Author Topic: Di2 cabling with a BSA BB and 30mm spindle  (Read 604 times)

Di2 cabling with a BSA BB and 30mm spindle
« on: June 21, 2019, 02:32:04 pm »
To cut a long story/rant short, I have a lovely frame that I built myself, but it has a BSA BB shell rather than the T47 that I wanted. This means that I am not sure that my cranks with a 30mm spindle will safely fit along with the Di2 cables that will need to go through the BB shell. The BB (Easton) has a plastic sleeve that would stop the spindle rubbing against the cables, but my initial fitting suggests that I'm really going to struggle to fit that (or even the spindle without the sleeve) with the cables in place.

Does anyone else have any experience/insight that could help?

Will the cables flatten a little if they're squished, and would that affect them adversely?

Would jamming everything in (even if it's possible) just cause friction and wear on the sleeve/spindle? I expect so!

Is it possible to dremel shallow channels to give the cables slightly more room? Or would this affect the integrity of the BB shell? (Not that I have a dremel...)

I'm going to be building the frame up as a single speed to start with, as I'm waiting for the new Shimano GRX to come out, but it would be nice to know that it's possible to get round this.

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #1 on: June 21, 2019, 03:36:27 pm »
the clearance is less than 2mm on the radius.  I'm guessing you have a steel BB shell; I don't think it would hurt to make a shallow groove in the lower part of the shell (after all some are slotted), but

a) the groove would have to be in a highly stressed part of the shell (near where the downtube meets) and
b) the wires would still have to bend around the corners to get into the groove and the slightest debris in the BB may cause the wires to snag and wear.

I wonder if it isn't better to cut the Di2 wires, and splice a length of different (thinner, individual strands, or ribbon perhaps) cable into the Di2 harness. This could be bonded to the inside of the shell with epoxy resin.  Worst case if it doesn't work is that it costs you a harness?

Fundamentally it feels wrong to be cutting the frame about for the sake of the gears; a bit 'putting cart before horse' if you like.  Its easy to be blinded to this but the priorities in any bike ought to be

a)- frame
b) - wheels
c) - transmission fundamentals
d) - everything else.

so you might be putting d) ahead of a) if you start cutting the frame about.  Its bad enough that mere fashion has probably caused you to have holes in highly stressed parts of the frame anyway...?

cheers

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #2 on: June 21, 2019, 03:56:08 pm »
SRAM wireless or 24mm spindle cranks would seem to be the more straightforward options to consider.

Quote
cable into the Di2 harness

Modern Di2 doesn't have a harness, it has two-core twisted pair cable in a soft rubber sheath, and the junction boxes common the two cores across. It is quite amenable to splicing and hacking.

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #3 on: June 21, 2019, 04:13:43 pm »
just in case it isn't obvious, if necessary you could use multiple strands in a thin ribbon cable in parallel to improve reliability/current capacity whilst keeping the profile as low as possible.

cheers

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #4 on: June 23, 2019, 01:11:29 pm »
I know I'm being stupid, naive and ignorant of a subject that shouldn't concern me but can anyone explain to me why it is essential that Di2 cables go inside frames. If there is one thing more than any other that puts me off about it it's that!

Zed43

  • prefers UK hills over Dutch mountains
Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #5 on: June 23, 2019, 07:53:27 pm »
It's not essential, but it looks tidy ;D (and maybe, maybe, slightly more damage resistant, but when was the last time that the wire to your rear light got damaged?)

rr

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #6 on: June 23, 2019, 07:59:58 pm »
To cut a long story/rant short, I have a lovely frame that I built myself, but it has a BSA BB shell rather than the T47 that I wanted. This means that I am not sure that my cranks with a 30mm spindle will safely fit along with the Di2 cables that will need to go through the BB shell. The BB (Easton) has a plastic sleeve that would stop the spindle rubbing against the cables, but my initial fitting suggests that I'm really going to struggle to fit that (or even the spindle without the sleeve) with the cables in place.

Does anyone else have any experience/insight that could help?

Will the cables flatten a little if they're squished, and would that affect them adversely?

Would jamming everything in (even if it's possible) just cause friction and wear on the sleeve/spindle? I expect so!

Is it possible to dremel shallow channels to give the cables slightly more room? Or would this affect the integrity of the BB shell? (Not that I have a dremel...)

