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TT helmet musings...
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TOPIC: TT helmet musings...

TT helmet musings... 8 years, 3 months ago #25330

  • Ron Ruff
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I'm on my way to Moriarty tomorrow, so TTs are on my mind. Regarding helmets specifically, I've gone from a LG Rocket last year (too wide for my large head), to a Giro Advantage 2 this year (fits, but is bulbous), to (I think) a Limar Crono 05 next year. I actually just got the Limar, but my wife is going to wear it at Moriarty since it fits her ok even though her head is way smaller than mine. Amazing adjustability... it actually fits on me easily, and it is a one size fits all.

I bought the Limar because some guys in Australia have tested it and found that it works very well. Here is one of them: http://fishboy.triathlete.com.au/2008/0 ... sting.html

Even though it is relatively small (doesn't cover the ears) and does not fit against the back, it makes sense to me. All helmets are too tapered for a good aero profile... ie you will get flow separation regardless. So fitting against the back and tapering to a point is not necessarily the best. One thing the Limar has going for it is that it isn't as thick as most helmets... so if your head sticks up above your back a little, there is less FA.

Everyone is different... but if I could pick my "ideal" helmet, I'd get something like the Limar only with a bit more side coverage and longer tail... but one that does not taper to a point or fit against the back, but rather tapers optimally and abruptly ends... Kamm style.

Here are some action photos. http://www.kodofotos.com/gallery/794367 ... 0150_uiAzR

That is JV showing great form and winning a TT with the same Giro helmet I have. The guys at the top and bottom of the page are wearing the Limar or clones.

Re: TT helmet musings... 8 years, 3 months ago #25331

  • Dalai
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Fishboy (who's blog is linked above) also did some field tests comparing the Chrono 5 with the Giro Advantage and his results were confirmed in the tunnel.

The Limars were one of the first aero helmets tested as Australian Standards compliant and therefore allowed in Cycling Australia events which follow UCI rules to the letter. I initially bought the Speed Demon as it 'looks' faster with the longer tail. I also have an 07 Bell Meteor which I had used in Triathlons (rules allow non AS tested helmets) and initially tested both in the tunnel to see if there were any differences in the two helmets (The CE certified helmet can still be used on the track).

Then on fishboys suggestion I tried his Chrono 5. Although shorter, the Chrono 5 with minimal venting (none on the front section) offered me a noticeable wattage saving over the longer tailed, vented and sculptured Speed Demon. The Chrono 5 also compared favourably even against the Bell which with it's long tail sits nicely against my back. As you can guess, I immediately sold the Speed Demon and bought the Chrono 5!

My only design improvements for the Chrono 5 would be lower ear coverage and lower back to the helmet. As even with extreme turtling I have trouble trying to close the gap between the helmet and my back.

Re: TT helmet musings... 8 years, 3 months ago #25332

  • Ron Ruff
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Dalai wrote:
My only design improvements for the Chrono 5 would be lower ear coverage and lower back to the helmet. As even with extreme turtling I have trouble trying to close the gap between the helmet and my back.


I have a long neck and there is no way I can close that gap... but then, I'm not sure it is super important either. I'll try to do some field testing and see if I can measure a difference... but with our persistent and variable breeze here it is tough.

Re: TT helmet musings... 8 years, 3 months ago #25333

  • Dalai
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I'd be interested in the results if you do.

As you can see in the photo, my final position and best measurements were even still with a small gap, so you could be right. Though during testing, we continually worked to try and reduce that gap as best as possible... My neck was very sore the next day I must say!

Re: TT helmet musings... 8 years, 3 months ago #25334

  • Ron Ruff
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The Limar Crono looks exceptionally good on you in that position. Some more photos here: http://www.fairwheelbikes.com/forum/vie ... =33&t=5605

Is that the same position you use in races now, and if so, how much faster is it? Did you lose any power?

Re: TT helmet musings... 8 years, 3 months ago #25335

  • Dalai
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It is the same position I am using now. Can't comment whether a loss of power as I've only recently bought a secondhand SRM and this is on the road bike. Though honestly I don't think I've lost much at all given most of the changes other than a 2cm drop of the bars and helmet was an awareness of position (shoulder shrug and turtling) and trying to focus on keeping my nose as close to the stem as possible rather than looking at the horizon as seen in the photos of the initial tests from my tunnel session...

For comparisons, I raced an ITT last month on the same course other than the start line being back another 100m or so that was last years State Masters Championships. In much windier conditions (read blustery side winds) I decided to use my old Shamal on the front rather than the Stinger 90 and was a minute faster. Other ITT's on regular courses have also been consistently a couple of km/hr faster this year too, some of this would surely be attributed to racing the many more ITT's available this year. But I really do feel that the helmet change and lowering of the bars has made a noticeable difference.

Re: TT helmet musings... 8 years, 3 months ago #25336

  • kraig
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Thanks for sharing guys!

the whole helmet/head position interaction deal is a bit of a beast in my experience. Sometimes things that look "faster" aren't.

Here's an image that immediately came to mind when discussing flow attachment on aero helmets:

http://autobus.cyclingnews.com/photos/2 ... /test2.jpg

and here's some of what I've done in the tunnel with tufts and whatnot:

http://www.biketechreview.com/forum/vie ... php?p=8575
-kraig

Re: TT helmet musings... 8 years, 2 months ago #25482

  • fishboy
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Sorry, been off for the last month having a rest after worlds...

I was using a Giro Adv 2 for about 3/4 of a season (after switching from the Crono), but wondered why my times were slower... got around to testing and with the Crono back on immediately faster again. Taping the vents on the Giro does recover a lot of the difference, but not if an eagle eyed commissaire spots it.

It's the combination of smaller frontal area and no vents that make the Limar Crono a top choice for many (but probably not all) people.

Re: TT helmet musings... 8 years, 2 months ago #25483

  • Ron Ruff
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I bought a Limar Crono and immediately set a new PR in our weekly TT... so I don't think it is hurting me anyway compared to the Giro.

Practicing elbows together and turtling and shrugging on the trainer this winter...

Re: TT helmet musings... 8 years, 2 months ago #25493

  • fishboy
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