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  1. #1
    Clipless in Coeur d'Alene twocicle's Avatar
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    Is this a technically OK Single-Side-Drive w/ Gates Belt implementation?

    As we are moving to a Di2 installation, there is an example of a Single-Side-Drive (SSD) and Gates CenterTrack belt that is interesting me.

    As you probably know, Di2 currently (and for the foreseeable future) can handle only 2 chainrings. This restriction may leave open the opportunity to use the outer chainring location on the drive side for a Gates Belt, preferably the CDX CenterTrack setup as shown in the following photo:

    DSC02546.jpg


    The implementation above utilizes a standard FSA SL-K Light triple crankset, not a tandem specific model. The front cranks are standard FSA SL-K Light doubles. The setup includes some chainring spacers and longer bolts to provide enough separation between the big chainring and the CDX ring so that the Gates belt does not rub the chain at the two points (upper and lower) where the 12mm wide belt passes forward from the CDX ring.

    The photo also shows the use of a standard FSA 53t outer ring simply moved to the inside of the 130BCD spider. Our implementation would use a Specialites TA 48t instead. The clearance requirements between our big ring and the CDX should be no different than in the photo, as the largest clearance required is at the points where the belt passes the chain. Ring pins are inconsequential to the clearance needed as the chain width is the biggest factor.

    Another point likely needing a solution, is the use of an outer ring on a middle position. Middle rings alway have a bolt recess built in, which helps minimize the bolt head sticking out and interferring with the chain when it is on the granny ring. When moving an outer ring to the middle, there is no such recess in the inside. I have no idea about how difficult it may be to machine new recesses in an outer ring. Filing down bolt or nut heads may not be a great idea, as in this case these are holding both the big ring and the Gates ring... probably should use strong steel bolts & nuts (no alloy).

    Apparently Specialites TA does make middle rings in a 48T, but so far no luck sourcing one. Wiggle.com seems to have the best selection of TA rings found anywhere, but no big middle rings on hand. I currently have them on the hunt with their suppliers for a 48t middle.

    Anyone see a technical reason why the implementation above would be a problem?

    ---

    FWIW,

    Here's another example (below) using the Gates CDC belt setup. The CDC ring has a flange on one side, plus a built-in belt offset that helps eliminate (or substantially reduce) the need of chainring spacers. The narrower 10mm belt helps too.

    CDC SSD.jpg
    Last edited by twocicle; 11-09-13 at 10:01 AM.

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    Your chainline will probably be a bit narrower than it should be for a 145mm wheel. Having the timing belt out wide does increase its bending moment on the bike though it probably doesn't matter. The Paketa system of having it on the inside seems better to me. Looks tidier as well. Maybe Calfee could modify your chainstay to allow this while they are mucking around with the frame?

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    Talk to mark at house of tandems, he is marketing this same set up.

  4. #4
    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by Dean V View Post
    Your chainline will probably be a bit narrower than it should be for a 145mm wheel. Having the timing belt out wide does increase its bending moment on the bike though it probably doesn't matter. The Paketa system of having it on the inside seems better to me. Looks tidier as well. Maybe Calfee could modify your chainstay to allow this while they are mucking around with the frame?
    Already asked Calfee, and it would be a big thing to modify the spacing.

    Not going to get into discussing Paketa RSD, other than to say I have a list of issues with that design. Beyond scope of this thread.

    Based on our projected gearing (48/30 and 11-28 majority of the time) we will be running the "big ring" 48t at least 90% of our riding with a great chainline in that gear. It would be like running the middle ring, but a bigger version Actually, tandem blasphemy that it is, we will probably just keep using a 12-27 SRAM 1070 cassette. For the .1% of the time we ever use a top gear, we certainly do not "need" the 11t. We are pretty fast up & down hills, but do not care to push high gears and do not race it. For bigger, steeper hills, likely use a custom 12-34t made up of combining the SRAM and a XT cassette we already have.

    Agree the granny chainline will be a bit more to the inside (obviously), I believe it is still within spec/limits. I've tested the Di2 setup and it runs ok.

    It seems this use of a standard triple crankset has an advantage of being one of the narrower Q-factor setups achievable on a tandem using OOTB components.
    Last edited by twocicle; 11-09-13 at 03:17 PM.

  5. #5
    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by Bad1 View Post
    Talk to mark at house of tandems, he is marketing this same set up.
    The blue Calfee photo is from HoT It looks like a great idea.
    This query is for a broader scope of opinion.

