Two reasons they may be different:

TT position may be subject to UCI rules where Tri is not. The forward position in Tri is largely a UCI issue - UCI sets minimum setback of saddle nose from bottom bracket.

Triathlons are often much longer than TT's so comfort is more important for triathlon.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

Roadies do time trials, and infrequently. So the setup should utilise similar muscle recruitment patters to their primary road setup.
Also, roadies rarely do anything longer than a 40k, so optimising aerodynamics is also at a premium. Reduce frontal area, especially with narrow armpads.

TT's are usually done with 30second intervals between riders, on a closed road. So the front end can be silly low because you don't need to see ahead, you are not likely to pass anyone, just hammer away using the road edge line to your right to stay straight.

and, they do not need to run when they get off the bike. so the position is slacker to utilise glutes and hamstrings to power at intensity for a shorter duration than a triathlete.

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Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Muscle utilization is a red herring. Thinking you can ride lower for a TT just because it's a TT is not true. Or more to the point, thinking you need to ride higher because it's a triathlon is not usually true. Pushing the pads narrower for a TT and being really strict with head discipline are the two top things to focus on more for a pure time trial. Seat height, setback (if possible), reach, and drop should be the largely or completely the same.

The bike leg of a triathlon is fundamentally a time trial.

Hmm...as a roadie I'm not sure I agree with *any* of your assertions. :)

As a roadie who does TT's and also starting to do pursuits on the track I've been working on making my fit on both bikes UCI-legal since going to masters' nats is a possibility for both disciplines in the future.

Everybody always talks about the saddle setback limit (saddle nose must be 5cm behind the bottom bracket). Interestingly I found that to be no problem at all with a noseless saddle such as Fizik Mystics or Dash (currently evaluating both). For me the biggest change is the 80cm limit on extension length from the bottom bracket. On my previous TT fit my extensions were well beyond that.

On my pursuit bike with the Enve aerobars, I can use tilt to get the elbows lower and the hands higher, and still feel pretty stretched out without exceeding 80cm of extension. On my current TT bike, I'm limited on how low I can get the elbows and also lack a tilt adjustment, so it's more problematic. Currently the extensions end just past the heel of my hand and I can actually interlace my fingers in front of the extensions.

I suspect if you were to measure the extension lengths on the bikes of triathletes who are fit with a steep saddle position and long/low torso, you'll find they're using way more than 80cm unless they're really short or have t-rex arms.

We agree on something, happy days!

My position is the same for all TTs, be it 10 miles, 100 miles, or 12 hours (although I don't shrug as much for these). If I ever did a duathlon/triathlon my position would remain the same. I don't see why arms together should pose problems for triathletes (unless there's truth to the rumours of abysmal bike handling) and head position is easy enough to hold if you try (maybe this isn't as common because too many would lose an eye to poorly placed straws).

I think the real reason positions look so different between the two is that triathletes tend to get a fit and buy aero goodies whereas testers tend to invest their time and money into actually getting aero (read:position). Certainly the trend on this side the pond.

Going to pile on a bit here, but virtually none of this is true.

Over the last two years I've fit 13 Elite UCI World Champions in the aero position on both the track and for road TT. I write that not because it makes me any good at what I do, I'm quite sure they all would have done just fine without me, but, I do have information on those fits no one else does. No matter the size, from 5'-1" on up, all but one would come more forward if the regulations allowed for it. Their saddles are 5cm behind the BB not for muscle recruitment, but because we need the reach exemption for aerodynamics and, gasp, comfort! Yes, though not the primary concern for TT, the athlete still needs some measure of comfort to perform.

Now, I do see far too many Tri fits that are far too forward. It seems like every thread on fit has someone spouting, "Move forward and get lower!" Forward, forward, forward! You know what I think when I see that? Thank you...job security.

To the OP: the biggest difference between TT and Tri fit is all about economy of effort. You need to be able to run off your bike, so the Tri position is less aggressive up front for comfort and a more open hip angle. That's it. Saddle may be a little more forward, but nothing extraordinary, and we have no reach restrictions (at least none to worry about).

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Jim Manton / ERO Sports

For what it is worth:
Mark Allen (6X Ironman World Champ) used to lower his saddle a few mm for longer races, to account for the fact that muscles tend to shorten/tighten up a bit in the latter stages of a long, hard ride.
Peter Reid (3X Ironman World Champ) also used to lower his saddle a bit when training on his Tri bike for long races (for the same reason as Allen), but then would raise it a very slight amount before the race to account for the difference in padding between his training bibs versus the very thin pad in his racing tri suit.
UCI requires the saddle set back to be 5cm behind the BB; triathlon does not.
UCI has limits on the length to the aerobar extensions; triathlon does not.
UCI does not permit BTA bottles, so a rider can put the elbow pads as narrow as they want/need/can stand. A lot of triathletes use BTA set-ups which sometimes limit how narrow you can get the forearms.
I think the factors above would account for 99% of the differences in position.

Since Steve Johnson left and DBH came in, USAC has been making a number of changes to become more customer friendly. One of those was not strictly imposing UCI bike regulations on masters athletes. I would email whoever the current technical director is and see what you can get in the way of clarity before you attempt to conform to UCI rules.

Jim, could you please recommend a thread here (or perhaps another online article) which may be edifying for relative aero newbies? I started in TT recently and have been reading, looking at profile diagrams online, tweaking my fit while on training rides, looking at old threads from ST here, trying to learn and understand the balance of aero with comfort, breathing (and resultant power that comes with it), and now I'm not quite sure how I should decide on how far down to drop my armrests.

I'm trying to learn what I can for optimizing aero with consideration of:

• Balancing aero with good breathing for optimizing power output
• Comfort within reason (knowing it's a compromise) that helps to maintain aero position for sustained time periods

I began with an initial fitting and have been making very minor tweaks since, so I'm not distracted by comfort issues and can stay put. Now I feel like I'm in a comfortable (pretty easy breathing) position, but wondering how to maximize aero while maintaining the comfortable breathing and resultant power that comes along with it. I don't want to waste anyone's time with silly questions of experts asked by an aero newbie, would rather study up and honor the time and effort of those who have expertise and have shared discoveries (like you, thank you, btw).

For me as an individual, I'm a bit limited by an abnormally straight cervical spine, so if I get much lower in the front than I already am, I'm going to have to figure out how to watch forward/upward with eyes at an uncomfortable angle, because tilting my head/face up more than I can now in an aero position starts to make my vision blur from what seems to be a blood supply impingement. I'm very flexible in the lower back, so that's not a problem.

Thank you for any suggested reading on aero tweaking/optimizing. I'll read it all.

I'm not Jim, but I found this series useful (there's a Youtube interview version out there too).
https://www.a1coaching.net/introducing-the-david-millar-tt-system/

One of the key takeaways:

I have no reach restrictions, but bringing my saddle forward hurts my CdA and has negligible effect on my power...
Different strokes.

This is great, thank you. Will read it all, very interesting!

Did one on my setup the first time last week, time trial.

The goal there is to have a big fat zero left in the heart, lungs, and legs at the end. Preferably needing a catcher.

The aero position follows, who cares, balls out for less than an hour.

The same position slightly crippled by UCI rules.