I've been learning lots about biking through these forums but I don't understand how to find the "right" geometry for me. If someone could give me a "bike geometry lesson" that would be awesome. How does each thing affect the feel and whats best for my type of ride (freeride - drops, jumps, ladders etc.)?
Bike Geometry
- Thread starter King*Cole
- Start date
The best place to start is to find what you are riding now and what you like and don't like about the bike.
There are always going to be people that tell you that you need a long top tube, shot chain stays, slack head tube, or whatever... but you may wind up liking something a bit different.
That being said, there are general guidelines as you have alluded to...
Head tube: slacker=stabilty, steeper= better response
Seat tube: slacker=comfort, steeper=pedal power
Top tube: longer=relaxed reach, shorter=flickabilty
Chainstays: longer=stabilty, shorter=better manuals,wheelies,flickability
BB height: higher=clearance, lower=stability
Wheelbase: longer=stability, shorter=flickability
Saddle height: above bars=aggressive, below bars=relaxed
Bar width: longer=leverage, shorter=clearance
Crank length: longer=leverage, shorter=clearance
But understand that comfort plays any important role. None of this means $#!+ if fit is wrong... and don't go by height alone. Just because you are 6'2" tall doesn't mean that your arms and legs are long. Perhaps you have a tall torso and stubby legs. In that case, you would want a shorter seat tube but maybe a longer top tube. If you do not fit into the average range, then you need to look at your own needs. That is why you may see taller riders on smaller frames or shorter riders with long top tubes.
There are always going to be people that tell you that you need a long top tube, shot chain stays, slack head tube, or whatever... but you may wind up liking something a bit different.
That being said, there are general guidelines as you have alluded to...
Head tube: slacker=stabilty, steeper= better response
Seat tube: slacker=comfort, steeper=pedal power
Top tube: longer=relaxed reach, shorter=flickabilty
Chainstays: longer=stabilty, shorter=better manuals,wheelies,flickability
BB height: higher=clearance, lower=stability
Wheelbase: longer=stability, shorter=flickability
Saddle height: above bars=aggressive, below bars=relaxed
Bar width: longer=leverage, shorter=clearance
Crank length: longer=leverage, shorter=clearance
But understand that comfort plays any important role. None of this means $#!+ if fit is wrong... and don't go by height alone. Just because you are 6'2" tall doesn't mean that your arms and legs are long. Perhaps you have a tall torso and stubby legs. In that case, you would want a shorter seat tube but maybe a longer top tube. If you do not fit into the average range, then you need to look at your own needs. That is why you may see taller riders on smaller frames or shorter riders with long top tubes.
I've been asking this formula for quit a long time thanks for this info it makes much more sense about how my bike should respond to for my set up.
here's my take on it. only a slight edit/expansion.
Head tube: slacker=stability/comfort on steep downhill, steer by leaning the bike. steeper= faster response, less effort going up hill, steer by turning
range: 64-72*
Seat tube: slacker=comfort, steeper=pedal power
range: 70's (usually close to H/A)
Top tube: longer=weight is always centered, greater stability shorter=flickabilty, greater range of motion in cockpit.
(watch out for horizontal vs actual TT measurements and how seat tube angle plays into horizontal TT)
range(horizontal): 19 (BMX)-25 (6',6" guy's road bike) inches
Chainstays: longer=stability at speed, shorter=better manuals,wheelies,flickability, better climbing traction
range: high 15's (crazy short 26" or norm 24") - 18 (full-on DH)
BB height: higher=clearance, lower=stability, lower center of gravity:better/snappier handling watch for static vs sag measurements and different tires will give different measurements
range: 12 - 15
Wheelbase: longer=stability at speed, shorter=flickability
range(inches): upper 30's- low-mid 40's
Bar width: longer=leverage, shorter=clearance, faster response
range(mm): 660-900
Crank length: longer=leverage, shorter=clearance
range(mm): 160-180
an inch diffrence in fork axle to crown height ~= 1 degree H/A and S/A, 1/4 inch BB height, minimal horiz. TT change
hope this helps
Head tube: slacker=stability/comfort on steep downhill, steer by leaning the bike. steeper= faster response, less effort going up hill, steer by turning
range: 64-72*
Seat tube: slacker=comfort, steeper=pedal power
range: 70's (usually close to H/A)
Top tube: longer=weight is always centered, greater stability shorter=flickabilty, greater range of motion in cockpit.
(watch out for horizontal vs actual TT measurements and how seat tube angle plays into horizontal TT)
range(horizontal): 19 (BMX)-25 (6',6" guy's road bike) inches
Chainstays: longer=stability at speed, shorter=better manuals,wheelies,flickability, better climbing traction
range: high 15's (crazy short 26" or norm 24") - 18 (full-on DH)
BB height: higher=clearance, lower=stability, lower center of gravity:better/snappier handling watch for static vs sag measurements and different tires will give different measurements
range: 12 - 15
Wheelbase: longer=stability at speed, shorter=flickability
range(inches): upper 30's- low-mid 40's
Bar width: longer=leverage, shorter=clearance, faster response
range(mm): 660-900
Crank length: longer=leverage, shorter=clearance
range(mm): 160-180
an inch diffrence in fork axle to crown height ~= 1 degree H/A and S/A, 1/4 inch BB height, minimal horiz. TT change
hope this helps
My favorite type of riding is exactly what you like, jumps, drops, etc.
I really really really like the way my Trek Session 77 handles this kind of riding. Here is the geometry (I have a small):
I really really really like the way my Trek Session 77 handles this kind of riding. Here is the geometry (I have a small):
r464 mentioned bar width without including stem length. long stems put you more over the front wheel and force you to stretch out. short stems put you more toward the back. beyond that, you need to consider how they work in conjunction with the bar width for turning. the attached shows how bar width and stem length impact the radius of the circle they turn around the center of the stem (the red dot). the bigger the circle, the more leverage you have, and the more you need to turn the bars to turn the wheel. you can get the same leverage with narrow bars and a long stem as you do with wide bars and a short stem. however, each combo feels different and changes your riding position. something to consider.
sorry for the crappy microsoft paint image, but you should get the idea.
sorry for the crappy microsoft paint image, but you should get the idea.
thanks for all your input this is very helpful!