Page 1 of 2 1 2 LastLast
Results 1 to 25 of 28
  1. #1
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34

    Shimano CX70 Front Derailleur on MTB

    Hi, does anyone know if the Shimano CX70 FD works on an MTB with MTB chain rings (i.e. not road compact crank)? At 102 grams for a FD with a 34.9mm clamp, I'm considering it as a viable option to replace my current XT one given that it handles top pull as well.

    I have actually tried using the SRAM Red FD with a speen adaptor. Disappointingly, it doesn't work very well as I am using the 2 outer most chain rings of my MTB crank set and alot of force is required to shift the chain from the middle to big chain ring.

    Thanks in advance

  2. #2
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    79
    Sure it works, some dremeling will be needed though. I'll post some pics ASAP. This might help. Cheers.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Thanks, I'd appreciate the photos as I cannot really understand the spanish forums even after google translation :/

    Btw, care to share also what kind of dremeling wil be needed? Thanks

  4. #4
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    79
    Sorry for the delay in posting the pics, here they are:
    Shimano CX70 Front Derailleur on MTB-desv2.jpg
    Shimano CX70 Front Derailleur on MTB-desv1.jpg

    I suggest you apply some nail polish to avoid rust.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Wow, that's alot of filing/dremeling to do. Is the force required to shift from the inner to outer chain ring alot?

  6. #6
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    79
    The spring has a bit less tension than standard Shimano mtb mech's, so shifting becomes a pleasure . Really works.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Ahh, thanks alot for your pictures and sharing, I shall try it soon

  8. #8
    20 years in the woods
    Reputation:
    Join Date
    Feb 2008
    Posts
    182
    Hi guys,

    I'm running a 3x9 with XT shifters. I'm thinking about going 2x9 with this FD,any mods needed? The BB is 68mm,so I think the chainline issue won't be a problem (expecting some minor chain rubbing on big chainring/small cog also).

    Thanks!
    Gajas what?

  9. #9
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    @Nozes: As you can see from Rallyator's pictures, that's the amount of filing/dremeling you needa do (minimally).

    I just managed to get mine working after alot of filing (wish I had a dremel). In fact, I had to file down the inside portion of the FD too (where the metal touches the limit screws) in order to get the FD to shift further out. I think this is because I'm using the 2 outermost rings of a triple MTB crankset. Mine still has chain rub on certain combinations though.

    Rallyator, does your set up have any chain rub on extreme cog/chainring combinations? And I presume you are using a double MTB crank? I'm wondering if using a double crank will improve the chain alignment... can anyone help? Thanks

  10. #10
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    The chainline should be 43.5 mm. The outside ring should be 50 mm from the middle of the frame at most. It is made for road crankset so it doesn't go out very far. I have specialized mtb crank and double setup on my Stumpjumper HT with 22 and 38 rings and it works perfectly.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Ahh, bobi.k, you didn't need to do any modifications to the FD? No chain rubs on any combination?

    You mentioned that the outside ring should be 50mm from the middle of the frame at the most, is that how your crank is set up? I'm basically trying to see if it's worth it for me to change to a double crank. Thanks

  12. #12
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    Mine is 49 mm but the FD is not jet in the outmost position. It has 2 or 3 mm more space. Nothing is filled dremeld or modified. It just works.

    Shimano CX70 Front Derailleur on MTB-img_0106.jpg

  13. #13
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Thanks for the pict Nice that you got it working so easily! Looks like my problem is having to want to use the big (i.e. 40T upwards) and middle chainrings as opposed to the middle and granny...

    Maybe the question I should be asking is: Is the big chain ring (i.e. 40T and above) of a double specific crankset closer to the BB as compared to that of a triple, and if so, by how much?

  14. #14
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    Double specific crankset chainline should be close to 45mm or less. XX chainline is 49.5 mm so the big ring is 52-53 mm. http://cdn.sram.com/cdn/farfuture/U8...ifications.pdf
    But on the triple spider you can mount 40+ ring in the place of middle chainring. They have the same BCD. Lots of companies sell 40+ chainrings for middle mount. I know Specialites do Couronne Chinook VTT DuLight.fr - Le spécialiste des composants légers pour toutes les pratiques du cyclisme.
    So your chainline will be around 44 mm. Just bare in mind that difference in chainrings size can be 16 tooth or less.
    And be careful that your granny ring don't touch chainstay.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    You totally read my mind My current set up is 44T-32T (Outer - middle position with the granny position left empty). And I actually just ordered a 29T (to effectively replace the 32T) chainring (with a BCD for the granny position) to be paired with my current 44T chainring which I will move to the middle position.

