Advertise on Bikeforums.net



User Tag List

Results 1 to 16 of 16
  1. #1
    Erect member since 1953 cccorlew's Avatar
    Join Date
    Dec 2006
    Location
    Antioch, CA (SF Bay Area)
    My Bikes
    Roubaix Expert, Motobecane Fantom Outlaw turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
    Posts
    6,547
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Is there a 28 tooth chainring for Ultegra 6703 triple?

    Just what it say on the tin:
    Is there a 28 tooth chainring for the Ultegra 6703 (10-speed) triple?

    My Roubaix Expert Triple came with a 52-39-30 and I'd love it if it were just a bit lower. I really don't want to different cassette with wider gear spacing, so a lower small ring seems like my only option.

    I've been told Shimano doesn't make this ring, and their weird bolt pattern means no one else does either. True or false?

    If there is such a beast, where can i get it? Feel free to offer advice and warnings.

    Thanks!
    WANTED: Not a darn thing. I've got it all. Life is good.
    Website at curtis.corlew.com —— Bicycle blog at ccorlew.blogspot.com

  2. #2
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    39,805
    Mentioned
    25 Post(s)
    Tagged
    0 Thread(s)
    If the bolt circle is 74mm , yes. measure what you have,
    or go to one of the many bike shops in the east bay
    and they will tell you what fits.

  3. #3
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    20,480
    Mentioned
    44 Post(s)
    Tagged
    1 Thread(s)
    As said above, assuming the inner BCD = 74mm or (43.5mm from bolt to bolt on center) then there are smaller chainrings. Before buying, make sure that the FD has 3/16" (per 2 teeth reduction) under the chain to the closure on the cage.

    The other consideration is offset, or the position of the teeth relative to the outer (toward middle chainring) face. This varies, with some lining up with the face, and others being inward (centered on the ring). This isn't hyper critical, but if the teeth are too far from the middle ring the chain can drop between them and jam, or bend the sprocket.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  4. #4
    Erect member since 1953 cccorlew's Avatar
    Join Date
    Dec 2006
    Location
    Antioch, CA (SF Bay Area)
    My Bikes
    Roubaix Expert, Motobecane Fantom Outlaw turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
    Posts
    6,547
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    The distance between bolts looks to be about 55mm. This chart seems to say that's a XX BCD.
    Does that make sense to you more knowledgeable folks?

    IDIOT ALERT: See next message.
    Last edited by cccorlew; 02-18-12 at 12:57 PM.
    WANTED: Not a darn thing. I've got it all. Life is good.
    Website at curtis.corlew.com —— Bicycle blog at ccorlew.blogspot.com

  5. #5
    Erect member since 1953 cccorlew's Avatar
    Join Date
    Dec 2006
    Location
    Antioch, CA (SF Bay Area)
    My Bikes
    Roubaix Expert, Motobecane Fantom Outlaw turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
    Posts
    6,547
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    UPDATE:
    Shimano Ultegra-6703 3x10sp Chainring 30 tooth 92BCD: For 6700 (130BCD), 6703 (92/130BCD), and 6750 (110BCD) Ultegra crank models. 6703, triple version uses a proprietary middle chainring that doubles as interface for small/inner chainring mounting. SIS compatible duraluminum construction.

    Key Information

    • part #: Y1LK30000
    • speed: 3x10sp
    • BCD: 92mm
    • teeth: 30t (D)
    • color: silver


    Does that provide useful clues?
    WANTED: Not a darn thing. I've got it all. Life is good.
    Website at curtis.corlew.com —— Bicycle blog at ccorlew.blogspot.com

  6. #6
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    20,480
    Mentioned
    44 Post(s)
    Tagged
    1 Thread(s)
    You've got the ruler so you'd know better than we could.

    However it's possible and one way you could cross check is by the distance from the outer edge of the bolt to the shoulder where the teeth begin. Every tooth adds about 3/32" or 4mm to the radius of a chainring.

