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Supermau
09-05-2014, 03:47 PM
Went and got my new Trek FX tweaked after the first 100 miles yesterday and last night noticed some chain rub on the front derailer when I was in the 2nd chain ring and the small cog in the back. I spend a lot of time in the 2nd chainring and hadn't noticed any rub prior to the tuneup.

The mechanic told me it's cross chaining, but in this gear the chain is nearly straight front to back, certainly not your typical definition of cross chaining. He basically called it an annoyance and said it wouldn't do any harm but didn't take another look at it.

I'm still a bit intimidated by screwinging around with derailers as I'm just learning. What I did do was loosen the front just enough to give it a tiny twist away from the chain and tighten it down again. Seems good to go and no more rub. Shifting seems good.

Any thoughts on this? Do you think my mechanic was just being lazy? I've really got to get some hands-on experience and get over my derailer phobia.

PS - I know I've spelled derailer incorrectly, my iPad is doing the spelling.

cyclingfool
09-05-2014, 04:05 PM
Middle chainring to either the smallest or the largest cog is typically defined as crosschaining. That and largest two cogs (lowest gears) with big chainring and smallest two cogs (highest gears) with smallest, innermost chainring. I'd probably just shift to the big chainring and down a couple cogs in the back if I were you, but that's all personal preference.

Semantics and personal preferences aside, if you really want to ride in that combination (and if the chain is pretty straight in that combo then more power to you), you should be able to alleviate the rubbing by making an adjustment using the barrel adjuster at the front shifter. You just need to get a little more tension into the cable to help pull the derailleur a tad further outwards so it doesn't rub.

The barrel adjuster will probably looks something like this:

6555

Note there will be two barrel adjusters - one for the brake and one for the derailleur. It should be pretty obvious which one is which.

PS-Avoiding this kind of problem is probably the biggest reason I love my friction front shifting! :)

cyclingfool
09-05-2014, 04:21 PM
PS - I know I've spelled derailer incorrectly, my iPad is doing the spelling.

I tend to agree, but Sheldon Brown (RIP), one of the greatest bike minds ever, begs to differ (http://www.sheldonbrown.com/derailer.html).

Supermau
09-05-2014, 04:44 PM
Thanks for the tips. I love Sheldon, I found his site months ago a visit quite a bit.

The mechanic suggested I try using the third (largest) chainring as well. I guess my main gripe was that I had no rub before the tuneup.

It seems I spend 95% of my ride somewhere in the 2nd ring. That range seems to take care of business most of the time. Since tomorrow is my big commute day I'll experiment more.

I appreciate your response.

Cheers!

DismalScientist
09-05-2014, 05:03 PM
If you are in the large or small cog on the rear and the front derailleur rubs, you should trim (slightly move) the front derailleur to stop the rubbing. This is why front shifters are typically not indexed. This is not an indication that anything is misadjusted.

mstone
09-05-2014, 07:13 PM
If you adjust the front derailleur outward to stop the rubbing in that combination you make it more likely that you'll get more rubbing in a lower combination or even have trouble shifting to a smaller cog.

cyclingfool
09-05-2014, 09:31 PM
I still think the slight rub described could be corrected with a tweak of the barrel adjuster. That's what it's there for. And it's also completely reversible if it throws off other shifting as described by mstone.

Again, as I said, though, this sort of thing reminds me how glad I am to have smooth friction shifting with my bar end shifters. Something rubbing? Slight adjustment of the shifter makes it go away. :)

Steve O
09-06-2014, 11:41 AM
If you are in the large or small cog on the rear and the front derailleur rubs, you should trim (slightly move) the front derailleur to stop the rubbing. This is why front shifters are typically not indexed. This is not an indication that anything is misadjusted.

You can also adjust the limit screw without adjusting the derailleur positioning if it rubs at the extremes (small front/big rear or big front/small rear). This is what I would do first.

BTW - my front derailleur recently broke and I am probably going to get rid of it entirely. For the last month I tightened the limit screws so the front derailleur is locked in one position on the center chain ring. I did the Reston Century that way without issue. I need just one somewhat bigger one in the back to get down as low as I would like for virtually everything.
Like supermau I spend 95% of my riding on the middle one, so I think I will customize my gearing with a single up front and 9 in the back. Less stuff to break and adjust that way. I'll replace the outside chain ring with a chain guard and not sure what I'll do on the inside. I may need a solution to prevent the chain from falling off the inside.

If dcv can do Kill Bill with one speed, I most certainly can survive with 9.

DismalScientist
09-06-2014, 11:57 AM
Why bother with the limit screws? (The OP had a problem in the middle chain ring.) With a broken front derailleur (or front shifter), just remove it. Even then, if you are sick of the middle ring, you can shifted it by (greasy) hand.:rolleyes:

Dickie
09-06-2014, 12:04 PM
First, lets be clear about what sprocket combination you are talking about. You say the 2nd chainring.. I'm assuming you have a triple? If you are in the "middle" chainring and the smallest rear cog, this would actually be considered cross-chaining...but that doesn't matter as it's just words.

Cross chaining is not caused by derailer adjustment, it is caused by alignment of the front chain rings, axle length, and the spacing of the rear wheel and cassette. The rubbing on the derailer however is often the result and this occasionally be compensated for with a few tweaks. If you were able to ride in this combination before without any issue there isn't any reason why you shouldn't now. To me it sounds like a lazy mechanic unwilling to spend the additional time fine tuning your bike. The suggestion to just find another gear combination is offensive.... you have the gears, you have the combination you like, it should be adjusted properly to work as it always did.

Adjusting the trim as Dismal suggests is probably the best fix for now. I suspect that the limit screws being adjusted would help as well, but this can be tricky as too much adjustment can cause you to over-shift and drop your chain. The barrel adjusters on the rear derailer will not help this situation and if the bike is shifting correctly you shouldn't mess with it. The front derailer barrel adjuster is a bit of a crap shoot.

Supermau
09-06-2014, 02:44 PM
First, lets be clear about what sprocket combination you are talking about. You say the 2nd chainring.. I'm assuming you have a triple? If you are in the "middle" chainring and the smallest rear cog, this would actually be considered cross-chaining...but that doesn't matter as it's just words.

Cross chaining is not caused by derailer adjustment, it is caused by alignment of the front chain rings, axle length, and the spacing of the rear wheel and cassette. The rubbing on the derailer however is often the result and this occasionally be compensated for with a few tweaks. If you were able to ride in this combination before without any issue there isn't any reason why you shouldn't now. To me it sounds like a lazy mechanic unwilling to spend the additional time fine tuning your bike. The suggestion to just find another gear combination is offensive.... you have the gears, you have the combination you like, it should be adjusted properly to work as it always did.

Adjusting the trim as Dismal suggests is probably the best fix for now. I suspect that the limit screws being adjusted would help as well, but this can be tricky as too much adjustment can cause you to over-shift and drop your chain. The barrel adjusters on the rear derailer will not help this situation and if the bike is shifting correctly you shouldn't mess with it. The front derailer barrel adjuster is a bit of a crap shoot.

Thanks for the response. I do indeed have a triple. I should have stated that. I always assumed cross chaining was more to the extremes ( big ring - big rear cog, little - little ), but I get why he said I was cross chaining now. Certainly not extreme, but technically correct. You picked up my point...it wasn't rubbing before, so it shouldn't rub now.

What I did was loosen the front derailer enough to twist it a micro notch away. I did this very carefully so as not to screw up height. I rode 25 miles today without any issue. I'll bet I didn't do the right thing, but it worked. There's no rub in any combination.

I also took the shifting suggestion to heart and spent a lot more time in the big ring today, and shifting down to the middle when needed. I discovered that I really like the feel of the big ring! I haven't been shifting my bike to its potential.

Still, I do feel like my mechanic, and I use the term loosely, just didn't want to get it up on the stand again. I will master these confounded derailers. No more fear.

hozn
09-06-2014, 02:51 PM
I'll replace the outside chain ring with a chain guard and not sure what I'll do on the inside. I may need a solution to prevent the chain from falling off the inside.

I would just get one of those new narrow-wide rings (somewhere in size 38-42?) and forget about any chain retention devices or bashguard.

I periodically debate converting my commuter to 1x10, but realistically I use the full range of my 36/46 rings and my FD has 20k miles or more without drama.

TwoWheelsDC
09-06-2014, 02:53 PM
I also took the shifting suggestion to heart and spent a lot more time in the big ring today, and shifting down to the middle when needed. I discovered that I really like the feel of the big ring! I haven't been shifting my bike to its potential.



Sur la Plaque! (http://www.velominati.com/look-pro/look-pro-part-vi-move-sur-la-plaque/)

Supermau
09-06-2014, 03:02 PM
Sur la Plaque! (http://www.velominati.com/look-pro/look-pro-part-vi-move-sur-la-plaque/)

6557

Steve O
09-06-2014, 04:59 PM
I would just get one of those new narrow-wide rings (somewhere in size 38-42?) and forget about any chain retention devices or bashguard.

