New cannondale SYSTEMSIX road frame!

Discuss light weight issues concerning road bikes & parts.
TobinHatesYou
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by TobinHatesYou

willmac wrote:
Fri May 17, 2019 5:47 am
Tobin, I’m not going to get into an argument but at my saddle height, if you’re red line that you’ve drawn, vs the actual design calculations is wrong, which is highly likely as that photo may not be perfectly square, then you will get significantly wrong numbers. One degree is worth nearly 15mm so I will take the design engineers numbers rather than some work done in paint on a laptop somewhere

I mean you just replied, so you're continuing an argument. Look it's simple, the photograph depicts a real bike, and yes I measured the roundness of both wheels to confirm that the bike is on a plane perpendicular to the FoV. The geometry chart depicts...nothing...it's a drawing. The circle on the seatpost is nothing more than a metal lug for the clamping mechanism. I don't know why you keep talking about it. It's obviously not even in the same spot on the 15mm post.

Image

Image

Given that the depth of the seat tube is consistent across all sizes, the setback perpendicular to the seat tube will be consistent on all sizes. Yes, the horizontal setback will change with the STA, but that's beside the point. The seatpost is labeled as a 25mm setback post because it is set back 25mm perpendicular to the STA. The additional setback of the ST relative to the BB-c will also always be the same on all sizes. I just prefer the Trek way of reporting the setback of the seatpost...as a value relative to the line drawn through the BB-c at STA. In other words, the Cannondale "25mm" setback post should be listed as a 38mm setback post, especially since it can't be used on any other bike. Likewise it would be inane for Trek to call its 25mm setback post a 50mm setback post just because the clamp center is 50mm aft of the center of seatpost.

Got it?

by Weenie


willmac
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by willmac

I’m leaving this conversation.

TobinHatesYou
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by TobinHatesYou

willmac wrote:
Fri May 17, 2019 9:19 am
I’m leaving this conversation.

I’m glad you realized you were wrong.

Discodan
Posts: 96
Joined: Mon Oct 16, 2017 2:55 am

by Discodan

TobinHatesYou wrote:
willmac wrote:
Fri May 17, 2019 9:19 am
I’m leaving this conversation.

I’m glad you realized you were wrong.
Personally I don’t have the time or desire to waste emotional energy on being angry at everyone on the internet. I’m curious; are you actually that pissed off at the world or is it sport for you?


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Dan Gerous
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by Dan Gerous

Using catalog photos to take measures will never be precise... There can be lens distortion but you'd be surprised how much of these are just made up in Photoshop before the bikes are actually available.

Bluechip
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Joined: Thu Nov 12, 2015 2:04 am

by Bluechip

Tobin, what is the size of the pictured bike? At what angle did you use for your red line or did you just run it parallel to some part of the seat tube? I measured it at 76° (simple protractor). In the modern age of bikes with unusual shaped tubing does a traditional seat tube angle really have any meaning? How would your red line exercise translate to a Cervelo S5?

DVR
Posts: 15
Joined: Tue Jun 05, 2018 5:48 pm

by DVR

willmac wrote:
Fri May 17, 2019 9:19 am
I’m leaving this conversation.
Good move :thumbup:
Thanks again for your contribution. Looking forward to my systemsix with the 15mm setback post.
Cannondale SuperSix EVO HM eTap
Cannondale SuperSix EVO HM Disc Ultegra
Cannondale SystemSix eTap AXS
Colnago C60 eTap
Pinarello Dogma F8 eTap

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

by TobinHatesYou

Discodan wrote:
Fri May 17, 2019 2:02 pm

Personally I don’t have the time or desire to waste emotional energy on being angry at everyone on the internet. I’m curious; are you actually that pissed off at the world or is it sport for you?

You could ask him the same question. He picked the fight and kept it going, and then announced loudly he was done. I’m just making sure.

Dan Gerous wrote:
Fri May 17, 2019 3:18 pm
Using catalog photos to take measures will never be precise... There can be lens distortion but you'd be surprised how much of these are just made up in Photoshop before the bikes are actually available.

Well, do you see lens distortion? Do the dimensions of the photographed bike look wrong or obviously composited? Connecting the metal lug for a saddle rail clamp bolt with the BB-c on a line drawing is less precise because it makes no sense. That metal lug has no purpose other than to provided a pivoting threaded interface in a carbon seatpost. It’s position is arbitrary based on the setback of the seatpost and the design of the clamp.

