I was very happy to read the definitive answers on weights for the S5 frames posted in the forum by webmaster. However, I am getting different answers about the stiffness and vertical compliance on the various frames being offered.

Some online reviews claim that the stiffness is identical across the frames as they go up, and others claim that the stiffness increases as you go from Basic- Team- VWD.

Does the vertical compliance remain the same across the range or do the TEAM and VWD frames get more vertical compliance as you go up?

Will someone give me a straight answer on both of these please?

Thank you for your time and insight,

-D

 Do you have a local Cervelo dealer?  Great resource

 Yes I have, it's been a couple weeks with no response.

Conventional wisdom tells us that a stiffer material has less elasticity.  That would mean that a stiffer frame, would feel not only more rigid, but also a bit more harsh due to less deflection of the frame material. That being said, depending on the layup, type of carbon fiber weave and resins used you could probably optimize the ride quality...  that part I'll leave up to the Cervelo engineers to answer, because only they know what's under that shiny paint.

From what I've read, vertical compliance is a fine balance between frame design, type of material and how it is used. In addition, your wheel type, tire choice and air pressure will likely help you achieve the best possible ride for any given frame.

I'm sure the engineering team that worked on the S5 considered stiffness and vertical compliance in the design process and the manufacturing stage, especially since this was the bike that was meant to be the successor to the S3.  Cervelo, likely produced a range of frames that feel fairly equal in terms of stiffness and compliance.  However, the S5 seems to have been focused on its aerodynamics first, with the other qualities more of a price option passed on to customers with different budgets.

Back to stiffness and compliance though, frame design, which is the same for all three would have been the starting point, but more importantly the type of carbon and the layup/orientation of the material on the frame would be the final step to accomplishing their targets for weight, stiffness, compliance, and of course, price.  If all the reviews are subjective and you can't test ride them all, you are going to have either go with your gut or get a direct answer from Cervelo Senior Engineer, Damon Rinard.

The three questions I would ask myself would be ...Do I want the lightest frame? ...Do I want the cheapest frame? or ...Do I want a black or white frame?

 So wait....you emailed your dealer?  Or you walked in and talked to them and it's been a couple of weeks since they called you back?

Last night I received two different replies from two different dealers after spending some more time on the phone and calling non-local dealers.

Will a Cervelo representative, engineer, etc. please get me a straight answer to my 2 questions?

Thank you.

Demonic1

While I am not an engineer, I will do my best to address your question.  The straight answer is that the difference between the S5 versions is weight.  The stiffness remains the same and we do not have a definitive test for Vertical Compliance. 

The question of Vertical Compliance is a tough one to answer.  In my opinion, what some one is really looking for when asking about Vertical Compliance differences is an indication of how the different frames will "feel".  I understand that question completely as I would want to be sure that the bike will be comfortable before spending the money and the time riding.  The problem I have with Vertical Compliance is that I am not certain that the measurment of deflection tells the whole story.  Is more Vertical Compliance really better?  At what point does increased Vertical Compliance start to have a negative effect on how the frame 'feels'? 

Different bikes have different characteristics; there is no question about that.  There are many factors that contribute to the overall 'feel' of the bike and each rider's response is subjective.  At this point all I can say is that I have been around the block on a S5 VWD and I can't wait to get one for myself.  Realistically though, I think I will end up on a team frame.

I know it is not the exact answer that you were looking for but I hope that it helps you out. 

 Thank you David, that was very helpful.

Realistically, I'm looking at a basic frame (wish it came it black) and a pair of good wheels with wider rims (Velocity A23, HED C2 or maybe Zipp 101s) due to the 23cm tire limit.

So I was wondering if I should spend the money on a Team frame for more stiffness/ vertical compliance differences and live with the stock wheels.

What it sounds like is that I should go with the basic S5 build since the stiffness is identical and nice wheel /  tire combo for any perceived ride quality issues.

Thank you again. I really appreciate it.

After chatting with our engineering department, I think I should post a clarification.  It is not accurate to say that we do not have a definitive test for Vertical Compliance.  In fact, this is something that is relatively easy to measure.  However, we do not treat this test as a definitive answer to the question of ride quality.  Remember; the frame is just one part of the whole bike + rider system.  All of the parts that make up the system play a role in the characteristics of the ride. 

The bottom line is nothing but a ride will give you a feel for a bike.

Demonic1:

... due to the 23cm tire limit.

Is the S5 limited to a maximum of 23 mm tires? There was a twitter that I saw (and maybe misinterpreted) that referenced 25 mm.

Cervélo @bdcheung - the S5 will take up to a 25mm tire

30 Jun

Some 25C tires *just* fit. Other 25C tires are taller and can hit the down tube! (These are probably the ones with anti puncture belt and lots of tread rubber.) A nice handmade 25C tire fits, depending on the tire maker's idea of how big a 25C should be...

Hi Demonic1,

Maybe I can answer your question directly.

The bottom bracket stiffness and torsional stiffness are the same between all S5 models: S5, S5 Team and S5 VWD, which are all 12% stiffer than the S3. There is a short statement to this effect in the S5 White Paper (linked in the upper right corner of the S5 splash page here: http://s5.cervelo.com/ ).

The weights do get lighter as you go up, as you've already mentioned.

What isn't mentioned in the White Paper is that the vertical compliance is also the same for all S5 frames. As you may have also heard, it's true that the vertical compliance of the frame is a minor contributor to total vetical compliance of the bike. *All* double triangle road frames (if they don't actually have suspension) are many times stiffer than other components in the load path. Tires (even at 8 bars or 120 psi) are the big softies, but also remember the saddle and bars, etc. are typically softer as well.

That said, the S5 has an engineered shape and carbon layup specifically designed to tune the right amount of vertical compliance (too much undamped compliance can lead to occasional excess rebound that can e.g. unexpectedly spring you off the saddle). The most obvious shape affecting vertical compliance is the brake-shielding seat stay shoulder, which curves in from the outside toward the surface of the seat tube. This curve, and the specific fiber type and orientation in this area, together provide an indirect load path between the bump on the ground and your body on the saddle. I encourage you to give an S5 a test ride when you can. The effect is subtle but real. Be sure to check the tire inflation pressure.

Here's a CFD image I borrowed from the White Paper showing the curved seat stay shoulder I'm talking about (as well as some surface pressure colors and velocity stream lines):

Of course we've probably all heard by now the aero drag is also the same for all S5s: 9 Watts less than the S3 (at 40 km/h or 25 mph).

Hope this helps clear things up.

Cheers,

Damon Rinard, Cervelo Engineer