Power and seat position??
I've read the articles on bike fit, spent time with the bike fit e-book, and one thing I didn't see is anything about where to put the saddle in relation to the bottom bracket. I just got a new frame that actually fits, so I could put the saddle anywhere between 2-3cm in front of the bottom bracket to 2-3cm behind. Assuming that I keep my hip angle where it's supposed to be by moving the bars up and down - where is the best place to be. Since I'm also investing in a power meter - would it be useful to use power data as input?
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Comments
Bob, it's going to come down to Rich's tradeoff: comfort vs. race goals.
At the same hip angle, the power generation should be quite similar throughout a range of seat locations. However, there are two different pieces to consider:
This is where it comes down to "it's up to you". Experiment (or work with a fitter) to find that point where you are comfortable as far forward (or with as flat a back) as you can handle, based on your desired level of comfort for the race you're doing. Saddle selection also becomes a factor as those who ride saddles like the Adamo or Cobb saddles will chime in with.
Hope this is helpful.
Mike
To add to Mikes comment, I have also heard that saddle position can change which muscles are used the most. I believe when the saddle is behind the BB, you tend to use more of your muscles and therefore can generally produce slighly more watts... whcih is when many people can put more power out on a road bike.
However, you are not aero at all in that position. If you lower the front of your body to get aero and leave your seat in the same position you close your hip angle and lose a bit of power. But if you can move your saddle forward as you lower your body, you can typically keep the same hip angle or close to it. As Mike pointed out, as long as the hip angle stays constant you shoule be able to produce similar power, but maybe slightly lower. Most people find that the slighly lower power output is more then compensated for with your increased speed from the new position though.
Basically, do what Mike suggested and make a decision on if you want comfort, speed, or somewhere inbetween, and that will guide you in the right direction.
when your are sitting back, you are using your hamstrings more, when you sit forward, you use your quads more.
I would recommend to sit as far forward as you feel comfortable (don't worry about other people sitting 3cm in front of BB if it's not working for you,,,)
The key is to keep optimal torso/hip angle.
If you have power meeter, you can experiment with different position and find a position that balance power output with aerodynamic position (easier said than done,,,)
lastly, I believe the best bet is a 1x1 fit session with a good bike fitter.
Quick fit notes, I think we explained this in the Bike Fit eBook:
Additional notes:
Moving the saddle forward allows you to drop the front end lower and lower (ie, get more aero) while still retaining a good and comfortable hip angles. When I had a normal saddle on my P3C, I had zero spacers and the saddle slammed all the way forward. I had about a 15cm drop on the front and I am textbook inflexible.
Forward stresses quads. When I've gone from riding my road bike exclusively (typical slack road bike seat position) to my tri bike, yes, my quads get worked but hey adapt in about two weeks. I see a loss of power but then after about 2wks my body has figured it out.
Power is not useful as a fitting tool:
Where I've learned this: I took Dan Empfield's first FIST class back in about 2003, I think. It sucked...seriously. I think/hope he is providing his graduates with more practical tools, but at the time the attendees were Tom Demerly, Gerard Vroomen of Cervelo, and a couple bike industry smartguy types. One other coach, Mike Collins of Orange County Multisports. It was a maddening weekend of smartguys trying to outsmartguy each other on non-bike-fit subjects...but I left with enough knowledge be dangerous, just paid attention to stuff as I sat in the wind for 5-6hrs at a time, and wasn't afraid to carry tools and monkey around.
Trial and error. As your body adapts and finds more efficiency in neuromuscular recruitment and/or becomes more flexible you may be able to continue to drop the front-end and move the seat forward to retain hip angle = more aero with same power. Some like to sit back more and recruit the glutes and hammies more. I'm stronger there myself BUT cannot run off the bike as well as forward seated.
Vince
I'm all the way forward on my P3 and that is after alot of tinkering with alot of diff setups to get me areo, powerfull, and able to run for IM's. My power goes up and front end goes down and i can hold that position. If your position is off, your body will tell you because you'll be all over the bike. I would start level with the Bb and keep tinkering until I got the best of the 3 big points of power aero and able to run off the bike. you can be as areo as a pro cyclist but if you can't run ten steps off the bke, it does you no good. My 2 cents, keep the allen wrenches handy get a CT and start tinkering.
Pg.
Forgot to add one other thing. Your body will figure out where it's happy. The seat position doesn't dictate where your body ends up, it dictates how comfortable (or not) your body will be in that position.
Look at a UCI time trialist. They'll be in an aggressive, forward position, super aero (for the good ones, like Cancellara or Zabriskie). But, they'll be sitting on the tip of the nose of the saddle to do it, because of regulations. If they were allowed to slide the seat forward, they might be more comfortable (perhaps even get some support under those sit-bones), but they wouldn't be sitting in a different place relative to the BB. That's why I tend to try to get the seat as far forward as possible, to sit more on the sit-bones (I spent a year and a half riding the nose, and unfortunately kinda got used to it, so I'm trying to break the habit).
Mike
The thing about bike fit, and this is what I told people when I was doing some local fittings: this is YOUR bike fit. We're going to take some measurements, get you within some ranges, but your body tell us where YOU need to be within those ranges. At the same time I'll give you considerations for aerodynamics, comfort, etc, based on your personal goals, but where you end up is where you body says you need to be.
The worst thing you can do, in all of this, is to be afraid of taking a 5mm allen wrench to your bike and making changes if you need to. 98% of making any adjustments on a bicycle is nothing more complicated than a $9.99 set of allens from PepBoys and loosening/tightening a bolt. If you can do, you can make these changes yourself. DO NOT go to a "bike fit expert," who may or may not be an expert, because you're afraid to touch your bike with a tool. You will spend a LOT of money for dubious advice.
For me, the kicker is "has this guy trained for, ridden in an Ironman?" If the answer is no, then he just hasn't learned the lessons you get from locking yourself in the aerobars for 7-12hrs per week. This is especially true for road bike shops with no tri experience. I can tell story after story of people who've paid a lot of money for incredibly poor bike fits.
I turned Rich's post from yesterday (minus the last paragraph) in a wiki entry.