    A 74 BCD ring can take a 24t ring, while on a 94 the smallest is 29t. If you've only got 4mm room to shrink with a 30t, then then you need to look for a 94/29t sprocket (if it exists).
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  7. #7
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    20,480
    Mentioned
    44 Post(s)
    Tagged
    1 Thread(s)
    There may be a workaround that will serve your needs.

    various companies make 130bcd chainrings with built in triple adapters to convert doubles to triples. You might ignore the existing arrangement, treat your crank as a double and buy one of these adapter rings. Then you'll be free to use the granny of your choice.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  8. #8
    Insane Bicycle Mechanic Jeff Wills's Avatar
    Join Date
    Mar 2008
    Location
    other Vancouver
    Posts
    6,716
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cccorlew View Post
    UPDATE:

    Shimano Ultegra-6703 3x10sp Chainring 30 tooth 92BCD: For 6700 (130BCD), 6703 (92/130BCD), and 6750 (110BCD) Ultegra crank models. 6703, triple version uses a proprietary middle chainring that doubles as interface for small/inner chainring mounting.

    Does that provide useful clues?
    Yep. You can't replace the inner ring with a 28 tooth because a 28-tooth chainring with that bolt pattern would run the chain through the inner chainring bolts.

    However, If you replace the middle chainring with a Triplizer middle chainring: http://www.vintage-trek.com/tripleizer.htm . I think you can get a TA tripleizer from Peter White: http://www.peterwhitecycles.com/chainrings.asp (near the bottom of the page). With that installed you can go down to 24 teeth on the granny ring.
    Jeff Wills

    All my bikes.

  9. #9
    Gear Combo Guru Chris_W's Avatar
    Join Date
    May 2007
    Location
    Switzerland
    My Bikes
    Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
    Posts
    2,046
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I actually tried this out on an Ultegra 6703 crankset a few weeks ago. I removed the stock middle and inner rings to see if a TA tripleizer with 42 teeth plus a 28 tooth inner ring would fit, and it did so without any problem. I didn't actually ride it on the road, I just wanted to check that it worked in principle, but I cannot see why it would not work OK in use.

    The Dura Ace 7803 and 7703 triple cranks had the same arrangement, with the inner ring having a 92 mm BCD and mounted onto the middle ring instead of the spider. Shimano may have done this for weight saving, but I think that their main motivation was cost because it allowed them to use the same forging process to make the crank/spider assembly for double and triple cranks. With the 7703 they just had to provide a longer BB, and for the 7803 and 6703 they just have to attach a longer axle, and suddenly they had a triple without much extra manufacturing costs.

    I always wonder if having the inner ring bolted to the middle in this way reduces the stiffness compared to being bolted directly to the spider. Since Shimano have used this on their top-end cranks, I guess there is not much difference, but now they are even using it on their new Ultegra-level tandem cranks - a pair of tandem riders can put a huge amount of torque on that inner ring when climbing a steep pitch, so I'm doubtful whether this is really an ideal setup.

    IMO, the 6703 crank is the worst that Shimano have ever produced. All three rings are of a special design and it is a real problem if you want to change the size of any of them. A far better crankset is the 105 model, 5703, on which all three rings have a standard design and BCD. If you want to stick with the stock rings, then the 6703 is an excellent crank, but otherwise it is a big disappointment, and the 5703 is the best that is readily available (no, I don't consider any FSA crank to be a decent alternative to a Shimano).

  10. #10
    AEO
    AEO is offline
    Senior Member AEO's Avatar
    Join Date
    Jun 2007
    Location
    A Coffin Called Earth. or Toronto, ON
    My Bikes
    Bianchi, Miyata, Dahon, Rossin
    Posts
    12,245
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    yeah, 6703 crankset is a poor investment.
    Imagine my disappointment when I bought it for the same price as a 5603.

    however, the middle and outer rings can be swapped for regular 130BCD rings. It's just that it won't look as good.
    Last edited by AEO; 02-21-12 at 01:12 AM.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
    http://sanfrancisco.ibtimes.com/arti...ger-photos.htm

  11. #11
    Gear Combo Guru Chris_W's Avatar
    Join Date
    May 2007
    Location
    Switzerland
    My Bikes
    Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
    Posts
    2,046
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by AEO View Post
    yeah, 6703 crankset is a poor investment.
    Imagine my disappointment when I bought it for the same price as a 5603.

    however, the middle and outer rings can be swapped for regular 130BCD rings. It's just that it won't look as good.
    If you swap the middle ring for a regular, non-tripleizer, ring then you no longer have a triple - you would then have a standard double with a poor chainline.

