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two retul reports, same bike, different frame stack/reach numbers. Whaaaa?
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I had a Zin report prepared after a fit a few years ago. In the meantime, I made lots of incremental changes (replaced the saddle, new bars, etc), and got a second Zin report to compare old vs new.

Here's a screenshot comparing the two, side-by-each. My questions:

-how could the frame stack and reach possibly differ across these two reports? And not just by a mm or two ... but by, like, 2cm each? That's like a different frame! I would get it if armpad stack or other things had changed, but frame stack and reach are absolute, aren't they? And these don't really rely on the Zin operator, do they?
-How do I translate this information into "correcting" the rest of the measurements?





Last edited by: davetallo: Feb 9, 17 10:44
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [davetallo] [ In reply to ]
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Problem with 3D measurements being out is that you don't know whether the error was at the BB or the HT.
If it's the BB - everything that is referenced from that point will be wrong.
If it's the HT then other numbers will be fine.

What is the correct XY for your frame?
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [davetallo] [ In reply to ]
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Totally normal. Bikes have a tendency to expand over time which explains how your bike has effectively become two sizes larger with a much steeper seat tube. It may be time to replace your cranks as those are likely about 230mm now.
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [cyclenutnz] [ In reply to ]
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cyclenutnz wrote:

What is the correct XY for your frame?

Good question. 517/438. So that makes report #2 the culprit.
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [Pooks] [ In reply to ]
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Pooks wrote:
Totally normal. Bikes have a tendency to expand over time which explains how your bike has effectively become two sizes larger with a much steeper seat tube. It may be time to replace your cranks as those are likely about 230mm now.

Does this control for similar time - related expansions in the measurement tools? I want to be clean in my instructions to recalibrate.

Longer cranks and pf600 ordered and on the way.
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [Pooks] [ In reply to ]
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I thought they did that now so you don't have to replace your shifting cables when they stretch, but only for mechanical shifting frames.
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Re: two retul reports, same bike, different frame stack/reach numbers. Whaaaa? [davetallo] [ In reply to ]
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Very good catch on the BB. This phenomenon is the primary reason for the ever increasing number of BB standards.
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