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Technical Q&A with Lennard Zinn

  • By VeloNews.com
  • Published Jan. 7, 2003
  • Updated Sep. 28, 2010 at 4:45 PM EDT

By Lennard Zinn

Dear Lennard Zinn
I’m 50 and have arthritis in my left hip. I’ve been riding a pretty laid-back road bike for years (A LeMond with a 72.5 seat angle, seat all the way back)I do Yoga regularly, and that has helped, but my hips ache when I ride. I’m wondering if sitting further back might be “working” my hips more. The second part is that I have another frame I could have built up, but it’s radically different: 73.5 seat, 40.5 stays. The front end is almost the same as the LeMond. Both bikes are steel, the other frame is 753. I’m 6’2″ and weigh240. Some people have said the shorter bike would probably have a harsh ride and make matters worse. –John

Answer from Andrew Pruitt, former Tour DuPont medical director and current Specialized shoe designer:
Dear John,
Seat tube angle has more to do with femoral length and handling intentions of the builder and won’t really affect your arthritic hip. The most important aspect of fit concerning degenerative hips is stance width. Try putting a washer (2.5mm) between the pedal and crank. Some do quite well with just that much change others go to a pedal axle extender. There is a product called a knee saver which is a commercially available extender (2cm), custom pedal spindles are also available. Another idea would be a triple chain ring setup as they give you a wider stance also. Some forefoot varus posting (bio-wedges, between the cleat and shoe) can help your foot adapt to the new width as well. I have many patients in your situation and most can ride/race comfortably for years, as a matter of fact many ride better than they walk. Best of luck.
–Andrew Pruitt, Ed.D.
Founder/Director
Boulder Center for Sports Medicine
311 Mapleton Ave.
Boulder, CO 80304
303-544-5700

Question:
I have read your section on removing pedals in “Zinn and the Art of Road Bike Maintenance” (sec 9.4 – see Note) and it seems to me you have it backwards– you describe taking the right side pedal off in a clockwise motion – unless the right side is the non-drive side, then isn’t it the other way around? Also, when you are discussing fork materials, you describe steel as being harsher than aluminum (to soften the ride, use aluminum; to stiffen, use steel); isn’t it the reverse? –John

Answer:
No, you misinterpreted that section. It is not about removing the pedals. It is about removing the axle assembly FROM the pedal. It is correct. As for stiffness, the modulus of elasticity, which is the true measure of stiffness, is three times as high for steel as it is for aluminum. However, aluminum bikes often give a harsher ride than steel ones by virtue of the large-diameter tubes. Anyone who has ever ridden an aluminum Vitus (which used small-diameter tubes) knows that aluminum is NOT as stiff as steel. Aluminum is not a springy material like steel, and hence you get that “thwack” kind of a ride over bumps, which can be quite harsh. –Lennard

Question:
I recently purchased from an on-line Eddy Merckx dealer a 2002 Team SC frameset. The info that I received from that dealer was that the Campy Hiddenset was the correct headset to install on this frame. After having the local shop install the prescribed headset, I was surprised that that the top cap didn’t rest flush against the head tube. This was caused by the top cup not resting completely inside the head tube. When I questioned the mechanic about this, the owner said “that’s just Campy being different.” Since the headset installation, I have made it a point to review other integrated headset systems on other bikes. I have yet to see others with the same issue. All, including those with a Campy headset, have the ‘cleaner’ look I was expecting. This has caused me to have several concerns regarding safety as well as the long-term integrity of the frame and fork.

Do I have the correct headset installed? I have sent a follow-up email to the dealer as well as Gita Bike who is the importer for Merckx frames in the US. I am still waiting for a reply. If you could share your thoughts, I would greatly appreciate it.

As mentioned, the HS currently installed is the Campy Record Hiddenset with Alloy TTC (Tall Top Cap) for 1 – 1/8 steerer. –Brian

Answer, from Gita Sporting Goods, importer of Merckx:
I have already been corresponding with the customer about this headset. The top cup of the Campy Hiddenset does indeed stand proud of the head tube by about 2 mm, but when the top cap is put into place the actual gap should be only about .6 – .9 mm. I suggested that he check to make sure that the plastic ring in the headset is properly positioned and that the bearings are in with the correct orientation. If I can be of further assistance please feel free to contact me.
–Nelson Frazier
Gita Sporting Goods, Ltd.