    That will make the difference 15T, and I'm crossing my fingers that shifting performance will not be affected. You mentioned that the difference should be kept at 16T and below, but do you think at 15T, shifting performance will deteriorate slightly?

  16. #16
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    No, it is made for that. 16T difference means that at this ratio it will still work flawless. In extreme, it works also with 18T difference but than you must shift carefully and the ramps on the big ring must be good. I tried 42-24 and it was O.K. Just not good enough for racing. To dangerous for chainsuck on down shift. With extreme shifting the chain would miss the small ring and fall between frame and crank.
    No such problem with 38-22 setup. My cassette is 11-32. Weight reasons obviously.

  17. #17
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Alright, good to hear! Appreciate your help bobi.k

  18. #18
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Ahh sigh, had a disappointing attempt today. Unfortunately, the 44T ring (when mounted at the middle position) is too big and hits the frame because the shifting pins on the chainring cannot clear the chainstay. I'm using a scott scale btw. Is that the reason why I can't really find double MTB cranksets around with 44T as the biggest chainring?

    I'm thinking of trying a 42T instead but I'm wondering if it's even worth a try...

  19. #19
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    42T should clear the chainstay. Which crankset do you have. Can you put a spacer on the drive side? SRAM cranks have spacers on drive and non drive side. You can play with them. Or if you have threaded BB you can also put spacer on the drive side.

  20. #20
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    I'm using an Aerozine crank. I'm trying not to touch the external BB by placing spacers for because I don't have the tools to remove the BB haha. Ok, will consider getting a 42T ring... more costs yikes

  21. #21
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    An update: Some pictures to show how I managed to get the CX70 working... 93.6 grams including the carbon clamp, a pretty good alternative for a road FD + speen set up. Some filing had to be done to get the FD to shift all the way to the outer most chain ring of the triple crankset (I painted the filed portions with nail polish, so it's kinda hard to spot in the picture). However, it is easier to shift as compared to the SRAM red + speen (if you can get that to work well enough).





    I have decided to wait for an appropriate time to change my crankset to a double one so that the chainline will be improved

  22. #22
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    O.K. good job. But your big chainring is not properly installed. You should rotate it, so the catch pin is aligned with crank. It will also shift better, because the ramps on chainring are calculated for this position.

    BTW, nice sandals!

  23. #23
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Lol! Those are my mum's. Anyway, really sharp spotting there! Now that you mention, I didn't even realise the chain ring was mounted wrongly. Thanks!

    I suppose there's no special alignment for the middle chain ring... or is there?

  24. #24
    mtbr member
    Reputation:
    Join Date
    May 2008
    Posts
    35
    There should be a mark on it like a tooth. You can see it on this picture on the left inner side.
    http://www.chainreactioncycles.com/I...inal/38184.jpg

    Obviously aligned with crank.

  25. #25
    mtbr member
    Reputation:
    Join Date
    Apr 2010
    Posts
    34
    Ahh, yea I did a check and both the large and middle chain rings were coincidentally aligned in the same orientation but just not in phase with the crank arm, which explains why my shift quality has not been affected. Either way, a catch pin that is not hidden behind the crank arm is a little ugly, so I'll make the necessary adjustments tmr.

    Thanks again for the help bobi.k

Page 1 of 2 1 2 LastLast

Similar Threads

  1. Shimano CX70 (ultegra) down pull or top pull front derailleur?
    By aBicycle in forum General Discussion
    Replies: 3
    Last Post: 08-02-2012, 03:37 AM
  2. Shimano CX70 Fr. Der. - compatible w/ Campy Ergo
    By Erik_A in forum Cyclocross
    Replies: 3
    Last Post: 07-07-2012, 10:37 AM
  3. will 2x10 shimano m980 xtr front shifter work with sram xx front derailleur?
    By gideon in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 2
    Last Post: 07-01-2012, 07:28 AM
  4. Shimano front derailleur compatibility
    By ivko in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 0
    Last Post: 08-28-2011, 06:55 AM
  5. Shimano SLX Fd-M667 Front Derailleur ?
    By keen in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 10
    Last Post: 08-25-2011, 09:03 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •