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PostPosted: Thu Aug 21, 2014 4:58 pm 
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Joined: Thu Jan 21, 2010 4:18 pm
Posts: 89
Location: phoenix, az
Cervelo and many others get knocked for their head tubes being too tall, particularly in the larger sizes, but i will say that Cervelo's geo is one of the more sensible in the smaller sizes, they actually decrease the reach as the sizes get smaller. Look at the plot for the tarmac/venge, all Specialized does in the smaller sizes is make the seat tube steeper to publish a shorter TT length and shorten the head tube to lower TT height or provide greater standover clearance. The 49(XS), 52(S), and 54(M) Tarmacs all have a reach within 1mm of each other.

More constant sloping or linear stack and reach plots seem to make a lot more sense, IMO. Maybe Cervelo's curve is rising a little too steep for the larger sizes, but these charts make me appreciate the Canyon, Trek, Cervelo, and Swift plots.


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Posted: Thu Aug 21, 2014 4:58 pm 


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PostPosted: Fri Aug 22, 2014 1:38 pm 
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Joined: Sat Mar 16, 2013 9:21 am
Posts: 54
You cannot directly compare the reach of two frames if the stack is not the same. Look at the handy "spacer" guide lines on the charts - reach decreases with added spacers. Once you've brought the handlebar on a 49 Tarmac up to the same height as a slammed 54 Tarmac, you'll have lost a lot more than the 1mm of reach you see on the chart.


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PostPosted: Fri Aug 22, 2014 5:11 pm 
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Location: phoenix, az
Then you are comparing effective reach to bars and not the true reach of the frame, as stack and reach was intended to measure. Additionally, if you're riding a 49cm tarmac you most likely do not want the same stack as a 54cm tarmac, so why would you compare one frame with a ton of spacers and another slammed?

To reiterate, reach is measured to the frame's ht center, so it should be compared that same way across all manufacturers and sizes. If I'm a smaller rider that desires a frame with less reach, Specialized does a poor job of accommodating that, especially if I'm also seeking a lower stack height.


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PostPosted: Fri Aug 22, 2014 6:49 pm 
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Joined: Wed Sep 26, 2007 1:57 pm
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Location: San Francisco, CA
I think the point Fiery was made is if I just look at stack-reach, and I want a certain amount of drop, I might naively assume I have the choice between two frames of essentially the same reach by adding spacers to the smaller one. Then it becomes a matter of whether I want the adjustability range and lower mass and perhaps increased stiffness of the smaller frame versus perhaps lower trail, less fork rake, stiffer front end of the larger frame.

But spacers don't maintain constant reach, so you need to change stem length at the same time. That's why I put the 73 degree lines. So a longer stack bike at the same reach is still longer.

A similar comparison: suppose I'm deciding between a Trek Madone H1 and a Cervelo R5. I see the reach on the Cervelo is less. Does that mean shorter stem? Yes, but not just because of the reach difference. Adding spacers to the ultra-low Trek will effectively reduce the reach.

It's just something you need to consider.

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PostPosted: Fri Aug 22, 2014 6:53 pm 
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Location: Bay Area
The simplest solution is to slam your stem regardless, HTFU, and stop using spacers.

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PostPosted: Mon Aug 25, 2014 6:10 pm 
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Joined: Thu Mar 08, 2012 11:43 pm
Posts: 562
KWalker wrote:
The headset cap is easily replaced though, right? Does the stock cap affect stack & reach?

It will just affect stack[/quote]

Not quite. Assuming a 73d head angle each 10mm of caps/spacers will bring the reach back by 3mm.


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PostPosted: Thu Aug 28, 2014 7:32 am 
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djconnel wrote:
I think the point Fiery was made is if I just look at stack-reach, and I want a certain amount of drop, I might naively assume I have the choice between two frames of essentially the same reach by adding spacers to the smaller one. Then it becomes a matter of whether I want the adjustability range and lower mass and perhaps increased stiffness of the smaller frame versus perhaps lower trail, less fork rake, stiffer front end of the larger frame.

But spacers don't maintain constant reach, so you need to change stem length at the same time. That's why I put the 73 degree lines. So a longer stack bike at the same reach is still longer.

A similar comparison: suppose I'm deciding between a Trek Madone H1 and a Cervelo R5. I see the reach on the Cervelo is less. Does that mean shorter stem? Yes, but not just because of the reach difference. Adding spacers to the ultra-low Trek will effectively reduce the reach.

It's just something you need to consider.

That's exactly it. People know their effective stack and reach. When trying to decide if a frame can be set up to fit a rider, simply looking at its stack and reach measurements is not enough, one still needs to do some trigonometry.


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PostPosted: Sun Aug 31, 2014 3:47 pm 
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Location: San Francisco, CA
New Cervelo S5 compared to Trek:

Image

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