Chain line with compact and short stays -chain catching shift pins

[Wayne77]

I'm wondering if there is a workaround for this. I'm working on a neighbor's bike (friendly, smart, attractive lady so I gotta get this right :cool:). In the small ring / two smallest cogs, the chain rubs the inside of the big ring and is catching the shifting pins. Yes, I've explained to her the chain wear issues of cross chaining (blank stare). However, we all find ourselves in the small ring/small cog every now and then and its typically more a matter of noise with the chain hitting the cage and chain wear. Anyway, in this case, the chain is catching the shifting pins and trying to hop up onto the big ring and bouncing around a lot as it catches and releases. Not an issue in the 3rd cog and higher. The front and rear mechs are adjusted properly. I've never had this issue on my own bikes but I ride a 58cm. I heard this is a common issue with compact cranks and short stays. Is that true? This bike I'm working in is a 51 or 52cm, Shimano 10 speed DA cranks / 10 speed cassette / 10 speed chain. Cranks are 34/50 compact.

Would putting a BB spacer on the drive side help with this? (moves the crank outboard a bit, decreasing the angle of the chain from small ring to small cog). Someone mentioned on another forum putting spacers on the spider between the chain rings themselves, but that sounds like a bad idea to me... There were two spacers behind the cassette (I presume due to the fact that its a mavic 10/11 speed compatible hub). I was able to remove 1 spacer to move the cassette slightly inward (while still being able to fully tighten the lockring), but that didn't have much of an effect.

Any other work arounds? If not, I can set the front der lower limit so it is just enough to keep the chain off the pins...which obviously creates more der cage noise when cross chaining...but that's better than this irritating chain hitting the shifting pin issue.

Thanks!

[Cicli]

No real workaround. Its a problem with the spread of the chainrings and short stays. Maybe a 36t inner chainring?

[drewellison]

Would an 11-speed chain help? If I understand the difference correctly, the interior width is the same (so should work on the cogs and rings just fine), but the outside width is narrower. So maybe it'd be less likely to catch.

[Wayne77]

Would an 11-speed chain help? If I understand the difference correctly, the interior width is the same (so should work on the cogs and rings just fine), but the outside width is narrower. So maybe it'd be less likely to catch.

I was wondering the same thing, but worried the narrower width might impact rear der shifting between cogs.

[Wayne77]

No real workaround. Its a problem with the spread of the chainrings and short stays. Maybe a 36t inner chainring?


Thanks...not surprised to hear that. 36T inner ring is definitely an option. - good idea

[cachagua]

I have worked around this by adding a washer between the spider and the inner ring. I use copper washers I got in a plumbing supply place, my calipers measure them at about 0.8mm.

They would allow your friend to use more cogs, but not all of them. There will still be the don't-cross-chain warning noise when she puts the chain in a position she isn't supposed to. Tell her, that's her bike's voice, saying "Ow! Quit it! Ow, ow, OW!!"

The other work-around, of course, is a single chainring.

[Peter P.]

No real workaround. Its a problem with the spread of the chainrings and short stays. Maybe a 36t inner chainring?

THIS.

Either increase the size of the inner ring, decrease the size of the outer ring, or both.

[ultraman6970]

IMO the solution is simpler, is not better just have the rider to do not crosschain like the best???

34x12 is the same than 50x16, and the chainline will be almost straight.

[oldpotatoe]

I'm wondering if there is a workaround for this. I'm working on a neighbor's bike (friendly, smart, attractive lady so I gotta get this right :cool:). In the small ring / two smallest cogs, the chain rubs the inside of the big ring and is catching the shifting pins. Yes, I've explained to her the chain wear issues of cross chaining (blank stare). However, we all find ourselves in the small ring/small cog every now and then and its typically more a matter of noise with the chain hitting the cage and chain wear. Anyway, in this case, the chain is catching the shifting pins and trying to hop up onto the big ring and bouncing around a lot as it catches and releases. Not an issue in the 3rd cog and higher. The front and rear mechs are adjusted properly. I've never had this issue on my own bikes but I ride a 58cm. I heard this is a common issue with compact cranks and short stays. Is that true? This bike I'm working in is a 51 or 52cm, Shimano 10 speed DA cranks / 10 speed cassette / 10 speed chain. Cranks are 34/50 compact.

