Results 1 to 17 of 17
  1. #1
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022

    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?

    I was planning on getting a dura ace triple for my bike but I don't know if it will fit.
    The chainline is 45mm on those and the middle ring is 39t, but I was planning on getting a 41 or 42t and those have a radius of 85mm. magic formula here. framebuilding - How do I calculate the diameter of a chainring from the number of teeth? - Bicycles

    Has anyone successfully mounted a road triple on a hardtail mtb (@45mm chainline)?

    Now if i pull out my calipers and measure this, I just eyeball it, it appears as my prticular frame is about 98mm wide over the chainstays 85mm down from the BB tube. So I guess it won't work. Is this common?

    Also I was thinking of just getting a regular 104mm bcd 4 arm crankset (with 50mm chainline), and get a 41 or 42t middle ring. But I want steel rings, no alu crap for me. Does anyone know where to get a 104mm bcd steel ring in 41 or 42t size (or at least 40t), preferably thick and beefy and non ramped/pinned. Will be running 8sp chain and cassettes.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  2. #2
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    Well now when I think about it, maybe I could utilize the outer ring position on a road triple to get a chainline of 50mm. However then I get no antishred protection for my pants that the outer chainring would have provided if I ground the teeth off.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Dec 2005
    Posts
    336
    If it is not going to work, it will be for the following reasons:

    - All road cranksets have shorter axles. Road BB shells are 68mm BSA, 70mm italian style or all those pressfit nonsense in all its glory.
    - road cranksets are meant to be used with 43,5mm chainline with double and 45mm with triple. This translate to situation where you would like to run 39T in the place of the granny.

    It _might_ work, but I'd bet for 99% chance of it not working at all.

    Most MTB frames will not work well with 42T in the middle position. 38-40 is the usual max. 42 sometime fits, but with minimal clearance.

  4. #4
    mtbr member
    Reputation: veritechy's Avatar
    Join Date
    Jan 2008
    Posts
    602
    I agree with uzurpator...I got a road derailleur but it rubs a little.
    It's lighter if you don't mind a little rub.
    Your results may vary. Mine barely pushes "out" far enough.

  5. #5
    mvi
    mvi is offline
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,236
    Weird enough a road compact will fit before a road triple. The 130 bcd spider is the problem . Running 2 road compacts with the ring in the 34 outer on 2 different bikes (jet 9 and on one).

  6. #6
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
    Posts
    48,007
    Quote Originally Posted by mvi View Post
    Weird enough a road compact will fit before a road triple. The 130 bcd spider is the problem . Running 2 road compacts with the ring in the 34 outer on 2 different bikes (jet 9 and on one).
    Has to do with ring clearance. Most current road doubles have a ~45mm chainline (good thing for a mtb) but a 39T ring will not clear the stays of a mtb while a 34T will. Put the 34 on the outside of a road crank and you have just gone back to the too wide mtb chainline.
    mtbtires.com
    The trouble with common sense is it is no longer common

  7. #7
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    Quote Originally Posted by mvi View Post
    Weird enough a road compact will fit before a road triple. The 130 bcd spider is the problem . Running 2 road compacts with the ring in the 34 outer on 2 different bikes (jet 9 and on one).
    I can easily imagine the actual spider and the mounting holes of the actual arms that hold the chainrings touching the frame. If they are placed at 130mm bcd they are just barely smaller diameter than a 39t chainring. Well I wonder if I could mount a 42t ring in the outer position of a double/compact double, the compacts use 110mm bcd, and such rings are easily found in steel. I wonder if it will clear. at 45mm chainline it definitely won't but the outer on a double is a few mm further out.

    Then again. If I get a triple I'm fairly certain the 42t will clear at 50mm chainline/outer position, but then I'm back at square one again. since 50mm is the standard chainline on a mtb crankset, and with an mtb crankset I get an outer ring that can act as a chainguard.

    I guess the only benefit with a road cranks would be easier to get thicker steel unramped chainrings in the dimensions I want. Also bigger spiders/bcd. They look more estetic too. To my eyes at least. I like 5 arm spiders better too.

    This will need some consideration.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  8. #8
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    I have now recieved my dura ace non compact triple 175mm. Its the older less flashy version 7800. its totally bad ass.

    So I tried mounting it with my xtr outboard hollowtech 2 bottom bracket as it says in the xtr dox with 2 spacers on the drive side and 1 on the nds (68mm shell) but then the dura axle became too short. Way too short. So I removed all the spacers and voila now its almost long enough, like 2mm shy.

    On the drive side crank axle there are 2 parts mounted (easily removed). Some kind of dust shield and a black plastic spacer ring, there is a dust shield for the other crank too.

    I just popped it in and to my surprise it all clears. A 30 a 39 and a 53 or whatever the big one is. But its really tight, like 0,5mm on the 30 and 3mm with the 39 and about 5mm with the 53. The drive side crank clears the stays by about 7mm or so, going shorter than 175 would not have mattered much, if anything at all. The nds crank however.. hehe, well it clears by about 1mm and then its not really fully mounted onto the spline (but its as far inboard as it can go for now), 2-3mm left.

    So my plan is to ditch all the rings, its alu crap anyway 10sp too. All bolts were ti and not a drop of lube anywhere so they were stuck as muddafukka, soft crappy ti (ti is not very suitable for bolts imo) Maybe I can use them anyway. I have to grind some of them down a mm or 2.

