Time Trial / Time Trialling / TT

The fast lane presumably.

Because seeing where you’re going is for losers.

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I expect Marcin knows what he's doing, but CTT are exposing their blind spot by using that kind of image for publicity.

Silly isn’t it. With all their ‘head down kills’ which is does. You think they’d have told the company in charge of their social media not to use images like that. Doesn’t put forward the right image.

We got involved during the construction and have had some input into the software being used, all about making it better for the end user really whether they're a Boardman customer or an AeroCoach customer.

There will be another tier on top of the Boardman offering which will be an AeroCoach powered wind tunnel session, building on the >550 rider bank of knowledge we've got and also using the tunnel slightly differently from normal to maximise data, but those protocols will probably trickle down to Boardman tunnel sessions over time. Boardman are very happy for us to do that as it's attracting a different client base really.

I wonder how long it is before aero testing of road bike positions goes more mainstream. You must have seen quite a few pros for that. Especially those that win solo or breakaway riders.

Lea Valley CC Tuesday Tens- May 8th - July 17th

Lea Valley CC's Ten Mile TT series returns to the Lea Valley Velopark this tuesday.

Ride as many or as few of the weeks as you want – A rider’s six best times from the first 10 events qualify for the overall competition.

Sign on from 18:00 and first rider off at 19:01

Check site for more details.
http://leavalleycc.co.uk/tuesday-tens/

Yes we have done - for pros it’s an easy sell (to the team staff) but for the everyday roadie they’ve mostly got aero allergies. That is the group the Boardman centre is looking to bring in, time will tell whether a Performance Centre is intimidating or not to those people.

As an aside, we were in Amsterdam last week for some closed door discussions with Garmin, DC Rainmaker was there and we ran him through a session - very switched on guy.

If I was a domestic pro I’d be doing it. It’s a no brainer. There must be serious watts of saving in road position.

The wind tunnel makes a good apparatus for testing sprinters too. And given how sprints are lost by millimetres it’s worth it.

I did consider if it was worth it for ultra racing bike. But I concluded that at 15mph it’s not going to be huge savings.

Regarding Aero for ultras: I was under the impression from Specialized's Win Tunnel videos that aero reduction is pretty much the same over a given distance when measured in units of time (due to extended time riding when at slower speeds). Is that not the case? (genuine, non-rhetorical question).

Edit: I think I've looked at this from the wrong angle: hadn't considered the average margin of victory in ultras.

Force is proportional to velocity squared. So as required increases the force needed increases exponential.

Force (drag) = Density * coefficient drag * area * (Velocity^2)/2

So at low speeds (15mph) drag isn’t that high. At if you were to reduce coefficent drag, the proportional increase in speed is quite small, at overall low power production.

However if you’re travelling 25mph then due to the relationship the drag saved correlates to quite a reduction in power needed to over come the drag.

Margins aside (not a factor in my decision).

Quick calculation as I'm busy, but with some rough numbers. Ignores drag from rolling resistance and gravity, but these would be negligible change.
Speed in m/s so 15mph is 6.7 m/s which is about my average speed. Assumed cdA of .28 reduced to .24 only gives a 9w saving, which is 0.04 is very optimistic. So 0.2 cdA reduction gives a saving of 4 Watts.

Happy to be corrected if I got the numbers wrong.

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Drag is exponentially related to speed

Not quite. Drag is proportional to the square of velocity, so power required to overcome drag is proportional to the cube of velocity. Ptown's broad point stands, small absolute or relative changes in velocity make larger differences to the time taken to cover a distance if the initial velocity is small, because time taken is inversely proportional to velocity.

Small absolute change (ΔV=1mph):
15mph to 16mph saves 6m15s over 25 miles
25mph to 26mph saves 2m18s over 25 miles

Small relative change (ΔV=5%):
15mph to 15.75mph saves 4m45s
25mph to 26.25mpg sames 2m51s

Even after allowing that slow riders expend a smaller proportion of total power overcoming drag, because other resistance forces are proportional to the first power of velocity, time savings for the same incremental reduction in C_dA can be greater for slower riders.

Sorry yes, I realised my mistake and corrected before you'd posted.

Happy to be corrected if I got the numbers wrong

Well, you got the function wrong at first pass, but I see you managed to correct that while I was composing my post :)

Yeah sorry.

I did it the oter way round. Assuming Area of 2.5 to get reasonable velocities, reducing cda by 0.2, which might be achievable (?). I'd save 4 ish hours, at 150 Watts, which would be around total average.

Perhaps it's worth it...

But then again, you can't be ve

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ry aero optimised, as position needs to be comfort first.

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Googling disc 40mm+ carbon wheels...

And, does not bode well for my fluid mechanics exam tomorrow. Too many equations in my head.

then again, you can't be very aero optimised, as position needs to be comfort first

I think that's where road racers are going to be resistant to position changes for aero, if they have 100,000 miles under their belt in a position which they know works for six hours at a time, it's going to be a hard sell to move them, and problems caused by the new position could take weeks or even months to become apparent.

Assuming Area of 2.8 to get reasonable velocities, reducing cda by 0.02

ftfy, and I think you have your C_d about 3 times too low and your A about 3 times too high, not that it matters for these purposes but C_d of ~0.3 is modern car territory, not safety bicycle.

Thanks for the info! I'd assumed gains would be much more substantial just due to length of race (aeroweenie calc a similar story: ~1hr15m saved dropping 0.01 cda over 3500km @150w).

Yes I see, wasn't thinking. Due to missing some drag factors, the cdA is higher than would be, change still representative.

I checked some numbers off cyclingpowerlab. So these cda are high, but give a good speed (which is what matters).

The possible saving does seem to be in the region of 2-4 hours. So that is substantial. But as a % of overall time (220 hours) small. Plus is a carbon 24h rim more likely to break, hippy can answer that!

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Hoping for a bit of advice for the upcoming National 12hr TT which I plan on entering. It's on the bumpy Bentley course - H12H/8

@umop3pisdn - I will PM you for some specific questions if that's ok? I know you rode and wrote about it last year.

Main Questions -

I will have support from hours 4 -12. I was going to leave all my stuff at the Hen and Chickens Pub for them, but before that, I was going to label up bottles and have them at the official feed zone. Is this a bad idea or will it work ok?

I plan on having one bottle BTA that I swap each 20 mile lap, plus a backup bottle in a rear cage, just in case I miss one or need extra. Is there a go to BTA mount? I was planning on making my own if not.

Although I will tape food to bottles, I want a backup so planned on having a top tube bento box with backup gels, chews etc. Is there a good one out there? I have a narrow, quite pointed top tube so this one will prob not stay put. It also has poor reviews.

Will prob think of loads more questions, but that's it for now!

Colin

I will PM you for some specific questions if that's ok?

It's up to @umop3pisdn , but I vigorously discourage asking things which are not private in PMs. If you ask on the open forum, his answers will help strangers from the future and if we disagree with him you'll get to hear about it :)

Fair point. I just didn’t want to take over the thread with too many questions.