First TT bike fit

Hi team,

So I had my first time trial bike fit yesterday. (I have attached the results)

Really great experience. I can see that from a background in Olympic weightlifting I have some issues mainly with the width of my shoulders and internal rotation of the hip.

We talked about a less aggressive hand/shoulder position to start with, which I can bring closer as I get more use to the position on the bike. He mentioned there is room to bring the saddle up 5mm as my pedaling mechanics/ technique get better (I had a very toe heavy pedal stroke).

My question to you is how would I got about taking this raw data to actually building a bike up to meet my specific needs/ geometry. Is it worth deciding the cockpit and working back or is the frame alway priority number one? We looked at some bikes. Cervelo in a 51 came up as a good fit with some spacers.

Maybe a ridiculous question but is it possible to build up he bike with no need of spacers? If you get the frame and stem right and shop around for parts you could make it work?

At the moment I will carry on training with my road bike setup on the trainer and will gradually price together the train bike for next season.

I look forward to your thoughts and opinions.

Thanks,
Chris

Bike measurements Christopher Peck TT 29072019.pdf (1.8 MB)

Notes Chrisopher Peck.pdf (550.7 KB)

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I’d say bike geometry is absolutely what you should look at first.

Choose a frame that has a reach and stack closest to what was determined by your bikefit.

Its absolutely sensible to aim for no headtube spacers. Bikes are designed to not need them, but they’re provided so that the bike can suit as many different people as possible. The closer you get to your desired stack, the less chance you’ll have of needing spacers

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I should add, that I’m referring to spacers under the stem. You may need spacers under your extensions in order to get the best from both positions

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Yeah I guessed you meant stem spacers. For example would I be correct in saying that as I progress the position I would look to remove spacers from the aero bars and bring them closer as I get into a better position and can keep power output.

It’s very interesting. Would you prioritize stack or reach or both as equally priority?

I don’t want to speak to your specifics too much, especially since you’re bike fitter is much better placed to answer these questions than me. But if you can lower the front end and therefore reduce your frontal area, whilst maintaining the same power, then that is desirable.

Stack and reach are the 2 numbers I look at when choosing a frame. In my mind, those numbers tell me how I would fit on a frame, and the rest of the geometry numbers tell me how the bike will handle - wheelbase, head angle etc etc. As such, stack and reach would be of equal importance to me. One without the other is going to leave you with a sub optimal fit.

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Fantastic. Thank you :+1:

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You absolutely need to look at the cockpit and frame together, the frame size you need could well change depending what cockpit you want to put on it. And with the more integrated “superbikes” you pretty much have to use the cockpit it comes with.

The way I would approach it is to get your current stack and reach numbers, and also your fitter’s best view on how they might change over time as you adapt to the position, improve flexibility, etc. E.g. if he thinks it would be beneficial to get lower over time, then you need to make sure you’re on a frame/cockpit that will allow for that. Shortlist the bikes and cockpits you’re interested in, then go to their respective websites and most of the good ones will have some manner of fitting table where you can plug in your stack and reach numbers and see which bike sizes will fit.

Here’s a good example from TriRig (I have no affiliation with TriRig, just like their products and how simple they’ve made the fitting process for their cockpit) - https://www.tririg.com/store.php?c=alphaone&page=fit You can choose the frame you’re looking at, look up your stack number, then see what your options are for achieving that stack i.e. how many stem spacers and how much pad stack.

Similar link for Zipp cockpit - https://www.zipp.com/support/vukafit
Or Cervelo P5 - https://www.cervelo.com/en/p5

No stem spacers is a good goal, bike will look slicker and likely be more aero. You will want some spacers to raise the pads above the base bar (or pads that are raised by telescoping instead of spacers, such as the TriRig or Cervelo ones). Having some pad elevation above the base bar means that when you are on the base bars you have a lower and more aero position (may or may not be useful depending what kind of riding you’re doing), more importantly it gives you the option for dropping your pads to get a lower front end in future. If you have a slammed stem, and pads that are sitting right on the base bars, then you have no options for lowering the front end further, unless you can fit a negative angled stem which starts to look pretty quirky.

