I am planning on getting a Calfee tandem with the new Calfee carbon triple crankset. This set uses an Isis bottom bracket. I would like to get ceramic bottom brackets. On Ebay, the have ceramic Isis bottom brackets with 108mm and 118mm spindle lenths. I bet the Tandem Geek would know if these would work for the front bracket and rear bracket with a triple chain ring. Does anybody know the proper spindle lenghts to use? It is hard to find Isis ceramic bottom brackets, ceramic Isis brackets are not as plentiful as ceramic external bearing bottom brackets.
118 would be for a triple, 108 for a double. For captain I guess you could probably use either (for perfect timing chainline you would use 118, but 5mm is not going to make a big difference), for stoker (with triple chainrings) you probably need the 118.
As already noted, 118mm is the default for 145mm rear spaced tandems sporting triples. That's not to say you can't run spindles that are more or less narrow.
I have 108mm up front and 111mm in the back on our Calfee, but note that they are: a) square taper, b) daVinci cranks and c) Phil Wood BB's that allow for quite a bit of flexibility in off-set since they use 2-adjusting cups per BB instead of a right-hand fixing cup and left-hand adjusting cup. The latter allows for about +/- 5mm of left-to-right bottom bracket adjustability. However, off-hand I want to say that I've got the rear 111mm BB centered with zero off-set.
I've run 108mm front & back on our Erickson tandems with 145mm rear spacing; however, the stays on the Calfee are bit more meaty so I'm not in a position to say if a 108mm BB with a fixing cup like the ISIS models would or would not create a clearance problem between the granny ring and the right-side chain stay. Moreover, the amount of clearance could be different for each Calfee as the amount of material used at the major load points on Calfee's frames can vary based on the weight of each customer team when they are built-to-order.
Of course clearance is also dependant on chainring size. What chainrings are you using?
Another factor with the chainline besides clearance of the frame is rubbing of the chain on the middle chainring when the chain is on the smallest chainring. We use 113 BBs and 26 and 38 small and middle chainrings. The chain rubs on the middle chainring on the 6 highest cogs. I could adjust the chainline over to avoid some of the rubbing but haven't since we're fine just using the lower cogs with the small chainring.
It appears to me it's going to be trial and error unless you just go with the 118.
Data point, we have very little clearance between small chainring and chain stay on our Calfee, not much more than 1mm, with a 118 DA Octalink bottom bracket and Santana carbon cranks with standard chainrings (I think the little guy is a 30). I think you can get away with very small clearance, but a 108 would be a non-starter on our frame.
Originally Posted by TandemGeek
Last edited by mburchard; 01-14-09 at 09:19 PM.
My wife and I have a custom Calfee Tetra tandem that we took delivery of last September. I built the bike using the Calfee triple crankset and 118mm spindles on both bottom brackets. Everything works together very well and I would certainly stay with 118mm in rear.
Running FSA MegaEXO with Chris King bottom bracket, wonderful silky smooth. Campy shifters shimano rear derailer campy racing T front derailer shifting is perfect.
I recently did some looking in regards to 118mm ISIS Bottom Brackets. There are several available.
From reading posts about the added loads on the stoker BB, I tried to find something with added bearings.
Many BB's had three bearings, two on the right side and one on the left. This didn't sound great for the stokers BB
In the end I bought two Truvative 4 bearing BB's, 118mm long. I forget but believe they were a Downhill part. The units do have sealed bearings that with some light hydraulic press work should come off the axle.
Upon installation, I followed their directions, torquing each side. By design, the right side cup is secure, bottoming and tightening against the frame or eccentric. The left cup was torqued against the BB spacer housing. This method made the BB's somewhat binding. Because our frame uses a 68mm shell, and these were 68 or 73, with the clearance filled on the right with an aluminum spacer, and on the left an "O"ring, I made a change.
I removed the left side "O"ring, went by the shop and picked up two old school BB lock rings. These replaced the "O"ring and allowed me to properly torque the right side cup, and then tighten the left cup until it lightly seated on the BB spacer housing, then locked the cup with the lock ring.
No axial play, and spinning free, maybe not as free as a real high end BB or worthy of the OP's Calfee, but worlds better than how it was designed.
Chain alignment was good with our triple setup.