…… getting aero “in a Nutshell”
Some pretty basic wheel and tyre comparisons
Let’s start with the limitations of the testing methodology. I don’t have access to a low speed wind
tunnel. I don’t have access to a rolling resistance jig. So, these tests were conducted on three different
velodromes, and the results are based on comparison measurements, not absolute numbers. That said,
we race in real world conditions, not in wind tunnels with Crr apparatus.
So, what did I test ….
My own Super 9 disk and 808 NSW
A borrowed pair of ENVE 7.8
A borrowed pair of Parcours Chrono
A pre-Firecrest 808 (dimpled) and a HED-3 Trispoke
The three rear wheels were fitted with 25c GP4000 IIs and Michelin (green) latex tubes.
The 808NSW and the Parcours Chrono front were fitted with 23c Conti TT Limited and Michelin (green)
latex tubes. The ENVE front wheel was fitted with a 25c Conti TT Limited.
The older 808 was fitted with a 23c Conti SuperSonic and a Michelin (green) latex tube.
The HED-3 was fitted with a 20c Conti SuperSonic and a Michelin (green) latex tube (smaller size tube).
….. and what was my test methodology
All the tests were performed using my P3 with calibrated SRMs, with the off-set checked before and
after each test run.
Accurate / consistent speed measurement is required for testing. A rear wheel speed sensor was used
when testing the front wheels against each other, and a front wheel speed sensor was used when
testing the rear wheels. The Super9 was used as the rear wheel for all front wheel tests. The 808NSW
was used as the front wheel for all rear wheel tests.
Using the same reference wheel is important as the diameter of wheel and tyre combination can vary
from wheel to wheel, which knocks-on to the circumference, which is a parameter used to calculate the
speed from the number of wheel revolutions. I could have used a “roll-out” measurement for the
circumference of the different rear wheels, however, as soon as you put a rider on the bike the tyre is
compressed a little and the effective circumference becomes a little smaller. Using the same wheel, with
speed sensor, for all the tests, ensures that the measurements are consistent.
Environmental conditions were monitored using a Kestrel Portable Weather Station. Tyre and track
temperatures were monitored using an IR thermometer.
Copyright R J Barrett 27th March 2017
www.floataero.com
@float_aero
…… getting aero “in a Nutshell”
Front wheel tests at Welwyn, Palmer Park and Newport Velodromes
I ran all the tests against the NSW as the benchmark. I have a lot of data for my benchmark set-up at all
three venues. I used appropriate Crr values for each venue based on previous comparison tests with my
benchmark set-up. I used A-B-A-B testing, so each wheel was run twice against the NSW. I varied the
order of testing at each of the venues. Test speeds were 23 to 25 mph, a limitation of my power (!)
Here is the results table:
I estimate that the limit of accuracy with my methodology and Aerolab is about plus or minus 0.002. I
could probably improve that by doing more runs, but it would have to be a lot more runs. I’ll ask one of
my mathematician friends for some advice on the statistical significance but I think I’d have to go to at
least ten runs per wheel to get a significant benefit.
I expected the HED-3 to be the slowest as it doesn’t work well with the 3T forks in my P3. The result with
the SuperSonic tyre is marginally better than previous comparisons using a 20c GP4000 IIs, but it’s
within the 0.002 margin of error. I have a pair of Oval forks to test with the HED-3, but it’ll be a while
before I can do that, as I have other tests to do with my current set-up first.
I’ve tested the Pre-FC 808 against the NSW on multiple occasions, both before and after the Pre-FC 808
had its Zipp “hub upgrade”. Prior to the hub upgrade it was 0.006 slower than the NSW, and the same as
my 303 FC front wheel. After the hub upgrade it was testing the same as the NSW and 0.006 faster than
my 303 FC front wheel. I then decided to test it with the SuperSonic, and it has come out marginally
faster compared to the results with a Conti TT Limited.
The Parcours Chrono front wheel comes out very close to the 808NSW, within the margin of error, but
the wheel that tested the fastest on every occasion has been the ENVE 7.8 front wheel.
All the tests were carried out on relatively calm days with less than 2-5mph wind (irrelevant for Newport
obviously), however, I did test the 808NSW and ENVE 7.8 front wheels on a windy day back in
September 2016, and it was obvious that the ENVE was much more stable when cornering in the wind.
So, given that it tests the fastest and handles the best it would be my front wheel of choice.
Copyright R J Barrett 27th March 2017
www.floataero.com
@float_aero
…… getting aero “in a Nutshell”
The Parcours Chrono front wheel is 85mm deep section and being a medium weight rider (69kg) I did
notice that is was a little less stable than the NSW even in light winds, however, the Parcour Chrono
wheels, as a pair, costs less than an 808NSW front wheel, and much less than an ENVE 7.8 front wheel,
so they have their merits.
