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chojn1 03-16-14 07:05 PM

3 Attachment(s)
Twocicle,
Thanks for the heads up on the crank. I am a little disappointed that it will not work. But, your 48/30 crankset scheme seems to be working well for me. I may just stick with that for now.

The rain stopped just as I was completing the installation. So my wife and I took a spin on the thing around the neighborhood. Here is the bike during our ride:

http://bikeforums.net/attachment.php...hmentid=369225
Most people prefer an internal battery. But for me, it is so much more convenient to use the external - easier to bring the battery to the charger than to bring the charger to the bike. The shifting with the DI2 is precise and silent, the brake levers feels more secure, the ergonomic of the new shifter is more comfortable in my hands, and the wires and cables hides very cleanly.

Here is the wiring for the rear derailleur:
http://bikeforums.net/attachment.php...hmentid=369414

And here is my computer/DI2 controller mount. Notice how clean the wires hide away.
http://bikeforums.net/attachment.php...hmentid=369415

CJ

dwmckee 03-18-14 10:30 PM

Great information!

akexpress 03-19-14 12:49 AM

you have some incredible skills i love the way you recessed the di2 junction box with battery indicator into the computer mount

waynesulak 03-19-14 08:13 AM

Looks very nice. Extremely clean installation.

chojn1 03-20-14 06:49 AM

Thanks for the compliment. And thank you for the help and encouragement. I was in the process of packing the frame to send back when I got your encouragement to do it myself. Now I am enjoying this bike so much more because I contributed in building it.

Just in case anyone is considering repeating the process, there are a couple of things that I learned that were not quite clear in the posts. First, for the metal frames, you will need to cut a 5mm deep groove over about 270 degree of the eccentric. The Cannondale eccentric is the easiest one to use for this, but, you have to modify it to make sure it does not get stuck. I modified the Davinci/Bushnell model that came with my bike and so far has had no problem with structure or noise. If you use the Bushnell, make sure it is the feather light version as the original model is very heavy and is completely solid all the way around.

The second issue is the crankset modification. I am using the 48/30 set that Twocicle recommended. This is very easy to do by just removing the outer ring and replacing the middle ring with a 48t one. You do not need an extended clamp or even the FSA tandem clamp for this. A regular one will do. But, you will need five 1mm washers between the crankset and the inner ring to clear the fixing bolts of the 48t ring. The DI2 front derailleur works fine with this configuration. I also modified the rear derailleur per Twocicle using the longer cage and reverse pivot screw for the 11-32 cassette. It is working well, but I cannot say if it would have worked anyway without the modification.

Have fun!
CJ

twocicle 03-20-14 11:48 AM

1 Attachment(s)
Quote:

Originally Posted by chojn1 (Post 16594621)
Thanks for the compliment. And thank you for the help and encouragement. I was in the process of packing the frame to send back when I got your encouragement to do it myself. Now I am enjoying this bike so much more because I contributed in building it.

Just in case anyone is considering repeating the process, there are a couple of things that I learned that were not quite clear in the posts. First, for the metal frames, you will need to cut a 5mm deep groove over about 270 degree of the eccentric. The Cannondale eccentric is the easiest one to use for this, but, you have to modify it to make sure it does not get stuck. I modified the Davinci/Bushnell model that came with my bike and so far has had no problem with structure or noise. If you use the Bushnell, make sure it is the feather light version as the original model is very heavy and is completely solid all the way around.

The second issue is the crankset modification. I am using the 48/30 set that Twocicle recommended. This is very easy to do by just removing the outer ring and replacing the middle ring with a 48t one. You do not need an extended clamp or even the FSA tandem clamp for this. A regular one will do. But, you will need five 1mm washers between the crankset and the inner ring to clear the fixing bolts of the 48t ring. The DI2 front derailleur works fine with this configuration. I also modified the rear derailleur per Twocicle using the longer cage and reverse pivot screw for the 11-32 cassette. It is working well, but I cannot say if it would have worked anyway without the modification.

Have fun!
CJ

A longer RD cage is needed to uptake the extra chain slack that results from using a larger chainring difference, re: a triple or "super-compact". The longer cage does not provide extra clearance for larger cassette cogs. You can achieve extra clearance by maxing/reversing the B-tension screw (as you have done) and by installing a smaller 10-tooth upper jockey wheel.

Regarding the chainring nut->granny clearance, some thin spacers are needed depending on the size and shape of the chainring nut head. A little judicious filing can help to eliminate the chain from catching on the nut.

A nice way to finish off your outer crank spider appearance is to use either a chain guard (search for "fsa carbon chain guard" to find on eBay @ $30), or Race Face Crank Arm Outer Tab Spacers.

Here is a photo with the FSA guard:
http://bikeforums.net/attachment.php...hmentid=369999

Chris_W 03-21-14 01:09 AM

Why go to all the hassle to work around the protruding bolts inside the 48 tooth ring mounted on the wrong side of the spider when you could just get TA 46 tooth ring that is designed to be in the middle position, so has recesses for the bolts on the correct side? The two-tooth difference is not that important - the 4% relative difference would be equivalent to less than half a tooth on the rear.

chojn1 03-21-14 06:37 AM

Twocicle,
Thanks for the explanation. I have not change out the upper jockey wheel. But the system is running so smoothly for me, I am not sure how that extra step will help. Then again, I am only running 32t and not 34t or 36t cassette.

