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PostPosted: Sat Nov 19, 2011 10:43 pm 
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Location: UK
I had the choice of BSA or BB86 on an Addict and chose the BB86. Scott reckon the BB86 is the lighter and stiffer option.
The Campag BB86 cups are the lightest option as well. Not having a bonded threaded insert in the BB seemed like a good idea to me.
The only downside is the potential for the cups to creak but loctite can cure that.


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PostPosted: Sat Nov 19, 2011 11:55 pm 
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I assume you are talking a custom frame?

PF30 gives the most flexibility of using different BB standards with adaptors. Its also easier to make than BB30 as the cups don't need the same tolerances, and hence will last more changes.

You can then use an adaptor to run campy, then if/when campy comes out with a BB30 cranks you can easily change. If you then want a 386 crank there will be adaptors for that. And all these changes will not damage the threads or press fit of the frame.

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Posted: Sat Nov 19, 2011 11:55 pm 


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PostPosted: Sun Nov 20, 2011 2:23 am 
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Bb86 would only be advantageous if you are using a wide downtube, as you will have an extra 18mm of area to weld to on the bb. That will give you a stiff pedaling platform. The pf30 is the most futureproof of the options.

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PostPosted: Sun Nov 20, 2011 2:57 am 
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Do CAAD10s even use the entire width of a BB30 shell? Even if going custom Al you won't get a wider custom down tube than a CAAD10.

BB86 is not PF30. Different widths, and most importantly different OD/ID bearings.

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PostPosted: Sun Nov 20, 2011 3:35 am 
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Location: United Kingdom of Great Britain and Northern Ireland
laager wrote:
I guess the question is really press fit (all types) v BSA.


You know I have not heard of anyone having problems with BB adapters, but the word 'adapter' is enough to put some off.


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PostPosted: Sun Nov 20, 2011 3:46 am 
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If its custom, get the PF30. As far as the guys have mentioned, they are spot on. Its the most future-proof option and possibly the best in terms of backwards (at this point in time) compatibility too. And has all the stiffness benefits of PC86 as well as BB30.

The other good 'standard' would be the EVO386. But that has backward compatibility issues with older cup-and cone as well as cartridge BB's designed for ITA or BSA treads.


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PostPosted: Sun Nov 20, 2011 4:29 am 
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To me, this is a philosophical question (BB86 v BB30 (BSA disregarded here)):

1. Is the frame BB section too soft? Or is the spindle too soft? Former, you go w BB86, latter, you go with BB30/PF30.

2. As my rough drawing shows,

Pros and Cons of 86 are:
stiffer frame,
lighter cups,
thin spindle,
less ankle clearance,
narrow but thick walled crank arms
offset spider to maintain chainline
compatibility one way street.

So the conclusion is against BB86.

From a pure design perspective (and longer term view), outboard bearings have pushed crankarms too far out with very little room left for them. It now gives the BB shell plenty of room to be optimized but the overal system is pretty f*cked up.

Crank arms actually take MORE load than the BB shell but they have no room to go large and hollow and can only use thick walls to compensate (just put a Campy SR crank arm next to a R5/Evo downtube and compare). Pls look at the tyical cross section of a modern crank arm, a modern downtube and a modern BB shell (as well as thickness) in my little graph. Ideally you'd want to share the limited space between two feet among the various parts to achieve the best overall weight and stiffness. But manufacturering is fragmented hence hard to have a coordinated effort. Look's system is really an improvement but they are too damn proprietary (plus the triangle insert thing is absurd). This is why I thought I'd love BB386 but decided against it.

From a practical perspective, looks like the highest regarded cranks today would fit PF30/BB30.


Attachments:
crank.JPG
crank.JPG [ 33.52 KiB | Viewed 990 times ]

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PostPosted: Sun Nov 20, 2011 7:15 am 
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elviento- I like your point. However the down tube is responcible for alot more load bearing in different ways than the cranks. It effects torsional stiffness and handling, as well as pedalling loads. But you are correct, there is very little scope to go large section and thinner walls with BB86 and 386.

Laager- I think that is a poor execution of what can be done with BB86 or 386. However because the chain rings must be set inboard and around the DS of the frame cups you can't grow the DT/ST or CS outwards that way like you could on the NDS. Have a look at frames more like TREK or maybe even the new giants and you will see they are assymetric to use the extra width on the NDS.

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PostPosted: Sun Nov 20, 2011 7:52 am 
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Phill, you are right, and the downtube actually also holds the entire frame together. I am not saying the crank arm should be 50x60mm, but 45x30mm would go quite a long way to begin with.

Re the Fondie, looks like it simply extended the sleeve "just to be compatible" and did not take adavntage of the logic behind the design.

To answer Laager's question, this might still be better than BSA though. It's just that the wider platform is somewhat wasted because the downtube and chainstays didn't go wider. It's definitely not worse than BSA.

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PostPosted: Sun Nov 20, 2011 11:12 am 
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Location: Uppsala, Sweden
My vote goes on PF30 or bb30. then you can runs BSA, shimano,, sram campagnolo, clavicula, power arms and so on (every crankset). if you go bb86, there are left choice. crankset with 30 mm spindle, can work, as clavicle, than has a special bottom bracket for it, but then the bearings are very thin, which isnĀ“t so good. so if you can choose, i would go for PF30


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PostPosted: Sun Nov 20, 2011 2:23 pm 
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elviento wrote:
Phill, you are right, and the downtube actually also holds the entire frame together. I am not saying the crank arm should be 50x60mm, but 45x30mm would go quite a long way to begin with.


In a down tube you have basically 2 forces: bending and torsion. However in a crankarm the bending forces are a lot bigger than the torsion. It makes no sense to make the crankarms a lot 'thicker' it better to make the 'wider'.

I would choose the PF30.


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PostPosted: Sun Nov 20, 2011 8:25 pm 
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All my custom frames plus the one i just had made are all for bsa, still prefer it


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PostPosted: Sun Nov 20, 2011 8:36 pm 
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+1 on 386

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Posted: Sun Nov 20, 2011 8:36 pm 


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