The HOLLOWTECH II bottom bracket system has made changing cranksets less complicated. After a brief introduction to this system, I discuss current Shimano MTB crankset options.
HOLLOWTECH II cranksets have the bottom bracket (BB) axle fused to the drive side crankarm. While the non drive side crankarm attaches to a splined region of the axle using pinch bolts. The advantage of this system is that the BB bearings are externally mounted to the frames BB shell. Consequently the BB axle can be a larger diameter, making it stiffer and lighter and replaceable sealed bearing cartridges can be used with some bottom brackets. I use the Hope bottom bracket to avoid the one fault of some HOLLOWTECH II bottom Brackets, premature bearing failure.
Previously other bottom bracket standards such as with Square taper and OCTALINK had separate axle. Consequently, these are called three-piece crankset. Changing your crankset often needed a different bottom bracket axle length to achieve the correct chainline. This process was normally accomplished with a trip to your local bike shop.
The process of changing the HOLLOWTECH II crankset is simple enough to do at home. Daniel Lloyd shows you how in this GCN video ‘How To Change Your Chainrings and Cranks‘
Shimano Crankset Trends
Currently single chainring cranksets are driving the development of ever wider ranged cassettes. The SunRace MX3 and MS3 10-speed cassettes have 11-42T options, but 11-46T options are available from Shimano. On my hybrid bike my current cassette is just 11-28T, which is fine for my commute, as I still have a triple crankset up front.
While triple cranksets seem to have gone out of fashion they are still common place and are a great value way to upgrade to a HOLLOWTECH II system. Like many other people I’m planning to experiment with a single speed crankset. I’m going to modify my Alivio FC-M4050 triple to a single by removing the three existing chianrings and adding a narrow-wide chainring to the middle chainring position.
While I suspect many people have been going for 1 x 10 speed setups, if the glut of 2/3 speed left Deore and SLX shifters on eBay are anything to go by. I am perhaps stupidly considering a 1 x 9 speed drivetrain.
In the long run I might find that a double crankset is the best of both worlds for me, but time will tell. I have bought a spare Sora crankset from eBay and ordered a road compatible left hand shifter. Just to be prepared if my experiment fails.
Shimano Cranksets Available in 2017
This week I have gathered as much info from the Shimano specifications website about MTB cranksets. I found the data initially a little hard to digest. As I am a bit of a geek I though it might be useful if I crunched the numbers for you. I ended up writing a computer program in a language called Python, which turned out to be fun. I can recommend Codecademy if you ever consider learning computer programming.
Shimano Single Cranksets in 2017
I found 39 single cranksets in production for 2017. The minimum chainring size is just 30T and the maximum a whopping 46T. The largest single chainring is from theDXR crankset. These are for BMX racers and are very expensive. They look nice though!
Shimano Double Cranksets in 2017
I found 41 double cranksets in production for 2017. There are six double cranksets with the smallest 22T chainring, belonging to a 36-22T crankset. Only one double crankset has the largest 40T chainring. The 40-28T is an option on the Deore XTweighing 727.6g which is 10-speed compatible.
I would love to see some 46-26T cranksets but I suspect such a large front difference is not easy to handle by current rear derailleurs, although my prediction is that this may well be coming. I suspect it would need a long cage length to accommodate the chain slack.
However soon electronic Synchro Shifting should make doubles easier to use. By utilizing a single gear shifter that can control both the front and rear derailleurs through programmable gear mapping. This gear mapping could theoretically reduce chain length and cage length by preventing incompatible extreme gear combinations (cross chaining). A shorter chain could mean less risk of chain slap and dropped chains. Ideal gear combinations will improve the efficieny of the drivetrain and reduce wear on chain.
Shimano Triple Cranksets in 2017
I only found 26 triple cranksets in production for 2017. By far the most common triple crankset had 40-30-22T chainrings. Shimano has twelve different 40-30-22T cranksets. The higher end XTR and Saint groupsets don’t offer a triple crankset. The Saint groupset is for downhill mountain biking so that’s understandable.
If you have an 11-speed system the Deore XT has the FC-M8000-3 as it’s only offering. 10-speed groupsets have the FC-M782, FC-MT500-3, FC-M6000-3, FC-M7000-10-3 all of which are 40-30-22T.
9-speed groupsets include my Alivio FC-M4050 40-30-22T. I used to have the Alivio FC-T4010 Octalink crankset which had 48-36-26T chainrings. A HOLLOWTECH II equivalent substitute for the FC-T4010 is the Alivio FC-M4060.
With my former 48-36-26T I found I didn’t use the higher gearing enough so I switched to a 40-30-22T and tried to increase my cadence. Now my cadence is around 85 rpm, instead of the historic 70 – 75 rpm. Higher cadence can help reducing muscle fatigue. I’ve seamed to have a lot more knee trouble since switching to the 40-30-22T and reducing stress on my knee is the main reason I want to switch now to an oval chainring. I also like the ideal of a less cluttered handlebars by ditching the left shifter and my front derailleur.
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