Monthly Archives: October 2016

650B Conversion Misconceptions

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1980 Meral sport touring frame

A while back I received a hostile diatribe in my comment queue about my Meral 650b conversion.  I spammed the comment, but then thought it was potentially illustrative, albeit rude and obnoxious.   The moron’s comment appears at the end of this post, and because it is full of misconceptions and mythologies couched as “expertise”, I’d like to thank him for inspiring this post.

I purchased my 1980 Meral 700c sport touring frame after researching the ideal geometry and clearance requirements for a wheel size conversion. I consulted Sheldon Brown’s 650B conversion guide, as well as resources available from many other cyclists, mechanics, and frame builders. A particularly easy to read guide is available at Rivendell’s site. Since that time, I have done a number of other wheel size conversions, from 650c to 26 inch, and from 700c to 650c.

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Mafac Raid brakes-to supply adequate reach to the 650B rims.

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Before building up the frame I dry mounted many of the components to check for clearance and chain line.

Those of us who have undertaken 650B conversions understand the brake reach, tire clearance and other considerations that must be explored when contemplating whether to convert a bike to 650B.  My spammer, however, believes that one can alter the geometry of a frame by changing the wheel size.  Without a blow torch, that would not be possible.

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After the conversion to 650B, the bike looks beautiful and eats up the miles.

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Wine cork spacer for the rear fender.

The outer diameter of a 38 mm 650B tire is only a bit smaller than that of a 700c x 20 tire.  The effect of the 650B conversion is to give one a chance to ride on wider tires, making the bike more useful and comfortable, and to provide for fender clearance that didn’t exist with the larger wheel size.  And, as I have stated in past posts, you don’t want to convert a frame to a smaller wheel size if your frame has a lot of bottom bracket drop.  Rivendell recommends no more than 70 mm, but you may be able to get away with a bit more drop if you are using shorter cranks.  Many bicycles from the 1970’s on have way too high bottom brackets to begin with, so lowering the bottom bracket a bit will improve the bike’s handling and cause no negative side effects.

My own Meral has very little bottom bracket drop, so the conversion improved the handling, by dropping the bottom bracket height DOWN to 27.5 cm, still very high, and much higher than recommended by some frame builders.  My trail went from 43 mm to 41, and my wheel flop stayed the same at 12.  The world did not stop spinning due to my audacious acts.  What are the factors at work that cause these changes?

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Rake and Trail, drawing courtesy of Dave Moulton.

When you install smaller diameter wheels, there will be a change in the distance from the center of the axle to the ground, thus reducing the distance of the horizontal line between a straight line following the fork/headtube angle, and a vertical line from the wheel axis to the ground.  Smaller wheel diameter = less trail.  More rake also = less trail, which you can determine from the above drawing by imagining the vertical line through the axis, moving forward, reducing the trail line.  Less trail almost always equals less wheel flop, which can provide improved handling for carrying front end loads.  Wheel flop is a function of head angle and trail, so you can alter wheel flop also by changing to a longer or shorter fork, and/or to a fork with less or more rake.  But in a well thought out 650B conversion, there’s no need to worry about changing the fork.

Another misconception is that a 650B conversion causes fork shimmy.  Even though no one seems to know what does cause shimmy, I think we can say for certain that it is not caused by the “wrong combination of rake, trail and head angle.” which of course a 650B conversion does not affect anyway (rake and head angle being impossible to change without changing the fork).  Fortunately, I eliminated the shimmy on my initial build by using different tires – I switched from the ponderous Panasonic Col de la Vie tires to the comfortable, delightful and fast Loup Loup Pass tires from Compass.

Finally, here is the comment which inspired this post, in full and unedited, with misspellings and grammatical errors intact:

“As you state, the frames is well designed and its construction very well crafted; it was mostly likely built by Francis Quillon the head framebuilder at Meral..and he would be proud of it. However..he designed the bike around 700c wheels and would be astonished that you have fitted 650B, thereby upsetting all the correct design features that he had used in the frames constructions ie head angle, front end clearance, fork rake and trail…all those important features that govern how a bike handles..OH! not forgetting the height of the bracket.
Shimmy is often a result of the wrong combination of fork rake, trail and head angle..compounded, without doubt by using the wrong wheel size. So what you have managed to do is to take a delightful frame that was intended for fast road riding ie sportif use, and try to turn it into a type of randonneur…which it was never designed from the box of frame tubes , lugs etc to be.
As for the massive amount of handlebar stem quill that protrudes dangerously out of the fork column, Quillon would be alarmed at the thought ..and the sight it presents. The least you could do would be to buy one of those elegant Stronglight extra long headset lock-nuts that would both add about 30mms of extra grip to the quill while at the same time making the bike look less ridiculous than it does now…
Never mind the chrome hilights, the wonderful deep purple flamboyant paintwork..you have turned the bike into a travesty of what the designer/framebuilder intended and,
in doing so, insulted his skills.
If you really need so much seat pillar projecting from the seat cluster and such a high riding position, I suggest you get a frame that is more appropriate to your inner leg and body length.
Just a footnote…no French builder, large or small would ever let a bike with toeclip overlap leave their workshop or factory.”

