should be radial.

Redbullet

Bad news, then. Warranty or further investigation won't do much because the derailleur or setup have no mechanical issues and they work: they work as they were manufactured to work, but not as Tiagra GS was advertised to work. It works within all claimed range, but having poor (hesitating) performance with smaller cassettes. That looks as a design flaw or not honest advertisement about performances of the product, but no mechanic or dealer can assist with that.

Now, I wonder... If I call it a loss, can I trust Shimano that at least 105 derailleur will work in my setup if they say so?

Redbullet

I filled the whole material on the left of the red line. B screw contacts now the hanger area in the same way as original, but (roughly) 5 mm farther. If I screw it in 5mm now, I put the derailleur in the original situation with non filed hanger and B totally unscrewed. It has a big effect in pulley position and shifting, but only up to a level of chain tension.

Redbullet

After experiencing Tiagra GS, I also can say that maybe SS works better. However, Shimano manual lists SS as 33T capacity (vs my 34T) and 16T max front difference (vs. my 20T). Furthermore, triple is not mentioned for SS, but it is for GS. Overall, the manual says that GS meets all my requirements, while SS misses 3 requirements. Nobody would ever choose SS over GS for my setup, according to the manual. The conclusion is that for smaller cassettes, triple and large capacity, any Tiagra 4700 does not work, although Shimano claims it does. It does, in fact, but with low (hesitating) performance.

Kontact

Sure, but the reality is that you are on the extreme end of GS function and the SS would work better. There was no such thing as a triple rear derailleur in the past, just derailleurs with different capacities. The worst thing that would happen if you used the SS is that the chain would go slightly slack in the granny/12T crossover. And who cares about that?

oldbobcat

On big-big shortening the chain would pivot the jockey pulley downward slightly, but at this point the tension on the chain should render the change in distance moot. My purpose is to pivot the jockey wheel backward so it can be closer to the wheel axis on the middle and small rings, and by the looks of the current position, there should be enough slack to make this possible.

Shimano says the maximum range for the SS unit is 33t. This one is 34, so it might work if we don't mind a little looseness at small-small, which should never be used anyway. On the other hand, the minimum large-cog limit for GS is 25T, so this should work, too.

In the olden days before slant-parallelogram derailleurs with B screws were made, I used Sedis chains because they were slightly stiffer than the ones by Regina. Years later I found that there was less overshifting if I shortened the chain closer to the minimum that would go easily into big-big--less slack plus a shorter distance when using the small ring.

Interestingly, this chain-sizing approach runs counter to Shimano's instructions for triples of the generations before 11-speed. Of course, back then medium-cage rear derailleurs were made specifically for triples. I believe Shimano really didn't think through triple-ring performance when designing 4700.

Does Shimano still make chain push-pins for 10-speed? If so, I wouldn't hesitate to try shortening the chain after first determining that big-big would still be accessible.

Kontact

In this case, shortening the chain will pivot the upper pulley more down than back, and the net result would be more distance from the cogs.

Redbullet

Yes, I assume you are right. Shimano manual should reflect that also, but it does the opposite - thus, it is misleading. My first serious encounter with Shimano was 50% fail. I had difficulties with SRAM systems as well, but all were fixable and fixed.
The funny thing is that with Tiagra GS and SRAM cassette and chain, it is the first time when all my cross chain positions work smooth as they were middle combinations (using "trim" function of left shifter). It is a pity that shifting is partially spoiled. But I start to get tired and I think I should simply live with the poorest shifting of my systems. After all, it is about a cheap (trainer) bike that finally meets all the basic requirements. Hope that hesitating shifting will not prematurely wear the components.
Thanks for advises!

Redbullet

P.S.: I'm still thinking about that shorter hanger...

Kontact

You need a triple for a trainer bike?

I'm out. This is ridiculous.

Redbullet

It was the cheapest reliable road bike configuration I could get years ago for trainer (around 320 EUR, heavy but still usable as replacement for road rides). Upgrading from 8 to 10 cogs was 40% of its price. Upgrading to double might set it a little more comfortable, but it does not worth the expense.

Kontact

The cheapest double upgrade is to simply not use the granny.

Redbullet

What "granny" means? Small chain ring? Most cogs shift ok with small ring for my (filed) setup. The problems appear with higher chain tension combinations - that is where big gap between pulley and cassette appear.

Kontact

Road triple cranks are basically road doubles with a 30t chainring added on the inside. If you unbolt that inner chainring and use a short cage rear derailleur, the set up for chain length and everything else favors the two remaining chainrings - so the large ring isn't so extreme in its chain pull.