TT Bike Fit Advice

Jan 26, 21 8:26

Post #1 of 17 (2139 views)

Hi all,

I have been time trialling on my road bike for a few years with clip-on aero extensions and have recently made the jump to my first TT bike. I have started with a position setup similar to my road bike (but with the saddle further forward owing to the steeper seat angle). I'm still getting used to training in a TT position so balancing bike fit with new aches due to using muscles in a different way in this position. I was hoping to get a proper bike fit to sort my position but due to coronavirus it's not looking like I'll be able to do that for a while.

As a result I'm trying to do my own bike fit by making small changes and recording a bike fit video after each to evaluate aero vs. comfort etc. I'm sure there are many people on this forum with years more experience than me on TT bike fit so in lieu of getting a proper bike fit I was hoping to get some advice on my current position and what changes I should be trying. Here's the latest video:

https://drive.google.com/...c5q/view?usp=sharing

In general I think I have a reasonable understanding of the effect of hip angle on pedalling efficiency and aero bar drop and fore-aft for getting the back and arms at reasonable angles etc. but the bit I'm struggling to sort is saddle fore/aft position. I don't intend on taking part in any UCI events anytime soon so don't need to stick to the saddle nose 5 cm behind the BB. At the moment I've just put the saddle as far forwards as it will go (which is a couple of cm behind the BB, but it is a short-nosed Sitero). Pedalling efficiency feels fine in this position but I'm noticeably not on my sit bones which isn't the most comfortable, but perhaps just a case of getting used to it? My general plan is to keep dropping the front end incrementally once I'm comfortable in this position to get my back a bit flatter. I'm going to be doing most of my training for the next few months on the TT bike to get used to it / comfortable ahead of the season.

Any general critique / advice welcome!

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 26, 21 13:12

Post #2 of 17 (2077 views)

It's not a matter of being comfortable, it's a matter of being "comfortable enough" to stay in position for your race distance.

But your fit starts at the hands and works its way backwards. Otherwise it's going to be a long iterative process that a lot of us went through years ago.

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Re: TT Bike Fit Advice [ In reply to ]

Jan 26, 21 13:26

Post #3 of 17 (2070 views)

I can't see it as I don't want to click on Google drive on my work machine......

But.....instead of blindly lowering the front.......see if you can learn Chung Method aero testing and go out and see if you really gain that much with each drop in stack. You may or may not find something there. The lowest possible spot may drop power enough you don't gain it back in aero gains.

Next concept to keep in mind is you lose more power relative to aero reward by narrowing pad width. With stack and reach, you might lose some power output also......but you don't lose as much relative to the aero rewards.

Lastly, get an early visual of where you think you'll end up. Then investigate what helmets work with that. A lot of this is all waste if you setup a position that looks good but buy a helmet that works shit with it. Or the opposite, buy a crazy "cool" or "expensive" or "rare" helmet before seeing where your fit likely will end up and then force fit yourself to use it.

Next, when buying skinsuits........pay attention to the expected air speed and helmet styles it is designed for. Some are meant for helmets guiding air over shoulders, some not. Some meant for spending at least 50% of your ride over 28mph.........some opposite.

This stuff adds up to a pile of watts if not paid attention to.

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 26, 21 17:26

Post #4 of 17 (2030 views)

That's a great start.

It looks like you are having to bend over to reach the pads, which is uncomfortable. Ideally, you can rotate further clockwise and put your weight squarely on the pubic rami by lowering your pad stack. It should result in a lower position and be more comfortable than being 1/2 between your sit bones and rami.

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Re: TT Bike Fit Advice [brider] [ In reply to ]

Jan 27, 21 19:04

Post #5 of 17 (1935 views)

brider wrote:

But your fit starts at the hands and works its way backwards.

The fit starts at the feet. It's the only contact point that a fitter can guarantee will be in the same spot on each ride. Every fit I did started with cleat position, then moved to saddle position, then to armpad position (and hands).

Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 27, 21 19:05

Post #6 of 17 (1934 views)

Your saddle is just very slightly too high - lower it 5 mm or so. The armpads need to be moved forward 1-2 cm. And your bike needs to be two sizes bigger.

Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Re: TT Bike Fit Advice [trentnix] [ In reply to ]

Jan 28, 21 0:49

Post #7 of 17 (1891 views)

trentnix wrote:

Your saddle is just very slightly too high - lower it 5 mm or so. The armpads need to be moved forward 1-2 cm. And your bike needs to be two sizes bigger.