  12. #12
    Erect member since 1953 cccorlew's Avatar
    Join Date
    Dec 2006
    Location
    Antioch, CA (SF Bay Area)
    My Bikes
    Roubaix Expert, Motobecane Fantom Outlaw turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
    Posts
    6,547
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Chris_W View Post
    I actually tried this out on an Ultegra 6703 crankset a few weeks ago......
    Thanks for this in depth report. It was really helpful. I guess I'm just generally out of luck with my dream of a 28 tooth chain ring, unless I pretty much want to start over.

    I'm thinking that I'll get a Shimano Tiagra 12-30 cassette. That will give me the 1:1 I think need for a big double century with a ton of climbing. I know i won't miss the 52-11 gear. The Tiagra weighs more than the Ultegra, and more importantly lacks the cool factor, but really, who will notice other than me? And as a bonus almost all the middle gears remain the same.

    Code:
        12, 13, 14, 15, 17, 19, 21, 24, 27, 30      Tiagra   329 grams   --> 3 ounces more. 
    11, 12, 13, 14, 15, 17, 19, 21, 24, 28          Ultegra 242 grams
    Last edited by cccorlew; 02-22-12 at 09:19 PM.
    WANTED: Not a darn thing. I've got it all. Life is good.
    Website at curtis.corlew.com —— Bicycle blog at ccorlew.blogspot.com

  13. #13
    Gear Combo Guru Chris_W's Avatar
    Join Date
    May 2007
    Location
    Switzerland
    My Bikes
    Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
    Posts
    2,046
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cccorlew View Post
    I'm thinking that I'll get a Shimano Tiagra 12-30 cassette. That will give me the 1:1 I think need for a big double century with a ton of climbing. I know i won't miss the 52-11 gear. The Tiagra weighs more than the Ultegra, and more importantly lacks the cool factor, but really, who will notice other than me?
    Alternatively, you can assemble a 12-30 cassette that weighs 244 grams by combining most of a Dura Ace 12-27 cassette (minus the 16 tooth cog) with the individual 30 tooth cog from the Tiagra 12-30 cassette, plus a couple of well-chosen spacers in between. See my complete post on how I did this here. But if you don't want the extra expense then the complete Tiagra 12-30 works very well.

  14. #14
    Erect member since 1953 cccorlew's Avatar
    Join Date
    Dec 2006
    Location
    Antioch, CA (SF Bay Area)
    My Bikes
    Roubaix Expert, Motobecane Fantom Outlaw turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
    Posts
    6,547
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Here's my latest blog post that doesn't really clear up things.... yet.
    http://ccorlew.blogspot.com/2012/03/fight-fight.html

    Here's the best part: I'm looking at a serious double with a lot of climbing, so what does the box say?

    Insulting gear box by ccorlew, on Flickr
    WANTED: Not a darn thing. I've got it all. Life is good.
    Website at curtis.corlew.com —— Bicycle blog at ccorlew.blogspot.com

  15. #15
    Senior Member
    Join Date
    Feb 2009
    Posts
    3,969
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    I hate all the new and improved stuff that doesn't help us. This set will allow you to put a 24 on the inner ring. http://www.bikeparts.com/search_resu...p?ID=BPC375353

  16. #16
    Senior Member
    Join Date
    Apr 2007
    Posts
    3,499
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    I didn't read the thread really, really carefully, so excuse me if I missed something.

    My wife has a standard Shimano triple crank. Now, hers is 9 speed, but my solution to get her lower gears using a MTB cassette and RD still might work for you as an alternative to messing with codging together new chain rings. Her system works flawlessly.

    I happened to have a pre-10 speed Deore RD on hand (I don't know if it was originally on an 8 or 9 speed MTB), and her stuff is 9 speed which is very easy and relatively cheap to deal with, I understand you can do the same thing with Shimano 10 speed MTB cassettes. I've heard that you need to find a 9 speed MTB RD to use with the 10 speed road shifters and 10 speed MTB cassette, as the 10 speed MTB RD isn't perfectly compatable for some reason. This would actually be a good thing because the 9 speed RD would be cheaper anyway and probably is the same as an 8 speed too? You would have to check that out. There's been threads on this in bikeforums.net and roadbikereview.com.

    Another solution I've heard - depending on what cassette you already have and how many lower gears you need - is that some 28 or even 32 tooth cassettes can be made to work with Shimano long cage road derailleurs. I guess it depends on exactly how the derailleur hanger is designed and can vary from frame to frame.
    Last edited by Camilo; 03-10-12 at 02:44 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
  •