Tech letters for December 20, 2001

Edited by John Stevenson

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If there's a topic that always gets cyclists going, it's correctly fitting bikes to riders and riders to bikes. We've two long and thoughtful letters on that subject today, plus a strong opinion on integrated headsets, a comment on the ROTOR crank system mentioned in Tuesday's tech news, another use for old inner tubes and more on chainstays and fish.


Fit & frames
Integrated headsets
Inner tube tips
Chainstay protection

Fit and Frames #1

Greg Lemond's book has one of the most authoritative chapters on this subject around, but if you follow his instructions you'll end up buying a Lemond because he says 72 degrees and long top tubes are the way. They very well might be, I've never owned one.

Building a frameset for a person who isn't an experienced rider is, in my opinion, a gamble. It's not often a sure bet that the correct bike will please a novice rider because his/her body is going to go through dramatic changes as soon as the heavy miles begin. Most beginners think that fit = comfort. The "right" bike will seem large, uncomfortable, and probably skittish. As back muscles stretch out the position will change and the bars will invariably get closer and closer, the saddle will also seem lower and lower with each thousand miles put on. I've seen more than a few lugged dream machines sold for pennies on the dollar to someone holding immediate bucks.

The builder we worked with wanted to know everything about the bike that the customer was currently riding and what the intended purpose was of the new bike. One guy insisted that the builder use Excel tubing because he wanted a light bike. The builder told him that he was crazy and 2,000 dollars later the guy sold the bike because whenever you took your hands off the bars the whole bike became unrideable.

As for fit, this builder tried to get the middle ear, which is the balance center of the body, on the imaginary line that would run through the steer tube. Rake and trail having no effect. On a properly fitting bike this gives the rider a neutral and direct feeling when turning. Contrastly, if the ear is ahead of the line the rider will lean into a turn first and it will feel like he's turning and the bike is still going straight, placing the ear behind the line makes the bike turn but the rider feels like he's following.

Imagine yourself standing on a ball. Once you get your middle ear off the pole axis the ball will run out from underneath you. Only by keeping the ball under you are you able to stand.

The line is determined by three things, saddle position (to a much lesser extent), top tube length and head tube angle. This is why a touring bike that's seemingly way too big rides well, the relaxed 72degree angle moves the line back by a few inches, and this is why a track bike can be much smaller if it has a 75 or even a 76 headtube angle. The line moves away by inches.

A bike that is too big or small can be made to fit (comfort-wise) by changeing the stem length, but it will never have that sweet, dialed-in, wonderful ride-feel, although it may be serviceable. This is fine for a 1000 dollar production bike, but if you are having one built for you, you want it right.

I ride bikes of many sizes, the thing they all have in common is that the line hits my middle ear and the distance from the seatpost to the bar is 670 mm. I'm 72.5 inches tall with very short arms, so if I ride a 57cm top tube I need a 100mm stem. I have a track bike with a 55cm top tube, but the line's in the same spot and I have a 120mm stem. I have a Cinelli touring rig from the 70's that's got a 59cm top tube, so I have to run a 80mm stem. They all feel Perfect.

I once heard these quotes and I believe them:

Two bikes from different manufacturers that are the same size will ride much more alike than two identical bikes from the same manufacturer that are just one centimeter different in size.

Everyone wants to climb on a 900 gram frameset, but nobody wants to descend on one. – Ernesto Colnago

You will spend more time on your bike than you will making love to your wife, so make sure that you get the right one.

Cheap bikes aren't cool and cool bikes aren't cheap.

Paul Knopp
Deluxe Bicycles
Lincoln, NE

Respond to this letter

The notion that the steering axis should point at the middle ear is a new one on me, but if it results in bikes that people like to ride, then that's got to be good. I think fitting a bike properly has a hell of a lot to do with insight and experience and not that much to do with science, and a lot of the fitting 'systems' out there are attempts to codify the fitter's intuition or provide a starting point for it to work from.

Fit and frames #2

I am having one hell of a problem with correct frame sizing. The main problem is in getting the correct set back and thus the reach correct. I have sent my measurements off to numerous sites and each and every one comes back with some ridiculous frame sizing, none of which work for me.

My latest frame is the best fit I have had up to this point but it too is not perfect. Problem is I do not have anyone within 1500km of me who is qualified to fit properly. Most people just guess and it has cost me the price of five frames so far -- three stock and two custom.

