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Tech FAQ: Crank lengths, Campy derailleurs, and more

  • By Lennard Zinn
  • Published Nov. 12, 2013
A Campagnolo EPS rear derailleur can be easily adjusted during a ride by pressing a few buttons. Photo: Caley Fretz | VeloNews.com

Crank lengths

Dear Lennard,
I know you have addressed crank length extensively, but I have a question. For racers doing multiple disciplines (road, TT, CX, and MTB), should crank length stay the same on all bikes? While my legs don’t change length, I do know that different types of riding require different fits and positions. I have also noticed that mountain bikes tend to be spec’d with 175mm cranks, even on smaller sizes.

I have short legs and run 170mm cranks on the road with no issues, while my ’cross bike has 172.5mm and my mountain bike came with 175mm. Should I leave things as is and not worry, or get them all the same?
— Kurt

Dear Kurt,
I see no reason to keep them all the same. You can probably answer this as well as anybody, as you have experience with it. I personally use the same length on my road and cyclocross bikes (205mm in my case) and make the positions identical on all of them. I’m constantly switching back and forth between any of three road and three ’cross bikes during the season, and I want them all to feel identical.

When I am testing new bikes and component groups, it’s almost always with 175mm or 172.5mm cranks. And while I certainly feel the difference and have opinions about relative efficiency, I have no problems when I switch back and forth between, say, 175mm and 205mm on subsequent days, or even the same day.

For time trials (and triathlons, for more reasons yet), I’m convinced that a shorter crank is preferable, as it allows you to get lower on the bike without your hips binding and your thighs contacting the chest while staying within the UCI-mandated saddle setback positioning guidelines. Whether you generate power through high leverage at a low cadence or through higher cadence with lower leverage is much less important than reducing wind resistance as well as reducing joint impingement and having room to breathe. I also run 5mm-10mm shorter cranks on my mountain bike; my thinking is that, with a shorter crank, I can make abrupt changes in cadence that riding in undulating and technical terrain often demands.
— Lennard

Risks of heating chains during lube process

Dear Lennard,
Long a fan of slow, sticky, but long lasting factory lube, I am nonetheless intrigued by paraffin/PTFE soaked chains. My understanding is that paraffin soaking requires heating the chain to 225 degrees. What are the risks to the temper or finish of the chain at these temperatures?
— Chris

Dear Chris,
Temperatures like that won’t affect the temper.

According to Jason Smith of Friction Facts, “Tempering of carbon/alloy steel is typically performed anywhere from 400 [degrees] to 650 [degrees], with the exact tempering temperature based on the post-tempering material properties desired — hardness vs. toughness. In this example, reheating an already-tempered chain to 225 [degrees] for a wax dip will not affect the alloy crystalline structure achieved within the steel during the higher-temperature tempering process.”
— Lennard

Dura-Ace Di2 compatibility

Dear Lennard,
Regarding the Dura-Ace Di2 rear derailleur, do you think it’s possible to use the mechanical cages off of the new Ultegra 11-speed mid-range derailleur that has the capability to use an 11/32 cassette? I currently have a Dura-Ace Di2 version that is 11/28 capable. I’m looking for a way to accomplish this conversion, instead of having to step up for a new Ultegra Di2 derailleur.
— Allen

Dear Allen,
Yes. I’ve suggested exactly that change in this column in the past, and it works so well that we have done it in our shop on customers’ bikes, too.
— Lennard

Adjusting Campy derailleurs

Dear Lennard,
I have some doubts, as I’m new to [Campagnolo] EPS. I currently have two wheelsets — Zipp 404s with an 11-25 cassette and Fulcrum 3 with a 12-29 cassette. Do I need to reset to zero and reprogram my rear derailleur after each wheelset change?
— Barry

Dear Barry,
No, you most certainly do not. You just switch wheels and ride. In most cases, that’s all you need to do, since most manufacturers position their freehub bodies the same. However, if there is a slight difference between those rear wheels in the lateral position of the cogset relative to the end of the axle, you still don’t have to go back to the zero settings — you can make the adjustments while you ride.

If the wheel’s cog offset differs, the symptom could be that you have sluggish shifting in one direction or chain noise when on some cogs. To readjust it so it works shifts ideally and runs without excessive noise, all you do is hold down the mode button on the right lever until the LED on the EPS interface (the little unit on your stem, head tube, or brake cable) glows pink; this takes about 6-7 seconds. Release the mode button (the LED will remain pink), and click the appropriate shift lever to eliminate the symptom. For example, if it’s slow to shift to a larger cog, then, while the LED on the interface is glowing pink, click the finger lever (the one behind the brake lever that shifts to larger cogs) once or twice. Each click of the lever makes a slight position adjustment equivalent to about 1/8 of a turn of the cable barrel adjuster on a cable derailleur. Then push and release the mode button again to turn off the pink LED and return to normal running mode. Try the shifting now, and if you need further adjustment, go through this procedure again. You’ll find that it’s super easy and quick to do and may actually be easier to fine-tune the adjustment while you’re riding than a cable derailleur.
— Lennard

Dear Lennard,
A reader asked about his Campy derailleur rubbing when on the large rear cog. My own experience was as you suspected, with the derailleur crowding the chainrings as it is moved down the seat tube, which enlarges significantly as it approaches the crank. I simply rotated the derailleur to face the large cogs while still having plenty of outboard movement to accommodate the 11th or 12th cog. With my Campy Record, I can run the 50/11 having trimmed in one click!
— Tom

Tire rubbing on HED wheels

Dear Lennard,
I’ve really appreciated your advice over the years in your column but I finally have a question.

I love my Ridley Noah but I have wheel rub issues (rear only of course) near the NDS of the upper seat stay. All my race wheels are HED with the wide C2 platform, and I run 23mm tires. The tire rubs. What is the narrowest tire I can run on that C2 HED wheel, assuming I should stay with a 23 for all the advantages the rims give — stability, comfort and improved cornering?

I’ve tried many tires and they all measure about the same (with a caliper) when mounted on any of my HED wheels.
— Dave

Answer from HED:

Dear Dave,
20mm minimum tire width on the 23mm C2 rims, 22mm minimum tires on the 25mm Plus rims. As a tire’s air volume decreases, PSI will need to increase, so ride comfort will suffer a little compared to a 23mm or larger tire. It is my experience that cornering is still very good with narrow tires on our C2 and Plus rims.
— Andy Tetmeyer
Hed Cycling Products

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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