Mechanical Mondays: Single or Double Chainrings?

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double-fsa

To single or double? Let Daimeon show you how. © Daimeon Shanks

Thinking about what to do about your chainring this season? We’re looking back at an oldie-but-goodie Mechanical Monday that delves into the pros and cons of single and double chainrings.

Daimeon Shanks, pro mechanic and co-owner of The Service Course repair shop in Boulder, Colorado, has compiled his list of must-haves for the cyclocross pits. Prepare for the races ahead with a pro setup that’s sure to see you through to glory. Once you’ve read Shanks’ advice, check out our chainring breakdown in Issue 10.

by Daimeon Shanks

Single or Double?

There is a myriad of options for cyclocross bike setup. Choosing the correct equipment for your riding style, personal preference, and racing situations can be both befuddling and infuriating. Unfortunately, there’s no such thing as a ‘right for everyone’ setup – ask 10 people and you’ll likely get 10 varied answers.

Deciding between a single or double chainring setup is probably one of the decisions that people feel the strongest about. It can greatly affect all of your other equipment choices including, but not limited to, the shifters, front derailleur, bottom bracket, rear derailleur, and cogset.

I’m not going to go on record as a proponent of one or the other; I think there’s a place and time for both. Deciding on your best option is basically that: your decision. So here’s an overview of the two setups and their respective benefits.

Single Ring

 

The racer’s setup. A single ring upfront limits your gear combinations, but for most race situations, one chainring with a 10sp cassette gives you plenty of options.

pauls

Be sure you've got all the gears you need. © Daimeon Shanks

Probably the most common combo is a 42 teeth chainring and an 11-27 cassette. Just large enough for a tolerably good sprint, but small enough to slug through a muddy pit. Or if you’re just not that fit, as is my case.

There are two main benefits to a single ring setup: simplicity and light weight. It’s simple, as you no longer have to worry about front derailleur adjustment or left-handed shifting, and much lighter as you get rid of a front derailleur, cables/housing, and a left shifter.

The front derailleur keeps the chain on the chainrings during the bumpy stuff, so to run a single ring something else must be used to keep your chain from dropping. Obviously.

Some people run a chainguard both on the outside and inside of the chainring. To accomplish this, you must use a chainring bolt kit made for a triple crankset and spacers to keep the inner guard off of the chainring. Sometimes the inner guard needs to be smaller than the outer to accommodate the curve of the chainstay – as is the case for Allen Krughoff’s Ridley X-Fire.

k-edge-single

The K-Edge is a popular option for single-speed set up. © Daimeon Shanks

More common is the combination of an outer guard and an inner ‘chain keeper’ that basically prevents the chain from falling to the inside. Some, such as the K-Edge single ring keeper, have a lip that folds over the top of the chain to prevent it from coming off in the really, REALLY bumpy stuff.

Lastly, Paul’s Components makes a chain keeper that sits over the entire top portion of the chainring to keep the chain secure. Sort of a lighter version of a downhill chain keeper.

pauls

Paul's chainring guard wraps over the top. © Daimeon Shanks

In my experience, the K-Edge setup is the most secure (and best looking!), but, as with all things, you pay for what you get. The Third Eye chain keeper and a Salsa outer guard is the most economical bang for your buck. If you’re really cheap, you can even make a homemade chainguard out of an old chainring that you may have lying around – as long as you have a good file and some patience!

Double Ring

 

Doing a head count at the local ’cross race this last Sunday, I found that the double ring setup is much, much more popular than the single. The reason for this, I believe, is that almost all stock cyclocross bikes are sold with a double setup to make their bikes more utilitarian. Most average racers simply don’t mess with their componentry much when they’re purchasing an entire bike.

double_k-edge

The K-Edge adds a little extra insurance to a double ring set up. © Daimeon Shanks

Having a double DOES make the bike much more employable after the (regrettably) short ’cross season is finished. Many racers I know will throw on a pair of standard road wheels and some fenders and make their ’cross bike into a winter training bike. Or even an everyday commuter. The slightly higher, less aggressive geometry and comfortable ride qualities make cyclocross bikes great for putting in the long, slow early-season training miles.