Would putting a BB spacer on the drive side help with this? (moves the crank outboard a bit, decreasing the angle of the chain from small ring to small cog). Someone mentioned on another forum putting spacers on the spider between the chain rings themselves, but that sounds like a bad idea to me... There were two spacers behind the cassette (I presume due to the fact that its a mavic 10/11 speed compatible hub). I was able to remove 1 spacer to move the cassette slightly inward (while still being able to fully tighten the lockring), but that didn't have much of an effect.

Any other work arounds? If not, I can set the front der lower limit so it is just enough to keep the chain off the pins...which obviously creates more der cage noise when cross chaining...but that's better than this irritating chain hitting the shifting pin issue.

Thanks!

NOT uncommon with modern, multi gear bikes and compact, 50/34t cranks..with shift pins and such on the chainring and how the chain angle is. DON'T put in spacers and such..just don't go there..some cycling/shifting 'finesse' solves a lot of modern gear train issues.

And for right below. Spacers and such with shimano positional FD/LH shifter will cause more problems than solve. I vote 36t ring and a cogset that preserves her gearing, low gear-wise.

[Peter P.]

IMO the solution is simpler, is not better just have the rider to do not crosschain like the best???

34x12 is the same than 50x16, and the chainline will be almost straight.

I think the OP already explained that getting the rider to understand that solution elicited drool, and was equivalent to talking to your dog, thus the need to make it #%^*! proof.

[macaroon]

What chainset is she using?

I had this issue with a Shimano R700 compact fitted with some aftermarket (BOR I think) chainrings.

I then fitted some Shimano 11 speed (from a cheapo chainset) chainrings which I'm pretty sure eased the problem.

I've since swapped to a SRAM Rival chainset (as I prefer them to Shimanos) and the problem has completely disappeared.

[chiasticon]

just tell her to keep it in the big dog.

#problemsolved :beer:

[shovelhd]

Make sure you have the correct spacers behind the cassette. Mavic uses a special spacer. Use one with 10 speed and none with 11 speed.

[carpediemracing]

Not sure of chainring options but what about a 48T big ring? Or smaller, maybe even a 46? Like a cross ring?

What is the chainstay length, out of curiosity. Most geometries I see have a minimum chainstay length of about 40.5 cm (for a "race" bike), even for the smaller sizes. Except for an early Basso (51cm, 39 cm stay) pretty much all my 50-52 cm bikes had 40.5 cm stays.

[Ralph]

Don't see a problem. Just use the big ring more, and small ring only with big half of cassette. Shucks.....on my CAAD 10 with 39-52 old Chorus crank and 13-26 rear, 39 and 13 rubs. Common.

[cachagua]

What about a 48T big ring? Or smaller, maybe even a 46?

Excellent idea, I forgot about that. Put on a big ring that attracts the rider to use it.

"Set 'em up to win", we used to say, when I was doing child care. The general principle is to make the right thing for someone to do, the easiest thing for them to do.

Maybe this is the next best thing to a single ring. Although, there are some riders for whom two overlapping gear-changing mechanisms, doing different things in different circumstances, are just too opaque.

[Mark McM]

Not sure of chainring options but what about a 48T big ring? Or smaller, maybe even a 46? Like a cross ring?

What is the chainstay length, out of curiosity. Most geometries I see have a minimum chainstay length of about 40.5 cm (for a "race" bike), even for the smaller sizes. Except for an early Basso (51cm, 39 cm stay) pretty much all my 50-52 cm bikes had 40.5 cm stays.

Except for extreme cases, the effect of chainstay length on chain rub is a canard. As noted above, the range of standard road bike chainstay lengths has is relatively small - a "short" chainstay of 40.5 cm is only 5% less than a "long" chainstay of 42.5 cm, which is not much.

The largest contributors to chain rub are chainline and chainring size differential. With modern cassette hubs and 2 piece cranks (crank spindles built into cranks arm), chainlines have become standardized and fixed, and front and rear chainlines almost always match. That leaves the main culprit in most chain rubbing to chainring differential. As noted, chain rub is less common with smaller chainring differentials.

