Turner added the stack and reach values to the Czar geometry chart at some point in the past weeks/months. In reviewing them, I see an inconsistency that I'm curious about.
For reach, the delta value from one size to another is identical to the delta value for the wheelbase. For example, moving from L to XL, the reach and wheelbase both grow by 13mm.
This is mathematically impossible, unless the headtube lengths were constant, or the head angle is varying from size to size, or the rear triangle varies among sizes (none of which is the case here).
If the reach for a size L is known, then the reach for size XL should be:
reach(XL) = reach(L) + [wb(XL) - wb(L)] - cos(headangle)*HTlength
But this doesn't hold true for any of the reach values shown in the geo chart. Admittedly we're talking about relatively small measurements here, on the order of 6mm or so. But if a value is listed in the chart, I expect accuracy. Three other frame vendors I checked all held true to the formula above.
Am I missing something?
I happened upon this while attempting to compute the reach/stack on the XXL as a delta to the XL.
On a "normal" frame one could compute the reach directly if all the other dimensions are known, but its not possible with the Czar due to the "unquantified" shaping of the seattube.
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