  6. #6
    Clipless in Coeur d'Alene twocicle's Avatar
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    PS: there is a sweet set of 2012 Shimano Ultegra 10spd tandem cranks on eBay now

    see: http://www.ebay.com/itm/141110668655...84.m1555.l2649

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    I see a few potential problems.
    48/30 is beyond the 16T capacity of the Di2 front derailleur.
    also when you shift the front down you are going to need to shift the rear down 2 or 3 cogs first or you will be too low of a gear. Combining cassettes is asking for trouble. I tried it once with a. Shimano 12-25 and 11-28 for the same reason, to get rid of the 11T and gain a 16T. There was one gear that would not shift because the ramps between the cogs did not line up. I am now using a Shimano 12-30 and it works well. I have Di2 on my single and I like your idea but I would never give up my triple on the tandem. If they ever come out with a triple version of Di2 I would be interested. Agree on using steel chain ring bolts, I have had some alloy ones break.

  8. #8
    Senior Member waynesulak's Avatar
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    Depending on your skill level, drilling counter sinks to use an outer ring for a middle ring should be very doable. There are a lot of countersink drill bits available and aluminum is easy to drill. My main concern would be not drill too deep but careful drilling should do the trick. Use an old ring or even buy some aluminum stock from a hardware store to practice. Worse case is you ruin a ring and have to by another. Before drilling however I would try the ring as is to see if it works. With a 10 or 11 speed chain it may work just fine.

    I have used a lot of customized cassettes before finding our current Shimano 12-28. The all Shimano cassettes do shift a little better but many custom cassettes work well. I like the OP's approach to gearing. Find what works for your team and try not to be limited by what Shimano thinks is best to manufacture and sell.

    Is this a 11 speed project? If so I would also try a Camy cassette. They are expensive but have some interesting cog combinations. 11 speed spacing is supposed to be very very close for Campy and Shimano. The OP's top end gearing is similar to our top end and we can use a cassette a long long time.

    Is there a possible issue of damaging the belt if the chain is dropped? Even with an all chain system, having same side drive with two chains crossing always appears to me be a tangled mess waiting to happen.

  9. #9
    Clipless in Coeur d'Alene twocicle's Avatar
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    ^^^ responding to the last 2 posts...

    While 48/30 (18t gap) is beyond the Shimano 16T FD spec, I have tested it with the UDi2 FD and it seems to work fine. Ric's "super compact" setups typically use 53/34, a 19t gap, though he may favor SRAM FDs for those setups.

    Needing to shift rear gears when changing the front ring is no new thing, I do that all the time with mechanical shifters. Lastly, the range of gears we use and preference for tight combinations, does not require a triple front, a double is plenty. In fact, with a 48t big ring we will be using much more of the middle "sweet spot" on the cassette than with a more typical 52t or 53t ring, plus much less shifting front rings than with a triple setup. On the very rare occassion when a 34t cassette is needed, we'll put up with the XT 11-34 (or modified to 12-34) cassette.

    Gear selections are somewhat a non-factor to the technical SSD question at hand. With both the big ring + Gates ring mounted to the same 130BCD spider, I could see a monster power team maybe shredding the spider if they overloaded it with massive torque. We don't fall into that category and I suspect these cranks are spec'd to easily handle the ~900 peak watts I figure we can generate for short term efforts.

    We never once dropped the chain to the outside on our tandem with the 6703 FD. When setting up the Di2 6770 FD that initially did happen before it was adjusted properly. No harm done, there is insufficient room for the chain to jam between the belt and ring. It actually appears to be a nice chain catcher if that ever happens again (unlikely when the FD is adjusted properly).

    I like the inner shape of the FSA "Super Road" big ring shown. Those outer rings have a curve built into them, which probably helps shifting up from a compact setup. Unfortunately, FSA does not make those rings in a 48t. The TA rings are perfectly flat, but the pins seem to get the shifting job done nicely.

    I never seem to get a precise alignment with my cheap drillpress, so I would not want to try machining it myself. Perhaps my LBS or machine shop could, I'll need to check.
    Last edited by twocicle; 11-09-13 at 03:10 PM.

  10. #10
    Gear Combo Guru Chris_W's Avatar
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    We're running a similar setup on our tandem, except that our inner ring is a 26 and the middle is a 42, then the outer ring is Gates CDX CenterTrack (although we previously also used the CDC rings). We're using single-bike Shimano 105 triple cranks; the 5603 model because the crank arm is a bit wider on the 5703, giving less space for the belt-ring. Our main reason for doing this is that we both like to use 165mm long cranks, and there are no decent-quality tandem cranks available in that length.

