Zipp 454 NSW reviews

Discuss light weight issues concerning road bikes & parts.
NiFTY
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Joined: Sat May 26, 2012 11:26 pm

by NiFTY

But one yaw angle is meaningless. The average is much more important. Otherwise a deep narrow v rim manufacturer would just use a single test at 0 degrees with a narrow tyre and would be quicker than all the blunt edge modern rims.
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wingguy
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by wingguy

NiFTY wrote:But one yaw angle is meaningless. The average is much more important.

Sure the average is much more important... if you spend 50% of your time riding at 5 degrees and 50% riding at 12.5 degrees.

I mean, that's what you do, right?

by Weenie


NiFTY
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by NiFTY

Mate if you are looking for an argument go yell at the clouds. I stated that i was using the averaged data. Not a single point. The bikeradar used the two yaw angles summatively. So in response to your question i am more likely to spend 50% of my time at 5% and 50% at 12.5 degrees than i am to spend 100% of my time riding at both 5% and 12.5% simultaneously.
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wingguy
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by wingguy

NiFTY wrote:I stated that i was using the averaged data.

No, you said you should use the averaged data, and that therefore the difference between wheels is 25 watts not 40 watts.

This is incorrect. If BR's numbers were to be trusted you could, in certain situations, be at least 37w better off riding one set of wheels vs another.

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Pokerface07
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by Pokerface07

If we're talking about the recent BikeRadar test of deep section wheels (not 404 depth) - they were giving figures in grams of drag. This does NOT equate to watts 1-1!!!

So a difference of 38 grams of drag at 30mph would be around 4 watts difference (50 grams of drag at 30mph = 5 watts according to google).


**Unless they were listing power required to maintain 30mph.... in which case the spread is ridiculous!!
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otoman
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by otoman

Nice mic drop, pokerface07!
Age and treachery shall overcome youth and skill
Courir c’est mourir un peu

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Pokerface07
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by Pokerface07

Just gone back and looked at the test. They are indeed claiming the figures used are power to maintain 30mph on each wheelset. So they are claiming a near 40w difference between best and worst.

I'm surprised as I din't think even comparing a road and TT bike would yield this much of a difference.
Twitter: @FormerTTchamp https://twitter.com/FormerTTchamp

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Beaver
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by Beaver

I'm also not sure about these figures. :shock:

Tour magazine just claimed a maximum of 15w difference for a wheel change, 35w for a complete bike at 45kmph.

Image

And these 15w are the difference of a low profile rim vs. an aero wheel. The bike radar test only had high profile aero wheels, sooo...?

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cyclespeed
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by cyclespeed

Pokerface07 wrote:Just gone back and looked at the test. They are indeed claiming the figures used are power to maintain 30mph on each wheelset. So they are claiming a near 40w difference between best and worst.

I'm surprised as I din't think even comparing a road and TT bike would yield this much of a difference.


Bikeradar are sticking to their guns on this one and standing by their 40W difference, despite lots of raised eyebrows.

They also said that they didn't test any Campagnolo wheels as they would be 'cannon fodder' and no match for the 10 wheels they tested.

All sounds very odd to me.....

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Beaver
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by Beaver

Ah, one can find it in the youtube comments:

"At no point do we mention drag in grams. Drag is actually measured in Newtons because it is a force. The clever people at the wind tunnel convert it to watts because it's more relevant. If we say that on this wheel you have to put out an extra 8W then you know what we mean. If we say it adds 100g of drag (unrelated number) then that doesn't mean much to many people and even aerodynamicists don't know what that feels like on the road."

+Jamie Wilkins Something is very much wrong with your numbers if those numbers are actually in Watts (which you're saying the video). In other wind tunnel tests like the recent Tour test the difference between shallow aluminium rims and Zipp 404s is less than 10 Watts (tested at 40km/h so almost 30 mph like your test). And yet you're claiming differences around 40 Watts just between these wheels. So either a lot of these wheels must actually be worse than shallow aluminium rims or your have miraculously discovered that the gains from deep aero wheels are much larger than all previously published data. Or maybe it's just that something's wrong with how you processed you test data...

"First, testing at 48kph rather than 40kph will significantly increase the differences. Second, you don't state what angle that Tour test was run at - if it's a low angle then deep wheels offer less advantage. Third, the tyres may be different - the Rovals here pushed out a 25 to 29 when inflated which won't have helped them. Fourth, as 10W is worth around 1s/km, do you really think that a set of 404s will only gain you 40s in a 40km TT over shallow aluminium rims? Fifth, once a wheel has stalled, drag increases massively so some of the gaps may be between a wheel that has stalled and one that has not. We put a lot of effort into this test and involved some top experts."

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Pokerface07
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by Pokerface07

Somehow whenever Bikeradar 'independently' test anything they make balls of it.
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wingguy
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by wingguy

otoman wrote:Nice mic drop, pokerface07!

It would have been if he was right :wink:

wingguy
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by wingguy

Beaver wrote:Fourth, as 10W is worth around 1s/km, do you really think that a set of 404s will only gain you 40s in a 40km TT over shallow aluminium rims?

Yet if the whole ride was at low yaw their test says that 7.8s over CXRs would save two and a half minutes. Hmmm :wink:

Fifth, once a wheel has stalled, drag increases massively so some of the gaps may be between a wheel that has stalled and one that has not. We put a lot of effort into this test and involved some top experts."

Odd as well, because the gaps at 5 degrees were a lot bigger than the gaps at 12.5 degrees.

thumper88
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by thumper88

"Fifth, once a wheel has stalled, drag increases massively so some of the gaps may be between a wheel that has stalled and one that has not."


This part is the only thing he's right about -- and it's one huge reason the test is nearly useless. That "25m but really sometimes 29mm" tire stalled out a lot of wheels and at really shallow angles....and it probably had a really bad shape in addition to a bad size for stalling wheels.

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Beaver
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by Beaver

In addition to the 25mm tires they should have tested the recommended tire size. The CLX 64 suffer a lot with wide tires:

Image

http://bikeblather.blogspot.de/2016/03/ ... party.html

by Weenie


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