The downside to having a double is that front derailleurs just aren’t designed for the smaller chainring sizes found on ’cross bikes. Chainring combos typically run around the 38/46 tooth range, but rarely will serious racers use anything larger than a 48. Even a front derailleur designed for a compact (such as FSA’s or Campy’s) will not be able to be positioned low enough for the derailleur cage to clear the chainstay. Therefore, the front shifting isn’t that great, no matter what you do.

di2_k-edge

The Di2 has a powerful motor, so watch out! © Daimeon Shanks.

The obvious benefit for the ’cross racer is the added gear range. You effectively double the amount of gears you can choose from during a race (yes, I know there’s some overlap, but I’m no Sheldon Brown, so don’t go there…).  Does it matter? Depends where you race. Take your local race scene into account and decide if you really need the extra gear range.

Because of the poor front derailleur position on cyclocross bikes, it’s usually a good idea to use a chain keeper in combination with the derailleur, especially if you’re using Di2 as the motor that pushes the chain down is quite strong. Third Eye and K-Edge both make great chain keepers that work great with a double setup for extra security.

 

 

Cyclocross Magazine, Issue 22, Print and digital subscriptionsHave you subscribed yet? You're missing out if not. Get all-original content and your cyclocross fix throughout the year with a subscription and Issue 23 back copy, with features on Lars van der Haar, Jonathan Page, Elle Anderson and more!
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24 comments
kibail
kibail

I've been running a 34/42 and 34/44 chainring set up with a Sram Rival Fr Der. I'm able to get the traditional fr der set up specs of 1-2 mm above the chainrings with no problem. 

JP55
JP55

What about CLUTCHED rear deraileurs?

 

In articles about SRAM's upcoming XX1 it was stated that the system will work with a single ring and would not 'need' any type of chain guide because the clutch can keep enough tension on the chain to keep it on.  I am currently running a 42t single with a 11-36 cassette and want to switch to a Rotor Q-ring up front.  Instead of adding an outer guard and an inner keeper, I'm interested in getting a short cage X.9 TYPE 2 derailleur, which would actually cost about the same as the guards.  I'm also not sure how the clutched derailleur would work with the oval ring...?

bill
bill

I'm still running the sora FD that came with a 50/34 crank, now with a FSA 46/36 with a 11-26 rear. I thought it would be a real bodge fit, but it actually shift the smaller chainwheels better. Still trying to find a chain cather that will fit, pretty close between the pulley and the FD and the BB. The only drop I've had is from once dropping the bike during a remount. I am a East Coaster and don't see much mud. As a newbie crosser, I have to pretty much run what I can afford, so I'm still rockin Sora the shifters, which have been crashed and packed with sand, and washed out with a hose, and still seem to work. I considered going single, but the cost is close to what I could buy 105 shifters for.

Nolan Van Dine
Nolan Van Dine

What about a triple? I use a older (2006-ish) Shimano Ultegra road triple which I re-geared to a 42-35(I think)-26. I only adds 100g max.

Richard Allen
Richard Allen

Even a front derailleur designed for a compact (such as FSA’s or Campy’s) will not be able to be positioned low enough for the derailleur cage to clear the chainstay. Therefore, the front shifting isn’t that great, no matter what you do.

I must be missing something here - I've never experienced any problems with front shifting (Campag 46/39) or chain drops though obviously that's anecdotal evidence. Are the problems somehow related to the shift geometry of the mech being optimised for a larger outer chainring? I can't see how the front mech "...will not be able to be positioned low enough for the derailleur cage to clear the chainstay" in fact this just doesn't seem to make sense. Could someone clarify for me?

One thing that I found when I ran a single ring recently was that it was difficult to get a good chainline one extreme of the block or the other depending on whether I chose an inner or outer position for the chainring. Most modern BBs don't allow chainline adjustment though I suppose I could have 'shimmed' the ring a bit but in the end I reverted to a double set up.