    We use our tandem mostly for touring and relaxed-paced shorter rides, so we spend most of the time on the 42-tooth ring and in the middle of the 11-32 cassette, and just drop down to the small ring for real climbs, and then try to only use the lower 6 gears. Our rear hub is also a 145 mm, and the chainline looks pretty straight when in the middle ring and on the 5th smallest cog (out of 10). We can pedal up to about 50 kph when we want to (although often we don't bother when going above 40 kph), so the gear range is sufficient for us.

    In addition, I've previously run a 46-30 super-compact on a single bike using only the inner and middle rings of a triple crank. The 46 tooth was then a TA Specialites - I believe that 46 is the largest middle ring they make (which is also what this pdf says - apparently they make a 48-tooth inner for a double but not a 48-tooth middle for a triple). Good online sources for TA rings in Europe are xxcycle.com (a French site), who do list the 46-tooth middle, and bike-components.de (German), but they only list up to 44-tooth middles. I also have a crank with 46-29 chairings (a Lightning crank with a 94mm BCD double spider).

    With all of these super-comact combo's (26-42, 30-46, 29-46) I've been able to get them to shift OK, but I had to play around with the height of the FD until I found something that worked well (which wasn't necessarily a couple mm above the larger ring as it would normally be), and I found that double FDs worked better than triple FDs. Even so, front shifting is never smooth, and the shift between rings requires definitely 2 and often 3 compensatory rear shifts to keep the cadence somewhat decent; you soon get used to doing this, but you may still not like it even after you're used to it.

    I spent a LONG time finding the right chainring spacer combination that would make the 26-42-CDX triple setup work. I used triple chainring bolts and nuts (designed to be used when mounting 3 chaingrings on one set of bolts) and had a whole range of spacer sizes to play around with. Even once you've found a spacing that works then you also need to get the belt-rings perfectly centered on the spider. Even the inner nuts from the triple bolts are not long enough to extend inside the belt-ring, so there is nothing to keep the belt ring very centered. I therefore spent even more time loosening the 5 bolts, moving the ring a little, tightening the bolts and then seeing whether the belt tension was even throughout the crank revolution, and trying to get this right on front and rear cranks.

    People have mentioned the increased bending moment on the boom tube due to the exterior position of the belt-rings, but I can't say that I'm very worried. After about 5,000 km of riding (half of that fully loaded with touring gear), the bottom brackets are not showing any undue signs of wear. If we are losing any efficiency, the hopefully it's being made up for due to us having cranks that have a length that we're happy with, and are a bit lighter than most tandem crank offerings.
    Last edited by Chris_W; 11-09-13 at 05:24 PM.

  11. #11
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    I don't see why it's advantageous to put the belt drive on the outside. Taking a standard (3 piece) road triple and increasing the spindle length by 10mm will give you the optimal chainline (excluding the granny gear) for an 145mm wheel and ample room to mount the belt drive in place on the granny gear.

    My math might be off but I think the logic is sound.

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    There are only two potential problems that I can see.
    -Sometimes when you shift to the big chainring the chain actually goes a bit past the sprocket teeth for a few links before going on properly. You wouldn't normally notice it but it has caused some issues with our outboard timing chain drive. As to whether this is a problem would depend on the belt clearance and how tolerant it is of getting pushed a bit by the chain.
    -Also the shifting of what will probably be non shimano chainrings and of odd sizes. With a mechanical system if it doesn't shift great you can finess it on with the lever. With electronic when you hit the button it is shifting immediately and if it doesn't want to do it there may be issues with servos etc. However you did mention that it seemed to be ok from a bit of playing around you have already done.

  13. #13
    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by Bezalel View Post
    I don't see why it's advantageous to put the belt drive on the outside. Taking a standard (3 piece) road triple and increasing the spindle length by 10mm will give you the optimal chainline (excluding the granny gear) for an 145mm wheel and ample room to mount the belt drive in place on the granny gear.

    My math might be off but I think the logic is sound.
    This implementation is using "a standard (3 piece) road triple" instead of a more typical set of tandem cranks. The advantage of using a standard triple and mounting the Gates ring on the outside is a lower Q-Factor (-7mm in the case of FSA SL-K cranks) at 157mm, plus the elimination of 1 spider resulting in some weight savings, plus ability to use a proper granny gear (anything mountable on a 74BCD).

