Understanding Geometry
08-25-20, 05:16 AM
#1
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Thread Starter
Understanding Geometry
Ive only really taken an interest in bike geometry. Ive a back injury or two, which meant i just gravitated toward bikes where my position was less aggressive, more upright.
Id like to understand my choices a little more however, as my instinct is telling me that geometry has more to do with ride comfort, both long and short distance, and speed than bike weight.
Take my current bike for instance, Cube SL Road Race 2020
This bike is fantastically comfortable, just eats up the miles and is quick off the bat at traffic lights. Even though its handlebars are relatively wide, it feels very responsive.
Obvs its not going to be hitting crazy speeds but thats not its purpose.
Im interested in how this compares to something a little more oriented to speed and what are the key changes that really change the feel of a bike.
That question is not as specific as id like, but currently im unsure how to frame it better.
Id like to understand my choices a little more however, as my instinct is telling me that geometry has more to do with ride comfort, both long and short distance, and speed than bike weight.
Take my current bike for instance, Cube SL Road Race 2020
This bike is fantastically comfortable, just eats up the miles and is quick off the bat at traffic lights. Even though its handlebars are relatively wide, it feels very responsive.
Obvs its not going to be hitting crazy speeds but thats not its purpose.
Im interested in how this compares to something a little more oriented to speed and what are the key changes that really change the feel of a bike.
That question is not as specific as id like, but currently im unsure how to frame it better.
08-25-20, 05:35 AM
#2
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Here is a Cube "race" bike in the same 50cm size as your bike. Note the fork angle, headtube length, bb drop and chainstay length
for starters.
for starters.
08-25-20, 08:17 AM
#3
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Compared to a more upright riding bike, a faster feeling road bike will have 15-20mm shorter chain stays, 10-15mm more bb drop, a steeper head tube angle by 1-1.5 degrees or so, 10-20mm less trail, and lower stack height. A steeper seat tube by a degree or so is also common.
Small measurement differences, but they add up to a significant difference in feel.
Small measurement differences, but they add up to a significant difference in feel.
08-25-20, 09:23 PM
#4
Junior Member
Ive only really taken an interest in bike geometry. Ive a back injury or two, which meant i just gravitated toward bikes where my position was less aggressive, more upright.
Id like to understand my choices a little more however, as my instinct is telling me that geometry has more to do with ride comfort, both long and short distance, and speed than bike weight.
Take my current bike...is fantastically comfortable, just eats up the miles and is quick off the bat at traffic lights. Even though its handlebars are relatively wide, it feels very responsive.
Obvs its not going to be hitting crazy speeds but thats not its purpose.
Im interested in how this compares to something a little more oriented to speed and what are the key changes that really change the feel of a bike.
.
Id like to understand my choices a little more however, as my instinct is telling me that geometry has more to do with ride comfort, both long and short distance, and speed than bike weight.
Take my current bike...is fantastically comfortable, just eats up the miles and is quick off the bat at traffic lights. Even though its handlebars are relatively wide, it feels very responsive.
Obvs its not going to be hitting crazy speeds but thats not its purpose.
Im interested in how this compares to something a little more oriented to speed and what are the key changes that really change the feel of a bike.
.
The way I have learned frame geometry by the type of riding, and ride position that favor certain geometry. Criterium racing had geometry that dealt with cornering, like wheelbase and BB height for example. Tour racing geometry position riders for efficiency in wind, climbing, or downhill speed. Time trial favors geometry for aerodynamic riding position. In all cases comfort and handling is part of the trade space.
So intuitively to get a speed position, I imagine a long seat tube with short head tube to flattens your back. Add a steep seat tube angle puts legs over the pedals like a sprinter (recumbent bikes are not preferred for time trials). Shorter top tube and stem for an aero tuck.. Specified fork rake, wheelbase (chain stays), and wheel size would have to balance handling. There are rules of thumb and traditional setups if you stare enough at specs.
Lastly, I experience feel as proficiency, skill, conditioning, and ability to position myself appropriately for the task, given frame geometry (with adjustable seat position, stem or bar height, and crank length).
@msateglfr;
Notes small measured differences add significant feel. Alternatively, trying a beach cruisers, a mountain bike, or a kids bike and you’ll notice a different feel that is much about geometry.
