New cannondale SYSTEMSIX road frame!

Discuss light weight issues concerning road bikes & parts.
User avatar
themidge
Posts: 738
Joined: Fri Jan 13, 2017 4:19 pm
Location: Freeedooom!

by themidge

I'm so glad I ride a 54/56.. :D
:hello:
Cannondale Supersix 2008 (weight: 7.3kg)
B'twin Triban 540 (in bits)
Vitus "Benotto" 979 (weight: :? )
Pre-War Hetchins Brilliant (weight: it's a touring bike)

by Weenie


TobinHatesYou
Posts: 1528
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

wingguy wrote:
Tue Jul 17, 2018 8:03 am

I'm confused :noidea:

Thank you for your post, it's extremely informative - but I can't follow the logic. If 2-3mm is "nowhere near" the humanly noticeable difference in CS length, why are 405mm chainstays better than 410?

I suspect they are using the shortest chainstays they can get away with in combination with 25-28mm tires. If they want to officially clear >28mm tires, they may have to spec a longer chainstay. One benefits to shorter chainstays is less airflow separation around the seattube/rear wheel without increasing the profile of the seattube.

Hexsense
Posts: 481
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

I think weight balance is relative, chainstay length is a factor but rider position play a bigger contributor. I think crank length also.

A medium rider, 175cm tall using 172.5mm crank. If we assume this is a normal crank length relative to his height.
then
For a short rider, 165cm tall using 165mm crank. He is using a relatively long crank. Some stubborn at this height will refuse to use 165, but rather stick with 170 which is then very long relative to leg length. Long crank contibute to more forward position.
And a tall rider, 185cm tall using 177.5mm crank. He is using a relatively short crank compare to his height (and in reality, some may use even shorter). Short crank relative to height contribute to even more rearward seat position?

If we really want to scale everything at the exact ratio, I think we better start solving discrepancy from crank length first. And then work from there. Next place after crank length is the bb height, as it dictate by cornering clearance for a given crank length. Then from there we tune weight balance and handling. But does it have to be that equal? Most riders are not really that picky about exact set up.

TobinHatesYou
Posts: 1528
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

For crank lengths, I think the reality is most people are using cranks that are too long already. The longer the crank, the greater the hip flexion and the more closed your hip angle is at around TDC or 11 o'clock. Knee flexion is also affected. A shorter crank will of course force you to move your saddle slightly higher and more aft as well.

Someone who is 165cm should probably be on 150mm cranks. Someone 190cm closer to 175mm. This is of course a matter of preference more than anything and I am basing this on my own preference of 165mm cranks (178cm tall.)

Shorter cranks also allow for flexibility in frame geometry...more BB drop when necessary, fewer clearance issues with the DS chainstay, big-small chainlines (think Vector pod connectors,) etc.
Last edited by TobinHatesYou on Tue Jul 17, 2018 9:26 pm, edited 1 time in total.

bikesrdangerousmmk
Posts: 21
Joined: Thu Jul 30, 2015 3:54 am

by bikesrdangerousmmk

What’s the stem adjustability like?

DamonRinard
in the industry
Posts: 306
Joined: Fri Apr 29, 2011 8:32 pm
Location: Connecticut, USA

by DamonRinard

Hi bikesrdangerousmmk,

On the fork side, the Knot stem adjusts just like any normal stem: up and down with spacers. In fact the steerer/stem interface is 100% normal, you can even use other stems (and some SystemSix models do).

On the handlebar side, the Knot stem allows 8 degrees pitch adjustment so you can rotate your bars up or down as you like (within the 8 degree range). This 4-bolt cradle interface is only compatible with Cannondale Knot bars for now.

Because the bar and stem are separate (not a one-piece barstem) you can change stem length and bar width independently.
Stem lengths: 8 9 10 11 and 12 cm
Bar widths: 38 40 42 and 44 cm

Cheers,
Damon

Edited to add: All Knot stems install horizontal to the ground (with minor variation due to different HT angles on different sizes of course). -DGR
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

DamonRinard
in the industry
Posts: 306
Joined: Fri Apr 29, 2011 8:32 pm
Location: Connecticut, USA

by DamonRinard

Hi Calnago,

Just wanted to thank you for your post which inspired a good conversation about frame dimensions, fit & handling. This is one of the reasons I keep posting on Weight Weenies - the people here "get it" and can see through flimsy claims to what really matters and I appreciate that. Thanks also to wingguy, fa63 and others for your contributions to the discussion.

To address what riders can feel and what's important:
Some things riders feel aren't important, and vice versa: some things that are important, riders can't feel. I have two imaginary lists: the important list, and the feel list. The same bike attribute often ranks differently on the two lists.