    With a standard (3 piece) road triple, there is insufficient clearance between the granny position and BB shell. The Gates belt takes a lot of room to achieve the required clearances. The only way to achieve that is to use a set of cranks with an even longer axle and thus a wider Q-factor, and hope the ring w/belt clears your chainstays (enter Paketa's custom skinny yoke).

    Additionally, to mount a Gates ring on the inside of a standard triple, you must 1) either use a special 74bcd-130bcd adapter, or mount 3 rings to a single 130bcd spider, which means that 2) you eliminate the possibility of using a drive ring of less than 38T, ie: no granny!

    Regardless, discussing the merits of inner vs outer belts is pretty much out of scope here. The question was regarding potential technical issues with the given approach as shown.

    One addnl thought I had about this setup... the actual Gates ring distance from the tandem's centerline is not much different than a typical left-side-drive. Surprising, but it seems true. For example the last set of tandem cranks we had, used a 49.9mm left-side timing ring chainline, whereas this SSD standard triple has 45mm centerline + outer position + 3mm spacers. If one claimed benefit of SSD is a reduction of frame and BB twist, then perhaps a few mm increased centerline is maybe not a big deal. Comments?
    Last edited by twocicle; 11-11-13 at 10:21 AM.

  14. #14
    Senior Member waynesulak's Avatar
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    Quote Originally Posted by twocicle View Post
    This implementation is using "a standard (3 piece) road triple" instead of a more typical set of tandem cranks. The advantage of using a standard triple and mounting the Gates ring on the outside is a lower Q-Factor (-7mm in the case of FSA SL-K cranks) at 157mm, plus the elimination of 1 spider resulting in some weight savings, plus ability to use a proper granny gear (anything mountable on a 74BCD).

    With a standard (3 piece) road triple, there is insufficient clearance between the granny position and BB shell. The Gates belt takes a lot of room to achieve the required clearances. The only way to achieve that is to use a set of cranks with an even longer axle and thus a wider Q-factor, and hope the ring w/belt clears your chainstays (enter Paketa's custom skinny yoke).

    Additionally, to mount a Gates ring on the inside of a standard triple, you must 1) either use a special 74bcd-130bcd adapter, or mount 3 rings to a single 130bcd spider, which means that 2) you eliminate the possibility of using a drive ring of less than 38T, ie: no granny!

    Regardless, discussing the merits of inner vs outer belts is pretty much out of scope here. The question was regarding potential technical issues with the given approach as shown.

    One addnl thought I had about this setup, is that while the outer belt position may be further away from the centerline, it has been claimed that SSD helps to eliminate frame twist, so it would seem to be a wash regarding this being any worse twist-wise over a more standard left-side-drive. Comments?
    Within the scope of your question I think the conclusion is that is should work but only actual testing will determine if chain rub is an issue or not.

    Using a compact crank would allow for a second choice upgrade should the outer gates setup not prove to work as well as you would like. Non-tandem light weight compact cranks could fit a middle position ring of 33 rather than being limited to 38 and would open the possibility of using the 74mm inner ring as the transfer ring with a chain. A 30-34 transfer ring would not require frame modification as the gates ring does and not require another spider. You would still have same side drive and a light non-tandem cranks of you choice plus some weight savings from a shorter chain and smaller rings vs a standard tandem crank 42 ring setup.
    Last edited by waynesulak; 11-11-13 at 11:04 AM. Reason: removed reference to rough terrain

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    Any discussion on frame flex from LH or RH timing chains is purely academic. It just isn't an issue and even less so on a stiff frame like a Calfee.
    One does wonder though why you are taking off a crankset and shifting system that works very well to replace it with something that will probably not achieve much apart from limit your gearing options and lighten your wallet!

  16. #16
    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by waynesulak View Post
    Within the scope of your question I think the conclusion is that is should work but only actual testing will determine if chain rub is an issue or not.

    Using a compact crank would allow for a second choice upgrade should the outer gates setup not prove to work as well as you would like. Non-tandem light weight compact cranks could fit a middle position ring of 33 rather than being limited to 38 and would open the possibility of using the 74mm inner ring as the transfer ring with a chain. A 30-34 transfer ring would not require frame modification as the gates ring does and not require another spider. You would still have same side drive and a light non-tandem cranks of you choice plus some weight savings from a shorter chain and smaller rings vs a standard tandem crank 42 ring setup.
    ^^^ finding this suggestion somewhat baffling as compact cranks are 110bcd doubles with no 74mm/granny ring option, plus the Gates ring is strictly 130bcd.