    My plan is to make a thinner plastic ring that mount on the drive side axle so the cranks get symmetrical with regards to the chainstays, and then mount a 40/41t or so in the outermost position with short bolts, and put a spacer between the xtr cup and frame at the nds, then the chainring will clear by about 5mm, both cranks by about 5mm, the nds will engage the axle spline fully, and the spider will clear by about 4-5mm too.

    Gonna put up some pics of it tomorrow. Its gonna work.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  9. #9
    banned
    Reputation:
    Join Date
    Aug 2012
    Posts
    2,049
    My first MTB had a road crank ... Nothing else was available back then, and geometry was way different than it is today

  10. #10
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    I just had a look at the techdocs for the my Da cranks and supposedly they only come with 1 "dustshield", and it goes on the nds, i got 2 somehow, and they are apparantly 3 or 3,5mm spacers, can't remember. That solves the nds not engaging fully on the spline and shifting the ds further inwards. I have to try that tomorrow. Still have the nds crank too close problem though. Probably gonna make my own spacers anyway and get it perfect instead (because I want 2 dustshields), they look so shiny and pretty.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  11. #11
    mvi
    mvi is offline
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,236
    Don't be afraid for 1 mm non drive clearance as long as your heel clears the chain stay.
    I rode a campy compact road on my Jet 9 with that clearance. Would love to see pictures when finished. As I said , no road triple worked for me whereas road compacts do. Last projects have been replacing the spiders on Truvativ road cranks (= SRAM interface) and use them on the MTB. Still amazed that you clear that 130 mm spider arm.

  12. #12
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    221
    Sure I ran a 24 39 42 crank for a couple of years. On my bicycle a 30 tooth inner would have hit before the 39 tooth would. I think the duraace has a strange bolt circle and you may not be able to get a chainring smaller than 30 teeth.
    "Dish is illogical." Spoke of Vulcan.

  13. #13
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    Quote Originally Posted by mvi View Post
    Don't be afraid for 1 mm non drive clearance as long as your heel clears the chain stay.
    I rode a campy compact road on my Jet 9 with that clearance. Would love to see pictures when finished. As I said , no road triple worked for me whereas road compacts do. Last projects have been replacing the spiders on Truvativ road cranks (= SRAM interface) and use them on the MTB. Still amazed that you clear that 130 mm spider arm.
    allright some pics. pics of the frame with the cranks mounted, of the crank arm clearance both sides and chainring clearance, and the spline not engaged fully. Remeber this is with the dual spacers on, and its only supposed to be on the nds according to shimano tekdox.

    well you all se whats going on and how all this is solvable

    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-1.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-2.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-3.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-4.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-5.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-6.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-7.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-8.jpg
    Has anyone used a road triple on a mtb? Also, big steel rings, 104bcd?-9.jpg
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

  14. #14
    mvi
    mvi is offline
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,236
    That is close! I could not make a triple work on mine. Looked at some pictures and the compact on my jet 9 crank cleared the stay by 1 mm without problems but it was a weld at the lower part of the crank. Frame flex under power might make yours hit the stays.
    Maybe you can use a shimano MTB left crank that is more bowed out , and you don't have to worry as much for stripping it in a worse case.

  15. #15
    mtbr member
    Reputation:
    Join Date
    Apr 2009
    Posts
    2,340
    Try a road BB....the cups may well be just short enough to get the NDS crank engaged further.

    Lets hope your frame has NO flex in it at all.
    Rimmer - "There's an old human saying - if you talk garbage, expect pain"

  16. #16
    Plays with tools
    Reputation: customfab's Avatar
    Join Date
    Jun 2008
    Posts
    4,207
    Quote Originally Posted by AlexRandall View Post
    Try a road BB....the cups may well be just short enough to get the NDS crank engaged further.

    Lets hope your frame has NO flex in it at all.
    The shimano mountain cups are narrower than the road version by 2.5mm total.

  17. #17
    ~ B A D A S S ~
    Reputation: car bone's Avatar
    Join Date
    Apr 2011
    Posts
    2,022
    The cranks will definitely strike the frame in use, the rings too.. I'm gonna make some new spacers for all possible positions. Remeber there should not be a dustshield spacer at the DS, and removing that 3 or 3.5mm spacer will move the crank inward. Or if I save the dustshield spacer and remove the black one and replace it with thinner one. I will also need spacers on the nds between the BB cup and frame to move the nds crank outward a bit. I just make spacers in 1mm size thats close enough for this. And worst case scenario I sand a bit of the inside of the cranks arms, not much just a little. Or I put it in a box and get something else entirely. I was thinking Saints or some howitzer cranks, or maybe some square taper ones. I have had good luck before with howitzer cranks. Its a solid interface.

    I'm also not sure my frame is symmetric over the stays. I should have measured left/right offset against the seat tube of course. But I didn't And now all the stuff is removed and packed in their little boxes for a week or so more. I also want symmetrical cranks. It has to be perfect.
    Rule #9 // If you are out riding in bad weather, it means you are a badass. Period.

    Quote Originally Posted by iheartbicycles View Post
    Specialized sucks ass.

Posting Permissions

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