The perfect ironman bike?
April 4th, 2007 by Robin Frankland
Riding a custom built Razzo at Ironman South Africa
Interesting topic for a blog post. I guess the question should be is there such a thing as the perfect bike? Let’s face it, everyone’s perception of perfection is different and what works for me will probably not work for you.
So having stated the obvious, I am going to explore the inner workings of my brain and will try coming up with what I perceive to be perfection.
First off I believe in the old adage of ‘Horses for courses’ and since this is a largely triathlon website, I will focus on a Triathlon/TT bike. These were once the reserve of the elite athletes or those with large bank balances but in recent years even the middle of the pack athletes are realising the benefits of riding a triathlon specific bike.
As to what makes a bike great as opposed to just good? I guess a combination of geometry, composition (frame materials), components and ultimately ride (or feel if you like).
Geometry
This is probably the single most important factor since everything else will be dependant on the geometry of the bike. There has also been a lot of debate about the various theories of which seat tube angle is best suited to triathletes but the one that I place most value on is Ian Garside and Dominic Doran’s “Effects of bicycle frame ergonomics on triathlon 10-km running performanceâ€. Feel free to read all the technical jargon but the bottom line is that an angle of 78-80 degree’s results in significant improvement in performance over the more conventional 73-75 degree angles of a road bike.
In my case I have determined that due to my awkward body shape (long arms and legs, short torso), combined with my years as a road cyclist I am most productive at 77 degree’s. In order to achieve this, I would either make use of a 76 degree seat tube angle with a zero offset seat post and the saddle slightly forward in the rails or a 78 degree seat tube angle for an integrated seat tube/post setup.
The other important angle is the head tube which needs to be combined with the fork rake to produce a predictable ride when on the aero bars. Too steep and you will probably end up with your face in the tar, too shallow and it will feel like you are steering a bus. My preference is for a 72 degree head tube with 45mm fork rake.
Other factors to consider are BB drop and most importantly top tube length all of which will combine to create the ‘perfect’ geometry. One thing to note is that when purchasing an off-the-peg frame is that your basis for determining the size is the top tube length. Get that right and the chances are pretty good that the rest will be a good fit too.
Composition
Titanium, Carbon, Aluminium, Steel, the mind boggles at all the combinations that need to be considered. Once again budget will be the probably the deciding factor but in search of the ‘perfect’ bike, I am going to stick my neck out and say that moulded carbon monocoque is the best choice.
Now here is where you have to be careful because not all bikes are built the same. The Scott Plasma for example looks like a monocoque frame but is actually fact made up of round tubes that have been bonded and then wrapped in carbon fibre to give a smooth appearance. The Trek TTX on the other hand is a true monocoque in that a single piece of material has been molded into a frame, usually around a series of balloons.
Scott Plasma on the left, Trek TTX on the right. Note the lack of tubes in the Trek
If price were a factor, I would play it conservatively and choose steel, not only because will it give me a solid ride, but it will outlast all the other materials as it is extremely slow to fatigue. Recent developments in steel have also resulted in some very light tube sets and these days you can get a frame to weigh around the 1,2kg mark which makes it pretty competitive.
Titanium gives a great ride but is typically very expensive and therefore doesn’t offer value for money while aluminium may be light but fatigues rapidly, even when not being used, leading to regular frame replacements.
A lot of you may be asking “But what about aerodynamics?†Well I have largely assumed that a carbon monocoque frame would be significantly aerodynamic to negate the need to discuss it. Personally I don’t value aerodynamics beyond the front fork, head tube and front wheel since these are the areas that break the air. Everything after that is so turbulent that it becomes largely irrelevant and with the exception of the rear wheel providing some benefit at certain Yaw angles. It is therefore not worth expending massive amounts of time or money in improving these areas.
Components
Here it is the age old Campagnolo versus Shimano war with SRAM beginning to challenge their established markets. My personal preference is for Shimano because I know the brand, having used them for over 20 years but in building the perfect bike I would probably only use their bottom bracket (BB), drive train and pedals. The remaining components are as follows:
- FSA K-Force compact Megaexo crankset (52/36)
- Zero Gravity brakes
- Zipp 808 wheelset
- Visiontech carbon base bar
- Profile T2+ Cobra carbon aero bars with F-22 carbon arm rests
- Bontrager XXX lite bar end brake levers
- Fizik Arione Tri saddle
I could wax lyrical about the benefits of each item but most of these are there because they are what I currently use and I would be reluctant to change them.
Ride/Feel
At the end of the day the sum of all the above will determine the ride or feel of the bike. The best frame and parts may not result in the best ride quality and depending on your needs you will have to make certain compromises. Being fortunate enough to have my own frame builder I think I will leave it up to him to comment on what should drive your decisions.
Here is what Deane Penfold – Razzo Bikes says:
Different bikes are needed for different types of racing. For ITU (draft legal) racing you need a bike that handles more like a road bike, so that it can be thrown around corners and get you out of trouble in a hurry in bunches. Hence the use of standard road machines with aero bars. For non draft legal stuff, one needs a bike that is more stable, because it requires less effort to keep the thing going in a straight line. Less effort = energy saved, especially useful for long events. One does not need to constantly jump in and out of the saddle, grabbing a handful of break to dive into a corner and then accelerate out of it, for the longer events. The racing is completed at a more controlled effort. Longer races also require a bike that is more forgiving in terms of comfort, i.e. you don’t need a super stiff frame in the vertical direction. One also needs to consider the effect of seat angles on muscles. Steeper seat angles appear to allow for more efficient muscle use in cycling and allow for a better run off the bike.
So, having made a short story long, a long distance TT frame should be vertically forgiving (comfortable ride), laterally stiff (for power transfer), relaxed/shallow head tube (easy handing) and have a steep seat tube (to force the use of specific muscles). BB drop will be slightly less than “normal” road frame to accommodate longer cranks and retain sufficient lean angle. Top tube and head tube length should facilitate a comfortable aero position.
One must remember though that these things can only act as a guide.The athletic unit of bike and rider is the combination of a bike that is somewhat adjustable and a rider that is somewhat adaptable. One should strive to create the ‘perfect’ unit, not the ‘perfect’ bike, alone.
