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Technical FAQ: Specialized’s aero claims, mixing parts, and more

This week, Lennard Zinn addresses reader questions about, among other topics, Specialized's recent time-saving claims

Specialized time savings for real?

Dear Lennard,
I’m fascinated by the 5-minute claims by Specialized. However, the article states that Specialized just added up the time savings for each piece of equipment and did not take into account how the parts interact as a whole. Is it really that simple or do the mathematics change when each piece is combined?
— Ben

Answer from Specialized:

That’s a good question. Simply put, the five things that we broke the 5-minute claim into are more or less aerodynamically independent and can be added (keep in mind that the 5-min claim was a bit conservative to take into account some differing interactions depending on the specific rider). To summarize:

— Frame, wheels, and tires: These definitely cannot be split apart and their individual aero gains summed due to interaction effects. As a result, we’ve lumped the total bike system aero gain into one number (keep in mind, the tire in this case represents the aero benefit of the tire, not the rolling resistance).

— SW Turbo tires: This is a pure rolling resistance number so it is independent of any aero claims and can be added in terms of time saved.

— Skinsuit, helmet, and shoes: These are all largely different and separated regions of the body so a more efficient solution in one piece doesn’t necessarily impact the others. For example, using a faster helmet doesn’t change the aerodynamic benefit of a skinsuit (except in fringe cases like a TT helmet in a low position shielding a flapping jersey).

So yes, where the aero interaction is critical, we took it into account by lumping into one system and time saved number (frame/wheels/tires) and for everything else that acts independently, you can sum the time savings.
— Dr. Chris Yu
Aero & Racing R&D Lead
Specialized Bicycle Components

Dear Lennard,
Stage 6 of the 2015 Tour de Suisse was 237km. If Specialized’s claims are true, then Sagan and Cavendish should have arrived in Bienne 32:47 ahead of everyone else.
— Paul

Dear Paul,
Actually, it doesn’t apply when riding in a peloton. If it were a 237km individual time trial ridden on road bikes, then Specialized’s claims could be tested, but even then, it would only apply to the individual. In other words, if Specialized’s claims were true, then Sagan and Cavendish should have arrived in the 237km ITT to Bienne 32:47 ahead of when they would have arrived on a Specialized Tarmac or similar road bike, while wearing their old shoes, standard bib shorts and jersey, road helmet, and while riding industry-standard racing tires. So they would have each had to ride that 237km ITT twice! That’s not something you’re likely to see them do.
― Lennard

Mixing drivetrain parts

Dear Lennard,
Can you use a Campagnolo Centaur 10-speed STI shifter with 9-speed cogs? Will this be OK, or will I have problems with the drivetrain in the long run? Will the index shifting be precise, or will it not shift, or will it have a hard time shifting? Do I need to change the cogs to a 10-speed, and if I need to will any 10-speed cogs work?
— Reggie

Dear Reggie,
That won’t work. You’ll have to get a 10-speed cogset, and it must be Campagnolo. Shimano, SRAM, etc. cogs won’t work in other than a class-B performance with skipping at some place in the range, because the spacing of their 10-speed cogs is narrower than Campy’s.

BTW, “STI” stands for Shimano Total Integration, so it is not a universal term for a brake/shift lever. “Dual-control lever” or “brifter” are generic terms for that. Campagnolo’s version is called “Ergo Power,” and SRAM’s is called “Double Tap.”
― Lennard

Dear Lennard,
Will Shimano 105 brake calipers work with Rival 22 levers?
— Tim

Dear Tim,
They will work, but in a class-B way. The SRAM lever has too much leverage and too little cable pull for that brake to work ideally, assuming you’re talking about a current Shimano 105 brake caliper. You could end up on your nose if you’re not careful when pulling the front brake hard.

However, that SRAM lever will work fine with an old (at least five or so years old) Shimano 105 brake caliper meant for a Shimano 105 lever with the shift cables exposed, sticking out of the sides of the levers. Shimano increased the cable pull of the lever and the leverage of the caliper when it went to the lever style with which the shift cable is concealed under the handlebar tape.
― Lennard

Dear Lennard,
Do you know if I can use SRAM RED/Force or Rival 22 shifters with my existing Campy Record Skeleton brake calipers? I wasn’t sure if the cable pull would allow them to be compatible.
— Chris

Dear Chris,
Yes, those will work fine together.
― Lennard

More on internal cable routing

Dear Lennard,
In response to Abdul’s internal cable routing dilemma, I have a cheap method that has worked for me several times when trying to run internal cables. First you will need to find some thin, flexible, moderately strong string (kite string works great) some masking tape, and a vacuum with a hose. I use the tape to tape off all holes on the frame except the two that the cable will enter and exit.  Then, take a length of string that is longer than the path the cable will run through and feed it into the smallest hole and then tape the other end to the frame near the entrance point. Now take the vacuum and use your hands to create a reasonable seal at the larger hole and suck the string out that end of the cable path. It sounds a bit goofy but it has worked perfectly with two different frames and along different paths. The final step for me is to then tape the string to some Teflon internal cable housing and then carefully pull the housing back through the path. I then run the cable through the housing and then, if desired, you can pull the housing out or just trim it a bit and leave it in place. This also works great with internally routed handlebars. I hope this helps.
— Steve

Dear Steve,
Cool method!
― Lennard