A Time Trialing Thread

Thanks, mate - means a lot to me!


The Aerodynamic Revolution in Cycling | Jean-Paul Ballard | Talks at Google - YouTube

Swiss Side AERO TIP - HYDRATION - YouTube

There’s a lot of this stuff becoming available on the web, and I have just grabbed what I hope are some representative screenshots. What I’m taking from these is that flow around the frame and wheels is pretty clean and low-drag. The big pressure differences and therefore likely drag is behind the rider’s saddle, legs, heels and - to a lesser extent - arms.
So, @Majoeric - I agree that putting something in the frame triangle could/should be drag-neutral, but the big opportunity to reduce drag is to put things into the low-pressure areas maybe?


This maybe shows that nothing we do is new :grin:
Rear fairing


I often wonder how much faster a bodged recumbent frame attached to my body would be on a TT bike.

Got my first twelve hour coming next week (14th), i think i’ve got most bases covered in terms of help, nutrition, pacing etc but does anyone who’s done these things before have any advice on things they wish they’d done with hindsight or any unforeseen things that arose?

trying to be prepared for all eventualities


I haven’t done a 12 - I really wanted to do that event (assume its the D12/1 you’re doing?) but I can’t get a pass. In terms of advice, I’d maybe just offer this; all the planning in advance is great, but once you’re 4 to 8 hours in, even the best plans can unravel! I would guess you’ll plan one or two actual stops, rather than refuelling on the move all the time? I’d suggest 10-15mins before you get to these, make a mental checklist of what you are going to do, or else you arrive, you’re in a rush to do everything and get pedalling again, and you may forget something like chammy cream or a gilet or whatever… and then 15mins after the stop, you are cursing yourself for forgetting! I hope it goes really well - but after the National 100, you must be in great shape. :grin:


but you have done much sillier things :wink:

yes it’s the D12/1, my pacing plan is for 265miles and allows for 10 minutes of stopping. One of my clubmates put that togeather for me and it was based on a 4:03 in the anfield earlier this year. I’ll have a helper on the day so should be able to feed from the bike but thanks for the idea re having a checklist for if/when i do stop, i might even write some bullet points down to help remember

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Has anyone been able to test the new sworks tt 5 helm yet?

Looks like it could be a great fit for broad shouldered riders like myself.

That’s true! :grin:

Sorry - I meant Anfield, brain fade on my part! I guess you know all those roads well, which will be a big help. Plus I understand there’s a new surface between Tern Hill and Prees Heath, which is a big benefit.

That’s seems like a good, achievable plan - both distance and hand-ups. I assume you’ll aim to stop 2-4 times for a more substantial re-fuel? The guy who finished second at the 24 only had 9 mins off the bike, and his strategy was (I think) for hand-ups every hour or maybe every 90mins during the night with a 750ml bottle, plus a bidon full of gels on the bike. Simple but very, very effective strategy.


Pro teams only at this point…no release date for a consumer version.

All the WT pros sponsored by Spesh but Yves Lampaert and look how it worked out :joy:

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only 9 minutes off in the 24 is mental!

yes hoping the works will be finished between Prees Heath and Tern Hill as it should make that section quick although as i understand it will only be 1 time down there then it’s Battlefields and Quina Brook (like the 24) though course is yet to be confirmed.

the plan will be to pass my helper approximately every hour/25miles and get handed up a bottle and a gel/solid food which will give me 120g/hr. I’ve done up to six hours on just mix and gels recently without any issues so hoping that beyond that won’t get any worse.

stops will be for nature breaks but i’ll try to hold off until near my helper so he can load up drinks and i can get anything else i need at the same time.

a good result should mean i win the local BAR, i feel like i’ve let it consume me a bit over the past few weeks so hopefully all the stress upfront makes for a smooth running day


You probably know this, but the Battlefield loop is lumpy; if you attack it with too much enthusiasm early-doors, it will come back to bite you! I had a 48/21 gear to get over there and it was not low enough.

After about 4-6 hours, the amount I could tolerate dropped off quite a lot, which was a surprise - but this is something that’s hard to test outside very long races. Maybe consider what you’d do as a fall-back? In the 24, the only things I didn’t get tired of were gels and the carb drink, but I hadn’t anticipated that.


My LBS told me they wont get the TT5 helmet in until very late this year :frowning: and they are an official Spec dealer that usually gets stuff. I would like to get my hands on one to test it, altho it would have to be really quicker for me in order to use one. I just dont like the idea of more fabric around my head - TTs here are usually warm enough.

Question, anyone have experience with BBS’s position measurements and Cda prediction?

Focus is UCI ~30km TTs. I’m stuck in winter and don’t have testing options until spring, but certainly will be testing.

My specific question is does the measurements option offer good feedback on positional changes that translate to real world?

Even more specificly, I’m interested in shoulder / elbow width. My Kms/hr seem low for my Ws. Bringing my shoulder blades together has given about 4cm of narrowing.


