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Di2 build help-bottom bracket or set up Di2 first?

by GMK
Mon, Jun 25, 2018 15:42
5

looking for some help please.

 I’m just completing my first bike build and I don’t know whether I should test the electrics first or fit bottom bracket.

All the cables are attached, except the front derailleur and I think it would be a good idea to switch it on, do and updates and check it’s all working before I fit the bottom bracket. But can I do that without the front derailleur on?

I don’t want to have to remove the bottom bracket if there’s a problem later. But I can’t fit the front derailleur properly until the chainset is on.

or should I just fir the front derailleur loosely now, check the electrics and then refit the derailleur once the chainset is on?

Also, where is the best place to put the smaller junction box? I thought I could wedge it better in the chain stay so it wouldn’t move but maybe it would be less likely to be affected by any moisture if it’s in the down tube?

 

grateful for any advice.

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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5 comments

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GMK | 6 years ago
0 likes

“y'know, gadgets...”

 

...so this! 3

There was a cable tie in the down tube I could have used to fix the junction box but it got away from me a bit.....

I’ve really enjoyed getting my hands dirty on this build and learning a lot about the bike, hopefully It’ll stand me in good stead when it comes to servicing and looking after it.

 

thanks again for the help and advice!

Avatar
GMK | 6 years ago
0 likes

“y'know, gadgets...”

 

...so this! 3

There was a cable tie in the down tube I could have used to fix the junction box but it got away from me a bit.....

I’ve really enjoyed getting my hands dirty on this build and learning a lot about the bike, hopefully It’ll stand me in good stead when it comes to servicing and looking after it.

 

thanks again for the help and advice!

Avatar
kil0ran | 6 years ago
0 likes

Good luck. In general once it's on you shouldn't have any issues. Just make sure the cable connections to Junction B are clicked home before burying it in the frame.

Did you get the little anti-rattle cable hooks with your kit? If you use those on the cables going to Junction B that should hold it away from the tubes.

FWIW the only issue I ever had with Di2 was when I accidentally yanked the rear mech cable out of the mech. Plugging back in and doing the crash protection reset didn't work, I needed to unplug the battery (which would be major surgery in your build - fortunately I was externally-cabled). 

Loved my time with Di2 but ended up going back to mechanical to part-fund a tourer build. I'll probably stick with mechanical now, but only because I'm more proficient at fettling them than I was back then. Ease of setup was my main reason for going Di2 (plus, y'know, gadgets...)

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GMK | 6 years ago
0 likes

Thanks for that, really helpful and all seems to make sense.

The battery is mounted inside the down tube (Canyon) so plenty of room for the internal junction box inside the seat tube. I might try and wedge it in with some foam so it doesn’t drop down and rest/bump around on top of the BB.

Thanks for your help, off to bleed the brakes now!

Avatar
kil0ran | 6 years ago
1 like

You can test everything off the bike, just keep your fingers away from the front mech when you do it. Junction B for internal cabling is usually placed inside the seat tube above BB and below battery. For external wiring I think the assumption is that it is screwed under the BB where your cable guide used to be. The whole system is weather sealed so it doesn't matter where you put the junctions. Once tested just make sure that you've pushed the cable connections fully home using the official Shimano tool. You could test the mechs on the bike without the chainset but make sure the front mech is clamped tight. There's a lot of torque in that mechanism and I wouldn't risk it jamming somewhere and scratching the frame

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