|A misunderstood component of a multiple speed drive train.|
Misunderstandings and misconceptions mixed in with a lack of education make this area of bicycle components and usage a murky water which in turn yields lots of conclusions which are not correct. First and foremost of these misunderstandings is how the multi-front chain ring system was meant to be used versus how many folks actually use the multi-ring front derailleur set up.
The first rule to understand is that your chain should always be kept as straight as possible. There are many reasons this is advantageous, but the one you will want to focus on is that it makes the rider more efficient. I talked about this yesterday in terms of chain line, which is what it sounds like- The "line" the chain makes between the front and rear cogs. This "line" should be as straight as possible. When it gets diagonal, or "cross chained", it is time to shift to a straighter combination. Poor choices in chain line make the rider less efficient and cause higher wear on parts. In case you haven't caught on to what I am saying- this is bad. Don't do it! (Unless you have 1X, then you are stuck, sorry!)
Keith Bontrager had a great set of 4 rules for derailleur drive trains which was published in a "Dirt Rag" back in the 90's which succinctly explained the way you should use a triple front crank set, but I've not been able to dig that up. So, I am going by memory here on what it was that Mr. Bontrager was pointing out. The principles are the same whether I get it exactly as Keith put it or not. That was one of the "rules" above, by the way.
|1X set ups have inherent cross chaining issues that cannot be avoided.|
That may come as a shock to many of you, but this is something that can squarely be blamed on marketing, public perception, and lack of understanding. Derailleur drive trains with multiple front chain rings have what is termed as overlapping gears. Now, the gears do not literally overlap one another, of course, but what is meant is that the final "gain ratio" of any given combination of front sprocket and rear cog may end up being very close to, or exactly the same as, another combination found on the same system. In other words, you may have certain gear combinations that are, effectively, the same thing on your bicycle. Your 2X 11 set up may not actually have 22 , different, sequential gears. In fact- it doesn't. Thinking that you go from "1" in the front, then shift from 11 to 1 in back, then go to "2" in the front, and shift sequentially from 11-1 again is not how it works at all.
You would be surprised to know how many folks think it is that way though. Getting your mind off of a numerical (mis)understanding of the drive train is critical to making the system work efficiently and how it was designed to work by the manufacturer. Can you cross chain your bike? Yes. Should you? Absolutely not, and many times you can find technical documents from Shimano and SRAM pointing this out. Trouble is, these documents are not often shared with the riding public, if at all. Why? Because is complicates the selling process at bicycle shops. Bicycles are very technical machines that require a high degree of skill and understanding to operate if they are equipped with multiple gear drive trains, not to mention suspension, or electronics, or the like. You simply just do not "get on and ride" these machines, although the bike industry basically says that is how it works through sales and marketing.
|1X road didn't work out very well in the Pro ranks.|
Finally, for this post, I wanted to cover the point Bontrager made in his original rules for gearing which stated that you should always use the biggest cog/chain ring combination if you have the choice, and you are not cross chaining. This is easier to figure out with a 2X system, but if you think hard enough, it can become a natural thing on a 3X crank set as well. The thinking is that a bigger cog/chain ring combo is more efficient since the power is being applied to a wider area (less wear) and the chain isn't being bent around in a tighter radius, which is less efficient. Minor, nit-picking, perhaps, but my observations agree with this. I would also add that bigger cogs/chain rings have less pressure on the shift ramps/pins/pick-up teeth enabling faster, more efficient shifting, so that would be another reason to use this philosophy.
Tomorrow I will cover why 1X may not be preferred in terms of cassettes.