Friday, January 23, 2015

Shimano Deore XT M780 Crankset

A quick upgrade post for my long neglected mountain bike! The Polygon Cozmic CX3.0 is a good value for money mid-range MTB that I got almost 2 years ago. With the recent year end sales on ChainReactionCycles, I found a good deal for a nice Shimano Deore XT crankset. This will go onto the MTB to replace the original Deore FC-M590-10 crankset.

The original Deore crankset actually works flawlessly, but I just wanted to refresh the image of the bike by upgrading the crankset. No real need to upgrade, but just itchy hands!

10 speed Dynasys Deore XT Crankset, FC-M780. Triple 42-32-24 teeth, 170mm length.

Same 42-32-24 teeth chainring sizes as the original Deore crankset. No need to reset the position of the front derailleur.

Steel inner chainring, steel+composite middle chainring and aluminium outer chainring. Lots of shifting ramps and pins on the chainrings for quick and reliable front shifting under load.

Deore XT left crankarm. Nice anodised surface finishing.

Common left crankarm as double cranksets, and even the trekking cranksets!

What's great about this CRC order is that it even comes with a new Hollowtech II MTB bottom bracket! And it is a high end SM-BB70 BB.

To see how many spacers to put under the bottom bracket, check out this post (right at the end).

How about the weight of the crankset? Comparing a Deore XT crankset to a Deore crankset, surely there must be some weight savings. Although weight savings is not the objective here, it would be good to know the weight for reference purposes.

XT FC-M780 right crankarm + chainrings, 552 grams.

XT left crankarm, 223 grams.

Together, the complete Deore XT FC-M780 crankset weighs 775 grams. This weighs about 100 grams more than the Ultegra 6800 crankset!

On the other hand, the stock Deore FC-M590 crankset weighs 844 grams. 

The old Deore crankset weighs about 70 grams more than the new Deore XT crankset. This difference is really small compared to the overall weight of the bike which is over 12kg. Therefore, upgrading the crankset from Deore to Deore XT is not an effective way to cut weight from the bike.

Brand new Deore XT crankset mounted on the MTB!

Overall view of the Polygon Cozmic CX3.0 with the new crankset. Looks pretty compatible!

Since I got this MTB 2 years ago, I have upgraded a few of the components, but did not really blog about them in detail. I shall write a summary of the changes that I made to this MTB, and compare the differences before and after the change. Look out for the comparison in an upcoming blog post!

Brief summary of the stock bike specifications:
Fork: Rockshox Recon Silver Solo Air, 100mm travel
Crankset: Shimano Deore FC-M590-10, 170mm, 42-32-24T
Front Derailleur: Shimano Deore FD-M590
Rear Derailleur: Shimano SLX RD-M670 SGS
Cassette: Shimano CS-HG62-10, 11-36T
Chain: Shimano CN-HG54
Shifters: Shimano SLX SL-M670
Brakes: Shimano BL-M445, BR-M446
Wheelset: Shimano MT55
Tires: Kenda Kharisma II, 26" x 2.10
Pedals: Crappy plastic pedals


  1. Decore XT cranks looks really nice , it's like a beautifully crafted sculpture. Better than Dura-Ace crank in the look dept.
    But with Saint paddle, the crank looks little bit dull, recommend to swap with your current road bike SPD.

    1. For the pedals, function is more important than looks. I'm not ready to use SPD for off road, so I will stick to platform pedals.

  2. I have XT crank, It is lovely. Was wondering what saddle bag that is, as can`t fit my pump in mine. that one looke a good size.

    1. Thats a Topeak Wedge DryBag, Large Size.