While it's true riders can't feel the small differences in CS length we're talking about, that doesn't mean they're not important to performance. That's one of the reasons we choose 405 even if no one could feel the difference to 410: it's 5mm shorter, which means it's that tiny bit lighter and stiffer. (CS length is far down the important list compared to other frame attributes, but not entirely off the list.)

Also, before disc brakes, many, many great handling road racing bikes had 405mm CS (maybe since that was the Shimano minimum...). Disc brakes have their plusses and minuses, but we chose to keep as many plusses from rim brake bikes as possible, including nice 405mm CS in this case.


More on rider feel
We don't feel bike attributes very well; we're better at feeling differences in bike attributes. That's why back-to-back comparisons are so valuable: Riding bike A versus bike B can reveal a lot more compared to just riding one of them. So that may be why some riders can't name head angles after a test ride; if the difference exceeds the JND though, they should be able to say which one was steeper.

Time between rides is also critical: we minimize the time gap, hopefully to a matter of seconds, so the feel of bike A is still fresh enough in our memory to feel a potentially small difference in bike B. For this kind of testing we go to great lengths to prepare bikes in advance, even practicing the pit stop until we get the time gap down.

But if the time is too long, you can feel differences that don't exist! In my racing days we noticed this across the season: a bike we loved and felt perfectly at home racing all summer suddenly felt awkward and strange in the spring after riding the winter bike. I'm sure others here have probably experienced something like this as well. (Ironically, pros aren't really allowed to ride other bikes, so we amateurs have the chance for a much broader range of experience there compared to them!)


Aerodynamics
Aero drag definitely affects performance, even if it's hard to feel. This is a counterexample to CS length: it's really hard to directly measure the performance benefit of different chainstay lengths, but really easy (okay, expensive) to measure the performance benefit of different drag forces. Aero drag is super important for performance even if we can't always be sure we're feeling it. (That said, a big enough drag difference is really obvious to many riders who are coming off particularly high drag bikes.) Basically, aero drag is high on the important list, but low on (most riders') feel list.

Everyone?
Of course not everyone prefers shortest possible chainstays. But a differences of a few millimeters doesn't seem
like a strong argument for a preference for a significantly longer CS in my opinion. As a colleague used to say, if you're going to make a change, make an effin change. If longer is better, what's the perfect length? Don't fart around in the millimeters when no one can feel it and performance effects can't be measured. CS length differences we're talking about are low on the important list and low on the feel list.

And yet... every road bike Cannondale makes, people ask for short chainstays. The Slate for example has huge manufacturing challenges we've mastered in order to keep short 405 CS with the wider 650B tires. This bike handles awesome, especially compared to other fat tire road bikes that have longer CS, and is one of the reasons the Slate is such a great (all-)road bike. Same for 'cross bikes, gravel bikes. Maybe Endurance bikes are an exception, with our Synapse at 413mm. But in general, from what we see and hear and can measure, people prefer short CS.

Let me wrap up by addressing a few of your insights:

- I agree with you 100% that all the factors make up the bikes we ride. It's very hard to isolate one factor. I know, we've gone to great lengths in our testing to try to do it. I don't think there are many modern production bikes that could do it. Maybe a vintage steel frame with horizontal dropouts...

- Percent of what?
Fork offset differences are best referenced to fork offset (or trail), because offset functions as a lever in the pivoting steering system.
On the other hand, CS length differences are best referenced to wheelbase, because that's their pivoting system.

- Ha ha, I learned to ride a unicycle in 8 hours one spring day in about 1982 I think. I get what you're saying there. But the differences in CS length we're talking about are still insignificant.

- Quote: "So... may the best marketing win." end quote.

I hope you're getting to know me enough that it's not just a marketing competition. As an engineer, I think one of the most important things marketing can do is help inform riders about the real differences and benefits we've engineered. A well engineered design that no one knows about is virtually worthless. Toyota defines customer value with two elements: something the customer (1) knows about and (2) is willing to pay for. I'm on this board as an engineer to help with the first: to let readers know about the engineered value we hope we're adding to Cannondales. Yes, our marketing colleagues are super helpful in getting the message out. But I hope you can see from the effort we've put into the engineering and the white paper, etc. that it's not just fluff: the message is about the features we've engineered into the SystemSix (and all Cannondales) that help give riders the choice to decide whether or not they're willing to pay for them.

