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Old 04-28-2020, 11:05 PM
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ANAO ANAO is offline
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How does a compact geometry affect fit?

I've been wondering something.

With all else being equal, how does a compact geometry differ from a standard geometry specifically as it relates to the rider's fit and relationship to the machine?

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  #2  
Old 04-29-2020, 02:06 AM
mhespenheide mhespenheide is offline
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Quote:
Originally Posted by ANAO View Post
I've been wondering something.

With all else being equal, how does a compact geometry differ from a standard geometry specifically as it relates to the rider's fit and relationship to the machine?

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Ideally, it doesn't. In theory, the bottom bracket, saddle, and handlebars all stay in the same position. You're just sloping the top tube down, shortening the seat tube, shortening the seatstays, and lengthening the seatpost.

Here's a simple graphic:
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Old 04-29-2020, 02:16 AM
robt57 robt57 is offline
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IMO, particularly good for folks which bikes tend to be too tall standover when long enough and/or adequate stack.
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Old 04-29-2020, 05:39 AM
Peter P. Peter P. is offline
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Originally Posted by robt57 View Post
IMO, particularly good for folks which bikes tend to be too tall standover when long enough and/or adequate stack.
Agreed. That's why they're good for mountain bikes, where you may dismount hastily on dicey terrain. Otherwise you might bang your privates on the top tube. Ask me how I know...

My road bike is built with a compact geometry for just the reasons you mentioned above. I have long legs and a short torso. So I ride a smaller size with a shorter top tube to better fit, but the bars are too low. So I spec'd a sloping top tube so that I could get a slightly taller headtube to raise the handlebars.

One more possible benefit of compact frames are the longer seatpost extensions which result. If you're using a carbon seatpost, you may be able to take advantage of the slight flexing properties of some carbon seatposts as a little suspension.
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Old 05-14-2020, 08:58 PM
boywonder boywonder is offline
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No difference,just easier to mount or dismount . It does lower CG of bike though.
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  #6  
Old 07-18-2020, 01:17 PM
Behruz Behruz is offline
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A standard frame chainset will typcially have 53-39 chainrings whereas a compact will have 50-34. Also, the pro's are able to ride a much smaller bike with less weight.
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  #7  
Old 07-18-2020, 02:23 PM
Peter P. Peter P. is offline
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Originally Posted by Behruz View Post
A standard frame chainset will typcially have 53-39 chainrings whereas a compact will have 50-34. Also, the pro's are able to ride a much smaller bike with less weight.
A compact frame has no bearing on what size chainrings the bike can accommodate.
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  #8  
Old 10-26-2020, 12:13 PM
Ken_F Ken_F is offline
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Head Tube Difference

I've noticed on a few of the frames with compact geometry on EBAY and here that the head tube is large.

Is this rider specific or a new geometry philosophy?

Thanks
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  #9  
Old 10-26-2020, 09:02 PM
ERK55 ERK55 is offline
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By “large” do you mean the headtube is wide (ie 44mm) or tall?
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Old 10-27-2020, 07:05 AM
Peter P. Peter P. is offline
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Quote:
Originally Posted by Ken_F View Post
I've noticed on a few of the frames with compact geometry on EBAY and here that the head tube is large.

Is this rider specific or a new geometry philosophy?

Thanks
If by "large" you mean long, then it's possible.

With compact geometry frames, the head tube length can be pretty much anything.

Your point of reference should be, if this frame were a non-sloping top tube, what would the head tube length be? For instance, if you rode a typical 56cm C-C frame with a 55-56cm horizontal top tube, the head tube would be within a very narrow range. I'm sure there are web sites which could produce that dimension. From that number, you could determine whether the frame under consideration has a top tube in the length that is acceptable to you.
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Old 10-27-2020, 08:38 AM
dave thompson dave thompson is offline
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The term ‘compact geometry‘ is sort of misleading. It’s not really geometry; angles, etc., it’s the dimensions and layout of the frame.
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