The protection on the outside is not necessarily to keep the chain on, but to actually protect my pants and other clothing. Although I use cuff holders and roll the cuffs, etc., sometimes when moving the bike around to lock it or put it on the car, etc, I manage to get grease on something. And it's almost always from the front chainring. This would not eliminate that issue entirely, but it would help.


I periodically debate converting my commuter to 1x10, but realistically I use the full range of my 36/46 rings and my FD has 20k miles or more without drama.
At different times I have broken all three things: cable, shifter and derailleur. So my luck has not been as good as yours. Although double FDs are less finicky than triples I believe.

Harry Meatmotor
09-09-2014, 07:51 AM
I'm just gonna drop this little stinker in here:

I get that it's annoying to have minor derailleur rub in cross chaining situations, but I'd tend agree with the opinion that you simply shouldn't use that gear anyhow. The basic premise is this: when the chain contacts fewer teeth on a gear, it greatly increases the wear on both the chain and the gear. Seriously, you're effectively halving the life of a chain, ime. Not only does it cause the valleys between the teeth to wear quickly, it wears out any shift ramps stamped or machined into the sides of the teeth because the chain is leaving the cog at a sharp angle. Cross chaining in the big-big combo isn't quite as bad, because the chain loading is spread over a greater number of teeth - however, the side loading caused by the exit and entry angles in the chain line will cause increased wear on the cog and chainring - especially to any fancy shift-enabling tooth shaping.

One thing you can do on most modern indexed shifters is to do a double-shift or triple-shift in the rear and a single shift in the front, at the same time. So, if you find yourself in getting near the small end of the cassette, try and get used to doing a double-shift down in the rear while at the same time doing a single shift up to the big ring. In most gearing combos, this will put you in just about the same number of gear-inches. You can do the same if you find yourself in the big-big combo, only in reverse.

One final rant - some newer front derailleurs (SRAM's Yaw technology, Shimano's Di2 system) will allow cross chaining with no rub on the FDer cage - but in my experience the chain, cassette, and chainrings still make a huge racket even when perfectly adjusted.

Supermau
09-09-2014, 09:06 AM
[QUOTE=Harry Meatmotor;94032...

One thing you can do on most modern indexed shifters is to do a double-shift or triple-shift in the rear and a single shift in the front, at the same time. So, if you find yourself in getting near the small end of the cassette, try and get used to doing a double-shift down in the rear while at the same time doing a single shift up to the big ring. In most gearing combos, this will put you in just about the same number of gear-inches. You can do the same if you find yourself in the big-big combo, only in reverse.

One final rant - some newer front derailleurs (SRAM's Yaw technology, Shimano's Di2 system) will allow cross chaining with no rub on the FDer cage - but in my experience the chain, cassette, and chainrings still make a huge racket even when perfectly adjusted.[/QUOTE]

Thanks for the input. I just started riding again this spring after at least ten years away, and even ten years ago I knew little about the nuances of shifting. I corrected all that on my last ride. I had a solid 25 miles to practice with. I did double shift and spent more time going between the big ring and the middle and I definitely learned a lot.

I must say though, my bikes make no huge racket unless I'm shifting under stress, which I try to avoid. They generally shift pretty smooth and quietly. Unless our definitions of "racket" just aren't the same.

Harry Meatmotor
09-12-2014, 10:03 AM
Thanks for the input. I just started riding again this spring after at least ten years away, and even ten years ago I knew little about the nuances of shifting. I corrected all that on my last ride. I had a solid 25 miles to practice with. I did double shift and spent more time going between the big ring and the middle and I definitely learned a lot.

I must say though, my bikes make no huge racket unless I'm shifting under stress, which I try to avoid. They generally shift pretty smooth and quietly. Unless our definitions of "racket" just aren't the same.

a small addendum to the SRAM & Shimano 22 speed stuff is noisy complaint: the noise is from the chain and chainrings - i think we're getting to the limits of drivetrain offset in terms of cassette width, tho not necessarily the number of speeds. I did see Phil Wood's tweet of a picture of a 13 speed cassette and I can't imagine how much that tweaks the driveline if you were to run that as a 1x13 setup.

dkel
09-12-2014, 11:07 AM
I did see Phil Wood's tweet of a picture of a 13 speed cassette and I can't imagine how much that tweaks the driveline if you were to run that as a 1x13 setup.

