Bike Fitting: On Buses and Bike Science

Friday, January 25th, the U.K. still in the icy grasp of winter, though snow had stopped falling in the south and temperatures looked like they might start trending upwards. I went through one last full check on my road bike, tossed my tri-suit in a backpack and headed out the door to the train station. The destination: Bike Science in Bristol for a Retül fit.

About half way to the station, I was waiting at a notorious stoplight in central Oxford (the junction of Broad Street, Cornmarket and Magdalene Street, where tourists are plentiful and bus drivers careless). The Bus next to me at the light had edged in at an aggressive angle, and rather than skip the light and cut through on the left curbside, I was waiting patiently for the driver to clear the right turn. Apparently said driver was either a hater of cyclists, or incompetent, because in the course of his wide arc, he managed to clip my shoulder with the rear end of his bus. I had my right foot down and left leg on the pedals (fortunately, I had dropped my seat to be able to toe touch when stopped and was riding unclipped).

The impact knocked me down hard onto the left leg, and left a group of twenty American tourists screaming “You should Sue!” I was rattled at first, but looking down noticed that the bus had completely missed the bike, and I was running late for my train. So I shook my head and set off towards the station. The leg took the impact well, but the shoulder is turning into an excellent bruise. But hey, the bike is fine.

For you frequent readers…yes, I seem to have the worst luck with bizarre injuries, I’m saving my good luck for race day!

The train journey to Bristol was uneventful, with excellent customer service from the station staff at Didcot Parkway informing me that the particular train was in reverse and the bike carriage would be at the opposite end of the platform. I mention this, because in four years of riding National Rail, this is the first time I’ve actually had an above tolerable experience with their station staff.

Once in Bristol, I looked at my map and headed off in what I thought was the right direction, however, having never been to the city before, I was caught out at the first major roundabout, and ended up on a West – Southwest road, rather than the Northwest one I was hoping for. I saw a street sign I recognized on a map, and having just come down a slight hill, ducked onto it to head north to my destination. As I completed the turn, which I felt was well executed and quite tight, and hammered down to regain speed, I realized that my short cut was not paved but rather cobbled in a lovely 18th or 19th century stone.

I am now absolutely positive that the various tinkering I have done on my bike was to standard, as nothing fell off or rattled out of position. But the entire experience was one of thinking “Ttttttt—-hhiiiiisss—-waaaaaaaasssss—-aaaaa—–baaaadddddd-dddd-dddd–ideeeeaaaa.” Good fun!

After all of that (half of which I will firmly accept my own culpability for!) I arrived at Bike Science an hour early, and was directed by Andy Sexton, my fitter, to an excellent little cafe down the street for a beverage and tiffin while he finished up with the last client.

I’ve made the assumption that most people reading this blog are familiar with bike fitting, but to just recap the basic concepts: Bike makers build stock based on average factors such as inseam length, arm length, etc. that they feel are reasonable metrics that allow a major bike chain or online shopper to look at a couple numbers and figure out what bike will be the right height and length for a rider. The downside of this, is that virtually no one is actually “average”, we all have various differences, muscle asymmetries (I have a pretty staggering hip flexibility asymmetry, likely due to years of long car commuting in Seattle with one leg relaxed and the other doing all the work) and variances that affect the way a bike will fit us.

By doing things like raise the saddle, shifting the length of the stem that connects the handlebars, or a variety of other small tweaks, you can take a bike that is an almost fit, and make it feel right for the rider. Bike fitters apply a variety of tools to their already substantial knowledge of cycling to help dial in these changes. Recently fitting systems such as Retül have mechanized the art of fitting and tried to quantify it. While they aren’t the answer by themselves, they allow an experienced fitter a powerful method of dynamic measurement.

We started by just having me pedal at a fairly moderate intensity (30 minute sustainable) so Andy could see how I was moving and look for any specific issues in my setup that would flag up problems I had identified in my pre-fit questionnaire. The big two of which were foot numbness and sore shoulders. After this came various flexibility examinations and angle measurements (I am, besides the hip issue, largely symmetrical, and my core strength and flexibility didn’t fall into the poor category, small victories folks!)

