This past Saturday Felipe Bastos visited us (he flew in from Alabama!) to work with me on his bike fit, and with Coach Al Lyman and myself on his run form. (Check out Felipe’s blog post here) I had worked with Felipe before on his bike fit via video, but he now has a brand new custom-painted Scott Plasma (Brazilian theme) that he wanted to make sure was dialed in. He first joined our Saturday 9am pain cave ride for 2 hours, and then we started working on run form and bike fit. Al ran him through some movement screening (he scored very well). Then we did some high-speed video of Felipe running outside and on the treadmill, and we threw it up on the big screen in the FitLab for some analysis. I think Felipe was very happy with the outcome – he is certainly a good runner with excellent mobility, but we were able to point out some things to work on. Next he spent some time on the TTFitBike dialing in his position which was already quite good. We finally transferred this to his new Plasma. I also provided him with a list of tweaks to try to further dial his fit. All in Felipe spent about 10 hours in the Lab. Look out for Felipe this season as he moves to IM distance. As a short-course focused athlete he is really a power- rider and runner. But his smaller stature, heat tolerance and low sweat rate should make him a natural for IM. With his new bike position and run form tweaks he should be able to transition from a power athlete to an efficient long course threat. We’ll see!!
Monthly Archives: January 2010
We’ve all seen it. A lot. Maybe YOU are even guilty of spacer abuse. Yes that’s right, spacer abuse: the egregious stacking of several centimeters of spacers on the carbon steerer tubes of our multi-$K carbon aero tri rockets. “So what” you say – A: The bike came with a fat stack of spacers, and B: I need them to get the “right” position. To which I say – A: so what, your bike also came with nifty reflectors but do you use them? and B: you either have a lousy fit, or you are on the wrong size and/or type of frame, or both.
Why should you care about how many spacers you use? Two reasons: aerodynamics and structural integrity. Have you checked out the newest aero super bikes being used on the Pro Tour these days? One common feature is stemless designs where the handlebars sit right on an integrated frame extension, bayonet or “nose cone”. There are no exposed steerers or round spacers on these bikes. Why? Because nearly vertical cylinders aerodynamically stink. Chances are, your aero bike has a carefully sculpted wind-cheating head tube. Why stack the equivalent of a drag chute on top of it? Cervelo’s Phil Wood told me in Kona 2 years ago that they were fighting to get their pros to stop “sizing down” their TT frames, because they were using too many draggy spacers. Bottom line: best aero= zero spacers.
There is also a structural consideration here. Some manufacturers send warnings with their forks that the maximum exposed steerer tube should be 8cm. This includes approx 1 cm of headset and 4 cm of stem clamp. So max spacers then are 3cm. Otherwise, you are risking a failure which would be decidedly ugly. Kestrel wisely ships their steerers precut so that you can only use 2 cm of spacers. The tri position puts a lot of weight on the handlebars – best not to tempt fate with a monster stack of spacers.
Ok, but what about adjustability? Don’t we need spacers to dial in the front end height? Well, that is the easy way, but not the best way. And you really only have 3cm to play with (really slightly less since your head angle is around 72.5 degrees). So let’s assume you will use ZERO spacers. And also let’s say you need a 10cm stem for the proper reach. How much can we adjust the height of your front end without spacer abuse? Actually, quite a bit.
In a perfect world. you would use a horizontal stem ( also know as a -17 degree stem). This means the wind never “sees” your stem as it hides behind your bars. From there, we could use a -6 degree stem (the most common angle these days) which still keeps most of the stem out of the wind. Going from a -17 to a -6 stem in a 10 cm length raises the front end 2cm. Not bad, considering those ugly spacers only give you 3cm (right?) of adjustment. But wait – there’s more! Most people never even consider using a negative stem. Everyone uses positive stems, so why not consider a negative stem if you need more drop? Bontrager and others make 25 degree stems. Flipped over, they give you about -8 degrees below horizontal. This is about 1.3 cm of drop in a 10cm length. So between the -25 and the -6 stem we have 3.3 cm to play with. Note that your reach is changing a tiny bit with the different angle stems, but only by a few mm. And yes, you could even use up to 1cm of spacer if you wanted to without messing things up too much. So now we have 4.3 cm to play with.
What if you need even more adjustability? You could even go with a 0 degree stem if you had to, giving another cm of rise. Or, you could look at aerobars with different pad heights and spacers. Many aerobar pads sit about 5cm above the stem clamp midline. Others can get as low as 2cm or as high as 6cm. So there you have a few more cm to play with.