I was wondering about the single chainring option with regard to this thread. If I ran a 1x10 (which I have considered), would that create additional chain wear from cross-chaining at both ends of the cassette? Obviously there would be no FD to rub, but it would be a wide range for the chain to navigate without relief of switching rings.

nsfnsfdave
09-12-2014, 11:23 AM
I've been riding many years and have built all my own bikes from frames with a variety of components, from 3x7 to 3x10 and many 2x9 and 2x10 setups. Cross-chaining should only result in slightly faster wear on all the components, in my opinion not enough to worry about. It should never result in excess noise. If both derailleurs are adjusted properly you should never get rubbing on the front derailleur no matter what the gear combination. And if you use good chain lube and keep everything else clean, you should hear little or no noise. I currently ride a 1996 trek with 53/39 and 11/28. I rarely get off the big ring and I frequently ride 53-28 on hills. This is cross-chaining at its worst, and I don't have any rubbing, chain noise, or other issues.

Take it back and have them adjust it properly. The front derailleur on a triple has very little room for error. It must be adjusted to a precise setting with the cable length and stops and more important, the alignment of the derailleur to the chainrings (rotating it on the seatpost) is very critical. But if the shop does it correctly, you should not have it rub in any gear combination.

hozn
09-12-2014, 11:38 AM
If both derailleurs are adjusted properly you should never get rubbing on the front derailleur no matter what the gear combination.

This depends on the frame geometry and the groupset. I cannot adjust my 10sp Sram Force FD on my 135mm rear spacing & 410mm chainstays road bike so that the chain doesn't rub the FD when cross chaining in the small ring. Unlike Shimano, Sram (this version, anyway) has no trim for the small ring. Doesn't matter, because I don't need to cross chain and spend most of my time in the big (50t or 52t) ring, but it's certainly not a universal truth that there will be no rub if the FD is correctly adjusted.

It sounds like this case, though, is one where some adjustment will fix the problem -- particularly since it used to be noise-free.

Harry Meatmotor
09-12-2014, 11:42 AM
I was wondering about the single chainring option with regard to this thread. If I ran a 1x10 (which I have considered), would that create additional chain wear from cross-chaining at both ends of the cassette? Obviously there would be no FD to rub, but it would be a wide range for the chain to navigate without relief of switching rings.

IMHO the jury is still out on this from a more or less typical 700c-wheeled commuter bike perspective. I can't think of any bikes out there aside from some very new race-inspired cyclocross bikes running a 1x11 setup. The 1x10 groups seem to be holding up pretty well, but again, they're usually 26" or 29" or fatbikes that see a bit different kind of abuse than a commuter. I'm interested to see how the 1x11 setup penetrates the gravel bike market - in fact, i think it was Wolf Tooth that introduced a 50T narrow-wide chainring at inter bike this week that when coupled with an 11-38 or 11-40 (or even 11-42) cassette could net you the same gear ratios as a compact (34-50) with an 11-28 cassette. The murmurs on the forums are that the narrow-wide chainrings work really well, but tend to wear out a little faster than normal chainrings. again, that's in the dirt on MTBs, not on commuter bikes or road bikes.

dkel
09-12-2014, 11:50 AM
IMHO the jury is still out on this from a more or less typical 700c-wheeled commuter bike perspective. I can't think of any bikes out there aside from some very new race-inspired cyclocross bikes running a 1x11 setup.

I saw the 1x10 on the Civilian Vive le roi (http://www.ridecvln.com/bikes/vive-le-roi-2/) when I was shopping for my Straggler, which is what got me thinking about it. Admittedly the Civilian is not really a commuter, but I'm pretty sure I could do my whole commute in my big ring (46T) except for the effects of cross-chaining the big cogs on climbs.

Harry Meatmotor
09-12-2014, 11:51 AM
If both derailleurs are adjusted properly you should never get rubbing on the front derailleur no matter what the gear combination.

I'm sorry, but that's simply not true. There's much more that affects the chainline on a bike that proper adjustment can't make up for in every single case on any bike with any mix of components. I don't disagree that on your bikes it hasn't been a problem, perhaps ever, but I've certainly seen combinations of BB width, crank design/chainring offset, seat tube dimensions/shape, rear axle spacing, and chainstay length that net noisy crosschaining that's not at all related the mechanic's ability to properly adjust a front derailleur.

DismalScientist
09-12-2014, 04:51 PM
I just checked the Deore front shifter pod (M-440) on my hybrid. The front derailleur is not fully indexed. While a major pull will shift gears, a minor pull will move the derailleur slightly to eliminate chain rub in cross chaining situations.

mstone
09-12-2014, 05:05 PM
That's the trim function. You usually get a bit more adjustability with higher end gear than lower end, but I think all indexed front shifters have some trim adjust.