Bottom brackets continue to confuse me. T
Ah the joy of BB's.
I tried the edge cases and lost much sleep and shop time several times.
So I do not have my new Vendetta booms in hand yet; but I already know they will be:
1) English thread 68mm.
2) The chain stays still uses a clamping bracket meaning we have to use a crank with a 24mm diameter spindle (the round bar that connects the left and right cranks)
3) A bottom bracket with "external cup bearing" that we can clamp to.
The challenge is that 24mm cranks are no longer the high-end part they use to be and are being phased out. To further complicated things is the fact that vendors have been improving the legacy 24mm tech in ways that aren't friendly to our Silvio's and Vendettas.
As of now, SRAM still ships with a S30/V20 compatible BB, but it's outer casing is weak and it is easy to over tighten the chain-stay clamps which can crush the bearing or wreak the free spin of the cranks. We have used those SRAM BB's on our Silvio's in the past because I had them on hand. They only last about 3000 miles and then they really degrade, making them pretty much a replace each spring part. Given that they are just a $30 part that's not surprising.
Meanwhile Shimano has been using smaller bearing, as of late, on their high-end stuff. As such the new stuff has a smaller external cup diameter that does not work well with the S/V clamps. In those cases you need to add shim-spacers to increase there diameter if you want to use the Shimano BB.
Lastly, in the big players, FSA has been shipping with a really rounded off BB cup that's hard to clamp too. With those you are almost forced to use spacers to push the cups outward to get enough surface area into the clamp for it to bite on to.
So what's a CBer to do?
For me I have settled on using just stuff from RWC on Vendettas and this spring the Silvios too, I won't use the BB's that come with the cranks anymore . The ones from RWC come with extra spacers and they are angular bearings. They come with a "pre-load" wave washer that goes crank side. That wave washer keep the angular bearing properly seated and the cranking spinning free after install. The tech-support is also really good. All of their BB's have sufficient surface area to clamp to. Lastly the bearings are replaceable cartridges so you can buy extra if you are worried about future availability of compatible BB's.
RWC will sell BB's with:
24-x-24mm cups for Shimano, Race Face, Rotor.
24-x-22mm cups for Truvativ, SRAM and Bontreger. (GXP)
Yes GXP is tapered on one side. That taper makes it really easy for beginners to install correctly. All you do is torque the non drive arm and poof it's installed correctly. You can't imagine the cursing in my garage the first time I encountered a non-GXP BB install. Lacking the knowledge to get the crank installed in 5 minutes cost me 3 hours, but afterwards I knew the ins and outs. In the end theses are the same BB. The GXP one just has a 2mm spacer inserted. You can pound out that spacer if you ever need to go from GXP to Shimano.
Now what about all the new standards?
- Well The new internal bearing stuff "press-in/press-fit" we can't use on the Cruzbike because there would be nothing to clamp too because the bearing go inside the frame. So BB92/B86 are out.
- The non-threaded stuff won't work either as it would spin and the front triangle wouldn't hold its shape. A lot of these new internal bearing stuff are bike frame specific, so they are very prevalent on TT Bikes and other specialty builds. They do crack me up with there "NEW"ness because they really are just reinventing square taper without the integrate shaft for better ecology.
- BB30 is an interesting development and the one that has the most steam across product lines, if one has to succeed long term I hope that's the one. Sadly even BB30 is under attack, so vendors can lock you in. But for now, the BB30 replaces the 24mm spindle with a 30mm one. The idea is:
- More strength with less weight from a thinner metal spindle
- Better spacing on the bearing
- Less bearings total
- Same load capacity
- Less component weight
- Better spin.
- You can get Internal or external bearings cups.
The external ones look just like the 24mm; but unfortunately because the spindle is bigger the bearings are further out and the cup is 2mm too big to fit into a Vendetta or Silvio chain stay clamp. And no you can't stretch the clamp and hack it, I tried and failed 1mm too little give; and not enough metal to drill it out.
So 24mm cranks are clearly now being phased out. Give it about 4 more years and they will probably be hard to find in all but a few styles. Why? because less and less frames are being designed for them, so as the old bikes age out of use there will be less demand for them.
Don't know about you, but I don't fancy myself buying go fast parts from Rivendell Bikes. No doubt future Silvio's and Vendetta's will either have a BB30 clamp or the will abandon the clamp all together and re-engineer the linkage between the stay and the boom. My money's on the re-engineering as I think there is potential to gain strength and stability there without adding weight; then we could be BB agnostic.
So for anyone that is confused if you want a good BB then here's my guide
Recreation Rider / Dry weather rider
Shimano Style go here:
http://www.enduroforkseals.com/id198.html
For SRAM style go here:
http://www.enduroforkseals.com/id484.html
Only the get the Stainless Steel $99 ones. It will probably last the life of your bike
Don't waste the money on the Ceramic ones; if you even think you need those then you need this next one.
If you are racing or riding in wet conditions
Shimano Style go here:
http://www.enduroforkseals.com/id240.html
For SRAM style go here:
http://www.enduroforkseals.com/id332.html
Yeah I know $199 for a BB? what the heck. it's not even ceramic.... You are MAD!!! Possiblly, but not for that opinion, I will venture that this $199 BB plus a $110 crankset will trump a $30-99 BB plus a $400 crankset every single day of the week. That opinion is bolstered by the fact no one that has purchased the XD-15 on my advice has ever complained it was a bad choice; and the XD-15 lasts for stinking forever.
Oh and their BB torque tool is brilliant get that tool