I'm going to be building the frame up as a single speed to start with, as I'm waiting for the new Shimano GRX to come out, but it would be nice to know that it's possible to get round this.
GRX is available now from Rose bikes and other German discounters.

Sent from my moto x4 using Tapatalk


Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #7 on: June 23, 2019, 09:48:11 pm »
I know I'm being stupid, naive and ignorant of a subject that shouldn't concern me but can anyone explain to me why it is essential that Di2 cables go inside frames. If there is one thing more than any other that puts me off about it it's that!

It doesn't. You can use this set of stick-on cable guides with this under-BB external junction box to route it externally.

I have a bike with this setup - you can see the black stripe under the downtube in the second photo here. The biggest issue is where to put the battery - I decided the external one was ugly so cheated and routed the cable inside to the seatpost via the frame drain hole (cable cutting and splicing required). I also routed the FD cable through the tube embedded in the BB shell for the mechanical cable (ditto).

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #8 on: June 24, 2019, 01:32:32 pm »
I also have a steel frame I built myself and fitted with internal Di2. BB is a standard BSA threaded shell. I am not familiar with your crankset but I have Shimano  Hollowtech cranks. The Di2 cables fit just fine in the grooves in the plastic liner on the BB axle. I have previously run the cables outside but internal looks neater.

If you have questions, feel free to send me a PM.
I am often asked, what does YOAV stand for? It stands for Yoav On A Velo

jiberjaber

  • ... Fancy Pants \o/ ...
  • ACME S&M^2
Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #9 on: June 24, 2019, 03:31:56 pm »
I know I'm being stupid, naive and ignorant of a subject that shouldn't concern me but can anyone explain to me why it is essential that Di2 cables go inside frames. If there is one thing more than any other that puts me off about it it's that!

It doesn't. You can use this set of stick-on cable guides with this under-BB external junction box to route it externally.

I have a bike with this setup - you can see the black stripe under the downtube in the second photo here. The biggest issue is where to put the battery - I decided the external one was ugly so cheated and routed the cable inside to the seatpost via the frame drain hole (cable cutting and splicing required). I also routed the FD cable through the tube embedded in the BB shell for the mechanical cable (ditto).

Have you got a picture of them fitted G?  I might use that for my rear dynamo light cable (currently using UV stable clear sellotape - but these may be better)
Regards,

Joergen

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #10 on: September 11, 2019, 07:55:26 am »
just in case it isn't obvious, if necessary you could use multiple strands in a thin ribbon cable in parallel to improve reliability/current capacity whilst keeping the profile as low as possible.


Brucey, I have the same issue and have just purchased some ribbon cable to attempt this. Do you have any experience with the stripping, splicing and soldering of Di2 wires? Do you know if there is any difference in approach needed for wires used with R8050 vs earlier generations?

TIA

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #11 on: September 11, 2019, 07:59:24 am »
@arminius How did you get on? Did you manage to get this sorted? I’m currently grappling with the same issue.

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #12 on: September 11, 2019, 10:01:45 am »


Brucey, I have the same issue and have just purchased some ribbon cable to attempt this. Do you have any experience with the stripping, splicing and soldering of Di2 wires? Do you know if there is any difference in approach needed for wires used with R8050 vs earlier generations?

TIA

I've done lots of wiring but not on R8050 specifically. However I don't see why it should be different from other Di2 systems. 

All the usual wiring things apply; you need to worry about insulation, waterproofness, and strain relief (soldered joints tend to fail if the tinned part of the wire  -which may be longer than you think-  is flexed). All the junctions can be slightly away from the BB shell so can be made relatively bulky if required.  In this case there is an additional constraint, in that the ribbon cable mustn't come away from the inside of the BB shell, else it will soon chafe through.

cheers

Re: Di2 cabling with a BSA BB and 30mm spindle
« Reply #13 on: September 11, 2019, 10:46:23 am »
Apart from the oddball first gen Dura Ace, all Di2 cables are the same - a two-core twisted pair carrying both power and signal in a squidgy rubber sleeve.

I did PBP (and many other riders) on a bike with two spliced Di2 cables. It was the least of my worries.

Though in this case I'd be inclined to cut a slot in the plastic sleeve (which is usually non-structural - it's just to keep dust out) and route the cable intact, maybe gluing it to keep it in the right place.

(but it's hard to know whether this would work without seeing the bike)