Follow-up question for Gita:
Is that the same plastic ring as on the standard threadless Campy headsets? So you turn the top cap over and push it down first? Is there a chance he has the wrong bearing in the top? Just the other day, a guy brought me a Chorus headset with the same issue, but he had the bigger bearing set in the top and the smaller one on the fork crown. Switching those and pushing down the plastic ring with the inverted top cap fixed it. –Lennard

Answer from Gita:
The plastic ring is the same as in the other threadless headsets; however, the bearings are the same top and bottom in the Hiddenset. It is possible to try to install the bearings upside down, though. I have had the plastic ring be very difficult to seat with carbon steerer tubes such as on the Merckx due to slight irregularities in the carbon surface. Using the top cap upside down as Campy suggests usually will seat it sufficiently. It is, of course, possible that the head tube was not properly machined. This is fairly unlikely as the tool for machining the head tube cuts the chamfer and faces the top of the head tube at the same time, leaving the correct length of cylindrical section above the chamfer. This distance should be 3 mm. In the very early days of integrated headsets I saw this a few times, but not recently. –Nelson

Question:
How does the Ciclosport HAC 4 measure power output? Is it as accurate as the SRM or Powertap? I know these two have strain gauges that accurately measures power. I believe the HAC makes a projected calculation based on speed, altitude ascent, rider weight, etc. … can this be reliable? How might weather or something affect its reading? –Daniel

Answer:
You are correct. I would imagine that it only works well uphill, since it cannot know the wind speed and the rider’s aerodynamic drag. I just got one and am looking forward to trying it. –Lennard

There was a lot of feedback on Campagnolo chains. Here is a sampling:

Question:
I just read your Campy 10-speed chain article. This is not really a question, but a comment on the Campagnolo way of doing things. Again, they have re-designed a part that makes a specialized tool (an expensive one) obsolete in a short amount of time. This combined with the 3-4 different cassette lock rings I have to keep around is enough to make me switch back to Shimano. Speaking of which, I’ve been using a Shimano 9-speed chain with my 10-speed Campy Record for the past two years with no problems. What are your thoughts on alternatives to the Campy chain? –David

Answer:
The chain tool this time will not become obsolete until chains change completely. This one is basically a standard tool with prongs to hold the chain down – it would work with any chain.
I have used Shimano, SRAM and Connex 9-speed chains with 10-speed Record group on my own bike for years with no problems. –Lennard

Question:
A straightforward question: is an aftermarket chain available that will work with a Campy 10-speed that uses a removable link? I am certain that Campagnolo would not advocate using a non-Campy chain. However, the replacement pins and links required by Campagnolo are an expensive and unusual solution for regular maintenance. For me, this is a significant drawback to the Campagnolo system. –Scott

Answer:
Try a SRAM 9-speed. It has worked fine on my bike and has a master link.–Lennard

Question:
I mostly ride on flat roads where I live. I have all Ultegra components with Dura-Ace levers. I would rather not make the costly swap to a triple crank, new front derailleur and associated STI levers on the very few occasions when I make a trip up to the mountains to ride. Are there any technical problems with swapping my cassette to an 11-34 along with a long cage rear derailleur and chain? –Chris

Answer:
It should work fine, albeit a bit slower shifting. –Lennard

Question:
I was most impressed by the discussion of whether the rider in front ALSO benefits from another rider drafting behind them. Hence, the following inquiry: If you take two riders of equal ability and endurance, riding similar high quality bikes (say a Merlin Agilis, Dura Ace-equipped), are they faster riding individually or together on a tandem? You can assume that the tandem bike is of similar quality.–John Ladany

Answer:
On flat ground, the tandem will always be faster. On hills, due to the inefficiency of the tandem pedaling and difficulty of standing, along with no aerodynamic benefit, the single bikes will drop the tandem. –Lennard

Question:
Following on to the drafting question, I wondered about tail winds. Does the guy whose wheel you’re sitting on lose the benefit of a tail wind, or does the effect mentioned ( i.e. the pushing ) increase? –Raymond

From aerodynamics professor Dr. Chester Kyle:
The relative wind is what determines the wind resistance. In a head wind, the relative wind velocity on all riders is greater, and in a tail wind it is smaller than the bike speed. So in a head wind the benefit of drafting is greater, and in a tail wind it is less than it would be if there were no wind at all. The lead rider will get the benefit of a tail wind and the penalty of a head wind, no matter what.

