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Technical Q&A with Lennard Zinn – The demands of ceramics

  • By VeloNews.com
  • Published Mar. 25, 2008
  • Updated Sep. 28, 2010 at 4:48 PM EDT

By Lennard Zinn

SRAM’s ceramic bearings may need a bit of extra attention. Is it the bearings, the races or the seals?

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Are ceramics that delicate?
Dear Lennard,
In your article on ceramic bearings in the recent VeloNews Buyers Guide I got the impression that these things were not only smooth but durable as well. As a result, I ordered a ceramic SRAM bottom bracket with the Red crankset on my new bike.

To say the least, I was surprised when I read the SRAM maintenance instructions that came with it and saw the recommendation that one should disassemble and lube the bearings after every 100 hours of use and immediately after riding in the rain or wet.

This suggests that this ceramic bottom bracket is a lot more delicate than the conventional bearings, which seem to live happily with lubrication once a year. Did I make the wrong choice by sinking $200 into this bottom bracket?

I ride about 6000 miles per year, which translates into an awful lot of bottom bracket lube sessions, if I follow SRAM’s directions.
Bruce

Dear Bruce,
Those are hybrid ceramic bearings on the RED cranks, meaning that the ceramic balls run in steel races. Those races can still rust.

I don’t know why SRAM would suggest more frequent lubrication than with a steel bottom bracket, unless the seals are less effective, being designed for lower friction rather than offering the tightest seal.
Lennard

Handling after fork switch?
Dear Lennard,
I have a Surly CrossCheck cyclocross bike (52cm frame size, 72 degree head tube angle) with the original Surly steel fork (44mm rake). I am considering switching to the Ritchey WCS Carbon Cyclocross fork (48mm rake) to loose 1.1 pounds off the front end and soak up vibration. Will this result in steering that is too quick at typical ‘cross race speeds?
Jeff

Dear Jeff,
That will make the steering quicker, but you still will have 59mm of fork trail (as opposed to 63mm of trail with 44mm of rake). In my opinion, it will still offer a good amount of trail and will result in handling that is not overly quick for ‘cross racing.
Lennard

Regarding forks for big guys
Dear Lennard,
Wound Up makes a great fork for tall riders. They make a fork with a 450mm steerer tube and can make that fork with a 500mm tube if needs be.

Their forks combine unmatched lateral stiffness with plush fore and aft compliance.
Jake

Dear Lennard,
Don’t forget that Kestrel still makes forks with a 310mm aluminum steerer tube, which are perfect for tall guys.

By the way, I’m 6-foot-5 and weigh 220, so I’m with you on the need for those big sizes.
Steven

Foot pain
Dear Lennard,
I read your recent column on foot pain and would like to point out that not many people know that the ball of your foot is like an upside down kneecap, with three bones. They are easy to break and they grow back bumpy sometimes. I did this doing a 50-kilometer ski race without insoles at age 18. Ever since, I had the same right ball of foot issues.

For all my shoes I use a Dremel with this little mace-like attachment (rough ball) to very slightly grind the hard sole down – allowing some space for that foot ball. Next I use Birkenstock boot insoles, which seem to be very hard to find. They are worth the trouble, since they go under the ball of the feet but do not go under the toes, preventing the usual problems with numbness when you fill up the shoe.

Furthermore, since they are made of cork, they serve to keep your feet warm in the cold, and have that tiny ridge in front of the ball of the foot like normal Birkenstock sandals have. That ridge keeps your foot back in the heel of the shoe even if you are hammering at high rpms and jamming your foot forward into the shoe. I’ve found this works even with my shoes totally unfastened.

I’ve had about 30 pairs of custom orthotics, from all of the “experts” in the field. None of them made past a week and proved to be totally useless. It just amazes me that boot fitters and orthotics makers haven’t figured out that you put immense pressure on the ball of your foot in cycling and very little on the arch and heel. One day shoe makers will realize and put a softer material embedded into the hard sole.
Ara


Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, 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.”

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.

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

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