Well the conventional wisdom really is more that there is an ideal pressure depending on how bumpy the road is, the tire, and the weight of the rider.
If you are 175+ lbs then 120 would be around the optimal tire pressure for you according to Michelin for their Pro Race 3.
Some tires can go up to 160psi though, have you tried that? =)
I’ve yet to see a single test anywhere that supports the conventional wisdom that lower pressure is lower Crr on a road.
Well the conventional wisdom really is more that there is an ideal pressure depending on how bumpy the road is, the tire, and the weight of the rider.
If you are 175+ lbs then 120 would be around the optimal tire pressure for you according to Michelin for their Pro Race 3.
Some tires can go up to 160psi though, have you tried that? =)
I’ve yet to see a single test anywhere that supports the conventional wisdom that lower pressure is lower Crr on a road.
I did try 140psi and the results were marginally better than at 120psi on a “normal” road…but well within the margin of error of my field testing. Not incredibly bumpy and not chipseal but decently paved. Combo of bike and rider is around 180lb in full race dress. I typically stick around 120-125psi simply because 140+ can be pretty harsh on the tailbone! I’ve just never seen any test data ever (field or lab) that shows 100psi to be faster than 120psi.
what really made me question the data was the fact that their graphs show the Campag Bora to be faster than a Zipp 404.
what really made me question the data was the fact that their graphs show the Campag Bora to be faster than a Zipp 404.
Why? The boras only tested faster at approx 7-8 degrees yaw compared to the 404’s if you are looking at tubular. Clincher 404s are only slower at lower yaw angles. That seems reasonable to me.
Interstingely pretty much all wheels that have been added later on to the chart seem to start with much higher (about 15g) drag numbers at 0 yaw.
So maybe there was some difference in the testing protocol. Shouldn’t all wheels be about pretty much the same at 0 yaw?
Hope we’ll find the answer:)
greets
Benja
what I don’t get is it shows the lowest drag on the Zipp Sub 9 to be 60 grams, yet according to Zipp it has negative drag??? Quite coincidentally, the Stinger disc shows negative drag. Who’s right???
Hi,
Forgive my intrusion, I have a quiver of wheels for my quiver of bikes (both in 700 and 650c formats). My aquisition cost is roughly balanced for both hed and ZIPP…I am good friends with Andy Ording @ Zipp, I am a very longterm close friend with Steve, Annie and Tim @ HED. My biases and hookups have now been disclosed. There we are.
In consideration of the fact re-enforcement trend here at ST, ie; “Pics or it did not happen, or metrics or it doesn’t happen”. I find your negative tone comments to be a trifle off-putting, to say the least.
F**king-A, Dude! You get companies like Zipp and Hed to put out reams of WT and CFD data points and you still have the nerve to 'bitch about it? WTF?
Do you have any wonder why many companies NO LONGER POST OFTEN ON ST?
Where have Josh@Zipp, Tim or Andy@ HED, Montgomery @ Scott, Gerard @ Cervelo and others largely gone?
Probably away to places more time beneficial than this occasionally self important and self absorbed site.
Why are you and some of the other Tech-masters of ST being so obtuse to people and companies that are very passionate about the same things that WE are?
I hope that HED and Zipp keep changing and updating their products and resultant metrics.
I am not concerned by the fact that no product or wheel will improve the average ‘Propeller Heads’ IM bike split from 6:05 to 6:01.
I am going to stand my 6ft 3inch frame up on my rant box and Say a BIG THANKS to the passionate folks at Zipp and Hed.
“Thanks for giving so much of a damn about our geeky little activity, many of us are faster and more psyched about 2009 and beyond due to the fruits of your labours!”
Thanks ALL!
Tom Price
The Spartan Athelete
www.IronTom.com
Somewhere in the Northwestern United States
I am with TomP on this.
I want to say thank you to Zipp, Hed, Cervelo, Speciaized, Trek, and anyone else that has at least tried to present real technical data.
I do appreciate it and it does influence my buying decisions.
Please continue to bring forth the data, and please be honest in how you compile and test. thanks =)
Tom, I apologize if my comment irked you the wrong way.
However, we have NO IDEA WHERE THIS DATA CAME FROM!!! These companies are a business, designed to MAKE MONEY. Marketing divisions of companies get paid dollars in order to push product. Take one statistic that makes a product “appear” superior and blow it way out of proportion.
People bitch about supplements all the time while saying, “the research they performed doesn’t matter. It’s just to sell protein (or whatever). I want to see independent data.” This is the same idea.
