Making a fast bike faster

The accumulated intelligence of the triathlon community has not come to very good conclusions regarding where on your bike is the most aerodynamic place to carry your water bottles. This is no secret and if you read enough articles from enough varied sources and try to determine where the smartest people tell you to carry your water bottles you will wind up rather frustrated. It doesn’t seem that people have even decided upon the optimal number of water bottles to carry during a race of a certain distance. The jury is out and it’s not likely to be getting back to us before this season is up so it’s time to listen to the logic behind the arguments that are made and then deduce what you believe to be a somewhat intelligent decision based on those theories.

Bikes of all shapes and sizes come equipped to carry at least one bottle in a frame mounted cage inside the front triangle. The lone exception to this rule (Cervelo P4) is similarly equipped. Studies have shown that carrying a bottle inside the frame of your bicycle is not detrimental to the aerodynamics of the bike. In low virtual wind angle situations it has been seen to improve aerodynamics by aiding in laminar flow over the front half of the bike. Basically research shows that it doesn’t make sense not to carry a bottle here. Trek has tried to tell us that this situation can be improved by carrying an aerodynamic bottle… and they would prefer if we select the Bontrager speed bottle. The research hasn’t been done independently but it does make intuitive sense based on what the triathlon world has come to learn about the general properties of cylindrical shapes. Specialized came out with their own response to the Bontrager speed bottle, namely the specialize virtue aero bottle which is meant especially for mounting to a specialized transition frame to create the faring effect (legally here because it serves an extra purpose) of the bottle integrated into the Cervelo P4. For ~$50 odd dollars you can upgrade the aerodynamics of your bike to include one of these aero bottles. Unfortunately it will also mean that you have to decide not to jettison that bottle during the race unless you’re happy to throw $15-$20 overboard. For an Olympic distance race this might make sense, when consuming anything more than 750ml is unlikely and there aren’t going to be aid stations along the way… but for a long course triathlon the logic fails. The aero bottle doesn’t make sense because they can’t be replaced en-route at the aid stations.

Then the question must be answered…. how many bottles to carry? The longest distance between aid stations that I’ve ever heard of in a long course race is 30 km (two aid stations en-route), meaning that most athletes will not be riding for much more than an hour between stations. They do come even more frequently on occasion, as close as every 20 minutes in some races, perhaps enabling you to go bottle free if you are brave enough to drink at the command of the race course (an unwise plan if you ask me). As the 45-60 minute durations are more common between aid stations, and because for myself this is the situation for both of my races this year, that is what I was designing my plans around. Drinking the 700ml gatorade bottle every 45-60 minutes is pretty close to as much fluid as is consumed during a long course race in what I would consider normal temperatures and going with one bottle is perhaps an acceptable plan. Most athletes want to consume a sports drink but do not want to be bound by that drink for all of their hydration. Chasing a strawberry and banana flavoured gel with orange Gatorade can be a bit of a shock to the mouth and ultimately the stomach. Water is better for chasing down solid or semi-solid food than sports drink. It doesn’t lead to peaks in the sugar concentration in the stomach which can hamper digestion and absorption of the precious carbohydrates that you have so dutifully put down the throat. In my experience and personal preference having water along with the gatorade is a wise choice to keep from having the sharp variations in stomach sugar concentration. Water should go down with the gels or shot-bloks, it feels better with good reason.

So, two bottles are necessary. But where does the second one go? If you’ve got two frame racks, then that’s potentially your answer. If you don’t there are two other options. The first option is to put a bottle behind your seat. The behind the seat solutions are typically pairs of bottles which is more than is necessary. The debate was between one and two bottles, not between one and three. That extra spot doesn’t need to carry liquid, and it shouldn’t. That’s potentially another 2 lbs that you’re going to carry for the duration of the race. To shave two pounds of weight off of your bike would almost certainly cost in excess of a thousand dollars of upgrades, carrying the third bottle is an expensive mistake. A single bottle cage can be zip tied to the seat rails and centered behind the seat… that’s the cheap option and has been used by many a professional in the sport. The dual bottle cages can be used with one bottle and one of the sides can be used to carry the spare tyre and CO2 cartridges, another plan used my many a professional in the sport. The debate over which kind of behind the seat bottle carrier is most aerodynamic is still a debate. The logic at the moment seems to be that lower is better than higher. Maintaining laminar flow of the air flowing down over your back is very important to the aerodynamics of positioning and keeping the bottles (cylinders = bad) out of this important area is, well, important.