Let’s look at the maximum range here without ever touching one of those dirty spacers. A -25 degree stem with a set of Vision Tech base bars (about 2cm of pad stack) as the “low” option and a -6 stem with a set of Vuka clips with a 1cm aero spacer under the pads (about 6cm of pad stack) as the “high” option. The vertical lift range here is a full 7.3 cm. Concede to 1 spacer on the steerer and a 90 deg stem, and the range becomes almost 10cm. That’s should be plenty to play with eh?
So next time you are in the market for a frame, get your contact points dialed in (by a fitter who knows what they are doing) and then look for a frame with the right stack and reach. The “right” stack means zero spacers needed. Remember you are much better off using a drop stem on a higher-stack frame than you are using a big fat stack of spacers on a frame with a too-low stack.
The previous stack and reach measurements published for the forthcoming Kestrel 4000 were off in several spots. Steve Harad forwarded me the updated values a few days ago, and it is clear that Kestrel is positioning the 4000 more towards the short-and-high (reach-stack) end of the spectrum in the middle (and most popular) portion of the size range. Steve said they looked at thousands of actual rider setups and decided that this geometry will suit more real-world athletes. It is certainly true that their are way too many Cervelos and Felts (in the long-low category) in the transition area with massive stacks of spacers and upturned stems. I think some of this is due to poor bike fits, not necessarily the wrong frame geometry. That said, many folks simply don’t belong on long-low frames. The 4000 geometry will actually compliment the Airfoil well, as especially in the smaller sizes the Airfoil is the longest-and-lowest frame you can get. And seeing as Kestrel ships the steerers pre-cut to use a maximum of 2cm of spacers, you better be sure you can get the front end high enough, and you better be sure the reach isn’t too long. Remember that ideally you would use 0 spacers and a level stem for both aero and structural reasons. So you don’t want to get too far from that. Here is a table comparing the 4000’s stack and reach with some other popular frames. The Plasma is a short-high design, while the others are long-low:
Note first that the 47cm Airfoil is the low-stack champion of all bikedom. If you are small in stature and/or have very short legs, and you can handle the reach, it may be the only stock frame that will work for you. The 4000 geometry is Cervelo-like in the smallest and largest sizes, but in the middle we can see the stack goes way up into the Scott range. The 52.5cm 4000 will fit like a M Plasma. Note that the 55cm 4000 has the same reach as the 54cm P2 but a 2cm higher stack. It will fit more like the L Plasma. But then in the larger two sizes it drifts back into the longer-lower range. The 59.5cm 4000 will be a good option for 61cm P3c riders who want an even lower front end (me!). Some riders who think they are a “54” might find themselves on a 50-or 52.5 4000 with a longish stem. The bottom line – make sure your fitter-bikeshop etc determines the best stack and reach for you and then looks for frames that fit those specs.
This video was graciously forwarded to me by Craig Harris. Simon Whitfield et al. running sub-5 on grass. 1 mile and 2mile repeats. This is RUNNING. What I do is some other “sport” (slogging?). If you watch this and actually SEE what is going on with these athletes, how they use mobility and functional strength to drive the core forward, it is great for pre-run visualization! (Originally posted on the Alias Basil Blog)
Our friend and pro triathlete Alex McDonald stopped by the TriFitLab today to do a little position optimization on the TTFitBike. We have worked with Alex on his position before, but he is set to get a new bike this year, and he was very interested to try out the FitBike prototype. After checking out his baseline position and setting up the FitBike to match it, we warmed him up and ran him through some sub threshold intervals while we changed various fit parameters. In the latter half we blinded him as much as possible and randomized changes to seat height, drop, and seat angle independently (while he was riding at sub threshold) while asking him which changes he liked better. He wasn’t always aware of exactly what we were changing, and instead was focused on maintaining power and paying attention to his perceived effort.
The net result is shown in the picture below. We ended up about a cm higher on the saddle and about 3 cm lower in front. Alex felt more comfortable in the lower position, and it is fairly obvious that it should have some aero benefits from frontal area reduction and head position. He will have to use a negative stem to match this position on his trainer Trek TTX. Although I expected him to prefer a steeper seat angle in the lower position, he preferred his usual seat angle, which is not unexpected. We’ll see as he spends some time in this position if he ends up steeper. Check out Alex’s comments HERE