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Technical Q&A with Lennard Zinn

  • By VeloNews.com
  • Published Oct. 29, 2003
  • Updated Sep. 28, 2010 at 4:49 PM EDT

By Lennard Zinn

Technical Q&A with Lennard Zinn

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Dear Lennard,
I have two bikes. Each bike has the same saddle and handlebar.I set up both bikes with the same measurement from saddle tip to bottombracket. Each bike has the same measurement from saddle tip to the centerof the stem/handlebar. On one bike the stem blocks the view of the fronthub. On the other the front hub falls in front of the stem. I measuredand their is a 1cm difference from bb to front hub between the bikes.Should I be concerned that I can see the front hub? Should I usea longer stem? Will this effect my handling?
–Jeff

Dear Jeff,
Don’t sweat it. If you are happy with your position on the bikes, stickwith it. That bar-blocking-view-of-front-hub method is not worth the paperit’s written on.
–Lennard

Cranks for the smaller rider
Dear Lennard,
What about us small people?
I’m 5 foot 4 inches tall with about a 63.25cm saddle height. I ridehilly terrain, but am not a racer. What crank length for a road bike? If167.5 not readily available, 165 or 170?
–John

Dear John,
Well, I know that this would take a leap of faith, but I do know smallpeople for whom this has worked, at least from the perspective of alleviatingpersistent back pain. The method would be to multiply your inseam lengthby .21 or .22 to find the crank length. Now, I have taken the liberty ofestimating your inseam length by assuming your seat height was determinedby the “LeMond method” (i.e., multiplying 0.883 by the inseam measurementto find the distance from the center of the bottom bracket to the top ofthe saddle along the seat tube). Dividing your seat height by 0.883, Iget an inseam of 71.6cm for you. Multiplying that by 0.21 and 0.22, I geta crank length between 150mm and 157.6mm.

That may sound shockingly short. I do know people with leg lengths similarto yours using cranks in lengths like this who love them and are much morecomfortable on their bikes than before. I do recommend trying it, althoughit obviously takes a substantial commitment from you to get custom cranks,unless you can find some T.A. 150mm arms.

The shorter arm does decrease your leverage, so you may want to stickwith 165mm. However, you may also find that increased efficiency and asmoother, higher cadence with shorter cranks could make up for it. I rememberbeing amazed at how well I could keep up on group rides with 100mm, 117mm,and 134mm cranks when I was doing a crank test a number of years ago witheight sets of Boone cranks between 100mm and 220mm. And I have a 96.5cminseam!

Anyway, I recommend experimenting and seeing what works best for you.
–Lennard

Tires for the bigger rider
Dear Lennard,
I am doing my first cyclo-cross race this weekend and want to knowif I should put knobby tires on my road bike (will 30′s fit on a ColnagomasterXlight with Campy parts), or borrow a hardtail mountain bike (I havea full suspension rig)? I’m a pretty big guy (6 foot 5, 215lbs.) so alsoworried about the strength of the road bike…
–KB

Dear KB,
I doubt the 30s would fit. My guess is that the most you could usewould be a smooth 28mm tire in that bike or a very small knobby. If thecourse is dry, a big smooth tire might be fine, and you would be fasterwith it. You are definitely big for that bike and will abuse it some. Thinkof it as about the same as five times as many hours of road riding on it.
If it’s muddy, you will have to go with the mountain bike, I think.It will certainly take the abuse better.
–Lennard

To bolt or bond
Dear Lennard,
I’ve noticed that several bike manufacturers are mating carbon seatstaysto titanium mainframes. I was surprised when I saw one popular model,the Reynolds seatstay, bolted onto the rear dropout. How do you feelabout bolting together a frame as opposed to bonding (I imagine weldingis out of the question here) in terms of a frame building technique, ridequality, strength, durability and art? Is this standard for carbonseatstays and dropout joints or do some manufacturers bond these jointslike a carbon fork is bonded to its dropouts?
–Eugene

Dear Eugene,
All carbon stays are generally bolted to a rear dropout. It would betoo expensive to make dropouts in all the angles necessary to slip intothe stays at the proper angle for all frame sizes. The dropouts thereforehave a pivoting plug on the upper end that is bonded inside of the seatstay.This is bonded the same way that a carbon fork is bonded to its dropout.It’s just that in this case, the dropout angle is critical because it ismet by tubes from two directions, so the pivot is important. The pivotis either a bolt or a rivet or a pin of some sort, and the movement isfrozen by bonding it to the lower part of the dropout.
Here are examples from Litespeed, Merlin and Quintana Roo below.
–Lennard

Answer from Litespeed, Merlin and QR:
I am not sure how all other manufacturers do it, but I assume thatit is to some degree similar.

