Originally Posted by
topflightpro
It's not just about stack and reach.
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Also, bike sizing differs by company. One brand's 56 may be another's 54. So, while your endurance Topstone has a similar stack and reach to the racier Cannondale, that could just be due to how the two companies size their bikes.
You last paragraph is the best reason for stack and reach to exist- it normalizes what frame sizes are called. So yes while isnt just about stack and reach, you cire a good reason for those measurements to be heavily considered.