Chris,
The 48t outer ring is what I have on hand, so that was what I made work. The added shim is not that big deal, and the protruding fixing screw also help in the pin and ramp effects of a smoother shift.

I am not familiar with TA chainrings. Do they have pins and ramps or are they symmetrical? If they are symmetrical, can you rotate an outer ring around to get the indent on the correct side? I was already hesitant to go to 48t for the lost of the higher gear ratio but must do so for the 18t difference in the two chain rings. I am not sure I want to go to 46t.

CJ

seth10015 03-21-14 09:25 AM

CJ
Nice tandem! Sorry if I missed it, but what fork are you using? What is the rake? I'm waiting for Co-motions new tapered disk fork, but won't wait much more unless absolutely necessary.
Thanks, Seth

twocicle 03-21-14 04:12 PM

Quote:

Originally Posted by chojn1 (Post 16597736)
Twocicle,
Thanks for the explanation. I have not change out the upper jockey wheel. But the system is running so smoothly for me, I am not sure how that extra step will help. Then again, I am only running 32t and not 34t or 36t cassette.

Chris,
The 48t outer ring is what I have on hand, so that was what I made work. The added shim is not that big deal, and the protruding fixing screw also help in the pin and ramp effects of a smoother shift.

I am not familiar with TA chainrings. Do they have pins and ramps or are they symmetrical? If they are symmetrical, can you rotate an outer ring around to get the indent on the correct side? I was already hesitant to go to 48t for the lost of the higher gear ratio but must do so for the 18t difference in the two chain rings. I am not sure I want to go to 46t.

CJ

Just keep the jockey wheel info in the back of you mind should you wish to get a larger rear cog/cassette.

Chris, adding 1mm of spacers to the granny is likely less of a "hassle" than using an under sized chainring. I understand the 46T meets your needs, but a 46Tx11 is too tiny a top gear ratio for most people riding road tandems. A 48x11 is a slightly higher ratio than a 52x12 which is sort of the minimum... subjective maybe, I understand.

CJ, non-singlespeed/track chainrings come in inner, middle and outer types. As with most ring brands, only the middle and outer rings are pinned & ramped on one side only. You cannot flip pinned & ramped rings around and expect them to shift well, therefore you must keep the ring face oriented in the proper way. Specialites TA makes high quality, good shifting rings available in a wide variety of teeth. My favorite source for Specialites TA is Wiggle.com. Alize rings for 130bcd (outer type, but mounted in the middle position) and Zelito for 74bcd rings.

chojn1 03-22-14 06:38 AM

Twocicle,
Those TA's do look nice. I'll grab some once I put some wear on these FSA's.

Seth,
That is an ENVE cross disc tapered with a 47mm rake. They also make a lighter road version with a 43mm rake. But you are limited to 28mm tires.

I am off to morning coffee ride.
CJ

twocicle 03-22-14 03:37 PM

That all said, in my single road racing "A" crowd, a 50/34 x 11-23 cassette is not enough of a high end, nor is the 50/34 a good combination for cruising along at 21-23mph while training. The problem with that gear range is that at 21-23mph I end up cross-chaining either the 34 or 50 for much of my rides, then in races the 50x11 is not high enough to bridge/close gaps on fast downhills. Using a compact crankset for my single racing, a 52x11 top gear is needed at a minimum so I use a 52/36 on that bike.

On the tandem, we do not race and if we are riding with others the concept is to ride together, so a gear higher than 48x11 (equiv to 52x12) is not all that necessary for our purposes. If we were racing the tandem, I'd probably install a 53 or 54 big ring and a 36 or 39 small ring.

As it currently stands with the 48/30 "super-compact" chainring setup, we are riding > 95% of the time in the big ring and middle of my custom "ShimSRAMo" 11-28 cassette. This means we are doing very little FD shifting and multi-rear cog switching due to the 18T gap in the front rings. I'm really liking this setup.

Chris_W 03-23-14 01:06 PM

Quote:

Originally Posted by chojn1 (Post 16597736)
I am not familiar with TA chainrings. Do they have pins and ramps or are they symmetrical? If they are symmetrical, can you rotate an outer ring around to get the indent on the correct side?

TA makes all sorts of chainrings designed for all types of purposes, some of which may be symmetrical. The one I was referring to is a 46 tooth 130mm BCD designed for the middle position of a triple crankset. It's therefore not symmetrical and has the pins and ramps pointing towards the inside, the same side as where the bolt recesses are. I've found that the shift ramps on TA rings are not quite as good as those on a Shimano ring (even when using TA rings that have more standard sizes), but since Shimano offers very few chainring size options, the increased flexibility in ring sizes with TA is often worth the minor decrease in shift performance for me.

twocicle 03-23-14 01:36 PM

^^^ With the TA rings + UDi2 FD, we have been getting very quick front shifts and engagement - no studdering. These results were with an older Ultegra chain and KMC "Missinglink 10R" (re-usable) from last year. I finally installed a new chain and link last night, and so anticipate even better shifting on the RD and cassette.

Given that we are now shifting between front rings so rarely, I'm hoping the TA last a long time. Not sure what the overall concenus is for ring longevity/comparison, but have read posts that TA shifts better than FSA. With Shimano moving to weird 4-arm ring designs, new options from that mfr are becoming more limited.


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