I have unusual sizing which I am sure just throws people off who have no training and no racing experience in Europe. Most try to sell me a crit frame which here in North America is the number one racing pastime. But I prefer and my body prefers the more laid back frames that I was accustomed to riding when I was a boy in England.

I have been on one sizing frame they said a 53cm centre to centre with a 57.5cm top tube, 14cm stem and a 72 seat tube . With my size and strength I just think the top tube should be longer and the stem adjusted accordingly.

Zinn recommended a 59.5cm top tube on a 53cm frame. But where they all get it wrong is the set back . Even at 72 degrees the plumb line dropped from the front of the knee cap which is the way I have always done it falls in front of my cranks thus I find myself pushing my self back on the saddle then my spin speed goes up and I am also flatter in the drops but I cannot ride like this for very long.

Can you put me onto someone who can take my input and my measurements and come up with a reasonable sizing. I think I can get a sizing frame which I will have to rent if they will let me take it home . A starting point would be very helpful I could taake it from there if I can get the sizing bike. My present frame is a 53cm with a 58.5cm top tube and 72 seat tube.

Chris Ashley

Respond to this letter

Chris, all I can suggest is that you try and find a frame builder who is prepared to 'think outside the square' a little. What you're looking for is a pretty unusual set-up, though your experience reminds me of the debates our publisher Gerard used to have with his local bike shop over custom frames. He also likes a bike with a shallow seat angle (71.5 degrees on his most recent custom rig), and his bike shop pooh-poohed this for years until it got some serious fit and sizing equipment. After measuring Gerard up, the shop owner cheerfully admitted he'd been wrong all these years and his shallow seat angle really was necessary.

It sounds like you really do need to drop the seat angle back another degree. While this is unusual, it's far from unprecedented and you should be able to convince a builder to construct such a frame.

Integrated headsets

I may not be a mechanical weenie, but to me the new integrated headsets are a bunch of baloney! The whole "you need more strength at the head tube area"? I can't even remember ever seeing a frame break at the head tube. I've seen the forks snap off below the headset, I've seen the top tube and down tubes snap, but that wee little head tube: never!

Now that we've established that that strength is a bunch of hooey, let's look at the overall function of both a traditional headset and an integrated one. How do they function? Well, if both are installed correctly you will not notice a dang bit of difference in the performance of the bike.

So we've established that being stronger is not the real issue, and they "perform" the same, what do we have? Well, this is what I see. I see something that if you let it go unadjusted for a while, on the traditional headset you've got a toasted race that is cheaply replaceable. On the integrated headset, you've got a trashed frame.

Hands down winner is the traditional headset. Integrated is a way for frame manufacturers to build in a "new" frame for people more often and that's all.

Functionally: no different. Possible cost differential: huge!

Cassandra White

Respond to this letter

I don't believe that anyone in the bike industry is that cynical, Cassandra. I know lots of bike industry types would like us all to buy a new bike every three years instead of every five to ten, but deliberately using a component that destroyed the frame if you fail to adjust it right... nah. It smacks too much of conspiracy, and fifteen years observation of the bike industry tells me that when things are awry, the reason is usually a cock-up not a conspiracy, which is why we have flawed standards like the square taper bottom bracket axle.


This could get interesting. As far I can figure it (the English version of the site wasn't up), this product is very similar to Powercranks. Check out:

Dave Chen

Respond to this letter

As far as I can tell, they're not quite the same. Powercranks uses a clutch to decouple the left and right cranks so that you are, in effect, pedalling independently with each leg. This, the maker claims, forces you to train each leg to pedal more efficiently. ROTOR only changes the angle between the pedals as each one passes through the top dead center of the pedal stroke. When the pedals are at three o'clock and six o'clock that's the only position they can be, whereas with Powercranks you can have one pedal at three o'clock and the other anywhere you like.

Inner tube tips

You can use cut up portions of a road tube to go over CO2 cartridges to keep them from rattling around in your tire bag.

James Cushing-Murray

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Chainstay protection

In response to Jay Perley, although striped bass and flounder have been the chain stay protection choice for many years, times have changed!

Obviously the USA is again behind Europe in cycling technology as the use of striped bass (heavy, large at the head and slightly acidic), and flounder (flat, wind grabbing and not oily enough) have been replaced for the last few years by the lighter (lower fat content) and much more aerodynamic PIKE family.

Good God man! Get on the bandwagon!

Charles Manantan

Respond to this letter

Any more silly suggestions for frame protective fish? I don't want to carp, but this topic could very easily make us all eel