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Bike Geometry and Ride

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We all have our own approaches that’s for sure. 😀

There is nothing wrong with blindly following “ride - adjust - thrash”, and I admit we are all doing that to some extent, but there is also nothing wrong with wanting to understand the trade offs in a deeper way. I’m not a bike designer, so I reached out to the people here to help me get a better understanding of what’s really at play when bikes are designed. What happens if I use a fork with lots of offset? Why do people care about head tube angle? Etc, it’s all here for the past 8 pages.

I can see some people are loosing interest, and I haven’t been doing a good job presenting what we’ve learned yet. For me at least, there have been some moments of enlightenment.

It’s ok if people bail on this thread to be honest. I’m not offended. The people that are interested will continue to contribute. I’m not making anyone read this. 😂

Some people want to look up at the stars at night and wonder ”what all them sparky things are?” and other people want to figure out how they formed and what that tells us about our own sun. Neither approach is wrong. Just different strokes for different folks.
 
@Miq measurements for my 1936 Snyder fastback klunker.

Also this diagram for how I measured from geometrygeeks.bike:
Screenshot_20230228_162532_Chrome.jpg


1936 Snyder fastback klunker. My fav klunker, compared to my others this better climber, more agile and capable of small drops except threaded headset gets loose and trusses twist.
20220524_173149.jpg

Wheelbase c-c, 41" (rear axle sits towards end of horizontal dropouts)
HT angle 70 deg
HT length 5"
Fork rake/offset, 2" (51mm), need to remove fork for proper measure, but close enough.
Fork trail?
Stack 20.5"
Reach 16.25"
ETT 23"
ST angle 71 deg
BB hgt 11“
BB drop 2"

I have a feeling my other klunks will have numbers to shed insight on ride feel and capabilities.
More to follow.
 
Thanks for all the data to chew on @J-wagon !

One thing I have been thinking about that has come up a few times is the idea of being in the bike and not on it. Each of my bikes has one of these feelings more than the other.

When you set up a bike for efficient pedaling, you are kind of stuck with whatever that relationship is between your butt and the bottom bracket. Your saddle has to be a certain basic height above the BB for your leg to extend almost all the way. So how can you lower your center of gravity (CG) with respect to the the wheels (axles) when your butt is already a certain height above the BB? Drop the BB with respect to the axles. Then your CG moves down between the axles more.

To me it seems like that feeling of being more IN the bike instead of ON the bike has to do with how high your center of gravity is above the axles. A few inches of BB drop can go a long way to helping lower your CG and make the bike easier to handle and "steer from the hips".

@J-wagon your fav klunker has 2" of BB drop. My CWC has 2" of drop and feels easy to handle. But my Columbia with 0 BB drop and higher BB height overall seems like I'm on top of the bike more. Not sure about @SKPC 's 21st Century Snyder but it sure looks like it has a couple of inches of BB drop too.

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The trade off is that your pedals get closer to the ground so they will hit in turns and on top of rocks more easily.

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@Miq makes sense to me that more BB drop, the more stable at speed. Converse, the less drop, more stable slow speed. Seems road bikes often high speed situations, so more BB drop. Bmx often more slow speed situations seem to have BB rise. Mtb involves high and low speeds, so BB drop in between.

Higher BB seems easier to pull manual / wheelie, like bmx. Perhaps your Columbia geometry high BB easier to do manual.

Each of my klunkers ride differently, I wonder how their measurements will stack up to my ride impressions...
 
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This site is really neat: Bike Insights The Cyclopedia section has comprehensive info on what we are discussing. Specifically they try to explain "Why does it Matter?" for each measurement. Their "Why does it Matter?" write up on BB drop is almost word for word what we came up with last night:

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I def want to play with their bike comparison tools and enter some bike info in. I'll post results when I get more than one bike entered...

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It’s a great thread for someone with no vintage frames and aspirations to build a few Klunkers to spank and shine. The respect is worth the read alone. Carry on !
 
Excellent that you examine BB drop/height in more detail. It's a dimension I would want to know on a bike I am unfamiliar with. As you say, less BB drop and a higher BB give you the ground clearance needed for rocks and obstacles. A lower BB and greater drop improves the handling on paved surfaces and allows you to build a taller frame while the rider can come off the saddle and set both feet down.

Bikes seeing greater paved road use would often have lower bottom brackets, even prior to WWII. The ballooners often had higher BB (less BB drop) to deal with the rougher use of youths and children. You'll sometimes have people note that a ballooner they buy appears to have a normal overall height to the top tube, but then it feels "cramped" when riding. The BB height/drop is why. From a klunker standpoint, you'll want to know for ground clearance purposes and think about the kind of trail you want to ride.

Even prior to WWII some bikes were marketed as having lower BB height (more drop being part of that) and therefore being suitable for paved road use and for use in traffic.
 
I def want to play with their bike comparison tools and enter some bike info in. I'll post results when I get more than one bike entered...
Cool site. I entered my 1936 Snyder fastback, had to take additional measurements. Here's the insight on my build. Also will compare klunker to my modern rigid mtbs...
1936 Snyder Fastback klunker geometry.jpg
 
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