Yes I agree on saddle height, I plan to get a video from the back to check hip rock. re. the length I've moved the saddle back 20 mm to get the saddle position more comfortable so this is equivalent to moving the armpads forwards from a length point of view.

Why do you suggest a larger bike size is required? I know I'm running a fair bit of stack at the moment but I hope this will drop down as I get used to a TT position and become more flexible. In terms of length it's only a 100 mm stem which seems fairly reasonable to me from a bike handling point of view - any longer on the top tube and I would have to go down in stem length which would make it more twitchy.

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 6:05

Post #8 of 17 (1830 views)

Pulling the saddle back closes your hip angle a bit (which is compounded by lowering the saddle a bit). I'd prefer if you had more reach out to the armpads.

I'm suggesting a larger bike size because that one is too small. You look like a bear riding a tricycle.

You don't need to get much lower, and you've got massive stack with some headset spacers and at least 40 mm of armrest spacers. Two sizes bigger (there probably isn't a Planet X that is two sizes bigger but you didn't buy that Planet X because you wanted to be discerning about getting the right size) would add a couple of cm reach and probably 3-4 cm of stack. That would help fill the space underneath you with frame instead of spacers, and that's usually more aerodynamic and certainly more aesthetically pleasing.

Your flexibility plays no role in whether you can sustain a good aero position.

Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 6:24

Post #9 of 17 (1818 views)

louistate77 wrote:

trentnix wrote:

Your saddle is just very slightly too high - lower it 5 mm or so. The armpads need to be moved forward 1-2 cm. And your bike needs to be two sizes bigger.

Yes I agree on saddle height, I plan to get a video from the back to check hip rock. re. the length I've moved the saddle back 20 mm to get the saddle position more comfortable so this is equivalent to moving the armpads forwards from a length point of view.

Why do you suggest a larger bike size is required? I know I'm running a fair bit of stack at the moment but I hope this will drop down as I get used to a TT position and become more flexible. In terms of length it's only a 100 mm stem which seems fairly reasonable to me from a bike handling point of view - any longer on the top tube and I would have to go down in stem length which would make it more twitchy.

You need a larger bike because you have heaps of spacers to compensate for the fact that your bike is too small. A bike that uses *any* stem spacers, or any non-negative 17 stem, is by definition too big. Also, you have so many stack spacers under the pads that if you tilt it more, to where it *really* needs to be, you'll lose like 25mm of reach and 20mm of stack. At a minimum you need a 130mm stem and more tilt, but really you need a bigger bike.

E

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Re: TT Bike Fit Advice [ericMPro] [ In reply to ]

Jan 28, 21 13:17

Post #10 of 17 (1762 views)

ericMPro wrote:

louistate77 wrote:

trentnix wrote:

Your saddle is just very slightly too high - lower it 5 mm or so. The armpads need to be moved forward 1-2 cm. And your bike needs to be two sizes bigger.

Yes I agree on saddle height, I plan to get a video from the back to check hip rock. re. the length I've moved the saddle back 20 mm to get the saddle position more comfortable so this is equivalent to moving the armpads forwards from a length point of view.

Why do you suggest a larger bike size is required? I know I'm running a fair bit of stack at the moment but I hope this will drop down as I get used to a TT position and become more flexible. In terms of length it's only a 100 mm stem which seems fairly reasonable to me from a bike handling point of view - any longer on the top tube and I would have to go down in stem length which would make it more twitchy.

You need a larger bike because you have heaps of spacers to compensate for the fact that your bike is too small. A bike that uses *any* stem spacers, or any non-negative 17 stem, is by definition too big. Also, you have so many stack spacers under the pads that if you tilt it more, to where it *really* needs to be, you'll lose like 25mm of reach and 20mm of stack. At a minimum you need a 130mm stem and more tilt, but really you need a bigger bike.

E

Fundamentally the length is the thing which dictates whether a bike fits well and this frame fits me fine with a 100 mm stem. If I went up to a size XL I’d have to go down to an 80 mm stem to get the correct length to fit me and there’s a reason they don’t sell XL bikes with 80 mm stems (twitchy handling). I agree all the spacers aren’t ideal which is mostly due to the Exocet 2 having very low stack for the reach, 500 mm for size L (440 mm reach) whilst most equivalent size TT frames have a stack around 50-60 mm higher (e.g. Cervelo P series, Canyon Speedmax). I put the spacers under the arm pads on purpose so I could have the bars lower and keep the front end a bit cleaner and running high rise spacers under the aero bars is very common on TT bikes, especially for taller riders - just look at any world tour TT race.

https://cdn.mos.cms.futurecdn.net/...w7Hv5wfoNQogRvaX.jpg

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 14:18

Post #11 of 17 (1736 views)

FYI, Trent and Eric are both very highly regarded bike fitters. If both of them are saying your bike is too small, instead of arguing, you might want to listen. Just a thought.

