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Fore/aft seat postion for Time Trial(13 posts)

Fore/aft seat postion for Time Trialflying squirrel
Dec 31, 2003 8:01 AM
What is the advantage of moving saddle forward for short 5-10 mile time trials. I am currently pretty comfortable in my current postion but have been told that moving the seat forward while using aerobars would transfer more power to the pedals. Is this true?? Are there any other advantages or disadvantages?
Getting the rivet out of the way.shirt
Dec 31, 2003 8:33 AM
You've probably heard the term "on the rivet." This describes a position a roadie will get into when off or on the front for a short period of time and hammering for all he's worth. Old-timer saddles were rivetted leather, and there was a rivet on the very front of the saddle. By moving forward, you're able to use more hamstring than you normally do. It's more tiring, but in short stretches you can definitely generate more power by conscripting these muscles.

By sliding the seat forward, TTers are able to get "on the rivet" without the discomfort associated with actually sitting on the front of your saddle.

/shirt
maybe a compromiseflying squirrel
Dec 31, 2003 2:07 PM
Sounds like good advice. I'll try a slight adjustment first and go from there.
Would you need to use a longer stem then also?hrv
Jan 2, 2004 8:21 AM
Otherwise wouldn't you be more cramped and have a less flat torso, if you slid the saddle forward?

Last year I mostly left the saddle were it was, maybe angled it down very slightly, and just sat on the rivet, esp. when I really needed to , like cresting small hills, etc. Yes, I came away from the TT feeling like I just visited the proctologist, but no pain, no gain, right?
Seriously, when I moved forward, the power increase was amazing, felt like some turbo kicked in.

When you see the top TT guys on their TT bikes , they're still on the rivet, even with a forward position to begin with. So is there no limit to this forward postion (I guess if the nose of your saddle is touching the stem, you might want to back off a bit, huh?!!)

hrv
arbitrary limitationsDougSloan
Jan 2, 2004 10:19 AM
If you are talking about UCI ("top TT guys"), they have rules limiting how forward the nose of the saddles can be. But for the rules, they may well move them much more forward, then not be "on the rivet" all the time.

I had Cervelo with the reversible seat post head, and I could get the saddle *very* forward if I wanted, giving maybe even an effective 90 degree seat tube angle. This does allow a very flat and aero position, but it becomes difficult to hold your head up to see the road, and puts a lot of pressure on the perineum, rather than the pelvic bone area. However, breathing was improved, and biomechanically it worked well for the trunk and legs. Don't try this for a hundred miles like I did, though!

Douig
It's more than muscle recruitmentKerry Irons
Dec 31, 2003 6:31 PM
For many, their standard road position does not allow them to get a low, flat back without having their legs hit their stomach/chest. Moving forward (and raising the saddle slightly to compensate) opens up the angle between the legs and chest, and allows for better breathing. If I put aero bars on my bike, I can tell that it is easier to pedal while in the aero position, but at the same time it is harder to breath, so I am no faster. To gain the speed of aero bars, I would need to move my seat forward and up to allow me to breath.
here's the longwinded explanation of what Kerry said...DougSloan
Jan 2, 2004 7:53 AM
The key elements of a good aero position are:

Horizontal torso. Defined by having your chest, or better yet, your back parallel to the ground, this is absolutely the most important element, as it can result in large magnitude changes in aerodynamic drag. Unfortunately, it may be the most difficult to achieve, because as you approach this position, your thighs start to hit your torso. This interference imposes limits on your body's aerodynamic position, but is due to traditional bike geometry (i.e.; seat tube angles of 73 to 75º ). The way to overcome this limitation is to go to a more forward position, which will allow you to roll your whole body forward. Note of caution: a forward position seat post and long steeply-dropped stem may allow you to assume a good aero position, but will result in a bike that is not well balanced, and may be dangerous to ride. A much better approach is to buy a frame that is designed to be ridden in a forward position. These positions are uncomfortable in two ways. First and foremost, by rotating your hips forward to get your torso horizontal, you are rotating your weight right on to your soft and tender parts. Specifically, riding in this position may exacerbate the condition of prostatitis that is common among cyclists. Extra seat padding helps but does not eliminate the problem. A truly anatomical saddle that distributes your body weight over the whole seat might really help. Some riders try to alleviate this problem by tilting the nose of the saddle down, but this only results in a tendency to slide off the saddle and to strain your shoulder and arm muscles. Secondly, and to a much lesser degree, you tend to get a sore neck the first few times you ride, the discomfort lessens with time and can be minimized with stretching and massage. These draw backs are minimal because you don't have to ride the forward position daily to go fast on it. My experience with Team EDS, as well as my own bike is that you only need to ride it once a week (maybe less) to stay adapted to the position.

http://www.cervelo.com/tech/articles/article5.html
http://timetrial.org/slam.htmTime Trial dot org
Jan 6, 2004 8:21 PM
http://timetrial.org/slam.htm
http://timetrial.org/slam.htmskip work to ride
Jan 6, 2004 10:29 PM
Thanks for posting this. I have been looking for a better photo and measurement of what Cobb has been talking about. I looked at the top guys at the Worlds TT and they all go with this position (from what I can dissect in Adobe Photoshop). I would like to see some more discussion about handlebar/seat height relation since Postal went to a hgher postion and Ulrich and Millar stayed hunched over.
re: Fore/aft seat postion for Time TrialRIAN
Jan 8, 2004 3:59 AM
HEALTH WARNING - DO NOT TRY THIS AT HOME

Just to put a contrary view from a someone who is worth taking seriously. I spoke recently to someone close to
Graeme Obree who tells me that Graeme is back in training and is experimenting with a new position. It is basically his last 'Superman' position with arms fully extended forwards. UCI rules limit the distance the bars can be positioned in a forward direction, so to make it legal, the saddle position has been moved way back, possibly by as much as 9 inches behind the B/B. Being Graeme, there is another twist, as his new rig is built round a mountain bike frame salvaged from a skip, and has a 62x12 fixed gear!
so, it's like a 45 degree seat tube angle? nmDougSloan
Jan 8, 2004 7:20 AM
so, it's like a 45 degree seat tube angle? nmRIAN
Jan 9, 2004 2:53 AM
That's one way of putting it. Climbers have always claimed to generate more power by moving the saddle backwards, but combining this with an legal aerodynamic position seems to be a physical impossibility. If anyone can make it work, it's probably Graeme. Apparently he recorded a short '22' for a '10' on a cold windy winter's day on his first outing - a promising start, but hardly conclusive.
seems like it would be hard to breathe nmDougSloan
Jan 9, 2004 7:35 AM