I apologize that this discussion has been going on and I have not responded until now. I was not aware that my reply to a Cervélo customer was posted a public forum and that my words are being questioned. I regret that I could not have posted here earlier to help ease everyone’s concerns.
Please allow me to clarify my words for everyone's benefit. The S3 can have clearance issues in 2 places with certain components.
1. Specific to the aero chain stay, the non-drive side spokes of wheels that have a wide flange width can come close to the chain stay.
The form of the aero chain stay’s shape is based on the function that we witnessed in the wind tunnel. The aero chain stay shape has less drag than the original SLC chain stay shape and does a good job of cutting down the drag of the system. Cervélo has always been a company that strives to push the envelope in terms of performance. In this case the performance advantage only limits the owner in a few wheelsets they can use. We know the S3 will work with the world’s fastest aero wheels. It seems more beneficial have the our aero chain stays and lower drag with a limited selection of wheels (that are still the fastest wheels available on the market) than to have higher drag with the ability to use more (and less aerodynamic) wheels.
2. The clearance between the chain stay and the inner chain ring bolts of certain cranks.
The S3’s design is based on the SLC, a frame which had its final design established in late 2004. That was a couple of years before Campy developed the Ultra Torque design. The clearance between the aero carbon bikes (P2, P3, P4, SLC, SLC-SL, S2, S3) and the Campy Ultra Torque cranks are all the same. This not just specific to the 2009 Super Record group; I commented on the Super Record group in my initial reply to Paul as that was the question that was posed to me. These bikes are based on the same chain stay/BB designs. The S3 chain stays in the crank area do not differ to those of the other aero carbon bikes and only change after they pass the crank. It is simply a fact that the clearance that our aero carbon bikes’ chain stays (which were designed in 2004) built up with Campy cranks (which were designed in 2006) have less clearance than our aero carbon bikes’ chain stays built up with Shimano, SRAM and other crank manufacturer’s products. We are not the only manufacturer than has had this issue with the Ultra Torque’s design.
This is not to say that our aero carbon frames cannot be used with Campy Ultra Torque BBs. Many Cervélo carbon bikes have been built up successfully with Campy Ultra Torque BB with no issue. It has been done in the past and will be done again in the future. The S3 is not any different than any of these frames.
Please understand ALL manufactured parts, produced by ANY company will have some variability in their manufacture. Cervélo’s QC measurement for acceptable chain stay variance is quite small, and in line with other bicycle companies. Though the variance itself is a very small measurement, it is only significant when it amounts to a sizeable percentage or proportion of the actual clearance gap between the chain stay and the chain ring bolts. Additionally, this is only one half of the equation. The crank has variability as well:
1. How shallow the chain ring bolts sit in their bore,
2. How deep the crank bearing sits in the BB cup
3. How true the chain rings run.
Again these variances are not typically a issue unless they constitute a significant percentage or proportion of the gap between the chain stay and the chain ring bolts. When both extremes are brought together, the issue is more of a concern. The fact that the Campy’s Ultra Torque crank axle joins in the middle of the BB makes things more difficult. If the center fixing bolt loosens off, the crank has significantly more chain ring drift than a crank with an axle that extends all the way through both BB cups.
Compatibility depends a few measurements when the clearance between the chain stay and the chain ring bolts are as close as they are. I hope now you can see why I commented that the S3 may or may not work for Paul. I would rather be open about the possibility that the S3 may not work for Paul than to have him surprised after the point of purchase.
To comment on other points that we brought up in this posting the Campy Ultra Torque clearance issue mentioned above is not a due to frames with excessive alignment issue. The frames that experience this are within normal QC values and better than most values out in the market. The fact that some posters have taken some liberty in saying this issue is based on Cervélo shipping out substandard frames or that Cervélo employs a loose QC standard is incorrect and baseless.
Clearance between the chain ring bolts and the chain stay is not based on frame size. All of our bikes use the same chain stay dimensions for a given model. The 48 does not have a greater likelihood of having this issue than the 51, 54, 56, 58 or 61.
Cervélo works very closely with our dealer base. A dealer is never on “the hook” as we will always work with a dealer in extreme situations. The responsibility of the manufacturer and the dealer is to prevent these extreme situations from happening when they can.
In terms of considering a redesign one first has to quantify the issue. First we could ask how many framesets we sel? This figure is a small fraction of the Shimano and Sram bikes we sell. Of all the framesets on the market how many are built with Campy? This number is quite low (and surprisingly just as low on average in Europe as in North America). Then how many of them will be built with a part that might have a compatibility issue, and finally narrow down to the real number of how many will have a compatibility issue. Ultimately, we then need to determine if this number is worth a redesign that may affect the performance of all those riders that are unaffected by this compatibility issue. At this time, I do not know that answer, but you can be assured that our engineers are aware that this issue exists and will determine whether a redesign makes sense.
I believe the initial release of the Super Record group has been much stronger than any other Campy groups have been. This may be a reason that some are just becoming concerned with an issue that has been around since the release of the Campy Ultra Torque crank in 2007.
If anyone has any questions on this topic please feel free to contact me directly at Chris@cervelo.com