WPH

I would carefully check the specs for the latest Tiagra RD.

I bought one but could not make it work on my Shimano 10 speed road cassettes and gear levers.

This particular model (which looks good and seems to be very well made) moves further than all other Shimano 9 and 10 speed road RDs in response to a standard 10 speed lever cable actuation.

I was able to get good shifting on the two or three smallest cogs, but by mid-cassette it was not meshing at all, and was only worse from there on.

I did find info on the internets which explained all this.

Best of luck


Will

Msteven 

Look around the forum for di2 XTR 3x11 + saint hydraulic brakes. I posted a message about this setup on our CoMo Mocha. not flawless, FD takes some fussy set up. I run 52/39/30 + 11-42, You must get a wolftooth goatlink 11 and a longer M4 B screw (local hardware store is OK)

generally this works great. you can also save some $$ and run the XT RD. but you have to buy the $$$ XTR FD.

I scrapped the ETAP system that came with the bike. saved the parts for a single project over the winter.

Alcanbrad

the Tiagra is a one off situation. The rear derailleur is actually an 11 speed derailleur and the brifter is a one off that moves the derailleur at 10 speed spacing. You can pair any Shimano 11 speed road derailleur to the brifter as a 10 speed setup, but not a 10 speed derailleur.

WPH

Yes, that seems about right. So the current Tiagra cassette must have standard 10 speed spacing?

Alcanbrad

Yes it does.

Alcanbrad

I was finally able to coax the stoker to get back on this bike so I could capture video of what was going on. I had my GoPro mounted geek style to capture the issue:




We went to attempt a short 10% grade climb that we have experienced the issue with the Etap drive train and rode up it. True as clockwork, the issue occured and I caught it on video. I was very surprised to see that the issue was not ghost shifting but was in fact the chain slipping on the front chaingring (I can hear several of you saying "told ya!") In the following video I show about 20 or so seconds prior to the problem happening than I tacked on 2 copies of just the issue happening in slow motion. Be sure and click the setting gear and select 1080 resolution for good image quality:

(youtube.com/watch?v=gNg0ibm1iR0)

As you can see, there is no indication of anything going bad in the rear, and you can see the crank advancing faster at the moment the issue happens. I was sure it was not chain slip as the chainring and chain are brand new and the issue never occurred when in the largest cassette cog. I could always get it to occur in the second cog, and sometimes it would occur in smaller cogs, but never in the largest.

So why? We never had an issue with the triple when in a 30T small (10 speed), so why now?

The chainring here is a 74BCD 34T custom ring that House of tandems had commissioned for their Etap offering:





I have not been able to find a 34T in 74BCD, however, Vuelta has a large offering of chainrings so I assume they have some knowledge in how to manufacture them.

In addition to hearing the rotor rub as the climbing load increases, you can see some evidence of the frame flexing by looking at the wheel right where the lower jockey wheel covers it, and the timing belt ring looks to be either out of round or non-concentric, however. I checked this and it is both round and concentric, what I believe we are seeing is the frame flexing.

So why is the chain skipping now and didn't before with 30T and a 10 speed chain.

I could go to a real Sugino 32T 74BCD ring (if it works with the FD) or I could change to a real compact crank (110BCD). I have experienced worn chainrings several times in my cycling career and always fixed it with a new chainring, but I can't here.
Thoughts, suggestions, ideas?

reburns

Yeah, I hate it when that happens. Chain tension was probably just below the problem threshold in the largest cog. One upshift was enough to put you over the limit I would guess.

If it was me, I’d try the Sugino 32t and see if I could make it work with the FD. Your 34T is brand new, but doesn’t that tooth just about to engage the chain have a bit of that shark fin shape? As a special order, I wonder if there’s a chance it was made a bit out of spec in some way...?

tandemdr

This is an interesting thread in that it parallels mostly vast experience on 2 seat tandems, triplets, quads, and quints, having really high torque involved. The early on described symptoms, now mostly confirmed in the video, directly match the chain riding up and over the teeth of the small front chainring when under extreme load, where it blows off with a bang, resultant of a worn chainring, in all cases I have seen. Did this happen when the chainring was brand new? If so, the potential solutions to try, while maintaining the same gearing, would be a different brand new chainring with a brand new chain. Different brand 74mm 34T and 36T rings are available. https://www.precisiontandems.com/cat...htm#chainrings

New2Two

PrecisionTandems(dot)com has 74bcd chainrings from 24 teeth up to 36 teeth.

Alcanbrad

the problem showed at the very first ride. We have put about 500 miles over 20 rides on the bike since the conversion and it has been a constant issue. I am confident the chain and chain ring are not worn, but now I lack confidence in the chain and chainring.

i have a new 32 tooth Sugino ring and a new KMC X11 chain in hand and will try that.

in terms of excess torque or torque margin, would there be greater torque on a 34 front, with 35 rear, than a 30 front with 32 rear all other things being equal (team weight, speed, climbing speed)? Are there equations to calculate effective torque? I did a simple spread sheet a while ago and if I finoogled it right, there would be greater torque on the smaller of the rings And greater tension in the chain, all else equal.

tandemdr

I look forward to the results of the new chain and smaller ring test ride and will be surprised if it does not change for the better despite the greater torque from the ring and cog being smaller. Should that experience be positive, then you can run the 30 / 34 combo or try a different 34 / 35 setup by another manufacturer hopefully keeping your lower 34 / 40 or lower gearing which I think is your end goal if all is understood correctly.