The final remaining option is to put the other water in front. This has one distinct advantage over the other bottle placement plans. If you put a bottle up on your handlebars you wind up looking at it quite a bit, this inevitably means that you are reminded to drink more often than if you tuck it behind your bum. While a well disciplined athlete ideally doesn’t need the reminder, every less than perfect athlete does benefit from simple things like reminders. “Bottle In Front” can mean different things. The most common is to make use of the product that screams “triathlon bike” like no other, the profile design aerodrink system. Basically this is an open topped bottle with a straw up to head height that sits between the aerobars. There is a net or a sponge placed in the neck to prevent sloshing and splashing of the water but easy refilling on the go as a full bottle can quite easily be tipped into the container. The system seems to work although there are many people who like to complain about the bracket mechanism that is meant to hold it in place. Most people I know end up using zip-ties to hold the thing in there… which means it gets washed infrequently… but doesn’t come loose when you’re screaming down a hill at 75 kph. The up-front hydration system can also mean mounting a speed bottle vertically in between the aerobars and fitting it with a straw to drink from like a profile design aerodrink. This was seen on a pro bike at the world championships last year and causes a bit of a stir, it’s a smart idea to improve the aerodynamics of the aerodrink system which despite the name doesn’t seem to be overly aerodynamic. The speed bottle up front plan is a good idea except that it still requires filling like the aerodrink system. What if there was a way to carry bottles, real bottles, up front with decent aerodynamics?

Steve Larsen figured this one out and while I’m not sure if it’s been wind-tunnel tested, it does past my logical wind-tunnel tests. The issue with sticking a bottle somewhere on your bike is that it is cylindrical and inherently un-aerodynamic. Laying the bottle on it’s side makes the bottle look the least cylindrical possible. Placing the bottle onto the bike like this is potentially acceptable, and when it’s places between my forearms in my theoretical wind-tunnel it remains largely out of the wind. I have a habit of folding my fingers into one another while riding in the aero position. Photos here & here of the TT position, and there’s a bottle hiding in there in both images. This may not be as aerodynamic as is possible with my hands separated and gripping the aerobars but I find it keeps my shoulders relaxed which is important. If I hold on to the aerobars with any grip I am shifting my balance to be governed by the hands, whereas if I govern my balance through the armrests at my elbows my fore-aft balance is improved on the bike, my shoulders are relaxed and the end result of the relaxation is that my legs are free to operate independently of my torso which means big watts. I mention this to describe the reason that I am making a windshield for my aerobars with my hands. My forearms are spaced only slightly wider than a Gatorade bottle and as a result filling this space with a bottle is actually likely an aerodynamic improvement as the bottle likely behaves like a faring, filling in this gap. Keeping a bottle there can be done by a variety of means including just laying it on it’s side and hoping it balances between the aerobars. This doesn’t work very well for bumps but with the inclusion of a modified bottle cage, the bottle can actually be held in place securely.

I opted to design this modified bottle holder based on the Specialized Rib-Cage Pro Road. I didn’t go for the carbon version because I wanted to be able to cut it to fit. I cut the portion of the cage that is meant to grip the neck of the bottle off. This prevents sliding the bottle in and out to a large degree but not holding it in place. If I keep the angle of the cage with respect to the aerobars correct I can still add two more points of friction between the bottle and the aerobars. The neck-piece was un-necessary so it was removed. I also found that this cage design gripped the bottle equally firmly when the bottle was fully placed in to the point where it was approximately 1.5 inches from the bottom of the bottle cage. Because I wanted to keep the center of gravity of the bottle as far to the rear of the aerobars as possible and didn’t need that extra 1.5 inches of sliding room I decided to shorten the length of the cage as well. This meant that I was going to use the stem of my handlebar as the point at which the bottle “stopped” when fully inserted. The bottom corner of the cage was removed leaving the upper ribs to reach over the handlebar and brush up nicely against the armrests of my aerobars (Vision TT bar) allowing me to zip-tie these to the armrests to hold the cage in place vertically. I ran a zip tie through the upper mounting hole of the cage and around the bolt in my stem to keep it held back butted up against the stem horizontally. It took a few iterations of cutting the cage shorter to get it to fit like I wanted. I didn’t want to cut off too much too soon because there’s no way to put it back once it’s cut.

The result is what I consider to be the most functionally flexible and likely close to the most aerodynamic way to carry the second bottle on a TT bike. I am also partial to it because it is extremely simple to remove and drink from without stopping from pedaling and there is no need to break from the aero-position to remove or replace a bottle from behind the seat.

Leave a Reply

Your email address will not be published. Required fields are marked *