Thursday, September 06, 2018

Misunderstood Doesn't Mean "Bad"- Part 2

A misunderstood component of a multiple speed drive train.
Today I wanted to continue the discussion of multiple speed drive trains for bicycles, specifically derailleur based drive trains and the 1X and multiple chain ring set ups which are popular nowadays.

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.
 The second issue people generally have a hard time wrapping their minds around is that not all the gear combinations are good, should be used, or are meant to be used at all. 

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.
This is one reason why 1X appeals to many riders. It simplifies their experience. I get that. But it also introduces things that, if understood properly, may change some folks minds about eschewing multiple front chain ring set ups. On the other hand, 1X has its places- fat bikes, which when equipped with front derailleurs, just collect debris on the front derailleur mount and mechanism. Mountain bikes which feature complex suspension systems and/or short chain stays work with 1X where they wouldn't be possible with a front derailleur. 1X is great for cyclo cross and MTB due to cyclo crosser's and MTB's having to do more shifting under extreme pressure and where quick momentum changes happen. So, again- I am not advocating for 1X to go away. I actually like it on my fat bike. Not so much on a gravel bike.

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.


6 comments:

Marc Pfister said...

It doesn't help that every product manager who spec'ed their gravel bike with a 34/50 x 11-32 put your average gravel cruising speed right smack dab in the middle of the crossover range. So you're spending most of time in something like a 50x22 or 34x14. Since you're near the end of the range if you need to shift more than say, two gears in the wrong direction you have to do a front shift. Witth the big range in the front you then have to compensate with a couple of rear shifts. It ends up being way more work than it should be to find the right gear.

Neil Hodges said...

Mark: This is is why I still love a good triple. If the target gear ratio is smack dab in the middle of the full gear range, then it's close to middle ring to middle cog, which is consequently where I spend most of my time on the bikes I have set up with triples.

hank h said...

Howdy;

Think I'm understanding you. When I'm on my 3X8 MB, I usually keep the FD in the Mid ring and the RD in a mix of the 4 middle gears. When on the large ring of FD I tend to stay on the smaller set of 4 gears on the RD and when on the small FD ring I'm on the largest 4 gears for the RD. This something like what you are getting at?

hank h

Guitar Ted said...

@hank h- You got it.

Guitar Ted said...

@Marc Pfister- That's why I like 46/36 up front and an 11-36T in back. closely spaced ratios requiring less "compensation shifts" which suck your momentum away.

Skidmark said...

Many riders buy bikes and what they know about the bikes’ operation and function is self taught based on reading what is predominately advertising. These are often competent, intelligent people who assume that they should easily master something as simple as a bicycle. This is true even though they know that their own area of expertise requires study, skill, and knowledge. The fact that bicycles are considered “simple” hides the fact that like running or golf,etc., many years and a lot of experience are involved in becoming competent in the many related facets of the sport.