  17. #17
    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by Dean V View Post
    Any discussion on frame flex from LH or RH timing chains is purely academic. It just isn't an issue and even less so on a stiff frame like a Calfee.
    One does wonder though why you are taking off a crankset and shifting system that works very well to replace it with something that will probably not achieve much apart from limit your gearing options and lighten your wallet!
    • Going back to the OP, I have the desire to use Di2's precise shifting.
    • The current Di2 FDs will only work with 2 chainrings. So, Di2 is the main culprit if you will.
    • In order to achieve an adequate 2 chainring gear range, I chose a "super-compact" ring setup of 48/30.
    • Our previous tandem crankset had a 39T middle-ring triplizer mounted 30T granny. No option to get a 48T triplizer, hence replacing previous crankset with new, standard cranksets that have a 130/74mm BCD.
    • This selection will not require any extreme cassettes with large progression gaps. We will be fine using anything from a 12-27 (95% of the time), to 11-32 or 11-34 (rare 1% extreme). Nothing unusual here.
    • Our sweet-spot gear ratios work out to be 48x14-17, which is very achievable.
    • A side benefit is much, much less front ring shifting will be needed.
    • Agree with the last point, it does lighten one's wallet, plus a 1/2lb off the tandem.
    Last edited by twocicle; 11-11-13 at 12:03 PM.

  18. #18
    pan y agua merlinextraligh's Avatar
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    ^ I'm assuming your replacing the rear derailleur cage with a long cage?
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  19. #19
    Clipless in Coeur d'Alene twocicle's Avatar
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    ^ yes indeed. The Di2 RD-6770 (short cage only) needs a longer cage to handle the extra chain slack.

    I tried ordering some RD-6700A GS (mid-long cage) parts for $30 from Shimano, but they are out of stock until some future date - maybe January they said, so I went ahead and bought a full 6700A GS instead from a shop in CO for $95. I received a 6700A but SS version, which I need to return - but did go ahead and test the cage off that SS model to ensure it does fit the RD-6770. The 6770 cage seems to have a lower top jockey wheel and the cage stop in a slightly different position than the 6700 models, but the 6700 installs and rotates without any issue. I can't figure out why they made those 2 changes on the 6770, because those would only seem to effect the cage when no chain tension is there to pull the cage to its normal "sprung" operating position. Since the 6700A is designated with "30T" max sprocket size (and people report success using 32T cassettes), the fact that I already confirmed the cage fits indicates this modification should work fine.

    I may still install a 10T top jockey wheel just to improve clearance for if/when we ever use a 34T cassette. All told, this mod comes to $95 + maybe $35 for trick ceramic bearing KCNC jockey wheels, and this should work for up to a 34T cassette.

    Going this route is a lot cheaper than the $335 that KCNC wants for their RD mod, and that mod apparently voids the Shimano warranty. Swapping Shimano cages is a piece of cake, and maybe explains why they are currently out of stock on the parts.
    Last edited by twocicle; 11-11-13 at 04:02 PM.

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    Quote Originally Posted by Chris_W View Post
    I used triple chainring bolts and nuts (designed to be used when mounting 3 chaingrings on one set of bolts)
    Hi Chris,

    interesting! Where did you get those triple chainring bolts and nuts? We use a compact-crank (50-33) with a right side timing chain that runs on another 33 tooth (inside) ring. We managed to get this system working but could use longer bolts and nuts for the stoker-crank. We live in Germany. Thanks in advance!

    Karl

  21. #21
    Gear Combo Guru Chris_W's Avatar
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    Quote Originally Posted by Heidelfix View Post
    Hi Chris,

    interesting! Where did you get those triple chainring bolts and nuts? We use a compact-crank (50-33) with a right side timing chain that runs on another 33 tooth (inside) ring. We managed to get this system working but could use longer bolts and nuts for the stoker-crank. We live in Germany. Thanks in advance!

    Karl
    TA makes long chainring bolts (see here), but I'm sure there are other sources.

    Regarding the cage on the 6700 derailleur: I think the upper pulley position may be slightly different on the GS version than on the SS because it is only the SS that is rated for a 30-tooth cassette, I believe.