Cheers Rich

Philip Glowinski
Philip Glowinski

A lot more than 2g came out of my left hand ergo when I gutted it! My 1.X copy is almost identical in weight to the centaur mech it replaces and it doesn't require a chainguard, saving 100g or so. The chain is also shorter and there is no front mech cable (quite a lot of steel in those bad boys). The total saving is over 200g, around 1/2 lb.

I agree, that it is not enough weight saved to to warrant getting rid of a double set up, but if you are doing it for other reasons the saving is a definite advantage.

AB7
AB7

i need a lot more convincing on the merits of this "lighter" argument.

sure, a brake lever is SLIGHTLY lighter than a brake/shifter lever. about 2 g for sram s500 vs force, one of the most common levers on the course. no derailleur saves 89 g for a force FD. you add weight back for the chain guard on the inside, 23 g for a k-edge. swap a chain ring for an outer chain guard, no net change in weight. i'll give you the single saved shift cable and housing. what, 25g ?

so that's what, a savings of roughly 93 g, a little more than a pack of shot blox.

i just wouldn't personally make the decision based on weight. if you lived in portland, maybe the mud performance would be the deciding factor. but here on the east coast a double is worth it for all the reasons others have listed.

Philip Glowinski
Philip Glowinski

I've converted my #2 bike to single front this year. It needed new chainrings so I thought I'd use a 39 I had in the garage and buy a Superstar components guide (similar to an MRP 1.X).
The guide is designed for MTB cranks so needed some filing and careful setup to work with 130bcd, however it seems to work great now, with just a tiny bit of rub when using lowest with a 29 sprocket. I've used it in anger once and loved it. 11-23 will be fine for early season fast races, with 13-26 most of the time and the 29 when it's muddy and hilly. I'm tempted to do the same to my #1 bike for next season as running campag and full length outers I can change many sprockets at once and my gears seem to always work!

jonestim
jonestim

Another thing about the double is it gives you more shifting options when your cassette gets so clogged with mud that you only have a couple cogs left. I had one race this year that I was down to two of my 10 cogs, but by having a double I still had four gears.

pdxvelo
pdxvelo

I ran a single ring for 3 years in the B/ A Cat prior to entry into the SS category. I found that the single 42 tooth ring w/ two FSA chain guards prevented ALL chain ejections. A single FSA guard and 3rd eye also work flawlessly. The single ring is superior for mud and debris build up. There is far less stuff for mud to accumulate on. Unless the course has LONG sections of flat or down pavement, a single ring will always suffice. Its lighter, less prone to dropped chains, and works better when covered in peanut butter mud.

@swinborne
@swinborne

I'm in my third year of racing on a single 42 with an outer guard and a third-eye. While the simplicity is great, and for the most part the gearing accomodation of the courses, the occasional drop + hang up underneath the third eye and resulting 5-10 spots I give up while trying to fix it has finally pushed me into upgrading to a double.

The other advantage point to a double not discussed here is the speed at which you can throw it into a high gear without having to run through your whole cassette from bottom to top, handy for those sprint finishes or gap opportunities which begin just after a brutal climb or other low-to-high gear quick transitions.

Josh snead
Josh snead

I was surprised to read that a problem with the double setup is poor shifting- it certainly doesn't have to be! I've been running Dura Ace 7800 Shifters, derailleurs, cranks, chain and chainrings (39/46, with a 46t DA ring and DA 12-25 cassette) and it shifts at least as well as when I set up the same stuff with a 39/53 on my road bike in the summer.

I prefer this double setup (in conjunction with a Deda dog fang chain keeper) for it's fool proof reliability. I've had chain troubles so rarely that it's really not something I think about anymore.

The other benefit of the double is that if the chain does somehow bounce off, you can shift it back on with the from derailleur without stopping.

Another variable that wasn't mentioned and is critical to both setups is chain length. The chain should be as short as possible- this is often the easy solution to a drivetrain that is dropping chains often.