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Shockingly tall seatpost?

This diatribe points out how narrow minded some cyclists are –  adhering to the idea that if they do not personally experience something, then it must not exist.  One of the reasons the seat post and stem are tall is because I am using 160mm cranks, which help to eliminate toe overlap.  Shorter cranks means a taller seat post, which in turn means a taller stem.  And yes, this frame had toe overlap with the larger 700c wheels, and it was indeed designed that way – something that happens when small and even medium sized frames are built around 700c wheels.  Whether the builder considered this a necessary compromise to please a particular customer, we will never know.  Most disturbing about this rant is the ridiculous concept that style trumps comfort when setting up a bike for a particular rider.  Many riders know that taller stems mean more hours of comfortable riding.

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NItto Technomic stem, sanded to French size, a la Sheldon Brown, Shimano 600 French headset.

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A travesty?

Apparently, the original Shimano 600 French headset is an absolute eyesore, when paired to the tall Nitto stem.

So hideous is the bike that it is now a “travesty”.  Well, me and my travesty will see you out on the road.  Happy riding!

Vintage Cycling via the Written Word

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While recovering from my broken leg, I have had more time to devote to reading.  Which hardly makes up for the time I miss riding, but so be it.  Over the years, I have been building a library of vintage cycling books which reflect my own interests.  Here is a synopsis of some of the favorites in my collection, for your reading pleasure:

Eye Candy:

Racing Bicycles 100 Years of Steel by David Rapley.  A lusciously photographed collection of Australian racing machines dating from the late 1800’s through 2012.  There are some wonderful early path racers, and a great selection of Speedwells and Malvern Stars – for those not familiar with these Australian beauties – as well as other track bikes, club racers, and Tour de France winners.

 

Bicycling Through Time – The Farren Collection, by Paul & Charlie Farren.  This husband and wife team have spent their lifetimes collecting very old and very rare bicycles.  Paul has taken painstaking effort to restore most of the bicycles featured to rideable condition, machining parts as needed in his amazing workshop.  There are some robust examples of early safety bicycles and other fascinating contraptions.

Bicycles – Le Biciclette by Fermo Galbiati & Nino Ciravegna.  You won’t find these lovely vintage bicycles featured in other coffee table books.  There are some wonderful examples in this pocket-sized picture book, which is great to have on hand while riding the bus or taking a train.  The photos are top notch, and the collection includes Draisines dating from 1820 and Italian, French and British bikes built from the late 1800’s through modern times, all of which are original and in working order.

The American Bicycle by Jay Pridmore and Jim Hurd.  This collection provides a good counter argument to anyone who believes that 20th century American made bicycles consisted only of heavy, single speed balloon-tired clunkers.  In this collection are wood-framed steel lugged masterpieces of the “Gay ’90’s”, early racing and safety bicycles, and all kinds of machines representing the unique American contribution to cycling, all the way through the decades to Joe Breeze’s modified Schwinn Excelsior.  Includes lots of well-written historical insights.

Shop Manuals:

Glenn’s New Complete Bicycle Manual by Clarence W. Coles & Harold T. Glenn.  I affectionately refer to the author as “Dr. Glenn”, as he is pictured throughout this excellent repair manual wearing a pristine white lab coat.  This 1987 version includes complete instructions on overhauling most internally geared hubs, as well as step by step guides, with excellent pictures and illustrations, for overhauling every imaginable rear derailleur of the time.  It has all the other usual stuff you will find in a good shop manual.

 

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Eugene A. Sloane’s Bicycle Maintenance Manual by Eugene A. Sloane.  I include this manual here due to its chapters on frame repairs, frame painting, and a chapter on overhauling tandems.  These topics are often left out of modern and vintage shop manuals.

 

 

 

Cycling History:

Wheels of Change by Sue Macy.  This historical overview is aimed at the young adult crowd.  It’s a great look at the history of cycling through the eyes of women riders, with lots of rarely seen photos, including those of African American cyclists.  I learned a lot from this book.  The author took the time to unearth interesting historical tidbits as well as many photos I have never seen elsewhere.  This would be a great book to add to any teenager’s collection.

 

Framing Production – Technology, Culture and Change in the British Bicycle Industry by Paul Rosen.  In what began as a PhD thesis, the author thoroughly details the history and ultimate demise of the British cycling industry, focusing primarily on Raleigh.  The reading can be a tough go at times, but there are interesting perspectives here on the cataclysmic forces that lead to the end of bicycle production in England, and indeed throughout much of the Western world as economic and cultural changes shifted during the mid twentieth century and beyond.

 

Cycling Manifestos:

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“Dream Ramode Sunfighter Birthright” – Richard’s New Bicycle Book by Richard Ballantine. This treatise at the back of Richard Ballantine’s early editions of his repair manuals cannot be described – it must be read.  You might become radicalized, so be forewarned!  Even if you don’t make it to the end of this cycling guide for the masses, along the way you’ll find fun pencil and ink drawings of cycling’s days of yore.