Rear wheel tests at Palmer Park and Newport Velodromes
I ran the tests with the NSW front wheel as the benchmark, with a front wheel speed sensor. I tested the
ZIPP Super 9 Disk against the ENVE 7.8 rear wheel and the Parcours Chrono rear wheel. Test speeds
were 23 to 25 mph.
Here is the results table:
The Super 9 tested the fastest. No surprise really. The Super 9 seems to fit the backend if the P3 really
well. The Parcours Chrono tested well. The 85mm deep section is not a problem for handling “on the
back”. The ENVE didn’t test as well as expected. This maybe because it’s wider than the Super 9 and
doesn’t work so well with the P3 backend. It could be a similar scenario to the HED-3 not working very
well with the 3T forks. Results for the ENVE might be much better compared to a Super 9 when tested in
other frames.
Bottom line, starting from a clean sheet, and money no object, my choice of wheels for my P3 would be
Zipp Super 9 Disk and ENVE 7.8 front wheel. But that doesn’t give you much change out of £3500.00.
The Parcours Chrono pair come in at about £895.00 for the pair. The drag differential against the Super
9 and ENVE 7.8 front is going to be about 0.0130 for a price differential of £2605.00, or about £200.00
per Watt. To put that in context, upgrading from a second hand P3 to a new SuperBike frame would cost
about £4000.00 and probably be worth about 0.0100 gain max, so £400.00 per Watt.
Copyright R J Barrett 27th March 2017
www.floataero.com
@float_aero
…… getting aero “in a Nutshell”
So, a word or two on tube and tyre choices:
I like Michelin AirComp Green Latex tubes. Whenever I have tested a wheel with a Vittoria pink latex
tube it’s always tested slower than I expected. I change the tube for an AirComp and the result appears
to get better by around 0.006. I’ve done this on multiple occasions over the past three years with 808s,
ENVE and other wheels. Other people like the Vittoria tubes, and think they are at least as fast, or faster,
than the AirComp. It comes down to personal choice.
I have had experience of some Michelin tubes holding air better than others, some go flat in a few days,
others last up to 14 days before going flat. I’ve not done any testing to see if the faster deflating ones
are “faster” on the road than the ones that hold their air better. The Michelin ones that deflate faster
may be thinner and therefore more pliable.
Another test that I need to perform is running tyres / tubes at different pressures. There is a school of
thought that favours lower pressures to give lower rolling resistance. I did a very simplistic experiment
with one of my clients running tubs at 140, 110 and 95 psi. What we noticed was that the lower the
pressure the warmer the tyres got after ten test laps of an outdoor velodrome. We know that warmer
tyres and tubes are more pliable and in theory this should lead to lower rolling resistance. The heat to
warm the tyres must be coming from friction between the tyre and the track surface, and from the
deformation / restoration of the tyre / tube as the wheel rotates. Friction converts energy from motion
to heat. That energy / power is coming from the Wattage produced by the rider. What we need to find
out is “is the gain from lower rolling resistance greater than the loss of speed due to power lost to
friction”. First indications are that there is a gain to be had from using lower pressures.
Moving on to tyres. We want the front tyre to have the best combination of rolling resistance and aero
properties. The front wheel is the leading edge of the bike, therefore the aero properties of the tyre and
wheel combination are very important. Hitherto I had always used Conti TT Limited, however, it was
suggested to me that a GP4000 IIs might perform better on the front, because of the tread pattern being
more aerodynamic than the smoother TT Limited. Recently I’ve confirmed that the SuperSonic is slightly
faster than the Conti TT, so this gives us three options to test. And we haven’t considered the Vittoria
Corsa Speed G+ yet. This type of test is very difficult to perform without a low speed wind tunnel and a
rolling resistance jig.
Ideally, to test on a velodrome requires three / four identical wheels, with identical tubes, and the three
/ four different tyres. And then you need the right conditions so that all the tests are carried out at the
same temperature. The best I can do at the moment is test with my two slightly different 808s, using
different combinations of tyres, and then apply a bit of logic / maths to work out the comparisons.
I switched to Continental from Vittoria a few years ago. I was told the wet weather performance of the
Contis was better. I haven’t heard any reports on the G+ regarding grip in the wet. I have an open mind,
so I’ll be testing the three Conti options and the G+ over the coming weeks. If I get around to buying an
ENVE 7.8 front then I think the only one of the above branded as “tubeless-ready” is the G+, so it’s be
Hobson’s Choice. With tubeless you need to be even more careful of heat dissipation when descending.
Ends
Copyright R J Barrett 27th March 2017
www.floataero.com
@float_aero