Results 1 to 24 of 24
  1. #1
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449

    DIY 42T Cassette Cog

    So we all know about the new 10-42 11 speed cassette. I love the idea of having a 42t rear cog to go on my 1x8 setup.

    I had some time tonight, so I made it a happen.

    Heres how I did it:

    My idea was to make a 34t cog that you can bolt a chainring too.

    Here you can see the difference between the 34 and a 42. Pretty big jump, but not too crazy.

    DIY 42T Cassette Cog-img_0082.jpg

    I went to my hardware store and got some steel washers that are the same thickness as a cog and have the right size hole for a chainring bolt:

    DIY 42T Cassette Cog-img_0083.jpg

    The hardest part was trimming the cog to flush fit the washers. The steel is HARD. Here is the cog trimmed sitting on top of the chainring:

    DIY 42T Cassette Cog-img_0084.jpg
    Attached Images Attached Images  

  2. #2
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Next I bolted everything to an old ring and tack welded them in place:

     photo IMG_0086_zpscdbf70d4.jpg

    Once it was tacked and secure, I welded the washers soled from both sides and ground the welds smooth.

     photo IMG_0089_zpse28c387d.jpg

    I found these nylon spacers at the hardware store for cheap. They may not last, but I though I would give them a try. They are the perfect thickness for an 8 speed cassette:

     photo IMG_0090_zpsec75cbbb.jpg

    I bolted the rings together and this is what I ended up with:

     photo IMG_0092_zps205936d0.jpg

     photo IMG_0091_zps3ceea1ec.jpg

    Time to see how it "stacks up". First I used a bottom bracket washer and an 8 speed spacer to get the rings where they should be.

     photo IMG_0093_zps681eb18a.jpg

    Here they are on the wheel, with a 28 in the 3rd place. As you can see the chainging bolts dont interfere with the chain on the 28 at all:

     photo IMG_0094_zps23a68cd1.jpg

    Here is the whole cassette. Its an 11-42 8 speed. Ya the gaps are HUGE, but I am willing to deal with that:

     photo IMG_0095_zpsa0cd012e.jpg

  3. #3
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Here it is on the bike:

     photo IMG_0096_zps0754fac4.jpg

     photo IMG_0097_zpsf19a6fae.jpg

     photo IMG_0102_zps8f068ba0.jpg


    I havent had a chance to ride it yet, but on the stand it shifts pretty good. The 11-34 cogs are perfect, the 42 rubs a tiny bit on the upper derailer pulley. I need a longer screw on the back of the derailer. If it was 1/8 inch longer the derailer would totally clear the pulleys. A 38 or 40 tooth ring would probably not need this.

    Total weight gain was about 80 grams. Once I know it works, ill lighten it up like I did my chainring...

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    251
    Great mod! Let us know how it rides!

  5. #5
    Plays with tools
    Reputation: customfab's Avatar
    Join Date
    Jun 2008
    Posts
    4,124
    Curious to see how long it lasts.

  6. #6
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Ya me too. Part of me thinks its going to be pretty flexy, but its a fun project and totally worth trying. It only cost me about $6 because I already had most of the parts.

  7. #7
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,711
    Skills! Cool idea. How is the jump from your lowest cog to your new lowest 42 cog? Seems like a pretty large jump visually?

  8. #8
    banned
    Reputation:
    Join Date
    Aug 2012
    Posts
    2,049
    Subscribed

  9. #9
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    It's a pretty big step up, but it still shifts ok. If I had a friction a shifter I would almost add it as a 9th gear. I think there would be room for it.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Mar 2011
    Posts
    316
    could you make use of the 38 or 42 tooth cog that's available on ebay? it seems like it might last longer than this if you can get the spacing right.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Hmmm. I don't know. I didn't even know about the eBay ones.

  12. #12
    mnoutain bkie rdier
    Reputation: rydbyk's Avatar
    Join Date
    Oct 2009
    Posts
    2,711
    pic? link? thx

  13. #13
    Plays with tools
    Reputation: customfab's Avatar
    Join Date
    Jun 2008
    Posts
    4,124
    Quote Originally Posted by blown240 View Post
    Ya me too. Part of me thinks its going to be pretty flexy, but its a fun project and totally worth trying. It only cost me about $6 because I already had most of the parts.
    I'm guessing your washers are going to rip out at the first sign of serious torque. Since you didn't bother to grind the plating off and your ground down the weld they are pretty minimal.

