Bike Forums

Bike Forums (http://www.bikeforums.net/forum.php)
-   Track Cycling: Velodrome Racing and Training Area (http://www.bikeforums.net/track-cycling-velodrome-racing-training-area/)
-   -   Gearing Question (http://www.bikeforums.net/track-cycling-velodrome-racing-training-area/920171-gearing-question.html)

Trackliche 10-31-13 09:31 PM

Holy cow. You guys are awesome. I can't wait to dig up a 45t ring.

TC

Jaytron 10-31-13 09:40 PM

Big big looks cooler though. Maximum street credz

Quinn8it 10-31-13 10:00 PM

Quote:

Originally Posted by Brian Ratliff (Post 16208663)
You are right, there is no reason one gear will feel easier than another if they are the same gear combination. Steady speed in either a big-big or small-small of the same gear ratio will take the exact same power and cadence.

ok- so we are actually in agreement?

that basically means that we agree that half of this perpetually repeated statement is wrong?
Quote:

50x15 would suit Time Trial/Pursuit riders more due to the larger chainring, that is slower to accelerate but easier to maintain your average cadence (pedalling rpm), whereas your cadence will be obtained quicker with the smaller 47x14 chainring setup as the smaller chainring enables a much quicker acceleration hence this technique is better for short distance/sprinters.
lets start disproving the other half! ;)

Brian, you clearly have a far superior grasp on the science behind your arguments about this- so can you break it down for the dumb dumbs (me)?

you are not taking the normal approach i hear argued, usually a simple "its easier to get on top of the gear when you use a small ring".

tell me if i have this wrong- but your theory is based on the system holding more energy, due to the fact that the chain in the small/small gear combo is moving faster relative to the chain in the big/big gearing?
i just cant see the tiny increase inertia of the faster moving chain having any noticeable effect when compared to the massive inertia of the wheel...

Also- i often hear that the small/small gear combinations are "easier to start".. can your Chain-Speed-Inertia theory be applied to a Standing Start?

if all this science is technically correct- but does not add up to any amount of gain on a bicycle- then using the science to justify your gear choice is a total cover up for what is obviously a decision made for other reasons...

So far the only compelling argument i have heard for Small/Small gearing is because Bobby says to do it.. that guy is a bad ass!

Baby Puke 10-31-13 11:46 PM

Word!
I think it's probably psychological. But even this can have an effect, as I'm sure we're all aware. If you THINK it's faster, there's a good chance it will be.

Velocirapture 11-01-13 06:03 AM

[QUOTE=Quinn8it;16209454]ok- so we are actually in agreement?

that basically means that we agree that half of this perpetually repeated statement is wrong?


lets start disproving the other half! ;)

Brian, you clearly have a far superior grasp on the science behind your arguments about this- so can you break it down for the dumb dumbs (me)?

you are not taking the normal approach i hear argued, usually a simple "its easier to get on top of the gear when you use a small ring".

tell me if i have this wrong- but your theory is based on the system holding more energy, due to the fact that the chain in the small/small gear combo is moving faster relative to the chain in the big/big gearing?
i just cant see the tiny increase inertia of the faster moving chain having any noticeable effect when compared to the massive inertia of the wheel...

Also- i often hear that the small/small gear combinations are "easier to start".. can your Chain-Speed-Inertia theory be applied to a Standing Start?

QUOTE]


I think that whats being overlooked here is the Steady- State vs 'getting on top of' / easier or harder to accelerate. Agreed, absolutely no difference in steady state; the same gear inches, the same speed, the same feel. its got to be.

But people are saying that getting these combos going is what differs, and that DOES make sense, because inertia is a big factor when CHANGING speed; when accelerating or descelerating. and so yes, these gear combos should also have a effect on the feel of a standing start.

e.g. a truck going at 100mph is going at same speed as a mini at the same speed. exactly the same. but its a hell of a lot harder to stop/ start or turn the truck, because it has more inertia (due to more mass).
extreme example, but the principle is the same

Brian Ratliff 11-01-13 08:52 AM

^^^
Exactly. We are talking about accelerating the gear when we talk about the differences. At steady state speed, the two gears will feel alike.

With the big-big, talking about keeping average speed easier, this is because the gear combo with the larger inertia will be less willing to change speed once you get there. Say you ride an outdoor track with an upwind straight and a downwind straight. The big-big combo will be easier to get through the headwind section because you and your bike will have more inertia and the bike will not slow as much into the wind.

Quinn8it 11-01-13 10:03 AM

Quote:

Originally Posted by Velocirapture (Post 16209794)
e.g. a truck going at 100mph is going at same speed as a mini at the same speed. exactly the same. but its a hell of a lot harder to stop/ start or turn the truck, because it has more inertia (due to more mass).
extreme example, but the principle is the same

there is no change in Mass.. more likely a reduction in mass, as you typically use a shorter chain in the Small/Small gear combo..

more like a Mini Cooper(2200lbs) going 40mph and Fiat 500(2100lbs) going 42.5mph... is the Fiat harder to stop? and by how much?

Quote:

Originally Posted by Brian Ratliff
With the big-big, talking about keeping average speed easier, this is because the gear combo with the larger inertia will be less willing to change speed once you get there

how much more inertia will a lighter (shorter) chain that is moving 7% faster have?

Quote:

Originally Posted by Brian Ratliff
Say you ride an outdoor track with an upwind straight and a downwind straight. The big-big combo will be easier to get through the headwind section because you and your bike will have more inertia and the bike will not slow as much into the wind.