Also, the proportional decrease in wind resistance is still the same for drafting riders no matter what the wind condition as long as the wind is steady and is less than the bike speed, and provided the drafting riders can find the bubble behind the lead riders. Since cross winds will drift the slipstream downwind, a pace line must echelon to get the benefit of drafting in a cross wind. This becomes a problem when riding on the edge of a road. In other words, the wind resistance will still decrease between 30 and 40 percent compared to the lead rider, if you can find the bubble. –Chet Kyle

From aerodynamics expert John Cobb:

Most tailwinds are not strong enough to actually be pushing you down the road. It seems that would be the situation that would be required for the drafting riders profile to block the tailwind effect on the lead biker. What we found a few years ago is that tailwinds give the feeling of greatly reduced drag. We rotated several riders 160-180degrees in the tunnel and that had their drag down to 2 – 3 lbs. –John Cobb

Question:
I have severe back pain (the result of a weight training accident) when I ride my 56 cm (c-c) road bike (with 56 cm top tube). To combat this, I have used a Look Ergostem on my indoor trainer to experiment with stem lengths and heights. I have settled on a position that effectively has a stem length of about 40 mm, and a stem height that makes the bars the same height as the seat top.
My question: is it reasonable to have a custom road frame made with the following dimensions: 56 c-c seat tube, 52 to 53 cm top tube and 16 or 17cm head tube, without throwing the handling characteristics way off (seat angle 73 degrees)? I assume there is going to be pedal-wheel overlap, but at least I won’t have to take any Ibuprofen after riding! –Scott

Answer:

Yes, it is possible. I do it all of the time. You can try the quick, free “Fit” page on www.zinncycles.com to see what it estimates for you.
–Lennard

Scott’s response:
I just took a look at your web page and will try the fitting program. I guess I should’ve looked there first because some of the custom frame pictures look a lot like what I’ve been trying to simulate!
–Scott

Finally, follow-up responses to the last couple of columns:

Feedback on Schwinn Prologue freewheel:

You might pass it on to Phillip to try the Shimano Hyperglide freewheel, Sheldon Brown can get them all day for a good price. I would not think they are under 400 grams in weight but I’m not sure as I have never handled one.

But that would give him a huge top gear of 39/34 for less than 30 bucks. Here is the link, www.sheldonbrown.com
–Almon

Feedback on ProGold:
I have been using Progold and so far it works well on my chains. The incessant rain here will prove its worth shortly. On the “side effects” of PG, I offer this observation.

I have a Cycleops fluid trainer for rotten weather and got tired of scratching my quick releases so I used “Tool Dip” on the QR grabbers. I noticed today the grabbers were a bit sticky so I used PG to loosen them. After90 minutes on the trainer I pulled my bike loose and much to my surprise, the Tool Dip had melted. This probably isn’t a problem for most cyclists(let alone a question for you), but I found it interesting enough to share.–Lindsey

Feedback on foot problems:
Nice writing, and very useful. I have the same problem with Morton’s neuroma. Custom orthotics of course help and may even increase pedaling efficiency like those wedges you can put under the cleat, but there is also a simple solution which has worked for me and others:

Get a metatarsal pad or a piece of thick moleskin, bevel the edges and paste it on the sock liner or directly on the shoe so that it hits just behind the heads of the metatarsal bones. This lifts and separates them usually enough to eliminate the problem with the pinching of the interosseal nerve. I did the same for a fellow physician who then had no discomfort throughout the IMH marathon. The bottom strap on the biking shoes can squeeze the foot enough to cause symptoms. I prefer 50-dollar Diadora shoes of a few years back in which the top strap goes BACK and pulls the foot into the heel counter instead of pressing it down compressing the arch. I keep the bottom strap loose, and that makes absolutely no difference in keeping the foot in place. Orthotics can be helpful, but they can occasionally cause new problems, plus they cost a few hundred clams. –France

Flight Deck follow-up:
A follow up to Carlos’ solution of tightening the screws… I’ve also found that some of the Flight Deck computers that I work on don’t register shifts after a short period of time. After a lot of trial and error, I’ve come up with a couple fixes (beyond checking the screws). First is cleaning the connections gently with a pencil eraser to remove any oxidation (like rubbing a dirty penny with an eraser) which seems to work for riders that sweat a lot. Second is putting a small folded piece of paper behind the wires that stick off the harness pod that screws into the shifter body itself. –Geno


VeloNewstechnical writer Lennard Zinn is a frame builder, a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides “ Zinn & the Art of Mountain Bike Maintenance” and “Zinn & the Art of Road Bike Maintenance.” Zinn’s VeloNews.com 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 each Tuesday here on VeloNews.com.

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