New bike tune up

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:

[ATTACH=CONFIG]6555[/ATTACH]

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!

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.

@DismalScientist 93878 wrote:

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.

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.

@Steve O 93901 wrote:

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 1×10, but realistically I use the full range of my 36/46 rings and my FD has 20k miles or more without drama.

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.