# Reasons against using a single chain ring?



## CAT4ever (Sep 1, 2005)

I have a frame and fork and wheels (Ridley, full carbon, tubbies respectively)... and am getting ready to pull the trigger on the build kit at the team shop. But...

Are there good reasons to not go with a single chain ring up front? 

This is my only hesitation about the build. I have never used a single chain ring up front before. On one hand, racing the past, I rarely used my bigger chain ring. If I did my math correctly, it will also save about 1/2 lb. It also seems simpler. On the other hand, it is well so different..

Any input?

(I am planning on mixed chorus/centaur with a 42T and 13-27 with a back up 12-25 for fast courses - of which there are several in CO.)


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## Vegancx (Jan 22, 2004)

You probably won't save much weight. 

Sometimes even with the 27 in back you'll be overgeared. 

In a sprint finish, you'll likely be undergeared.

Do you like mashing the pedals at 55-60 RPM? 

A few folks who were vocal about single ring set ups have recently gone back to doubles. 

All that said, I love my single ring set up, and it's unlikely I'll be going back to a double anytime soon.


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## CAT4ever (Sep 1, 2005)

*Gear Ratio follow up*

So, in the past, the lowest I have gone is a 39T-26 combo. How different is that from a 42T-27? Would I really be overgeared?


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## Vegancx (Jan 22, 2004)

CAT4ever said:


> So, in the past, the lowest I have gone is a 39T-26 combo. How different is that from a 42T-27? Would I really be overgeared?


It's hard to know without knowing the courses you ride and your personal strengths. 

I'll say that if you like to maintain a fast cadence, going with a single ring will tend to make you muscle through difficult sections. 

I'm a pretty decent 2/3 cross racer, and I find I can ride everything with a 42 x 27, but there have definitely been some muddy races where a 39 or 36 would have been handy.


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## Kram (Jan 28, 2004)

A 42x27 is 1.5 gear inches taller. Not much.....FWIW-I used a 39x27 last year and was able to climb the nasties (and I prefer to spin). I wasn't esp strong last yr so I think you'd be fine.


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## roseyscot (Jan 30, 2005)

i've passed many a racer in the b's on steep hills because i was able to use my 36 while they struggled in a 42. i vote for the double (36-46) without a doubt. plus i don't think campy makes a 13-27 so you will probably be stuck with either a 13-26 or a 13-29.


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## CAT4ever (Sep 1, 2005)

*Double is sounding good.*

It's what's worked in the past. But any thought on 46-39 vs. 46-36? I am not sure that I would need the 36 necessarily...


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## welcomdmat (Jan 1, 1970)

I have found that I can turn a 46 in most situations and last year ran a 46/36 with a 12/25 in the back. This year I am going to run a 46/38 to give a few more options in the area that I like to turn the cranks. All of these gearing decisions though boil down to where you live and what kind of rider you are. If you are a masher who lives in a flat area, you can get away with a big gear setup. If you courses are usually very hilly or muddy or sandy or you like to spin alot, another gearing selection may be better. For the most options, the two ring setup with 3 or so different cassette combinations that you could throw on is a setup that I have found sucess with.


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## dyg2001 (Sep 23, 2004)

Last year I ran a 40x12-27 for every race and never felt undergeared and only felt a bit overgeared in one race that was all really deep mud (I am 185 lbs and race Cat 3 & Masters 30+). For that muddy race I should have taken 5 minutes to swap the chainring for a 38. When I did group road rides with the cross bike at times I was undergeared and had to spin like a mofo to keep up. According to Sheldon Brown's handy gear calculator (http://www.sheldonbrown.com/gears/), if you sprint at 120 RPM with a 40x12 gear you will be going over 32 MPH. If you find that you need to go faster than that in a cross race, you can use a 42 tooth single chainring with an 11 small cog and go 37 MPH at 120 RPM. 

One drawback of a single chainring drivetrain is that if you crash, your setup for keeping the chain on can go out of alignment, which can lead to more problems. Last year in a race I crashed and the chain dropped below the N-Gear Jump Stop. It took quite a few seconds to get the chain back on, and then the Jump Stop was no longer adjusted right, so I ended up dropping the chain again twice later in the race. Of course, if you run a double chainring drivetrain and crash you can have other problems, like a broken front shifter that won't let you shift out off the big chainring. If that happened on a course with a climb you would be cursing. 

This year I am considering leaving the 40x12-27 on one of my cross bikes, and setting up a second bike with something like a 44/38x12-27.


