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  #1  
Old 06-04-2021, 05:10 PM
bridgestonedude bridgestonedude is offline
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Join Date: Feb 2021
Location: San Diego, CA
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Making small bike fit well using longer cranks

At 6ft with long legs/short torso, I fit well on a traditional road bike (level top tube) with about a 58cm c-c (60cm c-t) seat tube and a 56-57cm top tube.

There's this one 56cm square road bike I'm looking at where the seat tube is 56cm c-t, so it'd have much more saddle-bar drop than I'd like.

If I usually ride 170mm cranks, could I make this bike work well for me fit-wise if I just substituted 175mm cranks in? Or would that not really change the fit much considering it'd only let me drop the seatpost around .5cm?

Just wondering if it's a common thing to make one-size small bikes fit better along the seat tube using a longer crank.
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  #2  
Old 06-04-2021, 06:38 PM
Peter P. Peter P. is offline
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No. You don't adjust the crankarm length to make the bike fit.

Crank length is selected for leg length and riding preferences.

Keep looking for a proper fitting frame.
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  #3  
Old 06-05-2021, 04:03 PM
bridgestonedude bridgestonedude is offline
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Thanks -- that confirmation is what I needed to resist the bike. Have to remember that much as a deal it is, if it doesn't fit well it's not worth it.
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Old 06-05-2021, 09:40 PM
Upcountry Upcountry is offline
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I'm a bit confused as to how you're correlating seat-tube length to saddle-to-bar drop...

A shorter seat-tube on the bike will mean that you have more seat-post exposed above the seat-tube of the frame, but that has no impact on the position of the handlebars. But seeing as you mentioned horizontal top-tubes, I'm assuming that you're expecting a shorter head-tube as well, and that's where you're getting deterred? Depending on your stem length, you might be surprised at how much the angle of the stem can have on the stack height(which is directly related to your desired saddle-to-bar drop). For example, on a 120mm stem you're looking at about 12mm of difference by going from a -6 degree stem to a 0 degree stem... There are also always spacers....

My takeaway would be that I'd always pick the bike based on my smaller dimension... Meaning in your case, I'd size the bike with a top-tube to fit.
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  #5  
Old 06-06-2021, 01:02 AM
bridgestonedude bridgestonedude is offline
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Thanks, that's a good to consider as well. Correct, I'm talking about a traditional, quill-stemmed, horizontal top tube bike. I know I can always get a higher rise stem to reduce saddle-bar drop but I'm not a big fan of that look aesthetically (and performance-wise the flex is not very confidence-inspiring). But your point makes me remember those 0 degree Ritchey Force quill stems that look pretty nice and can be useful for adding more handlebar rise without exposing too much quill. Hmm...
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  #6  
Old 06-06-2021, 07:42 PM
giordana93 giordana93 is offline
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I almost posted a flip answer last night ("no" written in all caps, no caps and in a couple of languages...) but refrained. Still, it's a terrible idea, and a bike that doesn't fit isn't a bargain at any price, certainly not something that would be fixed by a crank less than 1/4 inch longer. Also would warn against buying a bike on looks alone before it is set up for you. If you end up with a jacked up stem or saddle pushed outside the norm, it will not only look goofy, but probably handle poorly too.

Same advice we always give: figure out your contact points, meaning 1) saddle height and set back; and 2) reach and drop to the handlebar. Everything else follows from that: top tube length, seat tube angle, head tube length which are all fixed for a given frame. Notice I didn't mention seat tube length. Most people can fit on 2 or 3 different frame "sizes" if only the seat tube is considered. You should be more concerned with top tube and head tube lengths, as well as seat tube angle, to hone in on a suitable size. What would you change or keep about your current ride? If you're perfectly happy with it, get a good understanding of how to measure and duplicate those numbers on a different bike. There is leeway between sizes and geometries, but also some lines that shouldn't be crossed.
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  #7  
Old 06-07-2021, 01:13 AM
bridgestonedude bridgestonedude is offline
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Thanks, I haven't gone as far as to measure saddle setback and reach so I should probably do that as I get ready to invest in a nicer bike. I've based my fit preferences just from my experience riding different sized frames (again--all traditional, level top tube frames, which I prefer).
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