Data can be manipulated to provide the result you want, in any and almost EVERY situation.
damn dude yer still doing it.
we all understand your point but be tactful, the tone of your posts basically calls the reps that post here liars.
you can’t demand independent testing of zipp/hed, they can’t possibly arrange it, it wouldn’t be independent.
there is this though, which is nice 
Tom, I apologize if my comment irked you the wrong way.
However, we have NO IDEA WHERE THIS DATA CAME FROM!!! These companies are a business, designed to MAKE MONEY. Marketing divisions of companies get paid dollars in order to push product. Take one statistic that makes a product “appear” superior and blow it way out of proportion.
People bitch about supplements all the time while saying, “the research they performed doesn’t matter. It’s just to sell protein (or whatever). I want to see independent data.” This is the same idea.
Data can be manipulated to provide the result you want, in any and almost EVERY situation.
Tom, I apologize if my comment irked you the wrong way.
However, we have NO IDEA WHERE THIS DATA CAME FROM!!! These companies are a business, designed to MAKE MONEY. Marketing divisions of companies get paid dollars in order to push product. Take one statistic that makes a product “appear” superior and blow it way out of proportion.
People bitch about supplements all the time while saying, “the research they performed doesn’t matter. It’s just to sell protein (or whatever). I want to see independent data.” This is the same idea.
Data can be manipulated to provide the result you want, in any and almost EVERY situation.
I agree…and a little more “transparency” on the test methods, tires used, etc. would go a long way towards making this stuff “believable”.
As it is, this thread sort of “skirts” the ST policy on data presentation, since the actual data isn’t shown here, just referenced…
I’m still waiting on the data showing there’s actually a Crr advantage with the C2 rims 
the irony of course is that the chart you posted shows some of the ‘inconsistencies’ between hed’s data and some the ‘independent data’. The yaw angle weighting average on the chart you posted is a little funky, but it’s interested nonetheless.
The main questions I have about the Hed data: what tires were used, what windtunnel (I thought the data were all from the LSWT in SD, but now I’m not sure-if different wintunnels were used, I’m not sure comparing the data from different tunnels is entirely useful), do the clincher and tubular H3’s really have identical drag? (seems impossible to me). Also, as Tom mentioned, I need to see a test protocol and results before I believe the bit about the C2 clincher rim and lower Crr.
Lastly, what data points were left off?
it would be cool to get the full tour magazine test data instead of just the weighted average…i wonder if its out there somewhere, waiting to be posted on the innertubes?
I’m not calling them liars. I guess I would like more information about the testing protocol/procedure to make a better informed purchase decision.
I work in a retail shoe store. I tell my customers things that I don’t necessarily know as true. Am I a liar? I guess that’s for you to decide. However a pair of $20 insoles is completely different from a $2000 disc.
I do like that graph, as I’ve seen it before. I think one with 2009 wheels would be nice, but thats hella expensive to do, I’m sure.
I’m just glad that graph shows some goodness in the zipp and hed products.
probably can’t go wrong either way =)
I agree. It’s great firms publish their data but without a publicised methodology, it’s worthless. We can then debate the differecnes in the tests themselves rather than the numbers produced. In a journal, researchers disclose their methodology, why not here ?
I’m still waiting on the data showing there’s actually a Crr advantage with the C2 rims
seems pretty simple to test that theory…
g
I’m still waiting on the data showing there’s actually a Crr advantage with the C2 rims
seems pretty simple to test that theory…
g
how would you propose doing so?
I’m still waiting on the data showing there’s actually a Crr advantage with the C2 rims
seems pretty simple to test that theory…
g
how would you propose doing so?
umm… have one 19mm rimmed wheel and one 23mm wheel. Crr test one on rollers with a tire. move tire to other one and Crr test that. Compare the Crr results of each configuration.
g
I’m still waiting on the data showing there’s actually a Crr advantage with the C2 rims
seems pretty simple to test that theory…
g
how would you propose doing so?
umm… have one 19mm rimmed wheel and one 23mm wheel. Crr test one on rollers with a tire. move tire to other one and Crr test that. Compare the Crr results of each configuration.
g
well if that’s all you want, I’ll tell you the answer: there’s no difference…
I think the argument that hed is making (I think) is that ‘on road’ Crr is better. I’m not from the stone age, and I don’t discount roller tests for the relative ordering of tires. However, as I’m sure you know roller results don’t directly equate to the road, e.g. higher pressures (I’ve gone up to almost 200 psi) result in lower Crr–on metal drums…
In addition to road surface, there’s also tire angle. What about riding around a corner, or standing (when there’s significant tire lean). I have some random thoughts, but certainly no answers. Additionally, Hed recommends lower pressure for the wider rims. How will that affect things?
In short, I think it’s more complex (both the question and the answer) than you suggest.