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## CDB (Oct 20, 2005)

I have two setups on my bikes... one bike has a 40 and the other a 42, both single ring setups. I choose a 12-25 or 12-27 wheelset and mix and match those 4 combo's depending on the course. I've found that if I'm needing an easier gear than a 40x25 or 27, then I'm going to be faster running. For me personally, being taller and having a running background, at that speed, running is not as much of a burden. It might be for someone else. If you have course designers in your region that make you ride straight up long steep climbs and don't enable you to go fast for long spells, maybe a 36 could be useful for YOU. Those designers are really making mtb courses if they do that. Traditionally, cross is more fast paced and flatter in general, with lots of transitions and speed changes.

Weight-wise, you'd save a bunch due to not using a sti left shift/brake lever (use a non-sti left lever), plus the minimal weight of the chainring teeth on the big ring. You'd have a slightly lighter setup using a single outer guard and a 3rd eye inner chain watcher. Using the outer ring position for the guard, and your inner ring position for the toothed ring will enable you to have a better chainline while climbing too. (Imagine using your big ring and the big cog - bad). When using the second method of singlering setup, that where the chainring is sandwiched between two guards, your chainline is inferior (in my opinion). It is also more susceptible to clogging if the mud had significant amounts of grassy debris mixed in. (I actually beat Carl Decker in one race simply because he had grass packing up in his "double guard sandwich" setup and I had used the "single outer guard, inner watcher" method.)

One advantage of using a double ring setup, standard w/ a front derailleur, is that sometimes a course will have some long fast sections of asphalt. Unless these sections are longer than about 1-2 minutes of continuous pedalling w/o turns and braking, you'll be fine w/ a single. A second time where a double ring setup can be a little better is if you might be riding in quite muddy conditions and the muck packs up around the chain/cassette. Generally the muddy chain operates better on a larger cog in the back. If you use the big ring and a larger mid to high cog in back, you're running a similar gear to if you are in the small cog w/ a 40. If you need to sprint, you might be forced to shift up into a larger gear and spin to keep up w/ the pace. Of course, generally, if you need to be pedalling THAT hard in THAT MUDDY of condtitions, something seems odd.

One other advantage to using a double ring setup is for doing training rides mid week. If you're using your cross bike on the road, using slicks and are trying for intensity, you will be undergeared for flat roads. To get around this using a single ring, I just train my intensity on hills where the gearing is harder. Since training in the fall while working full time generally means night time riding, hills are safer anyways because the speeds are lower. You'd have to get rolling pretty darn fast on the flat roads to match that kind of effort, and when it's dark, that's a good way to get creamed by a car.


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## eyebob (Feb 3, 2004)

*I ride a triple.*

I've got 10 cent legs and it takes a triple sometimes to be able to climb the steep pitches. I know for a fact that it helped me finish one race last year several spots higher than if I had to run up the hill.

I'd go double. 

BT


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## argylesocks (Aug 2, 2004)

are most people with a single fine with a 109.5 BB, or do you need to go to 118 for the alignment?

also, i know you cant see the front ring... but how do you keep it clean with a double guard setup? is it hard to get in there & clean it?

thanks


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## allons-y (Nov 15, 2006)

argylesocks said:


> are most people with a single fine with a 109.5 BB, or do you need to go to 118 for the alignment?
> 
> also, i know you cant see the front ring... but how do you keep it clean with a double guard setup? is it hard to get in there & clean it?
> 
> thanks


i use whatever normal shimano double BB is fine. alignment prbly could be better, but it works and im cheap. 

as for cleaning, an old toothbrush or other small brush works fine. just pop the chain off (take the rear wheel off), stick it in there, spray on some degreaser, and spin the cranks. rinse with water, and it'll be shiny as new......


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## CDB (Oct 20, 2005)

It all comes down to your particular frame situation. They are all different and each frame manufacturer pays different levels of attention to those kinds of important details. It depends on how much space between the outside right face of the chainstay around the rings. When I rode for ALAN a few years ago, a 40t ring in the inner position was as big as I could go w/ my "shi shi" italian bikes. Two supposedly identical frames even had different amounts of space. Certainly I was not able to use an inner guard. The chainline sucked. With a standard double 109, even a 40 wouldn't work. A triple width bb at 118mm gave me terrible chainline and it would just rip the chain off the ring to the inside when I put it in the largest cogs. That was even while using the chainring in the inner ring position. I ended up using an xtr 112mm and a 39 or 40. I'm talking 9spd. octalink style cranks/bb, by the way.

With my Specialized frames now, I have amazing chain line, plenty of frame clearance, and a standard width double bb works just fine w/o any chance of chainsuck!


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## argylesocks (Aug 2, 2004)

CDB said:


> and a standard width double bb works just fine w/o any chance of chainsuck!


awesome, thanks guys. everything is ordered & im headed to the 'single scene' next week. my gf even ok'ed it


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## FlynRide (Feb 26, 2005)

I just set mine up with a 118.5 BB and the chainline works great. Specific to my frame: Serotta TIG 853.


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