While we might like to be able to use all the cassette sprockets in each chainring, there are practical and performance reasons that is not ideal. Most multi-chainring drivetrains have a large amount of overlap and redundancy in gear sizes between chainrings. So using the smallest sprockets with the small chainring does not give one extra gears, as these ratios are duplicated with the large chainring. If one uses the small/small combinations, not only are you more likely to suffer from chain rub, but you will suffer greater wear of both the chain and sprockets. From a performance perspective, the small/small combination has greater energy losses than the equivalent gear ratio combination in the large chainring. In other words, there is no advantage to the small/small combination.

In the end, it is best to learn to not use the small/small chainring/sprocket combinations. And so chain rub becomes a feature instead of a bug - If a rider inadvertently shifts into these combinations, they get a friendly audible reminder that they should shift to a more efficient gear.

[Wayne77]

Don't see a problem. Just use the big ring more, and small ring only with big half of cassette. Shucks.....on my CAAD 10 with 39-52 old Chorus crank and 13-26 rear, 39 and 13 rubs. Common.


With all due respect, I don't think you read my original post. I do know what cross chaining is and chain rub issues. that's not what I'm asking about. With this particular bike in the small/small combo, the angle is extreme enough that the chain catches the pin on the inside of the DA chain ring...and continually hops up partially onto the chain ring then drops down... I've NEVER had this issue with any of the countless bikes I've built and maintained over the years (all 56cm and up). Yes, I get what it means to avoid cross chaining. That's cycling 101. But we ALL find ourselves in that situation every once in a while. I race ALOT. When you're redlining over the crest of a hill...deep in the pain cave chasing someone its very possible to start dumping gears and not remembering to switch to the big ring every now and then.

So that's when you hear the chain rub and shift. But if you do find yourself in that combo accidentally (heaven forbid!) and the chain starts to partially jump up and then jump down...you get false neutrals, the chain looses its grip on the teeth and it could be your race. This is the issue I'm working around. Again...not common, but I'm skeptical of anyone who says they NEVER find themselves in a cross chain situation inadvertently.

Anyway, lots of great feedback in this thread...really appreciate it. For now I've addressed the situation by setting the inner limit on the front Der just enough to direct the chain away from the inside of the big ring in the small/small combo...which gives the familiar chain rub sound but keeps the chain from hitting the pin and going nutso.

Perhaps these DA 10 speed rings are a little thicker than normal or the shifting pins jut out more...

[zmudshark]

Perhaps these DA 10 speed rings are a little thicker than normal or the shifting pins jut out more...

I know nothing about Shimano, But I'm wondering if a 105 ring may solve the problem?

It may be more 'forgiving' that a pro level ring, given the situation. IDK

[Ralph]

With all due respect, I don't think you read my original post. I do know what cross chaining is and chain rub issues. that's not what I'm asking about. With this particular bike in the small/small combo, the angle is extreme enough that the chain catches the pin on the inside of the DA chain ring...and continually hops up partially onto the chain ring then drops down... I've NEVER had this issue with any of the countless bikes I've built and maintained over the years (all 56cm and up). Yes, I get what it means to avoid cross chaining. That's cycling 101. But we ALL find ourselves in that situation every once in a while. I race ALOT. When you're redlining over the crest of a hill...deep in the pain cave chasing someone its very possible to start dumping gears and not remembering to switch to the big ring every now and then.

So that's when you hear the chain rub and shift. But if you do find yourself in that combo accidentally (heaven forbid!) and the chain starts to partially jump up and then jump down...you get false neutrals, the chain looses its grip on the teeth and it could be your race. This is the issue I'm working around. Again...not common, but I'm skeptical of anyone who says they NEVER find themselves in a cross chain situation inadvertently.

Anyway, lots of great feedback in this thread...really appreciate it. For now I've addressed the situation by setting the inner limit on the front Der just enough to direct the chain away from the inside of the big ring in the small/small combo...which gives the familiar chain rub sound but keeps the chain from hitting the pin and going nutso.

Perhaps these DA 10 speed rings are a little thicker than normal or the shifting pins jut out more...

I understand exactly what you are talking about. I read your post.

[ColonelJLloyd]

I have this issue with a 44/28 double and a 13-28t 7s freewheel with an 8s chain. It's my bike and the 28t isn't used all that much so in practice it isn't much of an issue. But, I have considered using a 10s chain to see if it gets me one more cog. The dropouts are square, but I haven't checked frame alignment. I agree with McM that it's the size of the rings/cogs moreso than the length of the stays. My bike has 428mm stays (centered in horizontal drops).