At this point, we started setting up for the fitting itself, which involves the Retül device using 3-d capture to look at all the angles and measurements. This requires the fitter to attach sticky dots with velcro to major bone points and muscle junctions. After which a series of infrared lights is connected to them and recording started. It measures constantly over a 15 second period and averages all of the strokes into a angular average which gives you a good idea of how the rider moves and where significant issues are affecting the mechanics.

A major issue identified was the amount of forefoot varus that I demonstrated on the left foot (tendency to role the forefoot outward) with a minor bit on the right. What this was doing was causing my heels to roll outward so that the forefoot could apply pressure during the pedal stroke, causing large amounts of foot instability and dysfunction. The resulting fix took a while to dial in and required shimming under the cleats where they join my tri-shoes, to get the angle built up right. The numbness disappeared almost immediately, and the knees began tracking much straighter. (Note to everyone who ends up changing their cleat height, it takes almost as much time to relearn to clip in with them as it did when you first bought the cleats!)

The next major change involved the relationship of the seat to the rest of the bike. The first was to get the height of the seat dialed in to maximize force and efficiency. It turns out my seat was significantly low, and so we raised it about 4cm total. As the seat goes up, the support system moves backwards, so your relationship to the handlebars changes as well. Which means you either move the current seat forward (if you’re happy with where the legs are in relation to the pedal) or the handlebars / stem backwards. For Triathlon a very forward position is desired, limited by where the aerobars on the bike sit, since you have to have enough clearance to stand and pedal for power, if you get the size wrong, knee meets bar and then face meets road. The seat I had on the bike, which I’ve saved for draft legal short races, was a Specialized Romin that I purchased before Christmas to reduce some of the pressure ‘down there’ that I was finding with the Boardman standard seat. With the Romin’s profile, we couldn’t get it far enough forward on the seat (without replacing the entire seat stem) to make it work, so I started looking at other saddles. I tried one of the Adamo ISM saddles, which sadly was just not right for me (anything that puts that much pressure on my pubic bones has to buy me dinner first!) and then gave a Cobb saddle a shot. It’s the ugliest beast I’ve seen in a while, but allowed us to dial in a very excellent seat position, and so I’ve settled with it as a lovable but aesthetically failing solution!

At that point, the last small change we made was to rotate the bikes handlebars about 15% upwards, bringing the major points of contact considerably closer to my torso. This has sorted out the shoulder pressure issues, without having to replace the stem of the bike or shorten anything. I will confess that this alone would have been worth the trip as its made me rethink my understanding of bike componentry to include angles more critically.

The fitting ended with Andy running a Retül specific measuring device, called The Zin, over the bike to record all the angles and lengths exactly. While he was doing this I went to change into my street clothes and remove the velcro dots. I’m not sure what they use for adhesive on those things, but I’m pretty sure it could replace waxing as a hair removal technique. I have little hairless circles on my knees where the suckers clung on!

By the time I got home to Oxford, on a much more comfortable bike, I had an email from Andy with the full information from my fit, measurements of my flexibility (left and right, both static and while riding), all the dimensions of the bike as we set it up, before and after images of my riding position, and a list of possible hip flexibility and strengthening exercises to help that asymmetry. All in all an excellent experience, and I wouldn’t hesitate to recommend a fitting by Andy Sexton at Bike Science in Bristol to anyone in the UK who can make the trip. One thing that I will say, is that the more specific questions you can ask your fitter the better, Andy was great at both explaining what the changes he was making would do (in theory) and answering the various questions I had while we went through the process.

Tomorrow I’ll take the bike out for a long ride and see how things feel over a long distance, which I’m looking forward to greatly. As always, please donate to the Ironman UK 70.3 cause by clicking the link on the sidebar, or Here. Your support is appreciated and needed!

Yours,

Aerodynamically Efficient Pigeon