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Di2 Bottom Bracket HELP please!

Hi all

I'm just building up my new bike with Di2. I've routed all the cables internally and Junction box B is in the downtube receiving the wire from the front mech, rear mech, and seat post battery (there three wires are going through the BB area into the downtube) and the fourth wire comes from the handlebars internally into the down tube to join the Junction box B

I'm having difficulty getting a threaded bottom bracket in as it's such a tight squeeze with the three wires in the bottom bracket. I'm having difficulty getting the shell in and squeezing pass the Di2 cables.

Am I doing something wrong? What should I do? Help please

Many thanks

Posts

  • majstermajster Posts: 66
    I've just discovered if I remove the plastic shell and insert the two threaded bits of the BB and use the bottom bracket without the plastic sleeve then there is no problem accommodating the wires

    However, is this an acceptable method of installing Di2 internally ie. use BB without plastic shell?
  • First.AspectFirst.Aspect Posts: 9,208
    This will expose the inside of the bearings to anything getting up in there. So if your bike has drain holes in the BB area for example, then this could reduce bearing life. A surprising amount of censored gets in there.

    The other potential issue is that the wires themselves could drag on the axle.

    I have exactly this issue in a titanium 68 mm bb shell, with a 24 mm axle and aluminium sleeve for the BB (it is a KCNC, that it matters). Based on my experience, you have two options -

    (1) thin out the plastic sleeve to give you more room- probably you would need to do this a fair part of the way round, because it will probably twist a bit as you tighten the cups into the shell.

    (2) arrange the wires side by side and just install the BB. If you do this, one of two things will happen.
    (a) the shell will not seat and will break a bit. This will be annoying and you will hate me.
    (b) the sleeve will just about seat, likely with some irrelevant damage at the ends (it is plastic, so isn't a spacer). If it seats, those DI2 cables will be compressed inside the shell. Mine are. The cables have thick, squishy insulation. If it doesn't slice the cable (it won't) and if it doesn't move in use (it won't) all that you will be doing is deforming the plastic. Next time you replace the BB the cables will stay flat against the BB. The next one will go in fine.

    Make sense?
  • I would definitely use the shell, for the reasons mentioned above.

    It may be a bit of a hassle, but it can definitely be done. I did the same on my old 2014 Cube Peloton: https://photos.app.goo.gl/2Zw7x7U5W2wfucbd9.

    Originally I used a Shimano bottom bracket, but at some point I switched to a rotor BB. Their shell was a bit smaller (at the sides) and it was easier to get it past the wire.

    On my new bike there is plenty of clearance. This time I used a PraxisWorks BSA bottom bracket. Even if there wasn't enough clearance, the PraxisWorks BB would've made sure there was - one side of the shell does not have a raised edge so it's easy to get around wires.
    I run BetterShifting.com - Di2 help / tips / guides
  • majstermajster Posts: 66

    I would definitely use the shell, for the reasons mentioned above.

    It may be a bit of a hassle, but it can definitely be done. I did the same on my old 2014 Cube Peloton: https://photos.app.goo.gl/2Zw7x7U5W2wfucbd9.

    Originally I used a Shimano bottom bracket, but at some point I switched to a rotor BB. Their shell was a bit smaller (at the sides) and it was easier to get it past the wire.

    On my new bike there is plenty of clearance. This time I used a PraxisWorks BSA bottom bracket. Even if there wasn't enough clearance, the PraxisWorks BB would've made sure there was - one side of the shell does not have a raised edge so it's easy to get around wires.

    The Praxis BB sounds perfect, do you have a link or model number for one that would take an Ultegra crank and is English threaded. Really appreciate your help
  • Yeah.. sorry - should've linked it before.

    I got this one: https://www.bike-discount.de/en/buy/praxis-works-bsa-shimano-hollowtech-ii-road-bottom-bracket-964333
    There are some more photos here: https://es.wallapop.com/item/cazoletas-praxis-works-bsa-502932827

    I'll try to measure the shell tonight.. just to be sure.. (~3 hours from now)
    I run BetterShifting.com - Di2 help / tips / guides
  • I would definitely use the shell, for the reasons mentioned above.

    It may be a bit of a hassle, but it can definitely be done. I did the same on my old 2014 Cube Peloton: https://photos.app.goo.gl/2Zw7x7U5W2wfucbd9.

    Originally I used a Shimano bottom bracket, but at some point I switched to a rotor BB. Their shell was a bit smaller (at the sides) and it was easier to get it past the wire.

    On my new bike there is plenty of clearance. This time I used a PraxisWorks BSA bottom bracket. Even if there wasn't enough clearance, the PraxisWorks BB would've made sure there was - one side of the shell does not have a raised edge so it's easy to get around wires.

