xcsnail wrote:
Quote:
When the s3 first came out, cervelo had a white paper that said the s3 was 1.5% better than their non aero frame [r3] at 300 watts or 4.5 watts faster, and this was with rider aboard. Now the s3 is much much faster than the r3 and the s5 is faster still. Gerard confirmed the 1.5% when I asked specifically about this 2 years ago. Something doesn't add up... You are right, it is called marketing. In 18-24 months Cervelo will reveal another bike that is somehow 1.5% better and 18-24 months after that and so on and so on....
It's actually the S2 not S3 (my mistake)- but the S2 and S3 are very, very close in aerodynamics. Here's more of the 1.5% difference- in Gerards own words. To me- this doesn't add up- but... I still believe they are great frames and my household owns two S3s and one P3C.
http://forums.cervelo.com/forums/t/3192.aspx A very long
post by Gerard on the subject talking about his Cervelo aero road benefit.
"For the aerodynamics, first of all the aerodynamics don't work best at zero degrees (head wind), but actually in slight cross winds. Secondly, people seem to have a problem with the comparison of small effects. The discussion of what is more important, aero or weight, is a silly one. We need to know about how much weight and how much aerodynamics we're talking about. Between an R-Series and S-Series frame, it's around 150g. On a 68kg rider and 7kg bike, that's 0.2% difference. On a pro's bike, it's 0% different as we can make both the R and the S bike at the limit of 6.8kg. So the effect of weight savings is small (in absolute terms already, never mind in comparisons with other effects). If your speed was completely linearly related to weight (so all your resistance is connected to weight, and nothing to anything else), this 0.2% would mean you would save 7.2 seconds per hour (0.2% of 3600 seconds). The same applies to acceleration, a 0.2% faster acceleration is not noticable. Yes, it is true that lower weight helps acceleration, and if you can drop 3kg, you will notice the difference (which of course is what has happened to bikes overall in the past 10-20 years, but that's not the difference between an aero and non-aero frame (that's only that 150g we talked about)."
"When you do the testing thoroughly, you notice not surprisingly, that the rider is the biggest factor (around 80%). So just like with the weight situation, the rider is the biggest chunk. The rest is then divided in wheels, frames, etc, etc. In the end, the
difference between a "normal" frame and an S2 is around 1.5% of the overall drag.
Not a huge amount, so it is easy to see why the engine is still the most important (heck, if it wasn't, do you really think Phil and I would support pro riders, instead of winning the Tour de France ourselves?)
So obviously, that 1.5% is not that much, but it's more than the 0.2%. And in most riding conditions, total aero related drag is much bigger than weight related drag, so it's much better to save 1.5% of a big number than 0.2% of a small number. "
I then- started this thread in 2009 in response to the above and white paper they had on aero versus weight-
http://forum.slowtwitch.com/...0cervelo%20;#2224872 "
So- comparing an aero frame like the S2 vs R3 saves 1.5% (let's assume bikes/frames weigh the same for this discussion)- does this mean that if a rider going 40 km speed on 'flat/rolling terrain at 300 watts on the R3 would go the same speed on an S2 at 295.5 watts (a savings of 1.5%)? Or is that 1.5% from just the frame drag- and if the body is 80% and the bike is 20%- is it really 20% x 300 watts = 60 watts on the R3 and then 60 watts x 1.5% savings = 59.1 watts needed on an S2: for a savings of .9 watts? by the way: .9 watts = 2-3 seconds over 40km." I posted the above question- because it just didn't seem like the hyped up frame would only save 2 to 3 seconds over 40km over their non aero frames. When I posted the question- I actually had an S3 on order and was slightly disappointed at the purported savings (or lack thereof). ------------------------------------------------------------------------
Gerard Answers my questions- yes- it is only a 4-5 watt savings of an aero road frame over their R3- and the savings in the pack is now 1-2 watts: roady
Feb 27, 09 20:00
Post #3 of 9 (1468 views)
Re: 1.5% savings from Cervelo means?.. Zinn- lightweight vs Aero [mlinenb] [In reply to] Quote | Reply
I certainly could be wrong, but when he says, it seems pretty clear that he means 'overall drag', including the rider. Obviously, the smaller the rider, the bigger the percentage. As I said on that thread, the difference is pretty small (and when you factor in sitting in a pack, where wind resistance is reduced 30-40%, that 4-5 watts becomes 1-2 watts).
Still, it all adds up--and most often the most critical moments in a race are whey you're getting the least draft.
As far as your other question, I suspect 2 things: the Cervelo road bike isn't nearly as aero as a P2/P3, and a round tubed bike is better than the worst TT frames (and almost all giant-tubed road frames). ------------------------------------------------------------
gerard
Mar 1, 09 18:04
Post #7 of 9 (1220 views)
Re: 1.5% savings from Cervelo means?.. Zinn- lightweight vs Aero [roady] [In reply to] Quote | Reply
In Reply To:
Roady Quote:
I certainly could be wrong, but when he says, it seems pretty clear that he means 'overall drag', including the rider. Obviously, the smaller the rider, the bigger the percentage. As I said on that thread, the difference is pretty small (and when you factor in sitting in a pack, where wind resistance is reduced 30-40%, that 4-5 watts becomes 1-2 watts).
Still, it all adds up--and most often the most critical moments in a race are whey you're getting the least draft.
As far as your other question, I suspect 2 things: the Cervelo road bike isn't nearly as aero as a P2/P3, and a round tubed bike is better than the worst TT frames (and almost all giant-tubed road frames). (End of Quote)
Gerard's Reply:
10 points. And to clarify, for us the "average" size rider is our test dummy.
______________
Gerard Vroomen
blog.gerard.cc
www.twitter.com/gerardvroomen ------------------------------------------------------------------------------------------
Now their white paper says this- which shows an S3 not an S2- but the savings are a lot more than his statements above: