Wednesday, January 06, 2016

Front Derailleurs: Should We Really Lose Them?


Not all front derailleurs are weak, ineffective, or a hassle to use.
There is a move afoot by a certain purveyor of cycling hardware to rid the world of that pesky protuberance on the seat tube known as the "front derailleur". It's a pox, if you believe the hype, and should be gone so you can have a cleaner, more streamlined drive train.

I'm not going to go where you think with this rant, by the way. Nope. Gear range is a conversation for another day. What concerns me is something I've not seen mentioned by anyone until very recently. There was a review on an all-road bike posted recently on the "Bike Radar" site, and in the review on this particular bike equipped with a "one-by" drive train, you can find this gem:

Shifting across the wide 11-32t cassette is no different to any other SRAM DoubleTap groupset, with just a little extra noise in the biggest cog, where the chain is at its most extreme angle.
Did you catch that? The bit about the "extra noise" when the chain is in the "most extreme angle"? Think about that for just a minute......

What is it that you've heard preached about when using a multiple geared drive train? Long ago, Keith Bontrager had an article in "Dirt Rag" which covered the four cardinal rules of shifting. In that piece he described how one of the principle rules of multiple speed drive trains was to keep the chain line as straight as possible. Why? Because a straighter chain is more efficient. A chain that angles from one cog in the rear to another chain ring on the front becomes less efficient as the angle increases. This accelerates wear as well. In order to maintain a straighter chain line, the rider should shift the drive train into an appropriate chain ring up front. Then use the rear cogs on the back the more closely approximate a straighter chain. This keeps efficiency high and reduces wear to a minimum.

With only one front ring, there is no way to correct for extreme chain lines.
While it is true that materials technology has taken a huge leap since the 90's when Keith Bontrager penned that article, it doesn't erase the fact that we're still functioning in the same relative spaces when it comes to bicycle drive trains and that with narrower chains and slimmer cogs and chain rings. It would seem then that wear and efficiency would be even more important to pay attention to, yet for some strange reason, the front derailleur and multiple front chain rings have been targeted as being out of fashion. Why?

In my opinion it is because the appeal to riders is that it makes understanding the drive train easier. To a lesser degree, it also helps you to get a slightly lighter drive train. Finally, for mountain bikers it clears up enough real estate on the handle bar so that a dropper post remote has a place on the bar without being affixed in a strange, poor ergonomic position. However; it would seem nigh unto impossible to show that it is actually more efficient unless you spend the majority of your time in the middle of your cassette, in which case the higher gears and lower gears are essentially dead weight.

This also doesn't even touch how shorter cage rear derailleurs shift more quickly, and are lighter, or how you don't need enormous rear cogs which rear derailleurs aren't the most efficient at shifting into or out of. It doesn't begin to tell how that big cog/front ring chain line is actually more severe than a typical 2X set up. Nor does it touch on how some front derailleurs are actually quite easy to shift and these don't have to be electronic either. Finally, multiple front chain rings distribute wear across more material/teeth, and a single front ring is going to wear out faster.

While a "one-by" chain ring set up might seem really cool for your bike, it has its drawbacks and compromises. Something to think about before you "make the leap".

22 comments:

bostonbybike said...

Who knows, maybe one day we will see dedicated 1x cranks with special "floating" chainring that can pivot slightly to compensate for chain misalignment (My idea! Patent pending ;)

But as much as I like the 1x11 idea for its mechanical simplicity, there are still too many drawbacks of such solution:

Gearing range - can be nearly the same as a wide range 2x10 setup. Still, 1x12 would be actually closer to it.

Jumps between gears - obviously larger than at 2x10.

Weight savings - Going to 1x11 from 2x10 you lose front der., one shifter and cable and one chainring. But those savings are negated by a heavier rear der. (longer cage) and a much heavier cassette. Unless you are ready to drop $400 for XX1 cassette, weight savings are going to be minimal. And if you use two different wheelsets on one bike (e.g. with different tires, etc) than you need two XX1 cassettes. Ouch!

More weight on rear wheel - 1x11 setup fail here as it shift even more weight onto the rear axle. A much better solution would be an internally-geared bottom bracket, even though it would require a special frame.

Guitar Ted said...

@bostonbybike: Internally geared bottom bracket? You mean like this? http://www.cyclemonkey.com/schlumpf-innovations.shtml

sniffer said...

I'm trying to decide if going 1x on my fatbike is the way? Since we have gotten some snow I'm enjoying 2x. I never used the small in summer (yes I ride my fatbike year round). But this winter it has made a resurgence...

Guitar Ted said...

@sniffer- I originally had a triple on a fat bike, then moved to a 1 X 10 set up. I could "A-B" both bikes and I knew right away that the limited gearing range was an issue. While I haven't gone back to a triple on a fat bike because of tire clearance issues, I am not in a big hurry to get into a 1X set up again either. If I did, it would be because I need the room for a fatter rear tire and for no other reason than that. The 2X 10 set up I run now is perfection in terms of gearing, and I get the benefit of keeping a straighter chain line and because of that, a more efficient, longer lasting drive train.

Smithhammer said...

Good thoughts. Currently running 2x10 on my two primary bikes. Love it and see no reason to change.

Exhausted_Auk said...

I don't even like 2X. If you want a wide gear range, close jumps between gears, and the ability to stay in one chainring most of the time, triples rule!

Zach Bonzer said...

I have run 3x9 on my Fargo, 2x10 on my Mukluk, and 1x10 on my Krampus.

I rarely use the big ring on my Fargo unless I'm really bombing down some hills. It's my "do anything" bike, so there's no way I'll abandon the small ring.

2x10 on my Mukluk is perfect (though I'm currently having some front derailleur issues). I ride dirt, gravel, and snow with that bike. That tiny ring up front comes in handy. I don't think there was anyway I would have been able to break trail with a 1x10/11 after the snowfall last week.

With all that said, I do love 1x10 on my Krampus. I have a 30T up front and 11-36 in the rear and I'm able to get up all the hills I've encountered with that setup (mostly riding in Iowa) and I have yet to drop a chain. I do race as well, and in my own opinion, I don't have to focus on shifting as much. No needing to remember what gear I'm. Shift up or down on the rear as necessary. There's the benefit of one less mechanical failure during a race, and larger clearance for obstacles underneath the bottom bracket (29+ really helps with that too).

Choosing your drive-train type should depend on your need.

james said...

Well put GT. I'm sure this article will foster quite a few comments. Single ring vs multiple ring front setups is right up there with gun control, politics and religion.

Guitar Ted said...

@Zach Bonzer: I think from a purely racing standpoint, the system Shimano has on the current XTR, where it is a one button, auto front chain ring selector type deal, is killer. I know......Di2 and all that expense, but I am thinking this will get cheaper in the future and will be the go to set up for fast, furious paced riding. It will have "One-by" simplicity in the user interface, but will have all the benefits of a lighter weight, more compact, closer ratio drivetrain. Not to mention the efficiency and chainline benefits.

Tyler Loewens said...

IMO the 1x systems on road bikes was spawned by the compact crank. How many times have you ridden with people that have a 50/34 crank that never use the small ring? Turns out that 50 is enough of a difference from the old 53 that folks now don't care to shift to the small ring. I have a good friend whose big ring probably has 5000 miles on it vs the small ring that might have 200.

Doug said...

My bikes are all over the place with drivetrains. My 10 year old Pugsley started life with a triple. It's now a 2x8. I have no desire to switch to a 1x. I use both chainrings and it's a durable long lasting set-up.

And I'm no stranger to 1x set-ups. In 1978 I raced in the Intermediate Boys USCF National Championship Road Race with a 1x5. In that age class we had a gear restriction of 89 gear inches. The standard 10-speed set-up in that day had too many overlapping gears with that restriction. So I set it up as a 1x5.

Right now I also have a commuter with a 1x14 (Rohloff IGH), Brompton folder with a 1x6 (3sp IGH with 2 cogs), a custom road bike with 2x9, and an Xtracycle cargo bike with a 3x8. I guess I'm an oddball immune to the latest marketing hype.

Guitar Ted said...

@Tyler Loewens: You know, let's be frank here- The efficiencies of a bicycle are rather high for one thing. Even most department store bikes are better than walking, in this regard. So, I'm sure you can agree that you see a lot of low air pressures on tires, people using the incorrect gear ratios on hills or flats, and those that have oddball set ups that are not based upon good physics. You know what? Some folks don't give a damn. Some folks cannot even feel the differences. Some folks aren't in it to be the most efficient they can be, or don't have any reference points to even judge that by. Bicycles, by their nature, are already better at efficiency than walking or running, despite all of the above.

For them, this discussion is a moot point. I'm not saying your friend is one of these people, but maybe.......

For those who do want to reach for the most efficient way to motivate themselves down the road/trail, what I am discussing in today's post matters.

Hope that makes sense.

As for components- Component manufacturers respond to what the dealers/brands say will sell. Not to what is the best system, necessarily. Triple cranks are not/were not well understood by the masses, so that is why they were nixed in favor of the compact double, which, in my humble opinion, is a horrible idea, and it would seem that your friend, by his usage of his compact double, would agree.

jdee said...

GT - Interesting post. I always imagined Shimano engineers shaking their heads at the recent popularity of 1X given how knowledgeable they likely are of efficiency losses and drivetrain wear.

I often wonder if part of the appeal of 1X systems comes from the fact that bikes in the last 10 years rarely came with Shimano cranks and frequently suffered from poor front shifting as a result. Add to this the difficulty many people have with operating two shift levers and the fact that 1X systems just look a lot cooler and I think it goes a long way towards explaining the move to 1X.

Guitar Ted said...

@jdee: Thanks. If you really want to know what I think is driving the 1X thing, it is this; "I think it has a lot more to do with SRAM's not having the ability to produce an effective front derailleur/front chain ring design due to Shimano's patent stranglehold."- from a Facebook comment I made on the tread for this very post.

marcusb said...

@GT While i usually agree with most of your views this time i strongly disagree as your posting seems overly polemic. Firstmost compared with a traditional 2-3x9-10 setup the difference in wear due to the more out-of-line chain line is not that huge as we're only talking about 1 ring/cog horizontal offset at max. It's not as if with a 1x9-11 setup one suddenly had to deal with a 9-11 offset, because one would still center the front ring appropriately.

Second where is the advantage of wearing down two cogs and having to replace them half as often when you don't get a discount on buying two at the same time?

Furthermore having to deal with only one vertical position in the BB area allows for A: better optimizable full suspension travel handling due not having to care for multiple force vectors from different chain rings sizes and B: the space that has been freed on the seat tube can be used for other things such as linkage points to shorten the wheel base, etc.

my 2ct, cheers

Guitar Ted said...

@marcusb: Thanks for your comments.....

On your first point: The extreme angles are going to be the lowest gear/biggest cog-smallest cog/highest gear. On a 2X set up, that chain line angle is less, therefore it will cause less friction and be more efficient. If you don't care about wear and efficiency, then please ignore this. You also do not account for the 1X systems larger cogs in the back, which exacerbates the chain line angle, since the chain now has to disengage from the teeth of those larger cogs at a more downward angle, which also increases wear.

On you second point: You are upset that you do not get a discount on buying two chain rings? This is an argument against having a 2X? You'd rather replace a single ring more often? Sorry. I can't see this as being an argument that would dissuade me from using multiple chain rings.

On your third point: Obviously, it makes suspension design with regard to short chain stays and suspension geometry easier, but there are so many great full suspension designs out there that support multiple front chain rings that this commentary is not really an issue for most riders.

Tyler Loewens said...

So I am doing some Googling to find studies on efficiency and chainline. Here is one : http://www.bikeradar.com/road/gear/article/friction-facts-free-speed-from-proper-shifting-44016/

Tyler Loewens said...

This article has a brief mention of 1x systems being more efficient http://lavamagazine.com/sram-debuts-1x-force-rival-single-chainring-roadtt-drivetrains/?cbg_tz=360

DRIVETRAIN EFFICIENCY

That clean, concise chain wrap over the chainrings comes with a level of increased efficiency. Since the chain isn’t required to move laterally on in front and experience fatigue from cross-chaining, combined with teeth designed solely for power transfer (via a deeper tooth channel, absent ramps and pins), the chain—SRAM says—rewards with a fraction of a watt (under 270-watt input) of savings with 1X compared to a 2X drivetrain. McCarthy said it’s on the magnitude of effort taken to change gears

Guitar Ted said...