Shouldn't we stay away from random variables like wind?
if the Big/Big gear combo really is easier to maintain and harder to accelerate- then you are likely at a disadvantage on the downwind straight- since you would resist the acceleration created by the wind on your back.. Probably a wash?

Brian Ratliff 11-01-13 10:24 AM

^^^
First: In the small-small combo, the chain is moving slower, as shown in prior discussion. Usually the big-big combo will use a longer chain. It does with my setup.

Second: If we are in a perfect world with perfectly steady speed and no wind or perturbances (i.e. maybe rollers? Even a smooth indoor track has banking if you aren't on the pole), then none of this discussion applies. But, as a track racer, I'm more than a bit interested in the perturbances as these things affect me, especially as my local track has the trifecta of bumps, bad transitions, and wind.

Quinn8it 11-01-13 11:12 AM

Quote:

Originally Posted by Brian Ratliff (Post 16210525)
^^^
First: In the small-small combo, the chain is moving slower, as shown in prior discussion. Usually the big-big combo will use a longer chain. It does with my setup.

Second: If we are in a perfect world with perfectly steady speed and no wind or perturbances (i.e. maybe rollers? Even a smooth indoor track has banking if you aren't on the pole), then none of this discussion applies. But, as a track racer, I'm more than a bit interested in the perturbances as these things affect me, especially as my local track has the trifecta of bumps, bad transitions, and wind.

ah yes! i got totally turned around... this stuff far exceeds my tiny brain

ok.. so:
big/big has more inertia due to faster chain speed and more chain mass, due to longer chain.
small/small has less inertia due to slower chain speed and less chain mass...

more inertia=harder to change speed (thanks wiki!)

my KMC D101 1/8th track chain has 93-links and a master (94 links). it weighs 13.5oz, set up for big/big
its likely that a small/small set-up on my bike would use a chain with 92 links.. probably 13.25oz..
and i think we agreed the speed difference was about 7% (once you corrected my math )

is that difference in inertia noticeable in the middle of the drivetrain? would it outweigh lightening something at the pedal? does this explain why sprinters dont wear socks? is it to lighten inertia in the system and make the bike easier to accelerate?

i assume that whatever the differences in speed/mass/inertia are created between the 2 different systems is tempered by the fact that the chain runs slack on the bottom side of the drive train..

and i assue differences, if any are not present at noticeable levels- for either bike racers or power meters to detect.. I cant imagine these tiny differences showing up compared to the massive inertia created by the rear wheel..

Brian Ratliff 11-01-13 11:37 AM

Again, as for actually time/performance gain, I don't think I can be persuaded that big-big vs. small-small amounts to anything measurable absent the athlete. But the athlete's body is extremely sensitive to small changes, and these small changes can make a performance difference.

Quinn8it 11-01-13 01:19 PM

Quote:

Originally Posted by Brian Ratliff (Post 16210809)
Again, as for actually time/performance gain, I don't think I can be persuaded that big-big vs. small-small amounts to anything measurable absent the athlete. But the athlete's body is extremely sensitive to small changes, and these small changes can make a performance difference.

so the difference is not measurable? but the athletes body senses it? despite cadence being the same, speed being the same, stop watch reads the same and power is the same? what exactly is the athlete sensing?

the earlier comparison to saddle height doesn't really work for me.

i recently tested out a new frame. on my first track day (after a few roller sessions) i sensed that my saddle slipped. i pulled in and confirmed that my saddle had in fact slipped. I was able to confirm this with a very simple measuring device called a tape measure.. I sensed the change- and was able to measure the change. about 1.5mm..

Brian Ratliff 11-01-13 03:18 PM

Quote:

Originally Posted by Quinn8it (Post 16211140)
so the difference is not measurable? but the athletes body senses it? despite cadence being the same, speed being the same, stop watch reads the same and power is the same? what exactly is the athlete sensing?

the earlier comparison to saddle height doesn't really work for me.

i recently tested out a new frame. on my first track day (after a few roller sessions) i sensed that my saddle slipped. i pulled in and confirmed that my saddle had in fact slipped. I was able to confirm this with a very simple measuring device called a tape measure.. I sensed the change- and was able to measure the change. about 1.5mm..

Wouldn't it seem unreasonable to expect measuring a 1.5mm change in saddle height with a stopwatch? Some people add 1.5mm to their ass every winter! Would you expect a change in kilo time be measured if you had a change of 1.5mm in your saddle and couldn't feel it? What if you changed brands of shorts and ended up with 1.5mm less padding? Would the change in your kilo time be the same as if, instead of changing shorts (and having 1.5mm less padding), you lowered your saddle by 1.5mm?

I didn't say we couldn't measure changes in drivetrain momentum or response. I am questioning whether it makes a difference with a stopwatch absent the athlete; say you put a set of electric pistons on the bike. But anything the athlete can feel, a 1.5mm change in saddle height, a slightly worn pedal cleat, a slight change in handlebar angle, or how the chain takes up slack, affects the athlete's performance because the athlete can feel it and it can mess with their head and their body mechanics. There's a lot of stuff happening under the skin. Optimizing your bike is not just about getting power from the pedals to the road, it is about getting power from the your body to the pedals as well.

Quinn8it 11-01-13 07:46 PM

Quote:

Originally Posted by Brian Ratliff (Post 16211482)
say you put a set of electric pistons on the bike.

that explains why i cant feel the difference.. I have Electric Piston Legs..
:)

Velocirapture 11-02-13 07:28 AM

Quote:

Originally Posted by Quinn8it (Post 16212050)
that explains why i cant feel the difference.. I have Electric Piston Legs..
:)


Nice!! :lol:


All times are GMT -6. The time now is 01:44 PM.