Cheers,
Damon
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

jlok
Posts: 596
Joined: Tue Jun 30, 2015 3:30 am

by jlok

Hi Damon, any chance that SystemSix to be sold with 12-speed groupset at Xmas time this year? Is the geometries ready for 12 or even 13-speed?
Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

DamonRinard
in the industry
Posts: 306
Joined: Fri Apr 29, 2011 8:32 pm
Location: Connecticut, USA

by DamonRinard

Hi jlok,

Only the models listed on Cannondale.com are planned currently, no 12 speed at the moment.

For 12 (or 13?) speed, the SystemSix is designed to meet nearly all the currently-defined requirements from the major component makers, including Campagnolo, so you could either build up a frameset or start with a complete SystemSix and change the components.

Cheers,
Damon
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

DamonRinard
in the industry
Posts: 306
Joined: Fri Apr 29, 2011 8:32 pm
Location: Connecticut, USA

by DamonRinard

fosen wrote:
Tue Jul 17, 2018 9:48 am
Awesome, thanks. So it is also possible to remove the DuraAce mechanical, and run for example Ultegra Di2 with internal cables, on the same non-hi Mod model? With the junction box in the frame on the downtube? Or maybe in the handlebar?
Yes, exactly. The Hi-MOD and carbon versions share the same molds, including all the cable routing details, so you can do exactly as you proposed.

The Di2 box fits in the SystemSix down tube as you've seen, and in fact it's the same Shimano part you can install in the handlebar. This also can work with the SystemSix.

Cheers,
Damon
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

istigatrice
Posts: 818
Joined: Sat May 12, 2012 8:32 am
Location: Australia

by istigatrice

Hexsense wrote:
Tue Jul 17, 2018 5:28 pm
I think we better start solving discrepancy from crank length first. And then work from there
Respectfully disagree because cranks don't "fit" like the rest of the bike does. It is the same in that it affects your angles in a similar stem length/frame reach and stack height do (e.g. a change results in a change in body angles), but what changing frames/stems/bars etc. doesn't affect is your gain ratio which is (apparently) super important for endurance based events (e.g. road cycling). The "major" crank lengths of 170-175mm give us a good trade off between bike fit (e.g. body angles) and gain ratio. Taller riders may want to go longer (as angles allow) but I'd suggest shorter riders won't want to go any shorter than 170mm. I'd suggest this is one area where the science hasn't quite caught up/described the full detail. For sprint events (maximal power) I think the trade-off doesn't matter too much, and this is indeed reflected in the literature

I know this is a thread about the Cannondale but wanted to go slightly OT because I hate this trend towards shorter cranks by oversimplifying it.

On the note of chainstay length: If it was such a big deal, I'd suggest that track bike dropouts wouldn't offer about 3-5cm of adjustment on the chainstay length. This is way more than 5mm. However, I do disagree with Damon that "shorter" (e.g. 405mm) chainstays are the way to go for road - I'd argue that you want the shortest chainstays recommended by Shimano (410mm), but my only good reason for it is to be able to use as many of the 22 gears as possible, rather than to do with handling (which I believe is a moot point anyway).

So my take is that I'd let things like crank length and chainstay length be dictated by function, before handling/fit. Use the front centre/trail for handling (set chainstays as minimum req. for good access to 22 gears) and adjust your handlebars (stack/reach) or saddle height to obtain an angle/fit suitable for your 'optimal' crank length. But I'm not actually designing bikes so :noidea:
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

yltman
Posts: 8
Joined: Tue Nov 21, 2017 12:50 pm

by yltman

Damon, could you please answer one more question

have you ever compared systemsix (and supersix) with older bikes from cromo which have thin tube profiles compared to bikes produced now
so what is the difference in cda/watts between these bikes?
if you haven't done this, maybe you could provide an estimate or run cfd to get them, that would be awesome

p.s. great to read a lot of answers from an engineer :beerchug:

jlok
Posts: 596
Joined: Tue Jun 30, 2015 3:30 am

by jlok

Thanks Damon. I was hoping for eTap 24- or 26-speed. Let's wait for it.
Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

DamonRinard
in the industry
Posts: 306
Joined: Fri Apr 29, 2011 8:32 pm
Location: Connecticut, USA

by DamonRinard

Hi yltman,

Seems like a question some wind tunnel test should have already answered, but I don't recall a clean head-to-head against a classic steel frame. There was one with two completely different bikes (old v. new), but so many other components were different (wheels, handlebar, etc.), it's hard to say much about the frame drag.

Cheers,
Damon
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

natiedean24
Posts: 377
Joined: Wed Jun 10, 2009 2:16 pm
Location: Austin, Texas
Contact:

by natiedean24

Is cervelo dead?


Sent from my iPhone using Tapatalk

by Weenie


Post Reply
  • Similar Topics
    Replies
    Views
    Last post