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    Clipless in Coeur d'Alene twocicle's Avatar
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    Quote Originally Posted by Chris_W View Post
    Regarding the cage on the 6700 derailleur: I think the upper pulley position may be slightly different on the GS version than on the SS because it is only the SS that is rated for a 30-tooth cassette, I believe.
    Actually my comment (as spaghetti-like as it was) was a comparison of the Di2 6770 SS vs the mechanical 6700A SS (that was shipped in error). Both the SS and GS versions of the 6700A were revised to accommodate a 30T.

    Specs of the 6700A GS version:

    Max sprocket: 30T
    Max front difference: 22T
    Total capacity: 40T

    Swapping that cage to the Di2 6770 should allow this newer RD to achieve the same specs. Many people report the Shimano specs are conservative and have success using the 6700A with a 32T cassette without any issue (maybe using a lot of the B-tension screw, but that depends on your hanger length - some are longer than others). Further tweaks are to use a 10T upper jockey for a tad more clearance, which I am thinking may get this 6770(A) up to a 34T.
    Last edited by twocicle; 11-13-13 at 08:28 AM.

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    Quote Originally Posted by Chris_W View Post
    TA makes long chainring bolts (see here), but I'm sure there are other sources.

    Regarding the cage on the 6700 derailleur: I think the upper pulley position may be slightly different on the GS version than on the SS because it is only the SS that is rated for a 30-tooth cassette, I believe.
    Thank you, I think Iīve got those. They are still a bit short for tandem-drive-side-sync-chain-use since one needs to add washers to make room for the two chains that need to pass each other.

    As twocycle said, the RD 6700A GS was changed by Shimano to deal now with cassets up to 30T. I have used one for a single bike and changed the upper pulley-wheel to a smaller one made by tacx. In addition I have reduced the tension of the lower barrel-spring (the one that "holds"/pulls the cage), thus virtually amplifying the effect of the t-screw. It shifts up to 34T now. I will try a 36T cassette, but havenīt done so yet. I wonder if these changes could be successfully done to a RD 6770?

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    Clipless in Coeur d'Alene twocicle's Avatar
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    ^^^ Correct, that is what I am trying to do here... mod the 6770 with parts from a 6700A GS. Shimano's "EV" (exploded view) docs show these to be virtually identical, except for the two minor points I made earlier. So, I am trying to make up a "6770A GS" if you will.

    Hoping to use a long cage from a MTB RD, I looked through many of those EV docs online, but none seemed to show the same cage post axle type of the 6700 series. So I did not find a compatible MTB RD cage.

    I have no idea why Shimano skipped coming out with a GS (mid/long) cage for the 6770. Even the latest Di2 models that can handle 32T cassettes still do not have the increased chain slack handling of the mid-length cage of the 6700 GS series. Sort of a bizarre gap IMO.
    Last edited by twocicle; 11-13-13 at 08:44 AM.

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    Clipless in Coeur d'Alene twocicle's Avatar
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    So, I think I now have this SSD configuration ok and the clearances work fine on our 145mm spaced Calfee. Finding the perfect length chainring bolts & nuts was somewhat of a headache.

    Cranks used:
    Captain: SL-K Light double cranks, 175mm
    Stoker: SL-K Light triple cranks, 170mm

    Gates CenterTrack (CDX) rings mounted to the outer position and spaced away from the spider arms with Origin 8 3.5mm spacers.
    Drive rings: Specialites TA 48t outer ring mounted to the middle position, and a 30t granny. Shifting the 18t jump seems to work ok with a standar Di2 6770 FD.

    For the stoker cranks, ended up using e-13 (e-Thirteen) 15mm bolt/nut kit (sourced from UniversalCycles.com). The granny needed a 1mm spacer to move it away from the 130mm BCD nut head positions:

    P1030582 (Large).JPGP1030587 (Large).JPGP1030583 (Large).JPGP1030585 (Large).JPG


    For the captain's cranks, used Origin 8 12.5mm bolt/nut kit, plus a 1.5mm spacer on the inside of the spider to keep the nut head off of the carbon arm:

    P1030579 (Large).JPGP1030578 (Large).JPGP1030581 (Large).JPGP1030577 (Large).JPG


    Installed view w/non-final bolts. Also, I didn't bother getting the crank arms in sync for this shot, so ignore the out-of-phase:

    P1030493 (Large).jpgP1030494 (Large).JPG
    Last edited by twocicle; 11-28-13 at 07:50 PM.

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