[aclinjury]

I'm thinking about having a steel frame built up (using XCr tubings).
And I read this article below explaining the different types of bottom brackets.Bottom Bracket Standards - Slowtwitch.com

Basically, what the article is saying that wider bottom brackets using bigger diameter spindle make for a stiffer frame because manufacturer can pack more structural material around the bottom bracket area, therefore reinforcing the bb and hence making a stiff frame overall.

I'm thinking, most of these frames using these press-fit are also carbon frames, and it's easier to layer up more carbon material around the bb area. But for a metal frame, it's not like you can "layer up" more metal material around the bb area. Metal tubings come in certain wall thickness, and that's that.

I can't see how a BB90 would benefit much on a metal frame when it comes to stiffening up the bb area. Probably a 68mm BSA bottem bracket tube with thicker wall will make for a stiffer bb. However, I can possibly see that a BB30 can make for a stiffer bb and stiffer frame (on a metal frame) if the downtube is also oversized to take advantage of the BB30 bigger diameter (spindle diameter). But again, I gotta ask, how much stiffer? Probably not anything significant.

Anyway, my question is, i'm planning on having an XCr frame built for me, and I'm 130 lbs (nothing like a brute), should I just stick with 68mm BSA type bb? I can also have it built with BB30, but from all the "my BB30 is creaking" posts that pop up every few weeks, I'm kinda cringing at the BB30 option.

thoughts??

 

[cda 455]

I'm thinking about having a steel frame built up (using XCr tubings).
And I read this article below explaining the different types of bottom brackets.Bottom Bracket Standards - Slowtwitch.com

Basically, what the article is saying that wider bottom brackets using bigger diameter spindle make for a stiffer frame because manufacturer can pack more structural material around the bottom bracket area, therefore reinforcing the bb and hence making a stiff frame overall.

I'm thinking, most of these frames using these press-fit are also carbon frames, and it's easier to layer up more carbon material around the bb area. But for a metal frame, it's not like you can "layer up" more metal material around the bb area. Metal tubings come in certain wall thickness, and that's that.

I can't see how a BB90 would benefit much on a metal frame when it comes to stiffening up the bb area. Probably a 68mm BSA bottem bracket tube with thicker wall will make for a stiffer bb. However, I can possibly see that a BB30 can make for a stiffer bb and stiffer frame (on a metal frame) if the downtube is also oversized to take advantage of the BB30 bigger diameter (spindle diameter). But again, I gotta ask, how much stiffer? Probably not anything significant.

Anyway, my question is, i'm planning on having an XCr frame built for me, and I'm 130 lbs (nothing like a brute), should I just stick with 68mm BSA type bb? I can also have it built with BB30, but from all the "my BB30 is creaking" posts that pop up every few weeks, I'm kinda cringing at the BB30 option.

thoughts??

I would stick with the 68mm BSA bb.


Especially since you're at a pro-rider weight.

Have you checked to see how big (Oversized) downtubes are available? I like how an oversized DT is ovalized to be welded covering almost the whole width of the bb.

 

[tihsepa]

I agree with this ^^^^^^^^^ 68mm BSA will be around for a while. If I was having a frame built this would be it.

 

[aclinjury]

Alright I think I'm going with the traditional 68mm BSA type.

BSA has been around for a long time and probably will be in the future for a while too. And I intend to keep this frame as long as I can ride it, don't plan to sell.

Plus this morning I jumped on the scale at the gym and registered 126 lbs. Pretty sure there are lots of heavier guys than me riding BSA bb without much stiffness issue! BSA it is.

 

[Kerry Irons]

Plus this morning I jumped on the scale at the gym and registered 126 lbs. Pretty sure there are lots of heavier guys than me riding BSA bb without much stiffness issue! BSA it is.

At your weight you can likely go with very thin walled and fairly small diameter tubing. Unless you're hiding a very big engine somewhere you'll want some flex in there for comfort and good "planing" action.

 

[JoelS]

Stick with a BSA threaded BB. They're a lot less problematic.

 

[ACree]

Pretty sure there are lots of heavier guys than me riding BSA bb without much stiffness issue! BSA it is.

I'm one of them... I just don't see the point of the new 'standards'. The BSA with external cups has proven stiff enough for (over 200 lbs), and is easily removable and serviceable. Lots of complaints on the mtn bike sites about having to really hammer to get worn out press fit bearings out of a frame. BSA with Chris King BB FTW.

 

[aclinjury]

I'm one of them... I just don't see the point of the new 'standards'. The BSA with external cups has proven stiff enough for (over 200 lbs), and is easily removable and serviceable. Lots of complaints on the mtn bike sites about having to really hammer to get worn out press fit bearings out of a frame. BSA with Chris King BB FTW.

They're using BB30 in a mtb bike now? You would think that with all the pounding a typical mtb gets, they would stay away from the press-fit routine. I guess newer is not always better!

 

[ACree]

Nah, if it's lighter it will sell... maintenance is a problem after sale, and who cares bout that?

Lots of PF30 and BB92 mountain bikes out there, and lots of threads about creaking bottom brackets and how to get bearing cups out. Press fit bottom bracket bearings seem very impractical to me (in the rainy, muddy, Pacific Northwest).

They're using BB30 in a mtb bike now? You would think that with all the pounding a typical mtb gets, they would stay away from the press-fit routine. I guess newer is not always better!

 

[LookDave]

I'm 185 pounds, 2 pretty light steel frames in last 10 years (Landshark with BSA, DeRosa Corum with Italian). No stiffness/BB flex issues with either, and I can swap out external BB cups in a few minutes with simple and cheap tools. Unless you crank really huge power (and I don't), this whole BB stiffness thing is overhyped.

 

[aclinjury]

I'm 185 pounds, 2 pretty light steel frames in last 10 years (Landshark with BSA, DeRosa Corum with Italian). No stiffness/BB flex issues with either, and I can swap out external BB cups in a few minutes with simple and cheap tools. Unless you crank really huge power (and I don't), this whole BB stiffness thing is overhyped.

good to hear. But yeah I figure it's more marketing than substance, but still want to hear what people's experiences are