Menu

Technical Q&A with Lennard Zinn – Bearings, bottom brackets and cogs

  • By VeloNews.com
  • Published Apr. 15, 2008
  • Updated Feb. 16, 2010 at 10:47 AM EDT

By Lennard Zinn

Dear Lennard,
I’ve just read your article article about the SRAM ceramic bottom bracket and its maintenance. We at CeramicSpeed have been working with ceramic bearings for the past 11 years, introducing systems for bicycle applications eight years ago.

One of the first ProTour teams that used ceramic bearings was the CSC squad. In 2003 FSA learned about the ceramic bearings from the team and, two years later, FSA introduced its first ceramic bottom bracket to the end users. Since then, CeramicSpeed has built more than 10,000 FSA MegaExo bottom brackets.

Not all end users want to use the red FSA cups — therefore CeramicSpeed decided to re-work Dura-Ace bottom brackets and offers the Dura-Ace cups with CeramicSpeed bearings. We recommend that the end user do maintenance every 5000 to 10,000 kilometers, or when needed.

“When needed” is admittedly unclear, but it could be quite often if the bottom bracket is used on a pro team, where mechanics often use high-pressure cleaners or strong degreasers to clean the drivetrain. Degreasers make the cleaning very easy but you need to be sure that your bottom bracket, rear hub and pulley wheels has some lubrication afterwards.

With a high pressure cleaner, you can reach up to 200 bars — when bicycle tires are inflated “race” pressure can be 10-13 bars. Furthermore, some teams use hot water in the cleaners, just to be sure all dirt and contamination gets of the bike and into the rotating parts on the bikes. That, too, will require the bottom bracket to be regreased.

Twenty years ago, neither Shimano nor Campagnolo had rubber seals — only steel labyrinth shields that didn’t steal any energy from the rider. Service intervals were short… very short. Riders often had to do service weekly . Today the Dura-Ace bottom bracket has a text “do not disassemble” stamped on it (Maybe the goal is to have users simply buy a new one when needed).

That’s also why SRAM recommend service interval each 100 hours (better to be safe than sorry). From what we have seen, some SRAM bottom brackets have done a season without service. It really all comes down to how you take care of your equipment.
Jacob Csizmadia
Managing Director
CeramicSpeed

Dear Lennard,
In the reply to “Ben” in the April 8th Q&A , you quote Burt Hull at Alpha Q as saying they allow as much as 130 mm of steerer height above the frame (I assume that means the top of the headtube) which equates to about 90 mm of spacers under the stem.

This is far different than all of the other manufacturer’s recommendations I’ve read which limit 1-inch carbon steerers to 25mm of spacers and 1-1/8-inch steerers to 30-50 mm of spacers. I assumed this was a safety issue to avoid putting too much of a bending load on the steerer but maybe not if Alpha Q is correct. Are the others way too conservative? I’ve always parroted the 50mm limit when asked but is this unnecessary?
Dave

Dear Dave,
Bert Hull’s advice was specifically for the Alpha-Q Z-Pro fork, which I worked with True Temper on the development of many years ago in order to be able to offer a stiff, strong fork with a 450mm steerer for our super-tall bikes. That steerer is about double the wall thickness of other Alpha Q carbon steerer forks.

In general, 50mm is prudent, but I do believe that, at least for people under, say, 175 pounds or so, the 50mm recommendation is not as much out of concern about breakage as it is about reduced stiffness in the steering system.
Lennard

A tire gluing tip
Dear Lennard,
I have a technique for gluing on tubulars that involves the use of a 10cc “wall paper” adhesive syringe — basically a slightly modified medical syringe, found at my local hardware store.

I warm a tube of Vittoria or Continental glue in warm water and then put the warm glue in the syringe. Using a rim and tire that have already been coated with dried glue with the tire aligned over the rim, inflate tire to align, then deflate to apply glue. Now apply a bead of glue with the syringe between the tire and rim on both sides. This method avoids pulling the tire over the rim with wet glue. Perfect alignment with no more unsightly glue on the braking surface of the rim or sidewall of the tire. Can almost to it without gloves, but I still use them.

Have a look at my YouTube video to see how.
Ken

Dear Ken,
Well, that’s interesting. I decided to give Vittoria’s U.S. agent, Tom Petrie, a chance to take a look. Here’s his take:

Lennard,
I think it is probably more difficult to do with a new tire, but interesting nonetheless.

