Hollowgram SRM in BB386 bottom bracket

Discuss light weight issues concerning road bikes & parts.
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fa63
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by fa63

I have done some research and I think I have the answer, but would like to confirm. Someone brought me a new frame to build up with a BB386 shell. The old frame is PF30. The owner told me that based on his research, his Hollowgram SRM crankset will work if used with a longer spindle. I told him at the time that it was unlikely it would work, because a longer spindle would just mess up the chainline (the longest spindle in the box of parts he gave me is 125 mm, which I don’t think is long enough).

Anyone here have direct experience to confirm or deny my suspicions?

Thanks!
Last edited by fa63 on Mon Feb 19, 2018 12:28 am, edited 1 time in total.

alcatraz
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by alcatraz

I'm pretty sure that hollowgrams are fundamentally incompatible with bb386.

A 1x setup might be possible or if he is willing to "really" experiment you could maybe try to fit two chainrings both on the inside of the power meter using some kind of extra long chainring bolts and spacers. The latter would be highly experimental.

In either case the q-factor would always be wider than it should. If he is a big guy then the greater q-factor could be just what he needs. If not then it's not a good idea.

Hollowgram axles for mountainbikes are 130+mm.

/a

by Weenie


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ms6073
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by ms6073

As the owner of a couple of Hollowgram SRM's, I can say that regardless of spindle length, a Hollowgram SRM is a non-starter in any frame that is not BB30!
Michael - The Anaerobic Threshold is neither...

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fa63
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by fa63

ms6073 wrote:As the owner of a couple of Hollowgram SRM's, I can say that regardless of spindle length, a Hollowgram SRM is a non-starter in any frame that is not BB30!
Would you mind elaborating a bit?

morganb
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by morganb

As everyone else has said, the chainline will be completely off as will the Q-factor if you go with a mountain bike spindle, if it will fit at all. I've owned 3 Hollowgram SRMs and the non SiSL2 also required an SRM specific spindle because the clearance was tight even on a proper BB30 bike.

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ms6073
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by ms6073

fa63 wrote:
Mon Feb 19, 2018 12:59 pm
ms6073 wrote:As the owner of a couple of Hollowgram SRM's, I can say that regardless of spindle length, a Hollowgram SRM is a non-starter in any frame that is not BB30!
Would you mind elaborating a bit?
Unlike a BB86/BB386 cranks, the spider of the Hollowgram lacks any appreciable offset, so while a longer spindle - say a 132 mm versus the current 109 mm road spindle - would allow you to mount the spider, the chainrings would simply be pushed 23 mm further away from the frame/ideal chainline:

Hollowgram - no offset:
Image
BB86 - lots of offset:
Image
Last edited by ms6073 on Mon Feb 19, 2018 5:16 pm, edited 1 time in total.
Michael - The Anaerobic Threshold is neither...

by Weenie


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fa63
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by fa63

Great, thank you very much!

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