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 15:20

Post #12 of 17 (1717 views)

Trent and Eric are some of the best fitters, period.

Open your mind to what they are saying.

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 16:12

Post #13 of 17 (1700 views)

Just to throw in the mix... I'm currently on a Planet X.
I'm 6ft tall. Slightly longer legs / shorter torso than average.
I had to go to an XL.
(I still sometimes think I look like a bear on a kids bike. But the size L was like a bear on a gnat's bike.). And I'm only 6ft, not some 7ft 6 giraffe.

A shorter stem is a non-issue on being twitchy. There's nearly 2 feet long of extensions sticking out in front of the bars. 20mm here or there on a stem makes sod all difference to the handling really when in the TT position.

I had an 80mm stem on for half a season inc an IM (for reasons irrelevant to this discussion) - and the handling was no problem at all.

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 28, 21 17:13

Post #14 of 17 (1685 views)

You ever see the largest frame geometry of that Pinarello you have pictured? It doesn't fit anyone of any size well. Really, really tiny bike.

Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Last edited by: trentnix: Jan 28, 21 17:14

Re: TT Bike Fit Advice [trentnix] [ In reply to ]

Jan 29, 21 0:03

Post #15 of 17 (1630 views)

trentnix wrote:

You ever see the largest frame geometry of that Pinarello you have pictured? It doesn't fit anyone of any size well. Really, really tiny bike.

I see what you mean! Similar stack at 10 mm less reach than my size L Planet X:

https://roadbike.io/wp-content/uploads/Pinarello-Bolide-TT-Geometry-2017.jpg

Apologies for coming across a bit strong - I appreciate your feedback and I'm just trying to understand your points of view as I'm learning about all this TT stuff and need to change my way of thinking from road/gravel bike fit. Having looked around at the geometry of other TT bikes it seems I could definitely go to a larger size and more conventional geometry , something like 460 mm reach (20 mm longer) and 560 mm stack (60 mm higher) so I'll bear that in mind next time I go bike shopping. and on stem length it appears I have to eat my words as size L/XL TT bikes often come specc'd with 80 - 90 mm stems (e.g. Giant Trinity, Canyon Speedmax).

For now I'm committed to using this bike for this season as it's my first go at a TT bike so was always going to be a bit of a gamble on sizing without a proper pre-buy fit. It might look a bit ugly but at least I have the flexibility to work my position out on this adjustable bike and have a go at racing on a proper TT bike for a season or so. Then next time I know what geo. I'm after and can go for a better sized and more integrated setup.

In terms of working with what I've got and trying to clean up the front end would you suggest getting rid of the headset spacers and putting a -17 deg stem on then adjust the stack on the armpad spacers (which is what most integrated cockpit type bikes do now) or the other way around with no armpad spacers and adjust stack through the headset spacers?

Re: TT Bike Fit Advice [louistate77] [ In reply to ]

Jan 29, 21 6:22

Post #16 of 17 (1555 views)

louistate77 wrote:

In terms of working with what I've got and trying to clean up the front end would you suggest getting rid of the headset spacers and putting a -17 deg stem on then adjust the stack on the armpad spacers (which is what most integrated cockpit type bikes do now) or the other way around with no armpad spacers and adjust stack through the headset spacers?

No need for a -17 degree stem on your current bike, but you could use a longer stem. I'm not sure you can add more armpad spacers safely. That's a pretty tall stack as-is.

Trent Nix
Owned and operated Tri Shop
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter (back when those were things)

Re: TT Bike Fit Advice [trentnix] [ In reply to ]

Jan 29, 21 8:36

Post #17 of 17 (1511 views)

If it's the PD bars that I think it is (pic is a bit to grainy to be sure with my aging eyes !) Then the spacers are available up to a pretty whopping size (about 70 or 80mm I think)
They come with the required length bolts. And are an Omega shape (think of the Ohms symbol) so sort of 'lock' in to take the shear loads fore and aft. And are designed to be stackable up to a certain limit.

https://www.probikekit.co.uk/...p;variation=11674375

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