Friday, October 15, 2010

Helmet Test - Standard vs Aero

Ever since I purchased my Rudy Wingspan helmet (about 6 weeks ago), I wondered how much faster it might be.  I have raced with it twice now, and had really good bike splits for each race.  But I still wanted to find out just how much faster it was.  I remember seeing some articles stating that over a 40k (25mile) time trial, these aero helmets should save somewhere in the region of 1 minute.
So I decided to perform a (non-scientific) test.  Since I don’t have a fancy bike computer or a power meter I had to go by my perceived effort, HR monitor and simple cateye bike computer.
The Helmets
Bell standard road helmet vs Rudy Project Wingspan
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as you can see on the Wingspan, I used the mesh cover (right under the number from my last race).  The other options are a solid insert (no airflow) or no insert for maximum airflow.  I went for the middle.  I also had the tail cover installed (see pic below with the tail cover on/off)
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The test was conducted at Prince William Forrest, a great place to ride with a 7.25 mile loop that has it all, flat/rolling/fast and a some challenging hills.  I managed to get some time mid-week, so there were no cars.  For the whole ride I only saw 2 other cyclists.    I used my road bike with aero bars – exactly what I use when racing.
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the chart above (thanks to mapmyride.com) shows the course profile – harder than most of the triathlon’s that I have competed in.
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After a 10 minute warm-up I proceeded to complete a single lap using each helmet.  I started with the standard helmet then followed-up with the aero helmet.
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this picture shows the start/finish line – I began each lap with a standing start, the lines painted on the road made it easy to accurately repeat the start/end of each lap.
Since the laps were around 21 minutes for 7.25 miles – it would give me a decent indicator about how much faster it is, without having to spend the whole day testing.  Plus a the short laps meant I didn’t get too fatigued, although even 1 lap is a really good workout.  My level of effort was hard the whole way.

The Results
Lap Time Avg Speed Avg HR Max Speed
Standard Helmet
21:32.7
20.1
148
42.1
Wingspan/Aero
21:11.4
20.4
155
44.4
All speeds are in MPH.  The aero helmet was 21.3 seconds faster, a decent time improvement.  The average HR was a little higher, I think mostly because of the hard effort for lap 1, and my starting hr was higher.  I did rest for a few minutes between laps, which gave me time to take a few pics of the stats for the first lap.  The last time I rode 2 laps around this course my 2nd lap HR was higher by 6bpm, so another 7bpm this time is close enough.   My HR is always highest at the end of the lap, since the last mile or so is significantly up hill.
the 2 pictures below show my bike computer’s average speeds for both laps.  sorry, the quality is low.
Lap 1 average speed lap 2 average speed
I tried to pace myself evenly for both laps, not favoring one lap over another, however I think I pushed the steep downhill a fraction harder on the 2nd lap (max speed went up from 42.1 to 44.4) – the hill is short and steep so would not have made much of a time difference.  the helmet surely made a little difference in max speed too.
So taking 21.3 seconds per 7.25 miles and extrapolating over standard race distances, we get the following:-
Sprint Olympic half ironman Ironman
Distance (Miles)
12
25
56
112
Time Saving (mm:ss)
0:35
1:13
2:45
5:29
these numbers are of course all subjective, but I think they represent a decent indication of time savings.  Actually for a flatter/faster course with a higher average speed the time saving could increase.  I think my cateye computer also measures a little long, mapmyride.com shows the lap at 7.2 miles.  so these times above could be even better.
What I did notice was a big difference in how the 2 helmets felt, or more specifically sounded.  The standard helmet was very loud with all of the wind rushing past my ears, especially when riding over 23mph (which was for a good part of the lap).  The aero helmet covers part of my ears, and that really helps with the noise levels, so it doesn’t sound like you are going as fast.  As I moved my head around (up/down) there was one position that cut the wind noise to almost zero.  I’m not sure if that is a faster position, or just a better position with relation to wind near my ears.  It happened as I was looking down more towards my front wheel rather than out at the road in front. Comfort wise (heat/head temperature) I didn’t notice a difference.  It probably helped that the weather was perfect for riding (mid-low 70’s) with not much wind.
The last time I rode this course was 6 weeks before.  I used the same equipment as lap 1 (standard helmet) and had exactly the save average HR.  the differences were
Lap Time Avg Speed (mph) Avg HR Max Speed
6 weeks prior
22:25.3
19.2
148
~42
test lap 1
21:32.7
20.1
148
42.1
so I was almost a minute faster for the same effort, after 6 weeks of pretty hard training.
So we can conclude that there is really no substitute for hard training!  In 6 weeks I improved almost 1 minute.  The helmet added another 21 seconds.  But those seconds came at no extra effort.  Add that to the 2 minutes I usually save when wearing a wetsuit and it starts to add up.
In my opinion the helmet and wetsuit are the best time/speed saving for the money spent.
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a great day for a ride
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I had a lot of fun completing this test, and would really like to do some more.  Some thoughts on future tests, given time (and budget)
  • complete the same test with a power meter & better bike computer (edge 500)
  • road bike vs Triathlon specific/TT bike (once I get one, perhaps 6 months away)
  • race wheels vs standard wheels

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