Wednesday, July 16, 2014

Bianchi v. Surly

Some of the geometric elements of a bicycle. The head tube (not labelled on this figure) is the short tube at the front of the frame.


I am currently riding four bicycles:
  • A 60 year old department store 3 speed with nothing to recommend it except that both the risk and consequences of it being stolen are low. I use it when I need to ride the 3 or 4 miles to Texas Medical Center for a meeting. Other than that, nothing needs be said about this unfortunate bicycle.
  • A 1960 Bianchi Specialissima. This bike is very similar if not identical to the Bianchis that were being ridden in the Tour de France that year. This is the kind of bike I used for both racing and touring in the 1960s and 1970s. I am currently riding it once a week or so.
  • A 2010 Surly Cross-Check. This is marketed as a "do-everything" (except race) road bike, is the bike I used to complete my two 200K brevets, and is my go-to bicycle.
  • A 2006 (more or less) Bianchi Volpe. Similar in concept to the Cross Check, this model has been in continuous production since at least 1987. It has evolved, of course, from 6 cogs in the rear to 10, from a lugged to a TIG welded steel frame, but it has always been a steel frame, do-everything bike. My Volpe lives in California so that I have something to ride on my periodic visits there. I haven't been able to do side by side comparisons with my Cross-Check or the Specialissima, so I won't be discussing it as much in this post, though I will mention it once or twice.
My first impression when I got my Cross-Check was that it rode very similarly to my Specialissima. However, I have modified both of these bikes over the years and during the same time, differences which failed to capture my attention at first have made themselves apparent. As a result, when I recently returned to my Specialissima after some time off of it, I noticed some differences. Since then, I have tried to explain these differences both by researching the Internet and by making measurements of the two bikes, and in this post, I report on what I have learned.

Twitchiness, Trail, and Bike Fitting


Something I noticed right away is that the handling of the Specialissima seemed twitchier than the Cross-Check. A topic which is fairly hot in the randonneuring community1 is that of "trail", a measure of how far the front wheel trails behind the extension of the steering tube of the front fork. This is determined by a combination of wheel size, angle of the head tube of the frame, and rake of the fork. Most bikes have a trail of 50 to 65 mm. However, many randonneurs favor a bike with a lower trail than that, something in the range of 45 mm or so. Because I am interested in randonneuring, I wondered what the trail on my two main bikes were and if that might have something to do with twitchiness? The Cross-Check has the reputation of being a medium trail bike, and when I measured trail directly, I came up with a trail of 57 mm, smack in the middle of the medium range. However, I was shocked to measure a trail of 92 mm for my Specialissima, well outside the range of anything I had ever heard of! In my confusion, I consulted the cognoscenti of Bike Forums. They looked at a picture of my Specialissima and immediately they noticed that the angles of the front tube and seat tube were very different; the front tube was much shallower (farther away from 90 degrees.) This would explain the high trail I measured.

The picture of my Specialissima I shared with Bike Forum members.

Why would the frame designers at Bianchi do such a thing? A few different opinions were offered, but the one that rang most true to me is that it was a way to prevent toe overlap in a relatively small frame. Toe overlap is when you turn the front wheel sharply, like when you are track-standing while waiting for a light, or just starting up. On some bikes, the wheel will hit your toe if the pedal is all the way forward. You never turn the wheel that sharply when you are riding normally, so some people don't find toe overlap a problem at all, but others, me included, don't like it and some government agencies consider it a safety hazard. Let me explain what trail has to do with toe overlap. The fundamental problem is that I am short, 5 foot 6 inches. The average man is 5 foot 9 inches. There are many different dimensions and angles that can be varied on a bike frame (as in the diagram at the top of the post), but when a manufacturer describes the various "sizes" of bikes they make, they normally express that as the length of the seat tube. The average sized bike for the average sized man with average proportions has a seat tube 56 cm long. I normally ride a bike with a seat tube which is 52 cm long. There are many issues a manufacturer encounters when they scale an entire bike to accommodate different sized riders but perhaps the biggest is that you can't change the size of the wheels proportionately; wheels only come in certain sizes, and they are not freely interchangeable even among the available sizes. If I had purchased a Surly Long Haul Trucker instead of a Surly Cross-Check, Surly would have reduced the wheel size from the 700c wheel provided on the standard 56 cm frame to a 26 inch wheel on my 52 cm frame. The problem is, available tires for 26 inch wheels are fat, which is fine for a touring bike like the Trucker, but which is undesirable for many riders of a road bike like the Cross-Check, me among them. As a result, Surly couldn't change the wheel size on my tiny Cross-Check so they had to change something else to make it work. What they did was make the frame proportionately longer front to back. Something I had noticed, going back and forth between my Specialissima and my Cross-Check, is that the handlebars feel farther forward on the Cross-Check. This explains why. On the Specialissima, instead of pushing the handlebars forward, they "tilted" the front wheel away from the pedals by reducing the head angle to avoid toe overlap. However, this created the very high trail and the handling which I am describing as "twitchy." Finally, on the Volpe, they just scaled everything (except the wheels) and let the chips fall where they may. My Volpe has toe overlap.

