BB386 crank in BB30 frame - Chainline?

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

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.
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FSA-SLK-Light-Pressfit-BB30-BB386EVO-comparison02.jpg
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by Weenie


pdlpsher1
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by pdlpsher1

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.

vinuneuro
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by vinuneuro

pdlpsher1 wrote:
Mon Jan 29, 2018 5:33 am
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?
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Valbrona
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by Valbrona

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pdlpsher1
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by pdlpsher1

If you look at the picture, the rings on the right side crank has been pushed outward. Also, the centerline of each spindle line up with the other one. So the frame would sit exactly in the middle of each spindle.

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ms6073
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by ms6073

vinuneuro wrote:
Mon Jan 29, 2018 5:48 am
Since the spindle is longer, won't the BB386 have the rings outboard of where BB30 rings would sit, in a BB30 frame?
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.

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IrrelevantD
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by IrrelevantD

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.
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jever98
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by jever98

IrrelevantD wrote:
Mon Jan 29, 2018 7:07 pm
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.
That's pretty much it.
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Rudi
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by Rudi

Cervelo R3 - 5.4kg viewtopic.php?f=10&t=142420

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ms6073
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by ms6073

IrrelevantD wrote:
Mon Jan 29, 2018 7:07 pm
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.
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:
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 - The Anaerobic Threshold is neither...

wingguy
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by wingguy

vinuneuro wrote:
Mon Jan 29, 2018 5:21 am
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?
No, it will be correct.
(18.5mm is the difference in spindle length between the two standards)
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.
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?
One spindle is shorter than the other, at both ends. The spindle ends should not be lined up.

Hexsense
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by Hexsense

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.


IrrelevantD wrote:
Mon Jan 29, 2018 7:07 pm
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.
Either way, spindle are smooth for both bearing position (compare to narrow band of smoothness on BB30 spindle where it expect bearings to be).

vinuneuro
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by vinuneuro

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?
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61CFwRnmOCL._SL1257_.jpg
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AZR3
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by AZR3

I’ve used similar spacers with my Rotor 3D+ when I had it in my Hi-Mod, never had any issues but then again it was only for a few months till I bought an SiSL2

Bullet
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by Bullet

I’ve run a bb386 power2max crankset on my BB30 Cannondale CAAD10 for the past couple of years without any problems, it works great

by Weenie


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