This post addresses bicycle crankset compatibility in terms of mixing various speed cranksets with other components. For example: an 8 speed crankset on a bicycle with 10 rear sprockets and a 10 speed chain (a), or a triple chainring with a front derailleur (FD) constructed for double chainrings (b). It will also address mixing road cranksets with MTB FDs and vice versa (c).
Before you start, to avoid any misunderstanding:
please take the 5 minutes needed to read the compatibility articles use instructions.
Separate posts explain: standards of bottom bracket (crankset) bearings (and axles), as well as bottom bracket compatibility). That will not be taken into consideration in this post, but when acquiring a crankset, make sure that it’s bottom bracket (BB) standard is one that can be mounted on the bicycle frame.
In the post about FD compatibility, other factors important when matching FD and crankset are described. So, even if number of speeds and type of crankset and FD are the same, those factors should also be matched. In short: FD cage shape and number of large chainring teeth it is designed for should match the teeth number of the largest chainring on the crankset it is combined width. Detailed explanation of things one should pay attention to and try to match are listed in the post:
Compatibility – front derailleurs
1. Different number of speeds for crankset, and the cassette
Typical example: can a crankset for 9 speeds be used with a bicycle that has 11 speeds (rear sprockets) and an 11 speed chain (for 11 sprockets)? Or vice versa: can a 10 speed crankset be used on a bicycle with 8 speeds?
All the “speed” chains have almost the same inner diameter (roller width). Despite the fact that chains for more speeds have thinner plates and are therefore narrower (on the outside) than chains for less speeds, the inner width is the same. For detailed explanation look here: Compatibility – chains.
Because of this, teeth thickness of crankset chainrings doesn’t vary much. Also, adjacent crankset chainrings have great difference in diameter and are not as tightly spaced as rear sprockets. So there is no risk of chain, being to wide, to get stuck between two chainrings.
All this enables crankset chainrings to be freely combined with all kinds of chains (and, over the chain, various numbers of rear sprockets). The only complication is the thinner cage of the FDs designed for more speeds. This means, if using a (wider) chain for less speeds, chain will rub the cage with less cross chaining then if a wider cage FD was used. Cross chaining is not advisable anyway, so one can consider this and early(er) warning. Explanation of gear changing and cross chaining is here:
Bicycle gear ratios
Exceptions to this are single speed chainrings, made for wider, 1/8″ thick chains (they won’t work with multi-speed chains) and Shimano IG chainrings (that work only with chains for up to 8 speeds).
2. Mix-matching various types of cranks (chainrings)
2.1. Combining double chainring cranksets with triple FDs
Explanation of important attributes and differences of FDs can be found in these posts:
Front derailleur
Compatibility – front derailleurs
Triple FD has a longer cage (than a double FD), with inner part of the cage being a bit lower, to catch the chain off the third, smallest chainring. If the two chainrings of a double don’t have a big difference in number of teeth (14 or less), triple FD should work just fine on a double (with correct setup of the limit screws and cable, of course). Typical examples are standard road doubles 53-39 (14 teeth), or 46-36 (10 teeth) – a typical cyclo-cross crankset.
If using a popular “compact” crankset, with a large difference in number of teeth between the big and the small chainring, like 50-34 (16 teeth), or 46-30, shifting will be slower, with more possibility of dropping the chain when shifting onto the smaller chainring.
However, even if chainring difference is large, front shifts are usually quite rare (compared to rear shifts), so even then it might work acceptably well (depending on one’s criteria).
2.2. Combining triple chairing cranksets with double FDs
The biggest problem with this combo is that double FDs don’t have a long enough cage, with inner part lowered enough to catch the chain off the smallest, third chainring.
The quality of this pair functioning is affected by the following two factors:
- The lower the difference in teeth number between the largest and the smallest chainring, the better.
For example: 48-38-28 (20 teeth difference) is better than 44-32-22 (22 teeth difference).
Or: 50-39-30 (20 teeth difference) is better than 53-42-30 (23 teeth difference). - The number of large chainring teeth the FD is designed for should match the number of teeth of the largest triple chainring, or be slightly lower.
For example: FD for 50 tooth chainring on a 50-39-30 triple.
Or a FD for a 46 tooth chainring on a 48-38-28 double.
Bad idea is a FD for a 53 tooth chainring on a 44-32-22 triple.
2.3. Combining MTB cranksets with road FDs and vice versa
Road and MTB cranksets have slightly different chainring spacing. Still, this doesn’t cause much problems even to shifters and FDs when mixing them, as is explained in these two posts:
Compatibility – front shifters
Compatibility – front derailleurs
Difference definitely doesn’t bother the FDs. If the shifter, cable and screws for limiting movement are properly set, there won’t be any problems.
Related post – Bottom bracket compatibility:
Compatibility posts are also available in eBook (printable and Kindle) and paperback editions on Amazon:
If you have any questions (or additions and corrections), please use the BikeGremlin forum’s compatibility section:
https://www.bikegremlin.net/forums/bike-compatibility/
The existing comments posted under this article (questions and answers) have been moved to this BikeGremlin forum thread:
https://www.bikegremlin.net/threads/compatibility-09-cranks-ets-article-comments.119/
Hi Relja,
I am finding it hard to find an FD for my triple chainring with the largest ring being a 44t to a 9spd cassette. There seem to be a few which specify 40t maximum. Would using this work or should I keep looking for the correct size?
Many thanks,
Paul.
I would try to find the closest match and see what can be done.
If the only option is “unmatched”, I’d choose larger, rather than smaller (again, if available and unless it’s not way off in size).
