Isis Overdive

[jason]

Any views out their on the ISIS Overdrive bb idea? See www.isisoverdrive.com if you don't know what i'm refering to. Full Speed Ahead have the only bb unit designed for this standard in production so far. Seems very beefy indeed!
Is this the future? I don't know, but it seems reminiscent of the switch from 1" headtubes to the now standard larger diameter.

"Long is the way (road) and hard that out of hell leads up to light" - Milton, Paradise Lost. Apt in view of my last ride. Must be getting old.

[Dude]

I am not sure it will be fully embraced. The idea that there are different shell sizes for each material would turn many manufacturers off. They want to keep production as simple (IE cheap) as possible. Granted not many companies are producing Steel, Alu, Ti and CF in the same factory.

It would be interesting to see some new BB designs. I don't think "stiffness" should be the holy grail they search for. Can a bb really be THAT much stiffer. I think they should look to shave off some weight (campy) Cannondale was on to something with their oversize BB. I don't know if their claimed stiffness comes from the "integrated" BB, most likely the massive spindle. I suspect that their weight (in addition to their stiffness advantages) come from the fact that they used larger, thinner walled "tubing" for the spindle. Rather than a narrow hunk of al for their spindle (campy), they used (and shimano as well) a larger diameter, thinner walled spindle.

Performance wise, these are more or less the same. I don't know about durability of the c'dale design. Obviously the campy and shimano speak for themselves. I don't see much advantage to the phil wood design other than superior quality (manufacturing, quality). Thats all i have to say about that - from the mouth of a brash punk.

[Too Tall]

This appears to be a collaboration or parallel development of Phil Wood's idea to increase the BB shell diameter. The ONLY reason this was proposed was to utilize a larger bearing race size. Phil's monniker for this was American ISIS...it's hard to keep up ;) This is a win win in many ways as standard BBs can still be used with an insert adapter. I hardly believe roadies will benefit from a better BB interface but it will lighten the frame some. Tandems, BMX and Huck-A-Bike mavens will get some benefit from larger bearings....as if there was a problem. sigh. Gee, with that huge BB shell I guess there is enough room for an eccentric too? Fixed gear goochie item alert!

[jason]

I believe Phil Wood has now thrown his all in with Truvativ, King and FSA and accepted their specifications. I don't think there are different shell diameters for different materials as such. The standard measurement is for an internal diameter of 46.376mm with certain minimum wall thicknesses depending on the alloy used. I believe in the case of alu that a certain minimum wall thickness is recommended to satisfy it's mechanical properties. Ti, for example, would allow for a slightly thinner wall. Apart from that the shells would be identical. All Overdrive bb units would/should fit all Overdrive shells. That is the point of a common ratified standard that all parties produce to. It should work well if given time to trickle into the consciousness of the industry and market. Seems to be the final step in moving from imperial to metric. After all, this is the 21st century.

[BigMac]

Yes, this is very similar to the pleadings of Phil Wood when the original ISIS design was published. The result will not be reduced weight nor improved stiffness (at least to point of ANY significance in real world usage), at least if the final design is similar to what was proposed early on, the primary result is substantially improved lifetime BB durability. The huge bearing size increase should literally allow 100k mile service life BB's at very minimum. Sounds great to me, that's 12 fold better than the pathetically poorly designed Campy BB's of current; three times better than a current Phil square taper.

The downside is of course BB shell limitations. Does anyone really believe a new lugged BB shell would be developed to accomodate 48mm threads? The current is 34.8mm. So tooling would be simple for plastic, aluminum alloy and Ti alloy frames. Yes, TIG's and filet'd steel frames could be easiliy constructed but the classic lugged steel frame would likely continue to be built around current BB shells. Given the existing inventory of square taper cranks both in production and NOS, this would not be such a bad thing and Phil will certainly continue to build 1.37x24 threaded BB's. Some builders perhaps would even TIG or filet the BB while using lugs in more visibly present areas such as to accomodate the new BB 'standard' as it were.

It's a tough call. At present, I can get roughly 3 years of average service from a Phil BB, a simple 1 week's downtime including bearing service and shipping each way is certainly not bad. The 6 month service time for the Campy BB was completely unacceptable. The luxury however of 8-10 years between bearing service is awfully enticing even at cost of a lugged BB shell. I suppose if crank q is same or less, I'd choose the new standard based solely on bearing life not in any way on mass or stiffness, both of which are inconsequential on a component level. If the new design resulted in higher q crank designs as most new designs appear to, I'll stick with the tried and true square taper, and a Phil BB.

Ride on!

[jason]

Some Ti builders i've contacted seem to be unable or unwilling to contemplate building a frame with the new shell size (Moots and IF). They say suitable tubes are not available in such a large diameter (3/2.5 in grade 9). Possibly don't want the hassle of tooling up and sourcing such tubes at this early stage.

Is it not possible to have a trad. square taper sitting inside the new bb shell using an adapter of some kind? Truvativ would know about this. Garrett Smith is the Overdrive man there.

The other point to consider is frame design. With this enlarged shell the seat tube and down tube will be able to reach the outer surface of the shell around their full miterd circumference without intersecting each other before reaching the shell. This will obviate the need for the double mitering of each tube which we see at present on nearly all frames. This, i believe, would create a stronger attachment for both tubes with the shell and possibly enhance stiffness. Certainly it would reduce the mitering complexity for the builder by a little and make the welding process slightly easier.

Waiting six months for Campagnolo is a nolo nolo.