On the other hand, the 38mm setback I estimated based on the photo (pixel peep it) is close to refthimos’s own measurements on a real bike. This is probably not a coincidence.

Bluechip wrote:
Fri May 17, 2019 6:46 pm
Tobin, what is the size of the pictured bike? At what angle did you use for your red line or did you just run it parallel to some part of the seat tube? I measured it at 76° (simple protractor). In the modern age of bikes with unusual shaped tubing does a traditional seat tube angle really have any meaning? How would your red line exercise translate to a Cervelo S5?

I drew multiple lines, one point to point and one vertical, then rotated 16.1deg counter-clockwise. I made the latter layer/object invisible since the point to point one was pixel-perfect for the purpose of the photo.

STA has no importance in practical application other saddle positioning, and that can be adjusted with various setback posts. There is just one point I am making, the seat tube has ~13mm of setback from the BB-c in SystemSix (on an axis perpendicular to the STA.) On my Madone the ST is actually set-forward a couple of millimeters. I just think the listed setback on a seatpost should be relative to the BB-c and not relative to its own center axis.
Last edited by TobinHatesYou on Fri May 17, 2019 8:41 pm, edited 1 time in total.

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Dan Gerous
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by Dan Gerous

So someone actually measured it on a real bike? Why fighting over it and trying to both come up with flawed ways of measuring it for 3 pages then? :|

TobinHatesYou
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by TobinHatesYou

Dan Gerous wrote:
Fri May 17, 2019 8:32 pm
So someone actually measured it on a real bike? Why fighting over it and trying to both come up with flawed ways of measuring it for 3 pages then? :|

Because the whole reason I measured it on the photo was to confirm refthimos’s claim. When he said the setback was closer to 40mm, that made me go hmmm. Turns out he was pretty much spot on.

Then of course willmac jumps in with weird thoughts about meaningless metal lugs and now we’re here.

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Dan Gerous
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by Dan Gerous

I see, I got lost because the argument lasted so long! :mrgreen:

But I agree listed setback on a seatpost should be relative to the BB-c and not relative to its own center axis, not for round after market seatposts obviously but definitely for seatposts specifically designed for a particular frame like the SystemSix...

TobinHatesYou
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by TobinHatesYou

Dan Gerous wrote:
Fri May 17, 2019 8:41 pm
I see, I got lost because the argument lasted so long! :mrgreen:

But I agree listed setback on a seatpost should be relative to the BB-c and not relative to its own center axis, not for round after market seatposts obviously but definitely for seatposts specifically designed for a particular frame like the SystemSix...

I'm not sure there needs to be a "seat tube offset" measurement on a geometry diagram, though it wouldn't hurt.

To be honest, after a pause for thought it was obvious that the effective setback was a bigger value because the SystemSix's STA across all sizes is relatively steep compared to other bikes. In refthimos's case, he is coming from a 56cm SuperSix with 73.5deg STA and 25mm setback post to a 56cm SystemSix with a 73.9deg STA and "25mm" setback post. If the post was centered on the BB, his saddle would have to be placed farther back on the SystemSix post. Of course he indicated the opposite, that he needed to slam his saddle forward on that post instead. That can only be explained by the base amount of offset in the seat tube itself.

floriansantana
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Joined: Thu Dec 25, 2014 8:57 pm

by floriansantana

What I find really annoying is, that measurements for the SystemBar and the Knot stem are really inaccurate. I ordered my SystemSix with a 110 mm stem and a 40 mm bar only to find out that the stem is effectively a 130 mm stem and the bar is effectively 37 mm at the levers (even when rotated slightly outwards).

Since I had them already mounted and everything my dealer does not want to exchange them even though the measurements are way off from what I wanted.

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Dan Gerous
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by Dan Gerous

Your dealer should have been able to give you more info beforehand, for the bars at least...
Screen Shot 2019-05-22 at 10.13.53.png

bikesrdangerousmmk
Posts: 99
Joined: Thu Jul 30, 2015 3:54 am

by bikesrdangerousmmk

What are people's general thoughts on the knot wheels, specifically the internal nipple construction and only having 20 spokes on the front disc wheel?

by Weenie


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