Msteven 

a couple of things to consider:
1. some chains are directional, make sure the chain is installed in the correct direction if that applies
2. hollow pin chains wear much faster than solid pin chains on a tandem AND might not be able to handle the torque without twisting. Even the slightest twisting of the chain when under load (plus chain angle, plus frame deflection, plus chainring deflection) might be enough for the chain to climb the teeth on your chainring.
3. make sure the chainring bolts that are reversed do not interfere with the inner chainring/chain interface. under load, there might be subtle changes in the distance between the chain and the 52t chainring bolts.

I've had the same chainring/crankset/cogs/eTap set up from HoT. We had terrible shifting with hollow pin chains that aged prematurely. This also wore out cogs and chainrings rapidly. We did not see chain ride up the inside chainring and come off though. all symptoms of probably similar system wear.

Alcanbrad

Did you find and can you recommend a good compromise for chainrings and chain?

WheelsNT

Since you are in-phase, which leg is on the power stroke when it occurs? Is it always the same leg, or does it change?

Alcanbrad

Not 100% sure but the few times I made a mental note at the time, and in the video, it’s been during the left side power stroke.

reburns

Msteven wrote: 3. make sure the chainring bolts that are reversed do not interfere with the inner chainring/chain interface. under load, there might be subtle changes in the distance between the chain and the 52t chainring bolts.

I hadn’t noticed before that reversed chainring bolts lie right next to the teeth of the smaller chain ring. If there is interference between the chain and those bolts, I could believe that it could cause engagement problems between the chain and the chain ring which might be less severe when the chain is bent toward the largest rear cog.

Alcanbrad

I had checked this early on in my odyssey and it is not a problem for the 34T chainring. The teeth of the 34T ring are centered on the thickness of the ring which keeps the chain well clear of the chainring bolts. I tried installing the 32T chainring today and for this chainring, this is a problem. The chaining ring bolts fall directing in line with rings teeth and the teeth for the 32T ring are not on the centerline of the thickness of the ring, they are "side justified" so the teeth are closer to the large ring (and bolts). Reversing (flippling over) the ring did not work as the counter-bores for chainring bolts exhibited a tight interference fit with the mounting bosses on the spider. I was able to overcome the issue via adding a thin washer between the ring and crank arm boss for each chainring bolt, however, the FD could not handle the 32 to 50 difference in spacing.

I called Precision Tandems today and spoke with Mark (who has been part of this thread) and ordered a 36T ring. I will try this new ring with a new chain. I am hopeful and if it works, I will have my work cut out for me convincing my stoker that this will not be a problem

reburns

Best of luck. That has to be a maddening problem to have, especially on such a nicely outfitted tandem.

Msteven 

We went with Sram solid pin 11 speed chain for a few months. I also replaced the inner chainring with a 30 and the outer with a 48. We replaced the cogs with sunrace, but the shifting between the 6-7-8 position is not great. I'll buy shimano in the future.
ultimately we went away from eTap and installed XTR 3x11, ST-R785 and Saint hydro 4-piston brake calipers. This system works much better than the 2x11 system.

oldacura

So your final conclusion is that this was caused by the chain climbing off the top of the small chainring (at 12 o'clock)? Wouldn't all of the chain links (from 12 o'clock to 6 o'clock) have to disengage the chainring for the chain to slip? Several have suggested an solid pin chain and/or different chainring? The small chainring appears to be pretty worn for only 500 miles. Any chance they make a steel chainring in this size that would fit your crank?

Sounds like a difficult problem to diagnose.

Alcanbrad

Thanks Msteven. I thought about going to 32/48 but felt we would loose too much on the high end.

Alcanbrad

I am confident now that the chain is slipping one tooth across the entire engagement. In the video you can see the jockey cage snap forward with the "event" If the chain was climbing and then snapping back into place I would expect to the jockey cage would be moving forward then snapping back at the "event".

I can't comment on the wear of the small chainring, however, the issue exhibited itself on the very first ride when it was brand new (it only about 500 miles on it now).

I am waiting delivery of a 36 tooth ring from Precision tandems and I have a new solid pin KMC X11 chain to install with it. I don't know if the new ring is steel or aluminum. On thing I have observed is the barrels on the current SRAM Red-22 chain, the new KMC chain, and the older SRAM PC1050 10 speed chain all spin freely so there are, in fact, nice rolly wheels to ride up the tooth gullets on all chains. I wonder in the Red-22 barrels spin easier when under tension?

Alcanbrad

We were finally able to get out for the first ride on the new chainring and chain and did the same climb that I captured in the video above. The verdict: No chain skip!!!! In addition to the new 36 T Chain ring from Precision Tandems, and a new KMC X11 chain, I also changed the cassette from the Shimano 11-40 to the SRAM 11-42 (to compensate on the low end for the larger chainring) and I put the Digirit Large cage back on since I had eliminated it as a contributor.

For grins, I measured the depth of the gullets on the problematic 34T and the new 36T chain rings and the 36T gullets were noticeably deeper. Perhaps the 34T ring was shy on tolerances, or the tips of the teeth were worn down. I suspect the former over the latter.

I am feeling pretty good about it, my stoker, on the other hand said only "I still don't trust it". So it's going to be a while to regain confidence, but I think I got it, finally. I'll circle back in another 500 miles or so with an update.

This was a tricky one. It was taking the effort to set up a camera to "see" what was actually going on to know for sure.

Thanks for all the input and suggestions folks.

reburns

Glad to hear of your success. I have no doubt that your problem is solved. Check your chain frequently and replace at the first sign of wear to maximize the life of your new gears.

tandemdr

Very good to know! Thanks for the confirmation and the forensic analysis.