Still puzzled, part II
 

Various threads in 50+ and elsewhere make mention of triples, doubles, and compact doubles which I have some understanding of. In my case, I have a 50/39/30 with a 12/27 cassette. This bike has all Shimano 105 components if that makes it easier to visualize. I spend most of my time in the 39 ring for sure, but our area has some great flats as well as some super steep climbs, so I manage to use all three of the rings. The part that still puzzles me is the term cross chaining. I understand that it's bad and that the chain should not be at too severe an angle. Without getting too technical and with a couple of easy to understand :D examples, could someone "splain" it to me again?

Hi,
let's say you are climbing in your lowest gear. You go over the crest, and forget
to shift up front. But you are shifting the rear cassette. After about 3 shifts the
chain has to twist and that twisting is called cross chaining.

So the easy way to prevent that is to do 2 or 3 shifts and then jump a ring.

I thought cross chaining was having the chain on the outside ring up front and the inside ring in back, or vice versa.

Cross Chaining..........
 

This is from the Park Tool site........... Sorry the photo didn't come with the article.



Shifting Issues Related to Chainline

The following are typical problems that may be caused by chainline issues.

* Chain jumping off large chainring when front derailleur is correctly adjusted.
* Chain riding off lower derailleur pulley when derailleur or hanger is not bent
* Chain rattling on inner faces of front chainrings.
* Chain derailling off inner chainring when front derailleur correctly adjusted.
* Front derailleur cannot be adjusted to stop over shifts while still allowing good shifting.

On certain bikes, the chain may tend rub and rattle against the front rings while riding in certain gear combinations. This is common on many bike when riding in the so-called "cross-chaining" combination of the smallest front ring, and the smallest rear cog. An example of a gear combination that is likely to rub is shown below.
Cross chaining

Generally, the shorter distance from the bottom bracket to the rear hub, the more likely a rattle from gear combinations will occur. There may in fact be several gears that are unuseable on any given bike. It is possible to minimize or eliminate this problem by moving either the front or rear cogs. Even if the bike is has so-called perfect chainline, it may help the riding and shifting to create an "error" to solve shifting existing issues.

I guess it depends upon the adjustment of the bike.

No way would I call shifting up or down 3 cogs cross chaining.

Given the example above, a 27 speed bike would only have about 15 chain ring/cog combos.

I certainly don't follow that rule. I tend to judge by the sound of the drive train.

Tonight while in the middle ring (39) I used all ten cogs in the rear. Even though we were going up a really steep 3 mile grade, I decided to stay in the middle ring unless I absolutely needed the granny. Tonight I did not. I hear some slight noise when using the biggest cog and the smallest cog. Was I cross chaining? If so, what's the point of all those gears in the back if I can't use them? My LBS guy says it's no problem to use them all in that middle ring.

Don't use the big chain ring and big cog, nor the little chain ring and little cog. Look at the chain, it looks bent as it come off each ring/cog.

Check out the next cog up and down, see if it looks bent. If the chain seems to have a noticeable angle, even though it is obtuse, you are cross chained.

You got it. In either extreme, if viewed from above, the chain is tending to make a larger angle with the longways bike axis.

I'm not familiar with triples, but on most doubles, you can make a fine tuning compensation (aka "trimming") to eliminate the chain rubbing on the front derailleur cage. This is just a way of moving the front derailleur a tiny bit without causing it to move to the other chain ring. I mention this because a lot of folks new to the latest gear (or cycling) are unaware of this feature.

Some bikes are more forgiving than others - I would say that its not uncommon to get chain rub even with trimming on the extreme combinations (big-big, small-small). If I really take the time to adjust the derailleurs, I can eliminate most of it, although like most people, I'd rather be riding than working on my bike, so I live with it sometimes.

Yes, I am familiar with the trim feature and I use it. I'd rather be riding too!

Triple rings up front and 10 on the rear. The middle sprocket up the front can take about 6 of the rear cogs before the angle of the chain starts to get severe. Th big ring can take about 5 and the granny about 5. Do Big ring up front and use the 5 smallest sprockets' Middle ring and don't use the 2 largest or the 2 smallest rear sprockets and in the granny, Don't use the 5 smallest sprockets.

Doesn't really matter as you will hear when you are cross chaining. The rub on the deraillers will let you know. I ride with others that never get out of the big ring but use all 10. I am rarely out of the middle and use all of my 8 and Uphill it is the garanny with the big rear cogs.

Big thing I have found, is that chains do wear out. Someone that crosschains a lot will have a Knackered chain. They are also the ones that don't oil their chains and won't change them till they break either but that is another matter. All that sideways stretch on a chain is not good for it. Besides the wearing out- there is the friction involved that will slow you down. It will also wear out the cassette and the front sprockets.

Any one for a well lined up Single speed?

Stapfam hit on the real issue. I think after replacing a couple of those gawdawful expensive 10 speed chains, duaphin will be much less puzzled about this subject ;)

let's not do that! I will keep a straight chain...I promise!

Just a commentary but I like your setup with a 50/39/30 and 12/27. It provides a really good combination of gears for all terrains.

So far it's working like a charm!