bjamat

I appologize for how long this is going to be... If you get through it and have any suggestions, I am all ears!

I have a problem with my 2022 Madone (Ultegra DI2 12 Speed and Rotor Cranks). Since day one of having the bike I have had issues with chain suck and thought I finally got to the bottom of it... But then it happened again today. Any suggestions or help is greatly appreciated. But I've been in contact with both Rotor and my LBS... It's been 3 months of having this issue and I just feel a bit hopeless at this point.

I took the bike out for the first time in April. Less than 10 minutes into the first ride, I was climbing a hill, shifted the front derailleur down and BAM! Chain suck. I was able to back pedal very easily and the large chain ring was able to release the chain and I was on my way all in the fraction of a second. I thought it was just a fluke... But 10 minutes later it happened again as I was testing out the shifting on a quieter road. It happened again and I noticed that the chain suck caused my rear derailleur to fully extend and smack my frame. I now had 2 chips in the paint within 20 minutes of riding. I was furious and obviously didn't want to cause any more damage. I soft pedalled home and brought it back to my LBS the next day.

Here's a timeline of events since then

• LBS Looked at it, checked everything over and reached out to their Rotor Supplier
• Rotor sent replacement chain rings and asked to send the ones I had issues with back so that they could try and investigate further
• LBS installed the new chain rings and installed ride wrap where the rear derailleur had smacking the frame in case it happened again. Said nothing they could do about the paint other than add some clear coat.
• I did a deep clean of the drive train to get that crummy factory lube off the chain and applied my own. I also went through and adjusted all the derailleurs following Shimano's app
• It happened again. Not every ride as I mindfully slowed my cadence to <40 and kept power below 150 watts while shifting for most rides. The derailleur hit it with enough force to cut through the ride wrap as well....
• It has happened every now and then through a range of powers and cadences. It was not isolated to power or cadence and just seemed to happen all the time (was trying to see if there was any correlation)
• After numerous conversations with Rotor to see if things were set up properly, they asked to try a new chain in case there was a defect in the one that came with the bike
• I put on a new 12 speed waxed chain and thought the issue had been resolved as I went on a 100km ride without issue.
• 200 km in and it happened again today I am thinking waxing may have helped with the issue but did not resolve it
• Throughout I have kept my drive train thoroughly cleaned so it's not dirt and grime causing the chain suck...
• There doesn't appear to be any structural damage, a few small paint chips and very minor scratches... But my is it frustrating since it is new.

I don't take the bike on group rides or race on it for obvious reasons... I don't feel safe on the bike when going into the red, in case it happens and I crash or something. This is the first bike I've bought new and it's been an absolute nightmare! I no longer feel at all excited to ride it and it's not like I can offload it in good concience... At this point I don't know what to do because Rotor isn't really doing anything about it nor is my LBS.

Side note: I only got the Rotor cranks because I like something shorter and I couldn't get the Ultegra crankset at the time. I could try to get one now that shops are able to get them, but I also don't want to blow any more money on it if it's not an issue with the Rotor cranks.

I'd also post pictures... but i'm new to the forum and it says I need ten posts first 🤦

veganbikes

Why the face palm? Do you not enjoy bikes? If you enjoy bikes get ten posts by participating in ACTIVE threads, if not try your local shop or a search engine. However here it would be good to see photos if you want help but more importantly this is an awesome place if you enjoy bikes and judging by what you have you probably like them at least a little.

In terms of the bike I would check and make sure derailleur and hanger is aligned and that frame is straight and all of that. That could potentially cause issues but would love to see those photos first.

cxwrench

Without seeing the bike the only thing I will say is it's probably the chainrings. Or maybe more specifically the interface between the chain and the chainrings. I'd suggest Shimano rings.

Troul 

try a different rear wheel assembly, to include a new cassette, hub, etc etc (hence assembly)

Andrew R Stewart 

Chain suck is caused by their being too much tension on the portion of the chain that is crossing from one ring to the other.

Worn ring teeth can make this worse but with such a new set up I doubt wear is at play. Shimano has spent a lot of effort to reduce chain suck, hence the rings are "paired" to each other to align the teeth between the rings. But this is not a guaranty of no chain suck. I do agree with Shimano rings being about the best brand WRT chain suck reduction.

The number 1 way to avoid suck is to avoid tension during shifting. The statement "I was climbing a hill, shifted the front derailleur down and BAM! Chain suck." is the admission of guilty shifting technique. The inability of many riders to understand or correct this is one reason why the industry is moving away from 2 or 3 ring cranksets (and instead make us suffer with huge gearing gaps and reduced gear range).

As a rider who does enjoy riding in close quarters with others I thank you for not riding with us if you can't shift safely. I applaud the shop for being so willing to help but it's not really their place to fix your technique, note that you didn't say anything about their advise.

The usual best way to avoid this is to shift with zero chain tension, easiest to do when one has a higher cadence. (and the statement "slowed my cadence to <40 and kept power below 150 watts while shifting for most rides" suggest you are doing nearly the opposite of what many have found to work best. Learning to shift the front when you can soft pedal (not slow the cadence but loose that 150 watts thing, maybe remove your power meter all together) and doing so ahead of the actual need (yest your cadence will change after the shift, another reason to develop a wide range of cadence capability. Andy