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Re: Official Speed Concept Owners Thread [paxfobiscum] [ In reply to ]
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Here's what is going on:


The interface between the bar and stem is moving up and back along the steerer axis, just as if you were adding spacers under a standard stem. A given length & rise (in degrees) of stem results in an effectively shorter cockpit the higher you move it up.


The "reach" part of the numerical designations for the SC RXL stems is derived not from a horizontal distance between the headtube and the effective bar center, but a direct line between those points. So, no, it's not Reach as understood here at Slowtwitch, and perhaps shouldn't be labeled as such. Why did we?


Because the numbers associated with each stem are an attempt to put their function - that of taking up space between the frame and bar - into a more familiar context. People are used to thinking of stems in terms of length and (degrees of) rise. Rather than list each unique angular measurement, we chose to show direct-line length and vertical rise.


I can see, then, why the stem labels can be confusing. It's not that the #'s are incorrect per se, but they are not necessarily helpful...and if the user tries to use them at face value to derive the chart logic on their own they can end up with paradoxical results. The original 2-D working names for each stem (low-near, medium-far, etc) were really - IMHO - the more accurate representation of what each one was: the macro-adjust structure filling in the vertical and horizontal space between the headtube and the bar. They don't really need numbers any more than the frames do, so long as the logic built into the fit chart is grounded in physical/numerical reality and points you to the most appropriate answer for your fit needs.


Thanks for digging into it the way you did. It'll spark some discussions internally on how we present that chart going forward.


Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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In Reply To:

Thanks for digging into it the way you did. It'll spark some discussions internally on how we present that chart going forward.


I would highly encourage you folks to stick with the strict "X/Y" nature of the reach/stack nomenclature. You spent a lot of effort explaining pad and bar stack and reach in that .pdf, and to then "revert" back to "stem length and angle" on a part that really is just another "X/Y" locator is fairly confusing IMHO (edit: especially when you call it "reach" when you mean "length"). Then again, the stack and reach contribution of each stem will be different depending on the frame size due to the varying head tube angles...so maybe using stack/reach isn't possible to "name" the stems...hmmmm.

I agree, the "descriptive" names are probably clearer, just as the XS, S, M, etc. frame size names are used. As long as the chart gives you the final touchpoint locations (i.e. pad bar stack/reach) then all should be good.



http://bikeblather.blogspot.com/
Last edited by: Tom A.: Jun 1, 10 13:44
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Eureka! OK, I got that quite clear now. Thanks Carl. As always your inputs have been quite reliable and much appreciated.

Paul

p.s.
Did you guys use ceramic bearings for the BB30 bottoms on the SC?
I refer specifically to SCs equipped with Ultegra cranks.

Thanks.

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Re: Official Speed Concept Owners Thread [paxfobiscum] [ In reply to ]
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9-series SC's are BB90, and 7-series are BB86.5...no BB30. No ceramic bearings used for any test purposes, nor are any stock spec.


Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Oops my bad. I meant BB90. Thanks anyway.

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Re: Official Speed Concept Owners Thread [paxfobiscum] [ In reply to ]
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No worries. Turns out I was wrong on the ceramic bearings as well...the 9.9 comes with them stock.


Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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In Reply To:
The most direct comparison of an SC bar & stem vs a UCI-legal setup with comparable adjustability (steerstub plus RXL basebar/RXXXL clip-ons) on the production version of the bike showed a nearly constant offset out to around 12.5deg yaw and a slight convergence thereafter. Very much like that seen between the TCT and OCLV versions of the bike in the white paper charts.

Thanks Carl. So, would it be safe to say that those interested in the fastest UCI-legal bike should be focussing on the TCT curves instead? (On the assumpiont that TCT = SC w/ UCI-legal bars.)
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Re: Official Speed Concept Owners Thread [wsrobert] [ In reply to ]
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I've been hearing that stock built 9.9's have been showing up at bike shops around my area (Upstate NY). Just wondering if anyone has picked one up yet? Pictures?

Has anyone who ordered via P1 heard anything more about their estimated arrivals?

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Re: Official Speed Concept Owners Thread [Andrew Coggan] [ In reply to ]
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Hard data only supports a shape-wise comparision of the 7-series (TCT) & 9-series curves as a general indicator of how a steer-stub-equipped 9-series SC is likely to perform. Equivalency of offset magnitude doesn't (necessarily) follow.



Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Hard data only supports a shape-wise comparision of the 7-series (TCT) & 9-series curves as a general indicator of how a steer-stub-equipped 9-series SC is likely to perform. Equivalency of offset magnitude doesn't (necessarily) follow.


