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Bike Geometry and Ride

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Miq

Cruisin' on my Bluebird
I am starting a new discussion on bike geometry stemming from some of the discussion in this post. I am going too far off the original topic, so I'm starting this more general discussion of any bike geometry.

I am not a frame/bike designer so I'd like to start with making sure I'm measuring correctly and calling these measurements by the correct terms. Can you guys please let me know if these are correctly defined and of any interest to this topic? What other measurements should we be talking about? Are some of these less influential?

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I have these measurements for the 49 CWC Klunkmaster Deluxe shown above and for my 48 Columbia Cruiser.

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I took the angle measurements with a cell phone app that I zero'ed out on the ground.

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The rest of the measurements were taken with a tape measure and eyeballs. It was not exact but maybe +/- 1/2" on most longer distances.

I'll start putting together a table with the info. I hope some people can take some measures of their bikes too to add to the table and discussion.

@scott1race, @bloo @GTs58 @Schwinn Sales West @Headset Guy @Xlobsterman @Sportyworty @J-wagon @Porkchop & Applesauce please join in this discussion too if you would like to. @SKPC I'm hoping you can join us here too since you have already taken many measurements of your builds and have lots of experience in the differences in their rides. Anyone interested, please join.

One thing I read about that doesn't make sense from the descriptions I've read and pictures/drawings I've seen is Fork Trail. The rake makes some sense from the descriptions in the other post here and pics @Xlobsterman posted there, but Fork Trail is not making sense to me.
 
It sounds to me like you are trying to start with a level table. Many times, we are talking about the same things, but by using different terminology it's makes it difficult to follow the discussion. I think you might want to re-visit some of your terms before the topic gets going. Headset guy gave a great source, with a diagram in his post, it would be a good "universal" starting point.

John
 
Hi John, I now see the link @Headset Guy linked to at Calfee. It has great info. I will add pics for Rake and Trail to our thread. I think the rest of my drawings match. I'm not specifically calling out "front center". Haven't seen that one before. I've been getting confused at this blog.

Hi @J-wagon. Thanks for hopping in.

Other things that don't make sense to me yet.

Some of the measurements are based on the seat post height. But that is totally dependent on the size of the rider setting up the bike. Seems like every bike has some adjustment of the "geometry" or a range of possible geometries.

Shouldn't we be talking about the height of the grips vertically from the center of the seat bolt as well as distance from the grips horizontally to the center of the seat bolt? That makes a big impact on how your weight is distributed on the frame and how it feels.
 
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WHEEL BASE.......... OK
HEAD TUBE ANGLE........OK
HEAD TUBE LENGTH.........Not an important measurement unless you are replacing a fork and need to match a steerer tube.
STACK...........I've never heard of it before. I don't see how it would be important due to the differences in seats.
REACH............Never heard of it.
EFFECTIVE TOP TUBE LENGTH...........Never heard of it. it's more dependent based on the seat tube angle.
Should add, TOP TUBE LENGTH.........The distance Center to center of head tube and seat tube.
BOTTOM BRACKET HEIGHT..........OK (Note your tire sidewall height will make this number vary between different bikes)
BOTTOM BRACKET DROP.........OK
Should add, FORK TRAIL............use the diagram listed by Headset Guy.
Should add, CHAIN STAY LENGTH

I think this would be a start.
John
 
WHEEL BASE.......... OK
HEAD TUBE ANGLE........OK
HEAD TUBE LENGTH.........Not an important measurement unless you are replacing a fork and need to match a steerer tube.
STACK...........I've never heard of it before. I don't see how it would be important due to the differences in seats.
REACH............Never heard of it.
EFFECTIVE TOP TUBE LENGTH...........Never heard of it. it's more dependent based on the seat tube angle.
Should add, TOP TUBE LENGTH.........The distance Center to center of head tube and seat tube.
BOTTOM BRACKET HEIGHT..........OK (Note your tire sidewall height will make this number vary between different bikes)
BOTTOM BRACKET DROP.........OK
Should add, FORK TRAIL............use the diagram listed by Headset Guy.
Should add, CHAIN STAY LENGTH

I think this would be a start.
John
Thank you John

My main question I’m trying to ask is I assume road bike, and clunker are on opposite ends of the spectrum, and Cruisers are somewhere in the middle, but would a more laid back head tube be better for a road bike or a klunker? Longer wheelbase vs shorter better for a road bike or a clunker? Plus the other performance effecting measurements.
 
Hi John, I now see the link @Headset Guy linked to at Calfee. It has great info. I will add pics for Rake and Trail to our thread. I think the rest of my drawings match. I'm not specifically calling out "front center". Haven't seen that one before. I've been getting confused at this blog.

Hi @J-wagon. Thanks for hopping in.

Other things that don't make sense to me yet.

Some of the measurements are based on the seat post height. But that is totally dependent on the size of the rider setting up the bike. Seems like every bike has some adjustment of the "geometry" or a range of possible geometries.

Shouldn't we be talking about the height of the grips vertically from the center of the seat bolt as well as distance from the grips horizontally to the center of the seat bolt? That makes a big impact on how your weight is distributed on the frame and how it feels.
I think every dimension is important, but it gets a little confusing.

I think you should break it up into two different areas. #1 would be those measurements that are built into the frame/fork by the frame builder and that are not adjustable without a Saw-z-all.

#2 would be the dimensions that are rider adjustable by seat post height, seat clamp fore and aft adjustment, handlebar and stem fore and aft, as well as height adjustments.

John
 
I think every dimension is important, but it gets a little confusing.

I think you should break it up into two different areas. #1 would be those measurements that are built into the frame/fork by the frame builder and that are not adjustable without a Saw-z-all.

#2 would be the dimensions that are rider adjustable by seat post height, seat clamp fore and aft adjustment, handlebar and stem fore and aft, as well as height adjustments.

John
I see. Thank you. I’m not very concerned with the second part of the measurements. Yes I understand they are important, but they are more just to aid in the comfort and posture of the rider correct? I do own a saw-z-all and a welder…🤣. I would never dare on anything built before 1960 though.
 
Thank you John

My main question I’m trying to ask is I assume road bike, and clunker are on opposite ends of the spectrum, and Cruisers are somewhere in the middle, but would a more laid back head tube be better for a road bike or a klunker? Longer wheelbase vs shorter better for a road bike or a clunker? Plus the other performance effecting measurements.
Yes, all of the measurements play with each other. But before we start analyzing how to make frame geometry adjustments, we need to establish the rules (terminology) for the discussion, or we will be talking about different things.

John
 
The Calfee site has a terminology definition at the bottom of their page that would be a good start for our discussion.

It's best to not try and reinvent the wheel, this is a 100 plus year-old topic.

It should be interesting.

John
 
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