BB386 crank in BB30 frame - Chainline?
Moderator: robbosmans
Below are two identical cranks, except for the BB standard. Left one is BB386, right one is BB30.
Many crankset manufacturers use something like BB386 since it is wide and can be installed in narrower frames with spacers. But if you put a BB386 crankset in a BB30 frame with spacers, won't the chainline be way off? (18.5mm is the difference in spindle length between the two standards)
I ask because I want to use a particular crankset in my BB30 frame, but it only comes in BB386.
Many crankset manufacturers use something like BB386 since it is wide and can be installed in narrower frames with spacers. But if you put a BB386 crankset in a BB30 frame with spacers, won't the chainline be way off? (18.5mm is the difference in spindle length between the two standards)
I ask because I want to use a particular crankset in my BB30 frame, but it only comes in BB386.
2016 Diverge Expert
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I believe the chainlines are identical between the two. The picture clearly demonstrates that there's no difference in chainline. If I remember right the Q factors are also identical between the two. However on a BB30 crank you get more ankle clearance.
Since the spindle is longer, won't the BB386 have the rings outboard of where BB30 rings would sit, in a BB30 frame? The picture has the rings aligned, but you have to look at it from the perspective of the centerline of the frame. So if the spindle ends were lined up, the rings on the left in this pic would be higher than the rings on the right. No?
2016 Diverge Expert
No. You need to compare the backside of the spiders and you will notice that the BB386 has an offset whereas the BB30 crank does not.
- Michael
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Too many BB standards. I thought BB386 was just a 30mm spindle for PF86 frames? So, same spindle length as a standard 24mm Shimano, just thicker.
This being the case, if you wanted to use BB386 on a BB30 frame, you're going to need external bearings, but the chain line should be the same. Similar to if you're running a Shimano crank on a BB30 frame you need external bearings or an adapter.
This being the case, if you wanted to use BB386 on a BB30 frame, you're going to need external bearings, but the chain line should be the same. Similar to if you're running a Shimano crank on a BB30 frame you need external bearings or an adapter.
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That's pretty much it.IrrelevantD wrote: ↑Mon Jan 29, 2018 7:07 pmToo many BB standards. I thought BB386 was just a 30mm spindle for PF86 frames? So, same spindle length as a standard 24mm Shimano, just thicker.
This being the case, if you wanted to use BB386 on a BB30 frame, you're going to need external bearings, but the chain line should be the same. Similar to if you're running a Shimano crank on a BB30 frame you need external bearings or an adapter.
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Not entirely true, as FSA makes both an adapter bearing set to replace existing BB30 bearings, but also a simple set of spacers as mentioned in the BikeRumor article linked above:IrrelevantD wrote: ↑Mon Jan 29, 2018 7:07 pmif you wanted to use BB386 on a BB30 frame, you're going to need external bearings, but the chain line should be the same.
If you do decide to run an EVO crankset on a BB30/PFBB30 frame, FSA offers simple spacers to fill the gap between the bottom bracket bearings and the crankarms.
- Michael
"People should stop expecting normal from me... seriously, we all know it's never going to happen"
"People should stop expecting normal from me... seriously, we all know it's never going to happen"
No, it will be correct.
Spindle length is irrelevant in this particluar situation. Both a BB30 and BB386 crank are designed to put the chainrings the exact same distance from the centreline of the bike.(18.5mm is the difference in spindle length between the two standards)
One spindle is shorter than the other, at both ends. The spindle ends should not be lined up.So if the spindle ends were lined up, the rings on the left in this pic would be higher than the rings on the right. No?
OP's picture say it out.
Gold spindle (BB386) is long straight into the crank, further inside chain rings.
Silver spindle (BB30) have crank's material join up the spindle earlier, before reaching chain rings.
put spacer on gold spindle, that would take up space roughly to where black carbon join on silver spindle.
Gold spindle (BB386) is long straight into the crank, further inside chain rings.
Silver spindle (BB30) have crank's material join up the spindle earlier, before reaching chain rings.
put spacer on gold spindle, that would take up space roughly to where black carbon join on silver spindle.
Either way, spindle are smooth for both bearing position (compare to narrow band of smoothness on BB30 spindle where it expect bearings to be).IrrelevantD wrote: ↑Mon Jan 29, 2018 7:07 pmToo many BB standards. I thought BB386 was just a 30mm spindle for PF86 frames? So, same spindle length as a standard 24mm Shimano, just thicker.
This being the case, if you wanted to use BB386 on a BB30 frame, you're going to need external bearings, but the chain line should be the same. Similar to if you're running a Shimano crank on a BB30 frame you need external bearings or an adapter.
Thanks, I appreciate everyone's help.
As mentioned above FSA do make this $10 BB386/BB30 spacer adapter. Would there be any significant downside to running this setup in my BB30 frame compared to a BB30 crank?
FSA informed me today that the chainline is maybe .3mm outboard of their normal BB30 SL-K crank which came with my bike. In chainline terms is this amount anything to be concerned about?
As mentioned above FSA do make this $10 BB386/BB30 spacer adapter. Would there be any significant downside to running this setup in my BB30 frame compared to a BB30 crank?
FSA informed me today that the chainline is maybe .3mm outboard of their normal BB30 SL-K crank which came with my bike. In chainline terms is this amount anything to be concerned about?
2016 Diverge Expert
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