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 Post subject: Cheap di2 group
PostPosted: Sun May 14, 2017 2:35 am 
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Joined: Tue May 12, 2009 12:25 am
Posts: 110
Location: San Francisco
Hi all, can I get your thoughts on putting together a cheap 7970 di2 group. What harness's do I need? I want to use a flatbar with button shifters. Who sells the cateye buttons cheap now? Is the 6770 group cheaper to put together?


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 Post subject: Cheap di2 group
Posted: Sun May 14, 2017 2:35 am 


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 Post subject: Re: Cheap di2 group
PostPosted: Sun May 14, 2017 5:09 am 
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Joined: Sat May 12, 2012 8:32 am
Posts: 734
Location: Adelaide, Australia
can't answer the other questions but I'd say 6770 would be a better group to put together because you can upgrade it to 11 speed with 6870 RD&FD, and it'll be easier to find replacement parts (in the form of 9070/6870 parts). 7970 is hard to find parts for, but I think Shimano are releasing some 7970-A spare parts which may help but a quick google leads me to believe these parts are hard to find and expensive.

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 Post subject: Re: Cheap di2 group
PostPosted: Sun May 14, 2017 10:44 am 
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Joined: Wed Mar 17, 2004 1:38 pm
Posts: 1705
In 2017, 'cheap' and 'DI2 7970' don't belong in the same sentence. The 7970 is exceedingly rare at this point and Shimano stopped supporting it a few years back. Do yourself a favor and get some kind of DI2 with E-Tube - 6770, 6870 or 9070.

6870 can be bought quite inexpensively and you'd have the latest and it would be 11sp, without any potential headaches from keeping an extinct group going.


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 Post subject: Re: Cheap di2 group
PostPosted: Sun May 14, 2017 12:55 pm 
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Joined: Wed Feb 09, 2005 4:51 am
Posts: 1944
Some sites are beginning to 'clear' even 6870 parts/groups in view of the impending 8000 release.
You may be surprised at the prices compared to a NOS 7970 groupset.


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 Post subject: Re: Cheap di2 group
PostPosted: Sun May 14, 2017 2:36 pm 
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Joined: Sun May 16, 2010 7:28 pm
Posts: 1158
Don't bother with the cheapo old groups. Compatibility makes finding the perfect parts very difficult and expensive, especially the rear derailleur. At the very least I'd start with 11 speed as you'll have more opportunities to mix and match.
Also plan for all the little knick knack accessories it takes to actually attach components to your frame. PM me if you decide to do it and have questions.


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 Post subject: Re: Cheap di2 group
PostPosted: Sun May 14, 2017 4:17 pm 
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Joined: Thu Mar 28, 2013 4:42 pm
Posts: 812
Location: Pa USA
Agree with all the above. If you must have 10 speed, go Ultegra. 7970 has too many unique and nla parts. The 7970 derailleurs are very failure prone (I've had 2 die and seen many more) and the replacement 797a, while nice, is $500. There is a 9070 mini group in the classifieds now for 1k, much better deal if you're ok w/ 11.


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 Post subject: Re: Cheap di2 group
PostPosted: Mon May 15, 2017 3:11 am 
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Joined: Wed Feb 09, 2005 4:51 am
Posts: 1944
Of the 4, 7970 RD failures I've seen over the past few years, 3 were due to moisture ingress. And it was mostly from the connector cable not being set properly in place. the 4th one the failure mode couldn't be discerned clearly even after sending it back to Shimano factory to verify though

My 7970 has been running since day 1 ( since October 2009) and its still my weekly ride after all these years.

But I re-iterate, get a new 6870, its a better choice.


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 12:51 am 
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Joined: Tue May 12, 2009 12:25 am
Posts: 110
Location: San Francisco
maxxevv wrote:
Of the 4, 7970 RD failures I've seen over the past few years, 3 were due to moisture ingress. And it was mostly from the connector cable not being set properly in place. the 4th one the failure mode couldn't be discerned clearly even after sending it back to Shimano factory to verify though

My 7970 has been running since day 1 ( since October 2009) and its still my weekly ride after all these years.

But I re-iterate, get a new 6870, its a better choice.


Thanks so much ! I think I have found a set of front and rear 6770 for a 10 speed fairly cheap (about 200.00) for both. What harnesses would I need to make a complete system? I plan on installing the kit on a Dahon Folding bike, 20 speeds, and a bionx motor. I plan to run push button shifters on a flat bar. I already have a battery and charger from my 7970 system, would it fit? Would you please advise me? I used cat eye buttons for shifters on my last two builds, what can you suggest for shift buttons? Sorry for all the questions, there aren't too many articles that spell out exactly what harnesses are needed. Thanks in advance..