@Tyler Loewens: Okay, let's first take a look at this statement (and remember, this is SRAM's marketing talking here); "The move reduced cross-chaining wear, dropped chains and drivetrain system weight."

So, let's also remember that this is for racers that don't want to have to shift their front derailleurs- Pro and Elite level folks. (Extrapolated this from the Bike Radar post as well.) IF you do what the Bike Radar article suggests, you will have better efficiency, (using their data), than SRAM claims. Who is right? Hard to say. However, I can say a few other things about the above comment.

Other than mtb guys, I just am not seeing dropped chains, (assuming a correctly adjusted system), so that is a spurious claim. Drive train weight is less because SRAM is including shifter, cables, and housings in that, which could be argued depending upon what type of system you are talking about. (Remember Lance Armstrong's downtube friction shifter?) Anyway, that could be the case for many people in terms of weight. I'll grant you that point.

The final point is very debatable. Let's keep in mind that SRAM's "Wide Narrow" teeth actually contact the chain more than a typical multiple speed crank set's chainrings would. More contact actually means there is more friction, not less, and the Bike Radar piece also agrees with this point. Furthermore, as I stated above, the chain has to pull off and downward at a more severe angle from the 42T and 36T low cassette cogs at a much worse chain ring angle than you would have with a 2X or triple. Finally, all the statements in the Bike Radar article are pretty much in agreement with Keith Bontarger's 4 rules of triple drive trains: Keep the chain on the biggest gear combination possible, Keep the chain as straight as possible, which are two.

So, while SRAM has given a nod to trying to show its system is more efficient, I'm not buying what they are laying down here. It isn't convincing. Just like their saying it is "perfect for gravel rigs", which I would say is crazy unless the event is short and you are an elite level athlete. If you'll read the article, you will also notice they hammer on the simplicity and cleaner look point, AND admit it isn't the right thing for everybody, nor will it replace 2X systems. They kind of have to say that, ya know, since their flagship electric shifting system isn't 1X, which is telling, if you ask me.

Maybe at some point I'll see some more convincing evidence, but so far, I have not.

Thanks for those links.



Rannier Wolfcastle said...

I love the simplicity of 1x on my fat bike. I used to run a double bit the front derailleur would freeze up here in MN.

I would never run 1x on a road or gravel bike. It might have the same gear RANGE, but you lose the fine tuning of having a double.

Gino said...

I must admit I didn't fully read all of the comments here, but friction facts did some tests along these lines paying attention to power, but not chain wear. Stay in the big ring until the last couple of cogs.
http://www.bikeradar.com/us/road/gear/article/friction-facts-free-speed-from-proper-shifting-44016/
I just wonder how a single ring exactly compares. It's smaller which means more rotation friction, but with its more centralized position where would it have chainline friction deficient to a switch to a doubles smaller chainring.
As a shop mechanic while watching "racers" drivetrain progess I will say the switch from XX to XX1 has been better. Those guys just wouldn't shift out of the big ring and would destroy the big cog or chainring from cross chaining. I haven't noticed the same wear rate with the XX1. Yet.
Now if I can just get some of the roadies to realize they have a small front chainring too...

One Eyed z said...

Nice post Ted!
I have 1x of a few bikes. My Krampus came stock with it and it was... OK. When I built a new commuter/touring bike (Straggler) I started with 3x9 (used the parts off my LHT) then went 1x with SRAM stuff after I set up a customers CX bike with it and test rode it. Have been very happy with it so far. 42 up front with an 11-36 out back. I've done some light touring, commuting and single track with it and been very pleased. Figure if I was gonna do a heavy loaded tour I'd drop the front ring to a 40 or smaller. But so far so good.
I was so pleased with the SRAM parts that I switched the Krampus from Shimano SLX (which I could never get adjusted quite right) to SRAM with a Race Face narrow wide front ring.
I think it a great system. I'm considering it for my CX/Gravel bike but I think in reality I should stick with 2x10 on it.
As something to sell I think 1x is a big hit simply to how simple it is. Less to worry about or think about. For some reason front shifting is the place where may people struggle. I have a customer who is considering switching to 1x simply because he perceives it as being easier to deal with.
I remember when we were converting everyone's CX bikes to 1x9 because it was the thing to do. Then we were back to 2x10 stuff because it was "better" and now here we are at 1x again....