That is, for a 44 chainring, I would try with 48 T FD, before settling with a 44 T FD.
The closer matched it is, the better it works, usually. But it can work quite decently, depending on the particular setup and one’s criteria.
Hi Relja,
as I thought, but was hoping otherwise! I’ll just have to keep looking, although I’ve not found anything larger than a 40T so far. The retro bikes are a bit of a labour of love I guess. Many thanks for your help.
Cheers,
Paulus.
Have you tried asking in bikeforums.net?
It is the contemporary aggregate of human knowledge of cycling and bicycle mechanics.
That is: no one person knows everything, but there’s always someone who knows. 🙂
I’m not sure what mount your frame uses, but if it is “retro”, I suppose something like this could fit, just choose the appropriately sized clamp:
Out of stock at the time of checking: model 1 (it’s marked 6/7 speeds, but should work with 9 speeds, 42 teeth max size).
Model 2 – “9 speed”, 40 T max chainring, just confirm that the seatstay angle is matched as well (this one is for 66 to 69 degreees). Also out of stock at the shop, when I checked. Comes with adapters included, for 28.6 and 31.8 diameter tubes (34.9 without adapters).
Hope this helps at least in pointing you in the right direction.
Relja
Awesome, will check those out. I may yet be able to repair my existing one. I could also look at upgrading to a modern drive train too. Just keen not to overspend if possible. It’s an early 2000’s gt i-drive 2 btw. Good bikes in their day. Remembering past glory!!
Cheers,
Paul.
Forgot to mention the local (Serbian) 1st choice for components: look at the 2nd hand market, broken frame donors etc. 🙂
Getting a new drivetrain is also a viable option. Just a note – my personal opinion and experience, from a point of view of an avid cyclist, not a competing one where each split-second counts. Not directed towards you (or anyone else in particular), but when I hear “upgrades” (and I hear it a lot, it’s really pushed on by marketing), it often makes me consider the “real, objective needs” – let me explain:
When bicycles are in question, “upgrades” seldom improve (upgrade) anything, or, a bit differently put: not all the upgrades change anything for the better for the user.
They do increase the budget (amount of money spent), so are very beneficial to bicycle (component) manufacturers.
They also often make maintenance more complicated, or at least require different tools and that’s how upgrades bring more business to bicycle repair shops (but also increase their expenses for tools and even storage, mechanics education etc.).
I’d even argue that most improvements that came after the introduction of “threadless stem” (also called a-head) have been mostly to benefit manufacturers.
(This paragraph does relate to your question)
I wouldn’t shy away from sourcing 2nd hand derailleurs, as long as they’re in good shape.
Front hub of the bicycle I rode to work today is from 1974, or 1975 at “best”. 🙂 Friction shifters and derailleurs from the 80s. Frame from who knows when. It rides very nicely, shifts, brakes – what more would I need / ask for? Have at least one more set from a thrown away bicycle, so if any of the drivetrain components get damaged, donor parts are waiting.
It’s about riding, about joy of going faster than on foot, but still experiencing and feeling every scent in a forest, every, even the smallest incline and down-slope (on a bike you feel and appreciate those better than you do on foot 🙂 ). And about improving the “engine” – for challenge, fun and health. The bike itself is good as long as it steers, brakes decently and is the right size to not cause discomfort.
Many people I see worry too much about the bike.
Of course, having said all that, I fully understand, enjoy and appreciate the whole process of bicycle maintenance and, especially, bringing an old, thrown away bicycles back to life. See nothing wrong with that as long as one enjoys it. Likewise, I see no problem with buying the newest, most expensive frames and components – as long as one feels good about it (and can afford it). Just that I don’t consider those things real “upgrades”, they are often a purpose in and off itself. Call me a retro-grouch, conservative.
Sorry for the long “rant”.
New shimano GRX RX810 front derailleur allows 17 teeth difference and It looks like a triple front derailleur. I think someone should give a chance
I currently have a Sora FD and a Sora 50/34 crankset, and a 9v 12/36 cassette with Deore RD.
A close friend of mine would give me an FSA carbon crankset at a very convenient price but this is for 10/11 speeds. Do you think it will be compatible with the setup I have?
When talking about cranks, there are several things to consider, I’ll start sort of “from the ground up” – hope you won’t mind if I state some things that are obvious and you have already checked – I think this way is safer than telling you to “just go ahead”, then figure out it doesn’t really fit.
This is all with an assumption that your current setup is shifting nicely.
Things to consider:
– Bottom bracket – does the FSA crank fit your current bottom bracket? If not, is there a compatible bottom bracket for that crank that can fit your frame?
– Chainring size – FD that works well with 50/34 will handle 52/39 with no problems, as well as 46/30. But going below 45, or over 53 on the big ring, as well as going below 30 on the small ring might make shifting a bit slower.
As far as the speed count is concerned, the fact that crank is 10/11 speed one is not a problem – at least in my experience (though, just as a disclaimer, I haven’t tried the combo with an FSA cranks, only with Shimano). Yes, 11 speed cranks usually have chainrings put at a slightly larger distance from each other, yet I haven’t seen that affect shifting – think it is done primarily for a better chainline when riding in large-small, and small-large combos.
PS – this is my personal opinion:
Sora is a great quality groupset and I wouldn’t go out of my way to replace it unless the chainrings are worn, or the cranks are damaged. Of course, going “lighter and stiffer” at a bargain price doesn’t sound bad. Still, unless one is competing, there’s really not all that much to gain in my opinion.
Thanks so much this clarifies a lot.
Agree Sora is a great group, I was just evaluating my friend’s offer but thinking twice I’d rather save for a new wheel set than in a new crank set 🙂