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  #1  
Old 11-22-2017, 12:19 AM
adub adub is offline
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Stack/Reach the same on 2 frames with big Head Tube length difference?

Looking at purchasing a Stigmata with as close to the same Stack/reach as my C59 as possible. It mostly makes sense until I compare Head tube lengths;

Comparing the stack and reach between 2 frames (54s Colnago C59 vs. 56 Stigmata) the Stack is the same @ 582mm The reach is 3mm longer on the Stigmata @388mm, so basically identical S/R on these 2 frames.

Now the confusing part is when you look at the head tube lengths, the 56 Stigmata has a 12mm shorter HT than the 54s C59?? This is what is making me contemplate going with a larger Stigmata and running a 10mm shorter stem to avoid the 1cm extra spacer. The HT on the 58 Stigmata is 175mm, 3mm shorter than my Colnago HT.

They do not publish the head tube angle of the Colnago, could this be making the 12mm difference in head tube lengths yet having identical stack?

Any fit experts to offer some insight?
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  #2  
Old 11-22-2017, 12:49 AM
Andy sti Andy sti is offline
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The shorter head tube on the Stigmata is to compensate for the longer fork. The AC distance on the cross fork is much longer than the road fork. You need to shorten the head tube to maintain the same stack.
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  #3  
Old 11-22-2017, 09:25 AM
nooneline nooneline is offline
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There are a few things that can affect a difference in headtube length when bikes have the same stack. BB drop is one of them, fork length is another one, and yeah, headtube angle is another although the difference in length that would result from a 1 degree change is extremely small.

There's something about your post that doesn't make sense: you mention running a shorter stem to avoid using a steerer tube spacer. One is for reach, and another is for stack.

Sounds to me like you can just use the same stem/bar setup on your steerer to get your contact points within a few millimeters of each other. One thing to consider, though, is that since different bikes handle differently, you might wind up tweaking your contact points (and thus weight distribution) to hone in on how you want to ride the different bike.
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  #4  
Old 11-22-2017, 03:55 PM
adub adub is offline
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I mentioned the shorter stem to compensate for the longer TT if I went with the 58 frame. Shorter stem may even be a plus on a gravel bike.

Reviewing the Geometry again I'll be staying with the 56.

Thanks for the replies.
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  #5  
Old 11-22-2017, 07:37 PM
John H. John H. is offline
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fork length

As others have mentioned, fork length differs significantly-

Also- The stigmata runs slightly big in general- go with the 56cm.
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