Do let us know what you end up doing.

https://c6.staticflickr.com/9/8542/29854155685_e89bc59a33.jpg (https://flic.kr/p/Mu7moa)008 (https://flic.kr/p/Mu7moa) by ColonelJLloyd (https://www.flickr.com/photos/51002114@N03/), on Flickr

[austex]

Have you done a "string test" to assure that the frame is aligned? And a dish check on the wheel?

[BdaGhisallo]

I understand exactly what you are talking about. I read your post.

It's not a problem that you can tune away with the current setup. You either need to lengthen the chainstays on the bike, change the rings sizes to minimize the size difference, or teach your friend not to cross-chain. I would say the latter two options are your path to success.

[djdj]

As others have asked, what is the chain stay length of the frame???

[carpediemracing]

FYI I've used the same cassettes (and at some level the same wheels), cranks, and derailleurs between a 40.5 cm stay, a 40.5 cm stay, a 39.0 cm stay, and a 39.3 cm stay. This over the course of 8+ years.

There is a "tinging" in the small-small on the 39 cm that was not present on the 40.5s. It's almost not present on the 39.3 cm stay. On the 39 and 39.3 cm stay I've also dumped the chain over the big ring, i.e. while sprinting in a 53x11 the chain wants to hop over to the outside of the 53. To be honest I haven't done any careful checks to verify alignment as I just adjusted front derailleur appropriately.

All Cannondale SI cranks, Campy 10s, 53x39 (Praxis set or OEM FSA set although I ran a tandem 55x44 for a bit). Cassettes are all 11-25 or 11-23 except one which is a 12-25.

[oldpotatoe]

Have you done a "string test" to assure that the frame is aligned? And a dish check on the wheel?

Where the rim is(dish) has no effect on the cogset or crankset. This would happen if just a hub with cogset is on the bike in a stand, w/o a rim on at all.

[austex]

Where the rim is(dish) has no effect on the cogset or crankset. This would happen if just a hub with cogset is on the bike in a stand, w/o a rim on at all.

Stuck in my old "horizontal" adjustable dropout ways, though if chainstays are slightly unequal length, and dish has been "massaged" to accommodate, I will stand by my suggestion to confirm dish.

[oldpotatoe]

Stuck in my old "horizontal" adjustable dropout ways, though if chainstays are slightly unequal length, and dish has been "massaged" to accommodate, I will stand by my suggestion to confirm dish.

Groovy but dish/rim still doesn't effect how the chain and crank/chainrings interact, that line and angle.

[Mark McM]

FYI I've used the same cassettes (and at some level the same wheels), cranks, and derailleurs between a 40.5 cm stay, a 40.5 cm stay, a 39.0 cm stay, and a 39.3 cm stay. This over the course of 8+ years.

There is a "tinging" in the small-small on the 39 cm that was not present on the 40.5s. It's almost not present on the 39.3 cm stay. On the 39 and 39.3 cm stay I've also dumped the chain over the big ring, i.e. while sprinting in a 53x11 the chain wants to hop over to the outside of the 53. To be honest I haven't done any careful checks to verify alignment as I just adjusted front derailleur appropriately.

I think a little more data is required to reach the conclusion that the important variable is chainstay length. As the chainstay length increases from 39.0 cm to 40.5 cm, the angle the chain angle at the extremes of the cassette changes from +/- 3.52 degrees to +/1 3.39 degrees. At the radius of the shift pins on a 53 tooth chainring (approx. 10 cm), the variation in lateral chain displacement between these two chainstay lengths is approx. 0.23 mm. This distance is less than one often sees in the manufacturing tolerances for the BB shell face offsets (I've seen variations in BB of shell offsets between different frames of up to a few millimeters). There is also the matter of BB shell angular alignment - the angular orientation tolerance of the BB shell on different frames may be greater than the chain angle difference from chainstay lengths

While many people like to blame chain rub on chainstay length, the reality is that there are many variable that influence chain rub, and that chainstay length is actually one of the lesser ones.