ODB
ODB

Any advice on where to get 110 BCD cross sized chainrings?

I have found that it is nearly impossible to find a good 10 speed compatible chainring with ramps/pins for shifting in compact 110 BCD size. Bike shops don't have them in stock. Every online store is either sold out or doesn't have them. I was forced to pick up an unramped Sugino chainring for a big ring. It shifts OK but not great. Any tips on what brands/types of chainrings work well with 10 speed SRAM in the 42 to 46 tooth range?

Pfeif
Pfeif

As the neutral support mechanic for the cross crusade series, I have to weight in on the Paul's. Even when properly set up the Paul's will drop a chain, how I don't know it looks fool proof, but each week I had a few people come into the pit with a dropped chain. Once the chain is off there is no way it's going back on unless you start to dismantle it. I too agree with Erik, with some of the set-ups I have seen this past season It's not about weight as the riders are adding so much junk to keep the chain from coming off. I personally run a 42/39 set up as a single ring with a FD with STI and cable. I never shift the FD, the 39 acts as an inner chaingard. I did drop the chain at a race but quickly got it back on and regained my lost position. This beats having to run to the pit and asking for a tool.

A dropped chain will happen, it's the ability to quickly solve it that will save the day.

Cyclocross Magazine
Cyclocross Magazine

Hey Erik, you know we're a fan. Everyone has their own reasons or opinions, but lots of folks do like the simplicity (mechanical or mental) of one ring, or the weight savings. You may like it for not dropping chains but many folks yell back that many people, unless set up with double guards, drop more chains on a one ring set up than a double. Thanks for reading Daimo's article...how about sending in your own article as a response? We'd love that.

erikv
erikv

The main positive for going single ring is not saving weight or simplicity. It's to keep from dropping your chain! I yelled this at the magazine in issue 10 (I think it was 10) but nobody heard me. Maybe now you can add it to the article.

Raycarlking
Raycarlking

@JP55 have you tried out the q ring with the type 2 rd?! I wanted to do the same. Thanks!

Mark
Mark

I was wondering about triple as well. I am building up cross and debating the options. I waas going to go single for simplicity, but i also have a triple. I was thinking, if race and stay in the 39, it will not fall off on the out side, and if it were to fall off on the inside, it would fall to the 30 and i could shift to recover to the 39. Then if i wanted to ride single track, i would still have the granny 30. No?

Cyclocross Magazine
Cyclocross Magazine

Good points AB7. The thing is that not all readers don't have that nice of a setup. Singlering is often a big attraction for folks unsatisfied with their current setup. sometimes that's because of bad adjustments, but often it's because they're looking to upgrade an older or low-end component setup. buy a bike with Sora or Tiagra? it's 300 grams vs. about 120 grams. almost half a pound for one shifter. Front derailleur and ring vs. two BBG superlight guards? Still lighter. Not everyone is riding a Force bike...people with new, race-worth steeds are not always the only readers.

GregA
GregA

Concur entirely with Josh. I have been running double for 8 seasons. My set up has been either Ultegra or Dura Ace, 9 or 10-speed and either an FSA 36/46 or 38/48 and 12x27 cassette. I have had no chronic front shifter problems.

I run a compact on one of my road bikes and use a compact front derailleur. I have always assumed a standard front derailleur is no problem on the cross bike due to the 10 tooth difference in rings as opposed to a 16 tooth difference on the road bike.

mblock
mblock

I run 42/34t and currently use a Salsa 42t (110 BCD) for outer ring.  It is not ramped or pinned but it does shift okay.  I plan on getting a Thorne Koksijde ring from Cyclocrossworld.  They are ramped and pinned and come in 42t thru 46t combos in both 110 BCD and 130 BCD.

comptonius
comptonius

I used a triple on my first CX Frankenbike.  I'm in Colorado so we don't see much mud but do get a fair amount of climbing thrown at us.  I rarely if ever used the granny so I used the limiting screw to lock out the gear during the race season.  worked great.

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