Technical Q&A with Lennard Zinn

Photo:

We actually bond a titanium plug into the carbon stay (plus the titaniumplug actually has some serious “teeth” to it) and then it gets bolted withLoctite to the dropout.

The two photos show a Litespeed Ultimate rear and a Merlin Camena women’sbike. On Litespeed, the LiteTEC HP carbon seatstay is a monostay, versuson Merlin (Solis, Cielo, Lunaris and Camena), the seatstays are individualcarbon stays. That allows you to see the steps of the plug which usuallysit inside the carbon and help with further securing it.

Herbert Krabel
Litespeed Director of Marketing

Can’t wait to take my shoes off
Dear Lennard,
This season was my first on Shimano carbon-soled road shoes. They haveexcellent power transfer and I love them, assuming I limit riding to about2-3 hours. After that, the area around the balls of my feet are in a worldof pain. When I finish longer rides the first thing I do is rip those !@$@##@%^shoes off. I ride Campy Record pedals, which have stayed in my goodfavor.
I have ridden many stiff-soled shoes before, including Shimano andother brands. Never had I had a problem in the past — I am one of thoseblessed individuals who has good alignment and no foot/knee problems.

After asking around and doing a little research, I have reached an impasseand am unsure of the path to take. The folks at Shimano told me it’smy pedaling style, and that I should train myself to put more pressureon my toes. I’ve also been told by others to:Move my cleats back a bit to reduce pressure off the ball.

Buy Superfeet inserts for more cushion (I’ve tried other insoles/gel paddingto no avail). Others, including Shimano, have said cushioned insertswill reduce power transfer.

Buy a pair of Sidi shoes. This was the least welcome, given thatI had already forked out quite a bit for the Shimano shoes.The conventional wisdom of the past is that a stiff-soled shoe should eliminatehot spots or pressure points because of more widespread pressure distributionover the sole of the foot. But recent research from Tulane seems to contradictsuch thinking and points to carbon as the culprit of foot discomfort.See thisdocument at Tulane University.

What is your sage advice?
–John

Dear John,
Your problem sounds like Morton’s neuroma. I have this particular problem(the too-tight-handshake pain), that I have fixed with custom insoles (a.k.a.orthotics) specifically for cycling that have carefully sized and placedmetatarsal-arch support pads. The pads keep the metatarsals from movingup and down and irritating the nerves between them.

You don’t want to screw around with this, because you could end up insurgery, which seems to rarely work, given the number of customers I havewho have had this surgery seven or more times on each foot! My guess isthat, once it has gotten this irritated, switching to different shoes alonewill not suffice.

I use my orthotics in all of my shoes, which range from Sidis (somewhatflexible) to lots of pairs of carbon-soled shoes. I am in agony in a rigidcarbon sole without them.

I don’t know if Superfeet can be ordered with the metatarsal arch pador not. I do have some over-the-counter Linco footbeds that do have thesepads (they can be purchased with or without the met pad), and these arefar better than using my shoes with the insoles that come with them. Theyare much softer than my orthotics and do not offer as much support, sothey are a distant second best, but much better than nothing.
–Lennard

Junior-geared Dura-Ace?
Dear Lennard,
Will a 14 tooth first position cog be available for 2004 Dura Ace 10?Although one could meet the juniorgear restriction with a 45 tooth big chainring and a 12 toothrear cog, the 52 x 14 combination is more common. The described 2004Dura Ace changes in the shift lever throw, ergonomics and improvement inthe front derailleur sound like good news for juniors with small hands.
–Steve

Answer from Shimano:
Currently, there is no 14 tooth option for the Dura-Ace 10 speed cassette.The best option for junior racers is offered in the Ultegra 9 speed group.If the need for levers with a short reach presents itself, Shimano manufacturesan Ultegra level STI lever with reach adjustment. The model number is;ST-R600.
–Jason W. Leith
Bicycle Components Division
SHIMANO AMERICAN CORPORATION

Follow-up on headset problem from last week:
Dear Lennard,
In response to “Wobbly in Wyoming” with the Campy headset problem,it sounds like he was missing the plastic wedge that Campy uses to tensionits bearings and hold the steerer stable. I’ve seen several bikes thatdid not have it from the factory. Though he already replaced it with aCane Creek, the fix could have been an easy $5 part.
–Adam


Technical 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 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.

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