I do confess that when I found out that my Specialissima had a compromised frame design, I was heartbroken. The bicycle that was the apple of my eye now seemed spoiled. I am slowly getting over that but it has sparked in me a new interest in alternative sized wheels, like the aforementioned 26 inch and the ever so trendy 650b. Final point: my wife is 5 foot 3 inches tall. Think what these scaling problems do to her bike. In her case, I have even toyed with the idea of 24 inch wheels made for childrens' bikes.

Handlebar Height


In response to pain in my arms and shoulders after my first brevet, I decided to raise the handlebars on my Cross-Check, and ended up raising them by about three inches. In a previously posted picture, it looks like the tops of the handlebars on the Specialissima are now almost as low as the bottoms of the handlebars on the Cross-Check. To determine if this was true, I compared the relative height of the bars and seats on the two bikes by measuring the distance of each to the ground. According to this measurement, the Cross-Check bars are about 2 1/2 inches higher than its saddle, whereas the Specialissima bars are almost 2 inches lower. By comparison, last time I was in California, I measured the Volpe, and on that bike the bars are about 1 inch lower than the saddle. The Cross-Check feels very comfortable and I can easily ride on the drops for up to an hour at a time. (I have not had occasion to try much longer. Given a choice, I am more comfortable on the tops of the bars.) The handlebar height on the Specialissima now feels distinctly uncomfortable to me. I use this bike to ride a 30 minute time trial once a week, which includes another 45 minutes or so of warm up and cool down, and the handlebars are just tolerable for that. Interestingly, the Volpe, whose bars are only an inch higher, feels much more comfortable, pretty much OK for 50 miles, the longest ride I have tried on it.

To put this into perspective, I rode my Specialissima with the bars positioned as they are now from Boston to Montreal in 1972 and for a week long tour, averaging about 50 miles a day, in 1978, and it felt fine. The problem with the bars only manifest itself when I restarted riding in 2008, at age 59. You get stiffer when you get older, believe me.

Speed


Up until now, I have always said that the Specialissima felt peppier than the Cross-Check but that I was unable to detect any difference in actual speed. I was suspicious all along that the reason I could not measure a speed difference was all the variables that affect the speed of a ride, things like stop signs and traffic lights and how tired and/or fit I was on a particular day (not to mention my enthusiasm and mood) were creating so much "noise" that it hid the real difference in speed. I have now concluded that is true. My best estimate is that the Specialissima is about 0.5 miles per hour faster than the Cross-Check. Based on my experience, this difference would be very difficult to detect on a road ride with the aforementioned signs and lights, but I have been doing a lot more riding on the Rice Track which has no stops at all. Further, a lot of my rides are MAF tests where I ride at a fixed heart rate, removing mood and enthusiasm from the equation. Still, there is day to day variation due to fitness and fatigue but I have now done enough MAF tests to have a good sense as to how those will play out on any given day and although I have not done a lot of back to back comparisons, I now have done enough to be pretty confident that the Specialissima is faster, though I would not bet the farm that it is exactly 0.5 mph faster.

Why is the Specialissima faster? Is it because it is lighter? That seems unlikely, especially on the dead flat Rice Track, but I weighted both bikes anyway. I have a rack on the back of the Cross-Check to support a trunk bag full of spare parts, lights, locks, jackets, and the like. I took the bag off the Cross-Check but left the rack on. The Specialissima doesn't even have a rack. The wheels and tires on the Cross-Check are heavier, and there are other non-fundamental differences as well. This is not a "fair" comparison, whatever that means. All that said: Specialissima: 24 pounds, Cross-Check: 30 pounds.

Besides being heavier, the Schwalbe Marathon Plus tires I currently have on the Cross-Check were selected for durability, not speed. For example, they have a thick plastic strip down the middle to minimize punctures. The features that increase durability in general increase rolling resistance and thus decrease speed. I do have my Grand Bois Extra L├ęger tires that should be very fast that I could test on the Cross-Check, but another disadvantage of my Schwalbe tires is that they are very hard to get on and off the wheel, so this test may not happen for a long time. The Specialissima has sew-up tires, glued to the rims, paper thin, pumped to 120 pounds pressure. One can get faster sew-ups than these, but these ain't bad. This certainly could be part of the difference.

I complain about the low handlebars on the Specialissima. Low handlebars are uncomfortable but they also decrease wind resistance. On the other hand, I ride on the tops of the Specialissima bars and the drops of the Cross-Check bars, positioning me as low or lower on the Cross-Check. That said, there is more to posture and wind resistance than just bar height, so this could well be a factor.

Bottom line, I don't know why the Specialissima is faster, but I am glad that it is. My least favorite ride of the week is my 30 minute time trial. It takes a lot of motivation to get me to ride that hard, and being on my beloved Specialissima is just one more voice in my head shouting "Shut up, legs!"






1) Randonneuring is a kind of long distance cycling. To learn more about it, see the RUSA Website.

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