Other factor to discuss with your fitter is whether he thinks tilting your arms is a good idea. Seems to be all the rage these days, a lot of people find it more comfortable having a slight upward tilt which helps to lock your elbows into place, there is some evidence it may also be more aero. If you want the option to tilt, either now or as something to experiment with in future, then that may also influence your choice of cockpit (or bike with an integrated cockpit). Some cockpits don’t natively support any tilting and you’d need to achieve tilt by adding parts from another supplier such as angled spacers/wedges. Some cockpits support tilting but with fixed increments (5 degrees, 10 degrees, etc) using their own parts. Some allow you to adjust tilt without using spacers so you can have whatever angle you want.

Sorry if this all sounds a bit complicated, the challenge with TT bikes is that you’re locked into one hand/arm position for pretty much the whole race, so it’s critical that your pads and extensions can be put in exactly the place you need them relative to your saddle and pedals. Whereas on a road bike you can shift between hoods, bar tops, various different drop positions to get the right balance of power, aero and comfort depending on whether you’re sitting in the pack, climbing, descending, etc. The good news is that manufacturers have mostly recognised the need for a lot of adjustability, so most integrated bikes and standalone cockpits are pretty good on that front now, certainly compared to a few years ago.

The other good news is that you’ve done exactly the right thing going to a fitter first to figure out your position. Rather than buying a bike because it looked cool or was on sale, and then trying to work out how to fit yourself on to it after the event, which is all too common!

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Thanks for the great response. For me it’s great that you go into such detail. I am really enjoying the process. It’s a lot of fun trying to workout how to align the different geometry and component restraints to fit you as a rider, but to also take time into consideration (I am sure my position now will change slightly as I become a better rider)

Here is an example of how I interpret the numbers.
I am looking for 492/391 frame stack and reach.
For example Obera ordu M20/10 in a size Small has a frame stack and reach of 490/390 (Pulled from Slowtwitch)

In theory that frame would be a good option. From there I would be looking to choose a cockpit which can make up the difference between my frame stack and pad stack also for frame and pad reach? Very simplified version.

Like you said I would have to consider the cockpit and frame together.

But is that the right though process to have or am I way off :joy:

Thanks again.

Pad stack and reach (i.e. the first 2 numbers in the bottom row) is a better metric than frame stack and reach, since it takes both frame and cockpit into account. Normally frame stack and reach is simply a measurement of your existing bike, I guess since you don’t have an existing bike maybe those numbers refer to the Guru TT Bike that is mentioned at the top of the page?

What you need is a combo of bike and bars/stem that add up to your pad stack and reach numbers. So you need to know what range of stack and reach the bars will add to the frame and work back from there. The TriRig table makes this very easy for you - if you plug in the small Orbea and your pad stack/reach numbers (adding 60mm to your reach to get 486mm as TriRig measure to centre of pad not back of pad) then at 620mm of stack with no spacers your pads would be elevated 75mm above the base bars, and your range of reach would be 470-510mm. So 486mm puts you right in the middle of the range and that bar/frame combo works for you. Only concern is that you’d be quite close to the upper limit of how much you can elevate pads above bars, fine if you expect to drop a bit but to go much higher you’d need stem spacers. If you size up to a medium then you’re right in the middle of the stack range (with no spacers), but the bike is then a little too long for you (although you do also look a little cramped up in your fit picture, so might end up wanting a bit more reach anyway). Given you’re new to the TT position you might be safer to find a bike/bar combo where your current stack/reach numbers are both more in the middle of the range of adjustability, giving you more options to move in any direction.

Other bars might involve getting your calculator out. Most also allow you to choose your own stem (TriRig bars are one piece with integrated stem) which means you could have the option of going for the Medium Ordu where you won’t need as many pad spacers, and then choosing a shorter stem to get the reach right. Also easy and relatively cheap to swap stems if you need more reach in future.

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Amazing. Thank you. :+1: