Bottom Bracket Compatibility - how does it all work

[RRalphy]

Hi,

Sorry if this seems like a very basic question to be asking but I am new to building bikes so would like to clear this up as I am looking at buying a frame and buying a groupset (online) and building up a complete bike.

Are bike frames compatible with specific bottom brackets or can you install any bottom bracket onto an unused frame? I ask this as the groupset has the option of Italian or Englished threaded and I didnt want to order the wrong one (will be installing it on a Pinarello SDG - havent talked to the store yet about this as I was concerned I would look like a newby...)

If the question hasnt been phrased correctly due to my limited understanding about bottom brackets etc feel free to correct/educate me.

Thanks

[jimh]

Difference between English and Italian thread is that one has one side threaded clockwise and the other anti clockwise.

Google is your friend :
http://sheldonbrown.com/gloss_bo-z.html

btw: you'll look worse than a newbie going into a bike shop asking whether you should order English or Italian BB if your talking about ordering from the internet.

[Purt]

From a quick google. The frame takes a Most Croxover. Which is the same as an italian threaded bb (not sure why they went all crazy and named it different, maybe confuse people? )

[TMjpn]

As my experience is mostly Carbon frames, I can offer a short summary of what I know...

There are 2 main types of Modern BB's. Screw-in threaded, and press-in Type.

Screw in - BSA English Thread and Italian
Where the bearings are on 'cups' that are screwed onto the frame. They generally make the overall width of the bearings (outside face to outside face) roughly about 100mm wide. The crankset shaft (spindle) fits throught the bearings and generally has straight crank arms when viewed from the top plane. The long distance between the crank arms helps clear the chain stays which on some bikes flare out to be 100 mm wide not too far from the BB area. Shimano, Campag and SRAM GXP are typical conventional length spindles that fit this type of set up - but require a matching bearing as diameters of the spindle vary from brand to brand.

Press Fit - BB30, BBright, PressFit 30 (PF30), BB86 (BB90)
Confusing as all hell, but here goes:

BB30 is a standard where the bearings are pressed into holes housed in the frame. The width outside face to outside face is about 70mm - as wide as a Frame without BB 'cups' screwed into it. This allows for a shorter spindle in the crankset, but slighter bigger in diameter. The cranks are typically slightly 'S' Bended (viewed from the top plane) with the crank arms starting flush against the bike frame but flaring out to the end of the crank arms to become the same width as a standard crankset.

Typically there is less weight in BB30 Cranks. The slightly thicker & stubbier spindle allows for the same torsions as a longer, slim one in standard cranks.

You can use a standard crank in BB30, but you will need adaptor cups to make up for the extra spindle length and smaller diameter.

BBright is a Cervelo Std. It follows the same principles as BB30, but takes a longer spindle length. You can use BBright cranks in a BB30 but need a spacer. You can't use BB30 cranks on BBright.

Pressfit 30 is just like BB30, but the bearings are now in 'cups' that are still pressed into the frame with overall width ~70mm. Its in incremental improvement to BB30 to make life easier, as with BB30 you need to insert a set of clips into the frame before the bearings to prevent them from sinking too far in the frame. PF30 has cups have flanges with prevent them sinking in deeper into the frame. BB30 cranks work in this set up.

BB86 or BB90 (Trek Talk) is very much like PF30 in terms of bearing set up, but its overall width outside face to outside face is wider than BB30 (back to 100mm again) and the spindle diameter is smaller - it allows the use of standard cranks.

In a nutshell its stretching the BB area of a frame out to the width you'd normally have at the outside faces of threaded set-up. You just now sit the bearings inside the frame.

You can't use BB30 cranks here they only work in BB30 and PF30 set ups.

Happy to learn something new if anyone can correct me on points - I have zero experience with that Italian stuff. Shimano and SRAM yes

[MarkG]

Pretty much what he said

Example - previous frame was a Fuji SST which used BB90, current frame is a Specialized Venge which is BB30.
Both are press fit.
I am using the same (Dura Ace 7900) crank in both.
To run the DA crank in the Fuji it was simply a case of having Shimano-specific BB90 press fit bearings.
The run that same crank in the Venge, it was a case of pressing the BB30 bearing/cup assembly in to the frame, and then an aluminium adapter (Praxxis) in to those bearing cups.
Very simple!

BB30 Press Fit -

BB30 standard - note they are retained by a circlip which sits in a groove inside the BB.

BB90 - Press Fit-

BSA - threaded

[TMjpn]

Similar to Mark but working in the other direction:

I had a Cannondale that had a BB30 to BSA English thread adaptor pressed into it. The adaptor turns the larger BB30 port in the frame (70mm O/A) into a BSA threaded one for screw in cups (100mm O/A).

I bought a BB30 crank, So I had to press out the adaptor, leaving the larger BB30 port. I put in the retaining clips, then the bearings into the frame, then the BB30 crank.

Then I reverted back to shimano - So I bought some wheels manufacturing adaptor cups which press straight into the BB30 bearings in the frame. They reduce the diameter and fill the extra space along the spindle. Works a treat as well

thanks for the pics mark - nailed it!

[TMjpn]

One Last bit of Info: Spindle Diameters

For full length spindles:

Shimano - 24mm Dia Throughout
SRAM GXP - 22mm Min Dia (L), 24mm Max Dia (R)
Campagnolo - 25mm Dia

For Others
BB30, PF30 - 30mm
BBright - 30mm

In fact: http://www.roadbikeaction.com/Features/ ... kdown.html

[Mulger bill]

From a quick google. The frame takes a Most Croxover. Which is the same as an italian threaded bb (not sure why they went all crazy and named it different, maybe confuse people? )

That's what I found too, no fancy fat spindles like BB30 or PF 30, no ultrawide BB shells like BB86 just a bog standard BB shell with Ital threads.
For the record, the RH cup on a BSA BB screws in anticlockwise, the LH clockwise. With an Ital threaded unit, both cups screw in clockwise.

Hope this helps.

[JBark]

And so people don't get caught out like I did, FSA MegaExo cranks (and maybe other FSA cranks?) are not 24mm, but are in fact 24.07mm. You'd think that .07mm wouldn't make much of a difference, but trying to use FSA cranks with any high end BB like Hope or similar is an exercise in frustration. They'll work with regular Shimano BBs, which have a bit of plastic on the bearing surface, so there's enough give. But BBs like the Hope are have a much tighter tolerance and are direct metal to metal. Wanna guess how much fun it is to pound a 24.07mm aluminium peg into a 24.00mm steel hole?

[Summernight]

FSA cranks don't work with anything but FSA BBs, from my (limited) experience.

I tried fitting Shimano 105 BB standard with FSA MegaExo Omega crankset (the FSA BB died after only 11 months from purchase ) - same dimensions on the BB as on the previous FSA BB. But it was like riding a clown bike as they just didn't work together and I had to pull it off and buy a new crankset (better and cheaper in the long run to get rid of the FSA parts after the poor LBS experience I had about it and I upgraded to 105 too as the Omega is apparently the bottom of the FSA range and was more expensive a BB to replace for the bottom of the range. No thanks).