let's say you're getting a new bike and you want to replicate your position from an old bike. assuming the handlebar geometry is the same (same bar reach, etc.), what you need to start with is values for HX/HY. you can either direct-measure HX/HY, with a sici XY tool for example, of you can calculate it by taking your old bike, calculating the rise and run of the front end with the stem calculator, adding that to the frame's stated stack and reach.

what you might do then is go to this calculator. you know the HX/HY you want to achieve. you're changing frames, so, you put in the stack and reach of the new frame. this will give you a different HX/HY. keep sticking in new values for stem length, stem pitch, spacers, until you get the same HX/HY as your old bike. voila, you now know the stem and front end config to put on the new frame to match the position of the old frame.

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Dan Empfield
aka Slowman

Thanks Dan. So I calculated my HX/HY for the old bike, check, done. Added the rise and run from the stem calc to the frame's stated stack and reach. This is the HX/HY I want to achieve on the new bike.

I'm confused to the next part, specifically the part in red. Are you saying I input my calculated HX/HY into the bar to head tube calculator. Then repeat the whole process using the new frames stated stack/reach and playing with stem length, pitch, spacers until HX/HY is the same. I'm thinking I'm screwing something up.

Thanks again

No, you're right. Take your new frame stack and reach and play around with stem numbers in HxHy calculator until you get the stem you need to reproduce your HxHy numbers

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

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