Cheap di2 group

Discuss light weight issues concerning road bikes & parts.
yumseyo
Posts: 115
Joined: Tue May 12, 2009 12:25 am
Location: San Francisco

by yumseyo

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?

istigatrice
Posts: 793
Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

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.
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

BdaGhisallo
Posts: 1888
Joined: Wed Mar 17, 2004 1:38 pm

by BdaGhisallo

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.

maxxevv
Posts: 1958
Joined: Wed Feb 09, 2005 4:51 am

by maxxevv

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.

kulivontot
Posts: 1170
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

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.

glepore
Posts: 1103
Joined: Thu Mar 28, 2013 4:42 pm
Location: Pa USA

by glepore

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.
Cysco Ti custom Campy SR mechanical (6.9);Cannondale SS Evo Di2 7970 (5.79); Willier Cento Uno Air Di2 9070 (7.0); C40 Mk2 DA 7800 ; Anvil Custom steel Etap;1996 Colnago Technos Record

maxxevv
Posts: 1958
Joined: Wed Feb 09, 2005 4:51 am

by maxxevv

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.

yumseyo
Posts: 115
Joined: Tue May 12, 2009 12:25 am
Location: San Francisco

by yumseyo

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..

kulivontot
Posts: 1170
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

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.

yumseyo
Posts: 115
Joined: Tue May 12, 2009 12:25 am
Location: San Francisco

by yumseyo

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..

motorapido
Posts: 261
Joined: Fri Jul 30, 2010 7:08 pm

by motorapido

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.

kulivontot
Posts: 1170
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

Check techdocs.shimano.com.
External Junction B is sm-jc40, internal is sm-jc41. Front one is ew67 or ew90.

yumseyo
Posts: 115
Joined: Tue May 12, 2009 12:25 am
Location: San Francisco

by yumseyo

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..

Timujin
Posts: 350
Joined: Sun Sep 15, 2013 5:43 pm

by Timujin

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

Timujin
Posts: 350
Joined: Sun Sep 15, 2013 5:43 pm

by Timujin

yumseyo wrote:
motorapido wrote:
Is the E tube software hard to use?

Thanks again..


extremely simple

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