Results 1 to 23 of 23
  1. #1
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660

    Pugsley / Profile Racing bottom bracket modification

    Finally got around to modifying my bottom bracket for an optimum setup with Profile Racing cranks using the external cups.

    I took 5mm off the drive side shell, giving me a 95mm bottom bracket width. This lets me get both crankarms in tight to the frame as well as keeping the sprocket in close for a good chainline. Running a 30-tooth front sprocket for super low 1x9 gearing. Where I have the sprocket now it just barely clears the rolling darryl / big fat larry combo in the lowest gear but, of course, the nice thing about Profile cranks is I can always add a spacer if I need one.
    Attached Thumbnails Attached Thumbnails Pugsley / Profile Racing bottom bracket modification-pugsley-oct-27-2012__0084.jpg  

    Pugsley / Profile Racing bottom bracket modification-pugsley-oct-27-2012__0084-3.jpg  

    Pugsley / Profile Racing bottom bracket modification-pugsley-oct-27-2012__0084-5.jpg  

    Pugsley / Profile Racing bottom bracket modification-pugsley-oct-27-2012__0084-9.jpg  


  2. #2
    passed out in your garden
    Reputation: cmg71's Avatar
    Join Date
    Mar 2012
    Posts
    618
    i got a stiffy
    2012 Trek Rumblefish Elite
    Frankenbike (Pump/BMX track bike)
    1993 Colnago Elegant

  3. #3
    mtbr member
    Reputation:
    Join Date
    Apr 2011
    Posts
    2,481
    Looking great

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    853
    Sweet rig!

    How has the BFL/Darryl combo been working for you in the snow? How would you compare it to the standard 3.8/65mm setup? Thinking of doing something similar to my Pug, and wondering if it's worth it.

  5. #5
    mtbr member
    Reputation: nvphatty's Avatar
    Join Date
    Mar 2012
    Posts
    6,042
    I see some sort around various spokes what that be??

  6. #6
    Fat!Drunk!Slow!
    Reputation: JordyB's Avatar
    Join Date
    Oct 2007
    Posts
    1,401
    Why 95mm? Why didn't 100mm work? Just curious. Jealous of the 30t!

  7. #7
    will rant for food
    Reputation:
    Join Date
    Jan 2010
    Posts
    3,041
    Good idea. Never did like the unnecessary amount of spacing on the non drive side to get things symmetrical.
    Latitude: 44.93 N

  8. #8
    mtbr member
    Reputation:
    Join Date
    Feb 2011
    Posts
    259
    Nice,
    That was one concern that I had about the external bearing BB. I also would like to have a little more engagement of the crankarm on the spline (I currently have exactly 4 threads of engagement on each side and it makes me very nervous).
    Did you just use a facing tool, or maybe a pipe cutter?
    For what it's worth, I went to a 28 tooth since I wanted an even lower gear. I end up spinning like a hamster on the road though.

  9. #9
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by ultraspontane View Post
    How has the BFL/Darryl combo been working for you in the snow? How would you compare it to the standard 3.8/65mm setup? Thinking of doing something similar to my Pug, and wondering if it's worth it.
    It's been working like a champ. You can never go fat enough, I figure.

  10. #10
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by nvphatty View Post
    I see some sort around various spokes what that be??
    Those are tiny reflectors on the spokes, just for extra visibility at night. They weigh almost nothing.

  11. #11
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by JordyB View Post
    Why 95mm? Why didn't 100mm work? Just curious. Jealous of the 30t!
    Basically so I can get everything on the drive side (pedals, crankarm, sprocket) 5mm closer inboard. Narrower stance, better chainline. Also it helps get more 'bite' on the axle. With the external cups you are pushing the limits.

  12. #12
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by coldbike View Post
    Nice,
    That was one concern that I had about the external bearing BB. I also would like to have a little more engagement of the crankarm on the spline (I currently have exactly 4 threads of engagement on each side and it makes me very nervous).
    Did you just use a facing tool, or maybe a pipe cutter?
    For what it's worth, I went to a 28 tooth since I wanted an even lower gear. I end up spinning like a hamster on the road though.
    Yeah, me too. I had barely enough (ran the setup all last year with no problems) but I wanted more engagement on the splines.

    Had LBS do it... I believe they used a hacksaw for the rough cut, and then a facing tool to get it nice and even. Then they had to chase the threads deeper as well.

  13. #13
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    124
    how much engagement do you have with the crank arms on the spindle? i tried using the profile's and it didn't seem like it would work at all. the non-drive side would of hit the chain stay on a pug's.

    do you only have the spindle in half way on each crank?

  14. #14
    Self-defeatist
    Reputation: CLONG's Avatar
    Join Date
    Nov 2006
    Posts
    958
    When did you 86 the Alfine? Care to share the reason you went back to derailers?

    The bike looks great. Jealous of you running the BFL's. Looks like you have plenty of clearance, but I don't think they'd work on my 100mm rims.
    I'm covered in beer.

  15. #15
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by davefj40 View Post
    how much engagement do you have with the crank arms on the spindle? i tried using the profile's and it didn't seem like it would work at all. the non-drive side would of hit the chain stay on a pug's.

    do you only have the spindle in half way on each crank?
    I have quite a bit of engagement, more than half. I am running minimal spacers, both my crankarms pass within a few mm of the chainstays.