[dave thompson]

I'm wondering if there is a workaround for this. I'm working on a neighbor's bike (friendly, smart, attractive lady so I gotta get this right :cool:). In the small ring / two smallest cogs, the chain rubs the inside of the big ring and is catching the shifting pins. Yes, I've explained to her the chain wear issues of cross chaining (blank stare). However, we all find ourselves in the small ring/small cog every now and then and its typically more a matter of noise with the chain hitting the cage and chain wear. Anyway, in this case, the chain is catching the shifting pins and trying to hop up onto the big ring and bouncing around a lot as it catches and releases. Not an issue in the 3rd cog and higher. The front and rear mechs are adjusted properly. I've never had this issue on my own bikes but I ride a 58cm. I heard this is a common issue with compact cranks and short stays. Is that true? This bike I'm working in is a 51 or 52cm, Shimano 10 speed DA cranks / 10 speed cassette / 10 speed chain. Cranks are 34/50 compact.


Would putting a BB spacer on the drive side help with this? (moves the crank outboard a bit, decreasing the angle of the chain from small ring to small cog). Someone mentioned on another forum putting spacers on the spider between the chain rings themselves, but that sounds like a bad idea to me... There were two spacers behind the cassette (I presume due to the fact that its a mavic 10/11 speed compatible hub). I was able to remove 1 spacer to move the cassette slightly inward (while still being able to fully tighten the lockring), but that didn't have much of an effect.

Any other work arounds? If not, I can set the front der lower limit so it is just enough to keep the chain off the pins...which obviously creates more der cage noise when cross chaining...but that's better than this irritating chain hitting the shifting pin issue.

Thanks!

I ran into the same problem when I installed my first compact crank (seemingly a hundred years ago). IIRC I 'cured' the problem by switching the chain to a KMC. The original chain had pretty square shoulders on its outer plates which would catch on the soft pins, while the KMC is nicely beveled there.

I've since run KMC on all my bikes and the problem hasn't hasn't reappeared.

[cachagua]

Variation in lateral chain displacement between these two chainstay lengths is approx. 0.23 mm., less than one often sees in the manufacturing tolerances for the BB shell face offsets... There is also the matter of BB shell angular alignment...

All of this.

But, nobody digs the chainring washers? Is there a downside I'm not aware of? I've fixed this problem a number of times using that method, got 'em in a couple of cranks right now, but if I'm... you know... losing ten or fifteen watts in a sprint to washer flex, or something, well I'd want to know!

[oldpotatoe]

All of this.

But, nobody digs the chainring washers? Is there a downside I'm not aware of? I've fixed this problem a number of times using that method, got 'em in a couple of cranks right now, but if I'm... you know... losing ten or fifteen watts in a sprint to washer flex, or something, well I'd want to know!

Positional front der/LH shifter and with wider CR spacing may get some chain to FD rubbing at extremes..or it may just not shift well..

[Fatty]

Would putting a BB spacer on the drive side help with this? (moves the crank outboard a bit, decreasing the angle of the chain from small ring to small cog).



Thanks!

Did you try this? I would give it a shot. If it works easy low or no cost fix.

[thunderworks]

Have you done a "string test" to assure that the frame is aligned? And a dish check on the wheel?

A string test might offer some insights . . . if the rear triangle is not aligned correctly, chainline can be affected.

I'm with the Tater on the dish question - irrelevant to chainline. Other implications of course if it's not correct, but the relative position of the cassette to the chainset is not impacted in any way by the location of the rim relative to the rear spacing width.

Also, I have tweaked alignment before by adding a small spacer between the fixed cup on the drive side and the BB shell. For me, it worked fine and solved an annoying problem not dissimilar to the OP's problem.

[FlashUNC]

Just don't cross chain.

Its not rocket science.

[Wayne77]

Just don't cross chain.

Its not rocket science.

Per some earlier thoughts in this thread I posted, this isn't about "why is cross chaining bad" it's about something additional that is far worse IF someone does find themselves cross chained accidentally (which everyone does once in a while). In this case the shifting pins on these particularly thick DA rings grab the chain and yank it up but not all the way and then it hops back down with every turn of the crank, due to the more extreme chainline angle with my neighbors bike that has a compact crank and small frame. In some cases under load, there is a false neutral and the crank spins for a moment when the chain has no purchase on the teeth. I've had compact cranks on several of my personal 56-58cm bikes and never had this, if heaven forbid, I accidentally cross chained during a race or regular ride.

But yeah, I agree that cross chaining is bad due to the noise and wear issues.

[cachagua]

Positional front der/LH shifter with wider CR spacing may get some chain to FD rubbing at extremes...

Ah, of course. Forgot about that. All my front shifters are analog.