We Avoid Our First $5000 Mistake!
One of our little taglines here at Output Speedlab is "Don't make a $5000 mistake!" What could be worse than purchasing a new bike only to find out that the bike you thought would work is instead too small or too large or too steep or too short? Bike shops will usually do their best when selling you a bike, but unless they have a dedicated fit bike, they're only going to be making their best guess when it comes to setting you up on a bike that is going to allow you to be comfortable, powerful, and fast.
Dieter came to see us last month intending to buy his first high-end time-trial/triathlon rig. Like most life-long athletes, he had his share of physical limitations, as most of us do. We knew that more than anything, his aero position had to be comfortable and sustainable. After putting Dieter through our dynamic fit process, we ended up with a "Pad Y" dimension of 781mm (Pad Y is the vertical distance from the bottom bracket to the top of the arm pad—we measure it with lasers, which is awesome). Knowing that this would be a tall configuration, we dug into the bike geometry sheets we use and came up with the following prescriptions for him:
Scott Plasma 4 XL
Trek Speed Concept XL
Specialized Shiv XL
Cervelo P2 61
Cervelo P3 61
Cannondale Slice 60
Argon 18 E-117 XL
Anything jump out at you there? Those are all really big bikes! All XL or 60cm+ in frame size. Dieter is not a huge guy: probably 6'0" at most, but due to the height he needed to be comfortable (and remember, comfort = power = speed) on the bike, he was going to need an XL. Now, here's where things get interesting. Dieter went to River City Bicycles, where they looked at him, looked at the prescriptions we'd made, and suggested a P5, which is definitely a little blingier (it also came with some rad wheels and SRAM eTap, so all in all a pretty sweet bike). Dieter sent us an email asking us if this would work, and the rest of the exchange went as follows:
Josh: I looked at the P5 fit charts and the P5 is about 20mm too short at its highest setting. We can get you to the the correct reach, but it will be a little low. It's a sweet bike, but a bit aggressive. I'd be a bit concerned with that much of a deviation from the prescription. With some focus on flexibility, mobility, and a good amount of TT riding I think you could get lower, but a stretch (literally and figuratively) right now.
Dieter: The guy at the shop had me convinced the P5 was the most adaptable for fitting. Which numbers are you using? The stack height?
Josh: The P5 has an integrated (super bike) front end so a "frame" Stack Height technically doesn't exist. They only have Pad Stack and Reach. Your ideal Pad Y (Stack) is 780mm. The highest a P5 can get is 758. This is how I got the roughly 20mm difference (you need 780, the P5 can only get you to 758) The P3, on the other hand, has a "normal" front end, thus the ability to play around with stems to achieve a higher position.
Dieter: Ok! Changed to the P3 Ultegra Di2!
So this is exactly why we want to be in business and work with athletes like Dieter. Without our suggestions, he would have ended up on a bike more than 2cm too low in front! Coming from someone (this is Chris) who has been injured due to a too-aggressive front end, I can tell you that 2cm is quite a lot. We're very happy that things worked out this way, and Dieter is too! One other thing we are proud of is that we referred a bike sale to a local bike shop. River City Bikes is an institution in Portland, and we're happy to send business in the direction of any local bike shop. It's a brutal industry that's moving online, and writing prescriptions for bikes that keep people healthy and local shops in business couldn't make us happier.