    I have been using Profiles for five years on my Pugsley they work great. The external BB takes a little more finesse but you can always use the euro BB.

  16. #16
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by CLONG View Post
    When did you 86 the Alfine? Care to share the reason you went back to derailers?

    The bike looks great. Jealous of you running the BFL's. Looks like you have plenty of clearance, but I don't think they'd work on my 100mm rims.
    The Alfine was very reliable for me but ultimately I found it to be heavy, inefficient and sloppy feeling compared to a derailleur setup. For the past year I have been running a Saint rear hub with an XT rear derailleur which gives much more positive engagement. No problems at all with reliability or performance in the cold, even at 40 below.

  17. #17
    Nuts
    Reputation: bdundee's Avatar
    Join Date
    Feb 2008
    Posts
    5,188
    Now this is what the Fat Forums is all about!! Thanks for sharing this great idea.
    And I love beer!!

  18. #18
    will rant for food
    Reputation:
    Join Date
    Jan 2010
    Posts
    3,041
    I was thinking about this... you could use a 4 bolt spline drive spider to push a 4 bolt chainring out a little bit more if you wanted to go 100mm / BFL. Not entirely sure if it would add enough clearance, but it's an idea. Basically keep the crank in almost the same location but push the chainring teeth as close to the crank arm as possible.

    Of course, this wouldn't save you any money...
    Latitude: 44.93 N

  19. #19
    @adelorenzo
    Reputation: anthony.delorenzo's Avatar
    Join Date
    Aug 2006
    Posts
    1,660
    Quote Originally Posted by Drew Diller View Post
    I was thinking about this... you could use a 4 bolt spline drive spider to push a 4 bolt chainring out a little bit more if you wanted to go 100mm / BFL. Not entirely sure if it would add enough clearance, but it's an idea. Basically keep the crank in almost the same location but push the chainring teeth as close to the crank arm as possible.

    Of course, this wouldn't save you any money...
    I have a 4-bolt spline drive spider. It would push the chainline waaaay out there... You would definitely get the clearance for any tires you want but not sure the chainline would be doable. I think it would need a spacer or two to clear the BB cup as well.

    I am running 80mm/BFL which is the practical limit of the Pugsley frame AFAIK. I know that hundreds will fit in theory but I can't imagine it would work well in practice. You'd have to be pretty damn slick at mounting your tires to keep the wobble down to a minimum.

  20. #20
    mtbr member
    Reputation:
    Join Date
    Oct 2012
    Posts
    709
    this is a little off the op but it seems like you could use that crankset and BB to put a wider crank setup on a 73mm shell frame. to convert a frame that was made with normal crank width to fit a fat tire, if you have clearance for the tire in the stays of course.

  21. #21
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    847
    Quote Originally Posted by autodoctor911 View Post
    this is a little off the op but it seems like you could use that crankset and BB to put a wider crank setup on a 73mm shell frame. to convert a frame that was made with normal crank width to fit a fat tire, if you have clearance for the tire in the stays of course.
    If you are just trying for a 1x, single chainrring setup, then most any old MTB triple crank with a standard 68mm or 73mm bottom bracket can provide enough chainline clearance for a fat tire if you run the chainring on the outer ring position of the crank.
    I've got an old shimano square taper crank on my home-built fatbike, just used a rather long 135mm square taper 68mm BB spindle to get the inner ring far enough out to clear the tire (55mm chainline). I use it as a 2x chainring crank (22t&32t) with a conventional clamp-on MTB derailler (non-e type, non-direct mount) in order to be able to shift between the inner and middle chainrings, derailler unable to shift out to the outer chainring position with the long spindle.

    Difficulty of trying to adapt an old MTB frame with 68 or 73mm bottom bracket to run 3.7" fat tires is not so much the crank as it is just getting chainstay & seatstay clearance for the tires. A MTB designed for 26" tires will have chainstays way to short for fat tires and there are very, very few old steel 29er MTB frames that would make a good starting point for such a fat conversion, I really would not suggest trying to do such a conversion with an aluminum frame.

  22. #22
    mtbr member
    Reputation:
    Join Date
    Sep 2008
    Posts
    124
    Quote Originally Posted by anthony.delorenzo View Post
    I have quite a bit of engagement, more than half. I am running minimal spacers, both my crankarms pass within a few mm of the chainstays.

    I have been using Profiles for five years on my Pugsley they work great. The external BB takes a little more finesse but you can always use the euro BB.
    I have the 4 bolt spline spider and chainring, i think this maybe what is causing my problems.

    thanks,

  23. #23
    mtbr member
    Reputation:
    Join Date
    Oct 2012
    Posts
    709
    Quote Originally Posted by GrayJay View Post
    Difficulty of trying to adapt an old MTB frame with 68 or 73mm bottom bracket to run 3.7" fat tires is not so much the crank as it is just getting chainstay & seatstay clearance for the tires. A MTB designed for 26" tires will have chainstays way to short for fat tires and there are very, very few old steel 29er MTB frames that would make a good starting point for such a fat conversion, I really would not suggest trying to do such a conversion with an aluminum frame.
    I have an old steel 29erframe, but still no clearance for the wider tires I want to run. I was actually wanting to use an old suspension frame, and make a new rear swingarm to fit the wider tires. I want to try and use the 170mm rear hub, which is why I was thinking I would need the fat cranks/BB.

Posting Permissions

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