No - I use Golden Cheetah Aerolab, but I guess (I hope!!) all these work the same way; you take the power in = power out to: rolling resistance + aero drag + change in speed + change in elevation, and back-solve for CdA. With a long-enough piece of data (like 5mins or more) it should be repeatable. If its not, then something you are doing or assuming isn’t quite right, so have a critical look at the inputs and try again.
Once you can go out 5 or 6 times with same bike, same position, same clothing, etc, etc and get the same CdA result, you should know the margin for error. Just as a guide, for me, its probably about 0.005.
The biggest sources of error are (in terms of magnitude) 1) Traffic, 2) gusty wind, 3) braking (although @hvvelo has done a very good post showing how to account for this earlier in this thread), then things with lower impact are 4) CRR (and assumptions about road surface), 5) temperature of air, ground, humidity, etc.
If you are trying to get repeatable results, doing several test runs whilst thinking about/playing around with the above should be good enough, then you can do some back-to-back tests on position, helmets, skinsuits. Do ABBAABBA until you have built up enough data to show a difference. If there isn’t one - accept its a wash and move on.

All testing methods have their limits, but personally, I think the absolute gold standard is measuring as much data as you possibly can from a race, and using that. Bear in mind there are limitations with any testing - eg wind tunnel, where you aren’t necessarily pedalling hard, and you may come away with a position that falls apart as soon as you start trying hard!

Just.Get. Testing. And report back here on the results!! :grin:


Thanks Greg. I’ll report back once testing again. I’ll also read up on how people are Chung testing now and will check out your reference. I believe my position is holding me back for the power I’m producing.

Sharing my experience now as maybe others are also starting their testing journey and maybe experienced testers can point out errors and improvements.

My basic testing experience is with an AABBAABB approach. My first test was for different helmet positions for the same head position. BBS Cda data seemed good and showed consistency within the As and Bs and a clear difference between A and B. I felt the my testing goal was achieved.

Testing was at race effort, but not a specific set power target. Each test segment was about 4minutes one direction followed by the next second segment in the opposite direction. So, for AA tests, first A was west and the second A east. Remaining tests followed this pattern. Testing segments excluded braking for the turns.

Couple of mistakes I know I made in the testing, 1 - no speed sensor (only GPS, opps) and 2 - the road which I’d not used before was rough and variable in roughness. However, the road is rural and excellent for no cars and not bad for surrounding structures/hedges. Also the road is flat to the naked eye although I’m relying on BBS and my bike computer barometer data to consider elevation.

Testing when calm with only a light head/tail wind forecasted. Handheld anemometer couldn’t register any wind. Testing location is near an airport which BBS recommended as a good way to get good weather data. I plan to return here for testing and see if I can ride just either side of the centre line for improved road Crr consistency.

A long time ago I looked into Chung testing. At the time, I determined I was going to spend too much time trying to get spreadsheets to work. More recently, BBS assisted me with power pacing plans, now I’ve started using it for Cda testing.

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This is a great post, @canadiankiwijay - you’ve brought out some really good points that probably help anyone interested in this kind of testing.
For extra reading about how others are using this, try this link and the follow-on links within it:
Aero Testing guide - Main Topic Area - Timetrialling Forum
And Rob B is excellent, have a look through the blog section of his site:
Blog - Float Aero

This is a really good approach and check for whether you are getting decent data: consistent results from independent tests.

This is what I do, and for most people, out-and-back is the best we can do. Try to get somewhere near to race speed, as airflow when testing things like skinsuits is quite speed-sensitive. If you race at 50kph, testing at 40kph might not be good enough.

Speed sensors do help, in as much as they improve the accuracy/reduce the noise. If you don’t have one, just do a longer segment or repeat the test once more.

This is harder to mitigate. Again, I think if you are getting too much noise or inconsistency (which you aren’t), you would just try gathering more data from more runs. However, you have probably got more error in selecting a real CRR with a rough surface. This doesn’t impact consistency, but does make it harder to have confidence in the absolute CdA value; if you overestimate CRR, predicted CdA will be low, and vice versa.

I did a bunch of research and built some spreadsheets that I got working after a while, it was interesting, but did require a lot of effort. It helped me get my head around BBS and Golden Cheetah. But those apps are running the calculation for every single data point (ie every second for your test). Bottom line; trust the apps!

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Aerocoach finally updated their Rolling resistance data: apparently the changed casing on the Veloflex Record is MUCH slower (16W for the 2020 test).
The GP5000TT should with that be very very close to the fastest tire. It’s 23.1W for a pair of tires, vs 22.2W on the clincher Michelin Power TT vs 21.3W for the Vittoria Corsa Speed 25mm.

The aero benefit of the the GP5000 over the other two is some 0.5 to 1.5W, so it kinda makes up for that.

Now it’s really about which one you like best. I have made great experience with the Michelin, but will try the new TT


Good luck tomorrow for the 12h!

Thanks Greg,

provisional results but just under 253 miles and third place (second place about half a mile ahead of me, first place was about 15 miles up)

brutal day in the heat and they had started working on the road to Tern Hill again so we got laps to battlefield like the 24 course

few DNF’s mostly down to the heat/dehydration i imagine

all in, pretty happy for a first stab at a 12