Dumb question about chainguide/chaincatchers

[bicycletricycle]

Why are these little buggers around? Are new drive trains throwing chains onto the bottom brackets all the time or something? I remember in the 90s when mountain bike companies made all kinds of contraptions for drive trains, tensioners, guides, etc. then they all stopped because people realized they didn't need them in the first place. Am I missing something about modern road drive trains?

[weisan]

triceratops, why don''t you ask this "dumb" question on my thread? Out of respect? no worries, bro, go right ahead, I don't mind...especially since you already make the disclaimer:

..please don't take anything I say personally, I am an idiot.

[bicycletricycle]

You asked how to adjust a chain catcher, I am curious why they are making a come back . I didn't want to drift your thread but it looks like it is going that way anyways.

Oh well

[smontanaro]

I'm with @bicycletricycle. I only ride old stuff. Even my newest couple beater-ish bikes (8-speed rear) don't have any issues. I've never heard of these little beasties until I saw these two threads in my daily digest. What causes the (perceived?) problem? Is it the width of the cassette? Large jump between chainrings? Triples?

[oldpotatoe]

Why are these little buggers around? Are new drive trains throwing chains onto the bottom brackets all the time or something? I remember in the 90s when mountain bike companies made all kinds of contraptions for drive trains, tensioners, guides, etc. then they all stopped because people realized they didn't need them in the first place. Am I missing something about modern road drive trains?

With 11s cogsets, flanges that move inboard, the resulting chainline angle when going from big ring to small, bumpy terrain..sometimes you need these. Particularly those systems that just release the 'hold' on the front der and it smacks the chain.

[Cicli]

With 11s cogsets, flanges that move inboard, the resulting chainline angle when going from big ring to small, bumpy terrain..sometimes you need these. Particularly those systems that just release the 'hold' on the front der and it smacks the chain.

Well said. Friction shift nudges the chain down to the small ring. Some shifters just kick it off the big ring and it lands in the right place.

[oldpotatoe]

Well said. Friction shift nudges the chain down to the small ring. Some shifters just kick it off the big ring and it lands in the right place.

Also, 50/34 and 11s spacing, which has the CRs closer together and 16t difference. All add up to some chain shucks.

[jamesau]

I've only used the Jump Stop variety and consider it cheap insurance.

It's one thing to have a chain drop onto the BB shell where simply upshifting the FD will set the chain right again. It's quite another thing to have a chain drop and become wedged between the small chainring and the chainstay; which scenario may happen depends on the bike and its clearances, I suppose.

My first experience with a dropped chain was a hard lesson with my newish Y2K M2-framed Stumpjumper hardtail: a gouged chainstay and bent chain. In retrospect, this may have been preventable with a more carefully adjusted FD and the presence of mind to softpedal that shift and let up when things went bad. Suffice it to say I vowed not to have that happen again.

I also look at it this way (Shimano perspective). Compared to the RD, the FD's job is simply a tougher ask; its design is optimistic compared to the RD. Set the FD up according to the manual and it should work as intended. Then, things get a little dirty, a little worn, you get a little cross-chained, maybe things get bumpy, then the stars align, and it happens to you.

It's not uncommon to see gouged up chainstays on otherwise beautiful high end bikes on Ebay and elsewhere; it makes me a little sad.

[audi666]

theyre used in cross a good amount just as a secondary system to keep the chain on (even narrowwides rings) since dropping a chain, especially on the inside can equate to loosing many places.

[tlittlefield]

For $20 and 10 grams it is good insurance, especially with a carbon frame.

[Mark McM]

Why are these little buggers around? Are new drive trains throwing chains onto the bottom brackets all the time or something? I remember in the 90s when mountain bike companies made all kinds of contraptions for drive trains, tensioners, guides, etc. then they all stopped because people realized they didn't need them in the first place. Am I missing something about modern road drive trains?

I think there are several reasons that dropped chains are now more common. As OldPotatoe mentioned, cassettes have gotten wider, which results in greater chain angles; at the same time, chainrings have gotten closer together and chains themselves have gotten narrower. And as noted, the faster, more abrupt action of indexed shifting also may play a role. But I suspect the biggest reason is the unintended consequences of better front upshifting.

Before shift assist pins were added to chainrings, front derailleurs could only handle shifting up a 10-12 tooth chainring difference. Now, with shift assist pins (and better shaped derailleur cages) chainring differences of 16 teeth are easy to upshift. But downshifting still uses the crude "drop the chain off the inside of the big ring and hope it lands on the small ring" mechanism. And the bigger the drop, more likely the chain will miss the little ring, or bounce off of it without engaging. If we went back to 10-12 tooth front chainring differences, I think the need for chain stop devices would evaporate.

Mind you, this isn't a complaint. I'll take a large spread compact crank with a chain stop device over a triple crank with narrow chainring spreads any day.

[Formulasaab]

Just a couple things I've heard around the shop...

Schleck/ "chaingate".
Fear of ruining a carbon frame by dropping/sucking your chain into it. "Abuse/misuse is not covered under warranty."

[johnniecakes]

I am sure Andy Schleck wishes he would have had one a few tours back