 

Just Ride by Grant Petersen.  With  chapters such as “Carbs make you fat” and “Most bikes don’t fit” this good old fashioned practical cycling guide debunks much of what you may have learned about the “right” way to ride your bike.  Taking direct aim at the elitist, racing-focused “bike culture” he offers solid, if quirky, guidance on everything from bells, saddles, and macho competitiveness to a clip-less take-down.

 

 

 

Fiction:

Green for Danger by Christianna Brand.  This is a mystery novel set in a war-torn hospital in England during WWII, where a brutal series of crimes unfold.  The brief appearance of a bicycle is one of many clues to finding the killer before they can strike again.  The writing is a bit uneven, but the insight into British dedication in the face of unbelievable destruction is worth the read.

 

 

 

The Third Policeman by Flann O’Brien.  This metaphysical masterpiece about the nature of time, death, and bicycles couched within a mystery novel features some of the most evocative descriptions of bicycles and cycling I have ever read.  Here is an excerpt:  “This bicycle itself seemed to have some peculiar quality of shape or personality which gave it distinction and importance far beyond that usually possessed by such machines…I passed my hand with unintended tenderness – sensuously indeed – across the saddle.”

 

 

Injured Cyclist

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No, I didn’t break my leg while cycling. Instead, my accident occurred in the most dangerous place on earth:  my own home. Statistics indicate that slip and fall injuries such as mine will most likely occur in your humble abode.  In fact, statistically speaking, you are actually much safer out on the road – whether on a bicycle, on foot, in a car, or on a motorcycle.

To recover from a broken bone in the lower leg, generally there are two phases:  non weight bearing while in a cast or air boot, and weight bearing while in a walking boot. The former is the most challenging phase of recovery, as the bone can only heal properly if it is not subjected to movement. That means one’s mobility becomes seriously impaired. In times past, crutches were the only mobility aid out there. Anyone who has used crutches knows just how difficult and exhausting they can be, and can subject you to further injury if you are unable to master them in zen-like upper body strength fashion. Fortunately, bicycle technology blended with medical know-how has come to the rescue.

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Here is a “knee scooter” – an ingenious little 4 wheeled contraption which incorporates many cycling related components. There are cable brakes, an aluminum frame, a 90 degree head tube, flat bars, brake levers with lock out, bottle and basket holders, and a folding steerer.  This particular model was made by NOVA – a long time manufacturer of various medical mobility devices.  There are lots of other competitors out there, but this is what was available for rent from my nearest medical equipment retailer.  The only significant complaint I have about the device is that the steerer doesn’t handle bumps very well, so will turn in full radius when it encounters even a small surface anomaly.

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Of course, this has nothing to do with the quality of the machine itself, but with the geometry of its design.  A 90 degree head tube was probably deemed necessary to provide maximum stability when standing at rest over the scooter.  If the wheels were given a caster angle, that would cause the wheels to have “trail”.  As designed, its wheels have no trail.  Trail provides for a kind of “self steering” which you don’t really even notice as you ride your bike – you find that your bike tends to right itself even if you give it the wrong inputs. Trail is a critical feature in motorcycle, automobile and bicycle design – without it our machines would be unstable as they attempt to navigate curves and surface anomalies.  Low trail bicycles are great for front end loads, since they also have less wheel flop, but all bicycles must have trail in order to be rideable.

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While recovering, I took time to bone up (I can’t help the puns…) on front end geometry.  While Bicycling Science, by David Gordon Wilson, is an excellent resource, I admit that I haven’t spent much time absorbing the physics and mechanics presented in his well written tome.  But now, I took the time to review his chapter on bicycle handling.  As it turns out, there’s a reason why no one can agree on what makes a bicycle handle well: since a bicycle can only balance on two wheels with a rider aboard, studying its dynamics are nearly impossible.  Consequently, theories of bicycle motion and self-stability have not been validated experimentally.  However, stable machines such as trikes and 4-wheelers can easily be studied, and one thing everyone knows is that a caster angle on the wheels is necessary for the vehicle to naturally right itself under movement.

So why isn’t this nifty little device designed with a bit of caster angle?  That would produce some trail, which would help to keep the little scooter stable as it goes over bumps.

After researching the current knee scooter models available, I have found that there are some higher end models which incorporate a caster angle on the wheels, but such models are not typically available for rent, but can be purchased for a hefty price.  If your injury is quite serious and requires a long recovery, I think it might be well worth it to purchase a higher end model which incorporates a caster angle.  This would allow greater safety and mobility, especially in outdoor situations.

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Meanwhile, I’m working on keeping my little scooter maintained.  The brake cables were poorly adjusted, and the bottle holder clamp needs a washer.  I’m sure I’ll find a few other mechanical shortcomings during my recovery.  Even so, these knee scooters provide a clear advantage over crutches in terms of safety and comfort.