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 Post subject: Cheap di2 group
PostPosted: Thu May 18, 2017 2:35 am 
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Joined: Sun May 16, 2010 7:28 pm
Posts: 1158
I think that in addition to the shifters and derailleur, you need the front Junction box A, both new versions and 6770 versions are compatible. You will need Junction box B that sits under the bottom bracket or the internal one that sits inside your bottom bracket. You need a battery, charger, and the battery mount that mounts on the bottle cages. You also need etube wires from shifters to Junction A, one from Junction A to Junction B, and three more from Junction B to derailleur and the battery. I'd also recommend the shimano stick on wire covers so you don't have to zip tie to your frame. Measure these and go bigger than what you think you need because you can always wrap excess wire under the Junction box B. Get the stupid shimano etube tool, it's pretty cheap.


Last edited by kulivontot on Thu May 18, 2017 2:35 am, edited 1 time in total.

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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 3:52 am 
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Joined: Tue May 12, 2009 12:25 am
Posts: 110
Location: San Francisco
kulivontot wrote:
I think the in addition to the shifters and derailleur, you need the front Junction box A, both new versions and 6770 versions are compatible. You will need Junction box B that sits under the bottom bracket or the internal one that sits inside your bottom bracket. You need a battery, charger, and the battery mount that mounts on the bottle cages. You also need etube wires from shifters to Junction A, one from Junction A to Junction B, and three more from Junction B to derailleur and the battery. I'd also recommend the shimano stick on wire covers so you don't have to zip tie to your frame. Measure these and go bigger than what you think you need because you can always wrap excess wire under the Junction box B. Get the stupid shimano etube tool, it's pretty cheap.


Does any one know where I could get part numbers for the harness's ? Thanks..


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 7:19 am 
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Joined: Fri Jul 30, 2010 7:08 pm
Posts: 233
If your running Etube Di2, you will need to run a Shimano shifter of some sort. There is acanbus logic chip built in and Cateye buttons on there own won't work.
Your options are the brain electronics from a Normal drop bar shifter with Cateye buttons grafted into the switches, Not a route i would recommend.

An Alfine S705 flat bar shifter, not the best looking shifter but it works,

A SW600R climbing shifter, buttons are a bit small possibly, but it will work fine,

Maybe an XT Di2 shifter, never tried it myself, but in theory it should work,

in any of these cases you will need to run E tube software to configure and get it up and running.

Wiring harness is just pic the wire lengths that best suit your build, they come in 50mm increments from 250mm up to 1000mm i think.


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 10:28 am 
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Joined: Sun May 16, 2010 7:28 pm
Posts: 1158
Check techdocs.shimano.com.
External Junction B is sm-jc40, internal is sm-jc41. Front one is ew67 or ew90.


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 3:58 pm 
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Joined: Tue May 12, 2009 12:25 am
Posts: 110
Location: San Francisco
motorapido wrote:
If your running Etube Di2, you will need to run a Shimano shifter of some sort. There is acanbus logic chip built in and Cateye buttons on there own won't work.
Your options are the brain electronics from a Normal drop bar shifter with Cateye buttons grafted into the switches, Not a route i would recommend.

An Alfine S705 flat bar shifter, not the best looking shifter but it works,

A SW600R climbing shifter, buttons are a bit small possibly, but it will work fine,

Maybe an XT Di2 shifter, never tried it myself, but in theory it should work,

in any of these cases you will need to run E tube software to configure and get it up and running.

Wiring harness is just pic the wire lengths that best suit your build, they come in 50mm increments from 250mm up to 1000mm i think.


Thank You ! I found a couple part numbers on line: SM EW 67 A, SM JC 40, EW SD 50, SM EW 90 A/B (Junction A), sound about right?

Is the E tube software hard to use?

Thanks again..


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 4:51 pm 
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Joined: Sun Sep 15, 2013 5:43 pm
Posts: 350
motorapido wrote:
If your running Etube Di2, you will need to run a Shimano shifter of some sort. There is acanbus logic chip built in and Cateye buttons on there own won't work.
Your options are the brain electronics from a Normal drop bar shifter with Cateye buttons grafted into the switches, Not a route i would recommend.



ive done this on my P5, works perfect....

Image


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 Post subject: Re: Cheap di2 group
PostPosted: Thu May 18, 2017 4:53 pm 
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Joined: Sun Sep 15, 2013 5:43 pm
Posts: 350
yumseyo wrote:
motorapido wrote:

Is the E tube software hard to use?

Thanks again..


extremely simple


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 Post subject: Re: Cheap di2 group
Posted: Thu May 18, 2017 4:53 pm 


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