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  #16  
Old 09-01-2019, 01:10 PM
ultraman6970 ultraman6970 is offline
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THanks for the picture. Im just perplexed... even if he is off like 5 cm from what lemond says, clearly the frame is off for a lot.

I do not know what to think... this dude is one of those points in that spreadsheet linear regression to calculate the saddle height which needs to be excluded from the sample data... totally off...

Trek and spech have tall front tubes right?
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  #17  
Old 09-04-2019, 12:58 PM
rigged rigged is offline
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Location: Toronto
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Been thinking on this topic a little more, reading up on bike fit and interested to know if the following is logic holds.

The recent trend is around reach and stack rather than seat tube length. Leaving reach aside, since stack is comparable across bikes, can I use stack to determine if the bike will fit well vertically?

For example, if I require BB to saddle length of 82 cm, and I assume 20 mm in spacers under the stem and a saddle rise relative to handlebars of 8 cm, then I would subtract 10 (cm) from 82(cm) to get the desired stack i.e. I would need a stack of 72 cm.

Does this figure? The stack seems way too hi and I cannot figure out why.
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  #18  
Old 09-04-2019, 07:38 PM
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fa63 fa63 is offline
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You are measuring saddle height along the seat tube, but stack is a vertical measurement. For example, at a saddle height of 82 cm and a STA of 73 degrees, the vertical measurement would be 78.4 cm. Using your simplistic approach, you would then need a stack of ~68 cm, which is still quite tall. Trek Domane in a 58 cm frame has a stack of 61 cm. Throw on 30 mm of spacers and a flipped up stem, and you are probably getting close.

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Originally Posted by rigged View Post
Been thinking on this topic a little more, reading up on bike fit and interested to know if the following is logic holds.

The recent trend is around reach and stack rather than seat tube length. Leaving reach aside, since stack is comparable across bikes, can I use stack to determine if the bike will fit well vertically?

For example, if I require BB to saddle length of 82 cm, and I assume 20 mm in spacers under the stem and a saddle rise relative to handlebars of 8 cm, then I would subtract 10 (cm) from 82(cm) to get the desired stack i.e. I would need a stack of 72 cm.

Does this figure? The stack seems way too hi and I cannot figure out why.
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  #19  
Old 09-04-2019, 07:45 PM
rigged rigged is offline
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Quote:
Originally Posted by fa63 View Post
You are measuring saddle height along the seat tube, but stack is a vertical measurement. For example, at a saddle height of 82 cm and a STA of 73 degrees, the vertical measurement would be 78.4 cm. Using your simplistic approach, you would then need a stack of ~68 cm, which is still quite tall. Trek Domane in a 58 cm frame has a stack of 61 cm. Throw on 30 mm of spacers and a flipped up stem, and you are probably getting close.
Excellent point fa63. I wasnt factoring in the angle of the seat tube. Thanks very much clearing that up..
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