My procedure is to mount the tire first and leave it overnight or longer at full pressure to stretch the tire a bit. Then I apply a liberal coat of glue to both base tape and rim. I use an old toothbrush to really work the glue into the base tape fabric. I let both wheel and tire dry. Then I apply a fresh coat of glue to the entire surface of the rim and mount the tire while the rim glue is still wet. Because the base tape of the tire is only tacky, I don’t get the smear across the rim. Also, if you pretty aggressively stretch the tire onto the wheel as you’re mounting it, the last few inches will go on much easier than if you don’t.

Nevertheless, Ken’s approach seems viable. I thought the idea of warming the glue was a good one. I am skeptical that only the glue on the edges is what’s holding the tire on though. I think the pre-glued surfaces join and that the bead on the edges, certainly the highest stress point, provides a good first line of defense. I wonder though it if the tire would be more secure if there was a wet layer under the entire tire.

Also, I’ve re-glued base tapes with Jiffy-Tex carpet seaming adhesive. You can get this stuff at most carpet wholesale supply houses. I did this back in the days when I was poor and immortal. I never rolled a tire with Jiffy-Texed base tape, but this may have been the result of high pressure and a little bit of luck.

Tom Petrie
Velimpex Marketing, Inc.

Follow-up
Dear Lennard,
I found your articles on using a SRAM rear derailleur with Campy components (see March 17 and March 18) very interesting. I have the opposite situation: I own a lot of Campy wheels. Will they work with a SRAM rear derailleur and SRAM shifters? I would not like to give up my Campy Shamal Ultra wheels to try out the SRAM system. From your article, I think that they will but you did not say whether or not you had tried that combination.
Ed

Dear Lennard,
Thanks for a great tech piece on the compatibility, I have a question that you may have answered when you stated:

“It is well known that a SRAM 10-speed cogset shifts perfectly on a Shimano 10-speed-equipped bike, and vice versa. But Campagnolo 10-speed cogsets have slightly wider spacing and do not shift well in either SRAM or Shimano 10-speed drivetrains.”

Does this mean that if I have a Campy drivetrain, specifically the shifters and 10-speed cogset, that I can’t use a SRAM rear derailleur and get good shifting performance? Or is the key piece the shifters? I have both Campy and Shimano wheels, I would like to be able to use them both. I was hoping to buy a SRAM rear derailleur, keep my Campy 10-speed shifters and use both Campy and Shimano cogsets.
Mike

Dear Ed and Mike,
I just tried a Campagnolo cogset with the combination of a SRAM RED rear derailleur and Campy 10-speed Ergo Power levers. It does not work acceptably. If you recall from my original posting on this subject, the SRAM 10-speed lever actually pulls more cable than the Campy 10-speed lever — 28mm over its entire nine-click range, as compared to 27mm over the nine clicks for Campy.

It is close enough that the SRAM RD/Campy lever works with a SRAM 10-speed cogset (and presumably with a Shimano 10-speed cogset as well, as its spacing is the same as a SRAM road cogset). However, the spacings within a Campagnolo 10-speed cogset are wider than those of a SRAM or Shimano 10-speed cogset. So, combining the shorter cable pull of the Campy lever with the Campy cogset’s wider cog spacings produces a combination that will not work. It shifts okay for 3-5 cogs, and then it starts missing shifts.

The SRAM 10-speed rear derailleur with SRAM 10-speed levers will work somewhat better with a Campy 10-speed cogset, due to the SRAM’s longer lever pull, but it should provide the same (in my estimation poor) shifting that a Shimano 10-speed rear derailleur and Shimano 10-speed levers do on a Campy 10-speed cogset.

Here is a good chart on cog spacings.
Lennard

Regarding the January 22 posting on modifying an M5-Ligfietsen brake to work with Power Cordz:

Dear Lennard,
My idea didn’t hold up. I tried a couple Power Cordz and they all failed at the pinch/clamp. I spoke to the guys at Power Cordz (stand up guys who are totally behind their product) and they sent me some free ones to try. Unfortunately, the newer ones they sent suffered the same fate. I think it’s safe to say that Power Cordz and M5 brakes don’t work together. I don’t know if you want to post anything on the Web site as a follow up to my initial idea, but I thought I’d better get the word out.
Ted


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: / / /

Stay Up to Date on Everything Cycling

Subscribe to the FREE VeloNews newsletter