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Frame geometry and skidding/ back pedaling to stop

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Frame geometry and skidding/ back pedaling to stop

Old 08-15-10, 05:06 PM
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Frame geometry and skidding/ back pedaling to stop

So my first fixed gear was an se lager which has pretty relaxed road geometry. i have been riding my new vigorelli for over a month now and one of the big differences is how easy it is for me to stop using just my legs.

the lager i could skid but it was extremely difficult and i couldn't really slow down effectively using back pressure with my legs.

I'm relatively new to understanding road type bikes in general and geometry is a mystery to me as to why it makes such a drastic difference in performance. my knowlege really doesn't go past seat tube and head tube angle.

so is this pretty elemetary? has anyone else had experience with this? i just don't hear it mentioned much on these forums.
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Old 08-15-10, 05:09 PM
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Was the gear ratio the same on both bikes?
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Old 08-15-10, 05:24 PM
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46/16 for the lager. 48/17 for the vigorelli. that's one gear inch different. i don't know how substantial that is.
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Old 08-15-10, 05:43 PM
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Well that would help explain why its a little easier.
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Old 08-15-10, 05:45 PM
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That's almost two inches, which would make your skidding a lot easier.
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Old 08-15-10, 05:54 PM
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The actual difference is the much steeper seat tube.

Last edited by Kayce; 08-15-10 at 06:00 PM.
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Old 08-15-10, 05:57 PM
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it is a drastically easier to skid and to stop without skidding. skidding on the lager was nearly impossible. i can do seated skids with the vigorelli. there was no way i would ever go breakless with the lager and i've been breakless on the vigorelli with all the confidence in the world. (this is not a discussion on brakeless, we have plenty of that already)

i just can't believe it's all because of 1.5 gear inches.
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Old 08-15-10, 07:13 PM
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Dude, breakless??? OMG you're gonna die !
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Old 08-16-10, 12:14 AM
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You are absolutely right in your perception. And it is not because of the 1.5 gear inch difference. It is partly due to the difference in geometry but is also due to the fact that you have moved from cheap, heavy, flexy steel tubing to high quality, light, stiff aluminum tubing. Just as the frame accelerates faster due to the stiff light tubing (as it was intended to do on the track) it can be brought to a stop faster. Less weight, less inertia, less effort needed to stop. Stiffer chainstays, more of your energy is conveyed from the pedals to the rear wheel.
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Old 08-16-10, 09:40 AM
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For what its worth I made the EXACT same switch of gear ratios - 48/16 to 48/17 - and it made a huge difference I thought. After riding around on a somewhat high ratio, even a slight switch made a difference in my ability to skid and stop.
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Old 08-16-10, 11:29 AM
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so right now im at 39/16, i bought a 14t cog, so will it be easier to stop when i go 39/14?
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Old 08-16-10, 12:05 PM
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Originally Posted by Scrodzilla
Dude, breakless??? OMG you're gonna die !
I so badly want to unleash the spelling daemon in me.
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Old 08-16-10, 12:34 PM
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Oh, gimme a brake.
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Old 08-16-10, 12:39 PM
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Originally Posted by Scrodzilla
Oh, gimme a brake.
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Old 08-16-10, 01:10 PM
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Originally Posted by polobreaka
so right now im at 39/16, i bought a 14t cog, so will it be easier to stop when i go 39/14?
nope.
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Old 08-16-10, 01:13 PM
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Originally Posted by ianjk
nope.
oh i read the thread wrong. so when adding teeth, will make it easier to stop/skid.
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Old 08-16-10, 01:20 PM
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Originally Posted by polobreaka
oh i read the thread wrong. so when adding teeth, will make it easier to stop/skid.
Adding teeth to the cog will make it easier to stop, subtracting teeth from the chainring will have the same effect.
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Old 08-16-10, 01:21 PM
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Originally Posted by polobreaka
oh i read the thread wrong. so when adding teeth, will make it easier to stop/skid.
As you increase the size of your cog, your gear ratio drops, which will make it easier to pedal/stop.

https://www.sheldonbrown.com/gears/
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Old 08-16-10, 05:46 PM
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Originally Posted by amor fati
You are absolutely right in your perception. And it is not because of the 1.5 gear inch difference. It is partly due to the difference in geometry but is also due to the fact that you have moved from cheap, heavy, flexy steel tubing to high quality, light, stiff aluminum tubing. Just as the frame accelerates faster due to the stiff light tubing (as it was intended to do on the track) it can be brought to a stop faster. Less weight, less inertia, less effort needed to stop. Stiffer chainstays, more of your energy is conveyed from the pedals to the rear wheel.
Assuming the frame ways about 1/5 or 1/6 of his body weight, I am sure the momentum doesn't change much just because he has a slightly lighter frame.
=====
P=mv
=====
It's gotta be the geometry and maybe the different gear ratio.
maybe even a slight difference in geometry makes a huge difference in performance?!
Just like a small surgical correction to an ugly nose, can make a huge difference to a persons appearance.
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Old 08-16-10, 05:47 PM
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Ever try running uphill?
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Old 08-16-10, 05:59 PM
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Dude, common. Running uphill is more difficult because the angle between direction of motion and gravity is greater, not because your momentum is bigger.
Momentum is actually smaller when running uphill, assuming you're slowing down.
Again:
P=mv
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Old 08-16-10, 07:10 PM
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Physics makes us all its b***ches.
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Old 08-16-10, 07:17 PM
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Originally Posted by Vixtor
Physics makes us all its b***ches.
sig quality
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Old 08-16-10, 07:19 PM
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Umm, alright. I was thinking more along the lines of distance running. The accepted technique is shorter stride, similar to a person naturally running uphill. Vague metaphor to bicycle geometry, I know.

(P=mv)/flying squirrel
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Old 08-16-10, 07:33 PM
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if your squirrel can fly, then we probably don't need to worry about the angle anymore ...
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