No, it doesn't necessarily follow - but based on wind tunnel tests of bicycles (w/ and w/or riders) fitted with 3T Ventus bars versus bars comparable to the Bontrager RXL bullhorns used on the TCT, it appears to me that much, if not all, of the difference between the SC and TCT could simply be due to the former's non-UCI legal basebar.
Last edited by: Andrew Coggan: Jun 1, 10 12:55
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Re: Official Speed Concept Owners Thread [Andrew Coggan] [ In reply to ]
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No argument. I only wanted to reinforce for other casual readers that my affirmative answer only applied to curve shape. Otherwise they might also assume the magnitudes were the same when, in fact, using the 7-series vs 9-series comparison this way is probably conservative owing to the differences below the stem (frontal area, brake integration).


Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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In Reply To:
No argument. I only wanted to reinforce for other casual readers that my affirmative answer only applied to curve shape. Otherwise they might also assume the magnitudes were the same when, in fact, using the 7-series vs 9-series comparison this way is probably conservative owing to the differences below the stem (frontal area, brake integration).

Probably? Don't you have the data?



http://bikeblather.blogspot.com/
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Re: Official Speed Concept Owners Thread [Tom A.] [ In reply to ]
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In Reply To:
In Reply To:
No argument. I only wanted to reinforce for other casual readers that my affirmative answer only applied to curve shape. Otherwise they might also assume the magnitudes were the same when, in fact, using the 7-series vs 9-series comparison this way is probably conservative owing to the differences below the stem (frontal area, brake integration).


Probably? Don't you have the data?


You just took the words right out of my mouth. :-)

EDIT: In this post, Carl implies that a direct comparison does not exist:

http://forum.slowtwitch.com/...post=2849798#2849798

whereas this post implies that it might:

http://forum.slowtwitch.com/...post=2846627#2846627

Perhaps a comparison has been made, but it doesn't live up to Trek's standards? (I.e., both bikes tested on same day, etc.)

Either way, I still think the bars could have a lot to do with things...
Last edited by: Andrew Coggan: Jun 1, 10 13:44
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Carl, et. al., I posted this in its own thread, but since there is a lot of fit discussion here and I'm hoping to get some help, maybe I'll get lucky here. I'm trying to become a Speed Concept owner, but don't know what size to become the owner of. Thanks to anybody who can be of help. Here is what I wrote in the other thread:

Quote:

I'm trying to figure out which size Speed Concept 7 would be best for me. I read through Trek's Speed Concept fit and sizing guide, but most of is about the Speed Concept 9 because of its unique front end. (By the way, there is not a shop around here with a good tri fitter, but I am very comfortable with my current position, which I have tweaked during years of trial and error and lots of reading on Slowtwitch, measuring, and videotaping.) I know that the SC 7 is more flexible fit-wise because you can just stick a different length/rise stem on it, but I'm between a medium (54 cm) and a large (56 cm) and was hoping maybe Carl or others with experience could help me out.


Here are the numbers from my current setup, measured as shown in Trek's Speed Concept fit pdf .

My current frame is a 54 cm Cervelo Eyre Tri (650c), with lots of seatpost and a few headset spacers (it was a long and low frame and I'm pretty long-legged for my height).
Just the frame's measurements are:
Frame Stack: 480mm
Frame Reach: 440mm

And here are the measurements to the contact points, which is what should really matter here:
Elbow Pad Stack: 624mm
Elbow Pad Reach: 472.5mm
Reach to front of base bar: 668mm
Base Bar Stack: 524mm - 564mm (since the base bar isn't flat, those are the numbers to the flat part of it and to the end where the brakes insert)
Saddle Height (from center of BB): 776mm
Saddle Setback: 5mm

Any help would be very appreciated.
If those numbers don't get me anywhere, does somebody have the stock elbow pad stack and reach numbers for the 7 series? I know this is tough because stems change everything, but if I could see what comes stock on it (what the stem length and rise is, and what Elbow Pad Stack and Reach that creates, I could do some math.
Last edited by: nilloc: Jun 1, 10 13:45
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Re: Official Speed Concept Owners Thread [Tom A.] [ In reply to ]
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Do we have data from pairs of runs on different trips with different setups which I could point to in support of this statement? Yes. Does making the connection given those conditions result in a statement which stays on the scientific side of the ledger? Not so much as I'd prefer. I'm not trying to equivocate...I'm trying to stay out of trouble.


And I see AC has cottoned onto the gist this post already. Knew I could count on you guys.



Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Tom A.] [ In reply to ]
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This is why I'm getting the 7 series base model. In the last week I picked up a jet disk and stinger 9 front wheel for under 1k. Used Ventus run 600 bucks right now. if I was so inclined I could put on Zipp chrono cranks and the total price wouldbe less than the base model 9 series. And much more aero.
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Do we have data from pairs of runs on different trips with different setups which I could point to in support of this statement? Yes. Does making the connection given those conditions result in a statement which stays on the scientific side of the ledger? Not so much as I'd prefer. I'm not trying to equivocate...I'm trying to stay out of trouble.


And I see AC has cottoned onto the gist this post already. Knew I could count on you guys.

Aaah...I see...got it. But, is there any data from another setup that was consistent across both trips that could be used as a "standard" to compare against? I guess that's getting back to my comment earlier about having a "control" configuration, no? ;-)

BTW, this brings up something I've been thinking about since the statement was made that you guys ONLY like to present data that's taken on the same day. Why is that? Is the repeatability of the measurements really that poor across separate days? If so, care to share (or speculate even) why that might be? I'm trying to imagine something that wouldn't be able to be calibrated out...and I'm drawing a blank.



http://bikeblather.blogspot.com/
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Re: Official Speed Concept Owners Thread [Tom A.] [ In reply to ]
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Same day is a slight overstatement...same trip is our standard. Occasionally we may conduct a duplicate run on separate days within the same trip, but generally only if we feel the need to investigate something we see in the data which is not easily explained by an inadvertent setup error.


As I've mentioned before (in the white paper thread), we always try to establish some continuity to our last trip...but not necessarily across all trips. In the case of the comparisons which sparked this particular discussion, those two trips were separated by a third one.


Carl

Carl Matson
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Same day is a slight overstatement...same trip is our standard. Occasionally we may conduct a duplicate run on separate days within the same trip, but generally only if we feel the need to investigate something we see in the data which is not easily explained by an inadvertent setup error.


As I've mentioned before (in the white paper thread), we always try to establish some continuity to our last trip...but not necessarily across all trips. In the case of the comparisons which sparked this particular discussion, those two trips were separated by a third one.

My mistake...same trip...got it :-)

But, again, doesn't it make sense to have some sort of "calibration rig" so that you establish continuity across ALL of the trips?



http://bikeblather.blogspot.com/
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Re: Official Speed Concept Owners Thread [sentania] [ In reply to ]
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"that will make it a tough sell to the wife."


Where is this place that one may sell (and presumably buy) wives?

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Re: Official Speed Concept Owners Thread [wsrobert] [ In reply to ]
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Just put the $$$ down on a 9.9 in the white/grey/red/black today. Supposed to be here later in the week, I can't wait. Now I really need to get to work on the big ebay garage sale to get rid of old bikes/parts/etc... to help offset the cost of this beast. Nobody had better pass me in my next race or I'm going to be ashamed...
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Re: Official Speed Concept Owners Thread [TriBriGuy] [ In reply to ]
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wow that came out wrong <I guess>

;)


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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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Carl

Really appreciate you responding to all of the requests for info in relation to the Speed Concept!!!

I have read your response in relation to the REACH/RISE numbers of the SC RXL stem. I understand that your numbers in the Fit Chart are not directly related to STACK and REACH (as those terms are used commonly on this site) - No problem.

However, I still would have thought that as the stem length increases that would also result in an increase in the base bar reach. From the chart it seems that this is not correct. For example, with the Medium frame the base bar reach is 643 using the 50/10 stem, yet with the longer 60/45 stem the base bar reach is actually reduced to 633, this trend continues with the longer 80/75 stem which has a base bar reach of 623.

I understand that the angle of the head tube will result in the reach decreasing as the stack increases (given the same stem length), however, i would have thought that an increase in stem length from 50 to 60 to 80 would have resulted in a net increase in the base bar reach numbers. Is this correct? Perhaps i need to go back to my trigonomtry text books!!

Cheers
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Re: Official Speed Concept Owners Thread [potos] [ In reply to ]
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The confusion lies in what's behind the #'s of the stem designations. If you go back a little in this thread I think you'll find a related discussion.


EDIT: note how the stack (2nd #) is increasing much faster than the straightline measurement from pinch band center to effective bar center (1st #) in the three stems of your example. If you derive the reach by considering those #s to be one side and the hypotenuse of a right triangle, respectively, you'll see how those stem reaches actually decrease by roughly 10mm at a pop despite going "up" in size.


Carl

Carl Matson
Last edited by: Carl: Jun 2, 10 8:35
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Re: Official Speed Concept Owners Thread [Carl] [ In reply to ]
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The takeaway, everyone, is that the published pad stack and pad reach numbers ARE correct. If you don't like the numrical designations for the stems, just think of them as "low-near," "low-far," etc.



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