globecanvas

Hello racer techies,

I have an existing external-wired, external-battery 7970 setup. I'm looking at swapping it over to a new Venge frame.

If I keep the external battery, anybody know what I need to get to make it all work? I think the existing external-application harness won't work in an internal-wired application, because in the current application, the battery is mounted under the down tube, but it looks like there's a mounting point on the Venge under the BB, and I think I probably don't have enough wire to get from the shifter junction down to the bottom bracket. Even if I did have enough wire in the existing harness, I don't know if the external harness can be made to work in an internal application.

If going to an internal battery, anybody know what I need to get to make it all work? Is there a stock setup from Shimano that can work with the Venge? If not, there is an ebay seller who makes custom battery/harness setups for 7970 like this, which looks reputable and workable, but adds some significant cost.

shovelhd

Shimano never made an internal battery for 7970. Calfee and a few others made conversion kits, but they were expensive. You could adapt a new E-Tube internal battery, but that's not cheap either. What Teton and I did was make our own. I would be happy to share the details offline. If you don't want to go that route, there are two battery mounts available, long and short. The long goes under a bottle cage, and the short is used for frames with screws in the NDS chainstay. Check your frame for this. I have one of each that I do not need.

As as for wiring you need to decide whether to go internal or external. The internal 7970 harness kit is getting harder to find although your LBS may be able to order one for you direct from Shimano. Both battery mounts can be used with internal wiring. A custom internal battery will have to be adapted but it's not hard if you know how to solder. If you don't I would be glad to do it for you.

globecanvas

Thanks, that's great info. Predictably, this line of thought has got me pretty far down a rabbit hole.

I would definitely want to go with internal wiring. This kit looks like somebody doing exactly what you have done and selling the battery and custom-made harness for $360. I'll assume that fabricating something myself would cost an equivalent amount of money, time, and advice goodwill. So, $360 to set up my existing 7970 with internal routing & battery.

Or... I could sell the 7970 shifters+FD/RD+harness+battery+charger, and get new 6870 equivalents, including Shimano's internal battery & harness, and probably be out of pocket $400-500 (not including new chain & cassettes). That would be an upgrade to electronic 11-speed, but a downgrade in weight of about 150g.

I know I'm thinking the way Shimano wants me to think, but I'm disinclined to spend money to keep my end-of-life 10-speed electronics working (even though it all works great), and more inclined to spend a little more to get the latest stuff.

On the other hand, I'm already giving up 150-250g in frame weight for the new bike, so tacking on another 150g adds up. It's a bit offputting to spend a bunch of money for new stuff and end up with a bike that's almost a pound heavier. Going with 9070 instead of 6870 would eliminate 150g but cost $900 more.

Lots to think about...

shovelhd

Yup. I've already gotten the wheels taken care of. Now I need to start gathering 9070 bits.

The internal battery I use costs about $20. The waterproof connectors another $10. I found an NOS internal harness for $150. $360 is fair for what you are getting but it does not have to cost that much.

globecanvas

You are going to 9070? Can I ask why, vs 6870?

shovelhd

I think Dura Ace is worth the extra cost. In the old days I used Super Record. When I returned to riding I bought a bike that was all 5600 105. I upgraded that to 7800, then 7900, then 7970. I can tell the difference between Dura Ace and Ultegra, and I have been able to leverage clean used equipment and deals on new equipment to offset the premium.

globecanvas

I'm sorry to belabor this, but since I'm facing the exact same decision: do you believe that there is a functional or performance difference between 6870 and 9070? Beyond the difference in weight and appearance.

shovelhd

I can't say for 11 speed but I can tell the difference in shift quality between 6700 and 7970, especially with a 7900 cassette. The shifting is quicker, smoother, and quieter. That is, like for like. No fair comparing 7970 one-shift-at-a-time to E-Tube shifting speed and dump capability.

carpediemracing 

New BB30 bearings, installed a semi-worn 39T inner chainring. Inner ring no longer hits the frame. BB doesn't creak or grind or index.

tetonrider

probably not fair to compare an electronic group to mechanical....7970 is better than 7900 in shift quality, too.

bummer...i just tossed 2 internal batteries i made for 7970. might have some other harnesses and stuff that could be of use to you. for internal vs external you use the same front junction, but you need different wires for the DT, RD, FD and battery. you also need an SM-JC41 (easy to get; current product). shovel already covered the battery options.

you're concerned with the weight of internal (custom) vs external battery for 7970 due to adding weight on the venge frame (vs tarmac?). going to 9070 vs 6870 could save even more weight and save you from spending more money on 7970 and/or time to make your own battery.

in my experience, the ultegra di2 parts feel just a bit clunkier than 9070...but it's just a perception. i haven't measured it. in theory, it's electronic and should shift the same, but maybe there is something slightly different about the servos used.

shovelhd

I meant 6770 not 6700. Tron vs tron.

mike868y

considering the type of riding and racing you do, you should totally set your bikes up with a 1x10 setup

carpediemracing 

I rode a few months of 2011 without fixing my front derailleur issue (when I raced at the Rent in the 39T due to a broken cable stop) and just adjusted the derailleur for the big ring. I really appreciated the small ring when I fixed the stop and got the small ring back.

grolby

It's not just perception, DA uses more specialized, higher-end motors and shifts faster. My understanding is that Ultegra Di2 uses parts that are closer to being "off-the-shelf" rather than totally custom-designed and manufactured.

tetonrider

gotcha.

shovelhd

That was the case with 7970 versus 6770 but I don't know if that's still true with 9070 and 6870.

globecanvas

I think it is still true.



Here's a low tech question: in the fall I'm doing a fondo-type event with >10k feet of climbing, placing is based on cumulative time on the climbs. I will not be competitive (I might finish 5th or something, but I'll be 20 minutes behind the leaders).

14.5 lb bike with 39/28, or 17 lb bike with 34/28? If I were actually trying to win/place I'd go with the lighter bike for sure but my goal is more to survive.

shovelhd

How steep are some of the sections? If the goal is survival then I'd bring the gears. Any way you can swap cranks or rig up a 39/32?

globecanvas

I'd guess about 1000 feet of the 10k climbing is over 15% grade, the rest is in the 7-10% range. Doable at 39/28, but it will be a 30 rpm situation by the end of the event.

I don't have a BB30 compact to swap in. Maybe I could borrow one, but it would be adding weight (very light standard crank on that bike currently). 39/32 would need a different RD and chain, or else I'd need to be super careful about not crosschaining, but I'm not going to take that risk.

Grumpy McTrumpy

I will consider just using my 32. I don't swap any chains or RDs.

Creatre

I've done a few fondo's with 10k+ feet of climbing. I always use a 53/39 w/ 11-28 for all racing. I'll tell you though, every one of those rides I wished I had lower gears at the time. The last 20-30 miles if there are any significant climbs, and rpm's get crazy low and it just becomes crazy painful (even at crazy low like barely z2 watts after being cracked). I don't know though if I had lower gears if it'd improve anything though. Maybe I'd just be going slower and doing the same thing.

I'd say if you aren't wanting to be competitive ride the bike with the extra gears, just in case.

globecanvas

Are you able to ride 53/32 (presumably accidentally) or would that tear the RD off?

Grumpy McTrumpy

I'd have to check it again but as I recall, that was not an issue.

topflightpro

I'd gladly take 2.5 pounds for better gearing.

I was recently doing a rather steep mountain ride - lots of 15-18 percent for miles on end - and near the end of my ride, I could barely keep the bike moving with a 53-39 and 12-27. I was turning maybe 40rpms and going 3-4mph. It was just enough to maintain balance.

I've got a long weekend in the mountains planned for October. I'll be ditching my PM to put a compact crankset on the bike for the weekend.

Grumpy McTrumpy

or just stick with the 28. I did the Highlander with a 28 and it was fine. Those climbs are as steep or steeper.