  14. #14
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Well I took it for a short ride today. Everything is working VERY well. The shifting onto the 42t is a little slow, maybe 1-2 seconds instead of instantly. I am using 8spd XT rapid fire plus shifter with the matching derailer.

    Tomorrow I am leaving for NV to ride Bootleg Canyon and Red Rock Canyon. That will be the real test...

  15. #15
    mtbr member
    Reputation: gmats's Avatar
    Join Date
    Apr 2005
    Posts
    1,900
    Love it, great ingenuity. Good luck, hope it all works out.

  16. #16
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Just got back from a loop around Blue Diamond in NV. It was GREAT!! This setup works even better than I thought it would. Shifting onto the 42t was perfect, shifting off if it was a little slow, but doable...

    I had no issues with mis shifts, or chain suck. The gearing of the 32-42 is about as perfect as it could be. I had plenty of granny gear.

    All in all, I am 99.5% satisfied!!

  17. #17
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    OK, So I want to address the issue with this setup not liking to come off of the 42 onto the 34.

    I am thinking of shaving the top off of a couple teeth in 2 spots on the 42t cog. Hopefully that will give me a gate for the chain to drop thru.

    Right now if I want a fast shift off of the 42 to a higher gear then I need to shift down to the 28t. Other than that this setup if GREAT. I rode Bootleg Canyon on it Sunday and it really performed good.

  18. #18
    Plays with tools
    Reputation: customfab's Avatar
    Join Date
    Jun 2008
    Posts
    4,124
    You might try twisting the teeth first. Shift ramps and tooth profiles seem to be a cryptic science but with the cassettes of yester-decade they would take the straight cut teeth and rotate some of them so the unloaded side of the tooth pointed down the cassette. Might be worth a shot before you grind on them, as you could always do that as phase two.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Ya thats a good idea!

  20. #20
    mtbr member
    Reputation:
    Join Date
    Aug 2008
    Posts
    34
    Quote Originally Posted by blown240 View Post
    Well I took it for a short ride today. Everything is working VERY well. The shifting onto the 42t is a little slow, maybe 1-2 seconds instead of instantly. I am using 8spd XT rapid fire plus shifter with the matching derailer.

    Tomorrow I am leaving for NV to ride Bootleg Canyon and Red Rock Canyon. That will be the real test...
    Any chance of you coming to Bootleg again soon? I was planning on a 9 speed setup with the Ebay 41t cog but would love to try it before ordering everything.
    Thanks,
    Aaron
    I hope your car has a big trunk because I am going to put my bike in it.

  21. #21
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    Quote Originally Posted by mtnbikinggolfer View Post
    Any chance of you coming to Bootleg again soon? I was planning on a 9 speed setup with the Ebay 41t cog but would love to try it before ordering everything.
    Thanks,
    Aaron
    Im going back to bootleg in a couple weeks, but im not running the 42t right now. I swapped over to another frame and I got tired of the derailer cogs rubbing on the 42. I went back to a 3x8 for now. I plan on going back to the 42t but not until I can figure out a longer derailer hanger.

  22. #22
    mtbr member
    Reputation:
    Join Date
    Aug 2011
    Posts
    287
    Have you thought about giving 40T a go instead of sticking with the 42T?

  23. #23
    mtbr member
    Reputation: smilinsteve's Avatar
    Join Date
    Jul 2009
    Posts
    5,589
    The awesomeness of this creativity is getting me all choked up.


  24. #24
    mtbr member
    Reputation:
    Join Date
    Nov 2009
    Posts
    449
    I have thought about using a smaller gear than the 42. But the 42 is what I have, so thats why I used it. Really once the 34t cog was made, you could use any size gear. But I just got a new bike and put a 12-36 9 speed on it. I will come back to the 42 on another project im sure...

Similar Threads

  1. Cassette off, spins forever. Cassette on, not forever
    By westin in forum Wheels and Tires
    Replies: 2
    Last Post: 08-05-2012, 04:14 PM
  2. 9 spd cassette 8 spd der?
    By sbarnhart in forum Beginner's Corner
    Replies: 4
    Last Post: 06-30-2011, 04:15 AM
  3. different cassette
    By pernfilman in forum XC Racing and Training
    Replies: 2
    Last Post: 06-01-2011, 08:11 PM
  4. Cassette
    By bbell in forum All Mountain
    Replies: 6
    Last Post: 02-05-2011, 07:37 PM
  5. 7 spd cassette on 8 spd hub
    By didrek03 in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 1
    Last Post: 01-25-2011, 09:12 PM

Posting Permissions

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