    I have the same model of bike and I'm looking at doing something similar. I don't suppose you have any further photos of the BB area and how you managed to feed the di2 cables through. I know there is internal cable routing that comes out at the bottom of the frame but wasn't sure if there was a hole that fed directly into the BB area? Presumably you have drilled a hole in the seat tube for the front mech?
  • paulbnixpaulbnix Posts: 557
    At one time I had a bike with an FSA Mega Exo bottom bracket. This had a plastic tube but it was in two pieces that slid one over the other so it wasn't a complete seal against water.
    The BB lasted about 1k miles before rusting through from the inside.

    So I would not recommend leaving out the tube.
  • webboowebboo Posts: 4,265
    Is your frame supposed to be Di2 compatible. If so surely the manufacturer should be able to tell you how to fit the cables/ bottom bracket.
  • StillGoingStillGoing Posts: 5,207
    Shove junction B and the cables either up the down tube or up the seat tube out of the way. Up the seat tube would be best option in my experience.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • edited August 2020
    Sorry... I forgot about this thread :}.

    A better photo of the Praxis Works shell is here: https://photos.app.goo.gl/H3RCNXwoNE9xRPHP7

    The bigger bit is on the top of the image, smaller side is near the bottom.

    To answer feelgoodlost's question.. my Di2 wiring went from the handlebars into the downtube and then went to the junction B and battery, both of which I put in the seat post.Then two wires went from junction B out through the hole in the bottom of the frame/bottom bracket area - the hole the regular cable guide screws into.
    (these wires went to RD and FD)

    I had to take a drill to two bits:
    • Made the hole at the bottom of the bottom bracket (the one the cable guide screws into) bigger.
    • Drilled out the internal cable stop at the top of the downtube.
    And yeah. drilling frames is not recommended. Making existing holes bigger is usually OK and drilling out cable stops is fine. Be careful though, and do everything at your own risk. Don't drill things you can't replace if something goes wrong :).

    I run BetterShifting.com - Di2 help / tips / guides
  • Sorry... I forgot about this thread :}.

    A better photo of the Praxis Works shell is here: https://photos.app.goo.gl/H3RCNXwoNE9xRPHP7

    The bigger bit is on the top of the image, smaller side is near the bottom.

    To answer feelgoodlost's question.. my Di2 wiring went from the handlebars into the downtube and then went to the junction B and battery, both of which I put in the seat post.Then two wires went from junction B out through the hole in the bottom of the frame/bottom bracket area - the hole the regular cable guide screws into.
    (these wires went to RD and FD)

    I had to take a drill to two bits:

    • Made the hole at the bottom of the bottom bracket (the one the cable guide screws into) bigger.
    • Drilled out the internal cable stop at the top of the downtube.
    And yeah. drilling frames is not recommended. Making existing holes bigger is usually OK and drilling out cable stops is fine. Be careful though, and do everything at your own risk. Don't drill things you can't replace if something goes wrong :).

    Nice one! So from your explanation, it sounds like you didn't drill any additional holes for the mechs? I was looking at drilling an exit point for the rear mech at the end of the chainstay (where you'd normally find a hole for di2 frames) and then one for front mech?

    Apologies to the original poster - hadn't intended to hijack your thread!
  • majstermajster Posts: 66

    Yeah.. sorry - should've linked it before.

    I got this one: https://www.bike-discount.de/en/buy/praxis-works-bsa-shimano-hollowtech-ii-road-bottom-bracket-964333
    There are some more photos here: https://es.wallapop.com/item/cazoletas-praxis-works-bsa-502932827

    I'll try to measure the shell tonight.. just to be sure.. (~3 hours from now)

    Thank you for your really helpful advice. I can see Merlin have the BB in stock more locally but it is the 68/73 MTB version - will this work on a road bike if is ditch the spacer or do I definitely need the road version?
  • majster said:



    Thank you for your really helpful advice. I can see Merlin have the BB in stock more locally but it is the 68/73 MTB version - will this work on a road bike if is ditch the spacer or do I definitely need the road version?

    Possibly... I don't know - I think the Praxis Works documentation might help. :}


    Nice one! So from your explanation, it sounds like you didn't drill any additional holes for the mechs? I was looking at drilling an exit point for the rear mech at the end of the chainstay (where you'd normally find a hole for di2 frames) and then one for front mech?

    Apologies to the original poster - hadn't intended to hijack your thread!

    Yep, that's right - no additional holes.
    Unless you're splitting and re-soldering Di2 wires yourself the hole should be about 6mm (and to me 6mm looks like a pretty big drill). The Di2 wires are only 2-3 mm in diameter, but the plug itself is 5mm.. so you need a pretty big hole.

    I ran the wires along the chainstay and up the seatstay and then used SM-EWC1 (the shimano 'electric wire cover / cable cover sheath' to tidy things up a bit. The EWC1 comes in both black and white, I used the black one.

    I run BetterShifting.com - Di2 help / tips / guides
  • Run the wires on the outside and secure with electrical tape or cable ties.
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