Singlespeed & Fixed Gear - gear nerds

question: my old road conversion ran 42/14. my new pista rocks 48/16. both are 81 gear inches. so why does it feel like the pista's a tougher gear to crank (even with 5mm longer arms)? Shouldn't it be the same? What would happen if they were on the exact same bike? This is a more hypothetical question than practical.

Note: realistically I'm chalking it up to a month of not riding plus two weeks of holiday cheer. That or the pista's cursed.

jeff

larger front gear = less torque. and less torque will make it harder to push or get started.

there's a reason why shimano made the dura ace 10 track group way back in the day...interestingly, that reason is the same reason it was banned by the UCI not long after it was introduced....

IN BEFORE THE GOOGLE AD-BOT!

IN BEFORE THE GOOGLE AD-BOT!

In before pigbike.

The best part is how serious he looks.

I like truvativ cranks and wanted to get an ss model in a low chainring flavor like 32 or 33 - like the Stylo SS, but I notice they only make them in 172.5 and 175's whereas I'm quite comfortable with my 170's... shame. This has very little to do with anything... but... this is what happens when you follow pig bike boy.

larger front gear = less torque. and less torque will make it harder to push or get started.


Uhh....WHAT?!?

Something similar to that statement might be true if it weren't negated by the cog.

then why is a smaller chainring and cog that has the same gear inches as a larger chainring and cog easier to push?

excluding gear ratios...i've notice that smaller ring/cog configurations with exact ratios are easier to push than their larger counterparts...

like, say a 3:1 with a 14:42 is easier to push than a 3:1 with a 16:48....it should take the same effort to push because they're the same ratio...and yet?

if you push with a lever that is longer in relation to the size of the chainring, it will be easier to push. longer lever = greater rotational force. rotational force=torque.

The only difference I'm aware of is that with smaller cogs (same gear of course), the chain wears faster and is more likely to break. This is due to the mathematics of the thing, turning moments and torque etc, that means each tooth on the cog is excerting a bigger force on the chain; this is amplified by the fact that fewer teeth are engaging the chain, meaning the load of the entire chain-to-cog interface is spread over a smaller area of teeth.

If that makes any sense :beer:

you should go tell that to the BMX kiddies who like to run ratios like 25/9 nowadays....damn kids! why can't they just stick with 44/16 like everybody else did before them!?

ha ha (evil laugh).
this is exactly what I'd hoped for a post with talk of exerting ratios, rotational glayven, and torque whoosets. added bonus: pigs. seriously though the larger chainring less torque thing makes sense to me. I'll have to hit up Yojimbo's and check it out.

jeff

78 gear inches = 78 gear inches

The best part is how serious he looks.

I like truvativ cranks and wanted to get an ss model in a low chainring flavor like 32 or 33 - like the Stylo SS, but I notice they only make them in 172.5 and 175's whereas I'm quite comfortable with my 170's... shame. This has very little to do with anything... but... this is what happens when you follow pig bike boy.
I've got a set of 32 tooth Style SS cranks in 170. Chuckbikes had them before chirstmas and santa brought me a set. Don't know if they still have them or not. They're the older square taper variety, I think the new ones are ISIS.

IN BEFORE THE GOOGLE AD-BOT!

Damn, the bar has been raised, the gauntlet thrown

seriously though the larger chainring less torque thing makes sense to me. I'll have to hit up Yojimbo's and check it out.

jeff

The larger chainring/less torque thing is true. But it's negated by the larger cog in the back so the net amount of torque is exactly the same.

Maybe the tires are flat on your pista.

question: my old road conversion ran 42/14. my new pista rocks 48/16. both are 81 gear inches. so why does it feel like the pista's a tougher gear to crank (even with 5mm longer arms)? Shouldn't it be the same? What would happen if they were on the exact same bike? This is a more hypothetical question than practical.

Note: realistically I'm chalking it up to a month of not riding plus two weeks of holiday cheer. That or the pista's cursed.

jeffIf all things are equal (including cranks), they will be the same.

Punch up Sheldon's Gain Ratio (http://www.sheldonbrown.com/gain.html) calculator for the real scoop.

is a 52/13 good?

could be something to do with rotating mass/momentum.

but i doubt it. might just be that the cranks are the wrong length for your legs.

fssb
sparky

Stoped by my bike shop and they not only said bigger chain ring does NOT equal less torque, but they kinda laughed good-naturedly about how others thought so.

It looks like OneTinSloth and Billig are flying solo (or tandem) on this one.

Bombusben- yeah my tires are inflated, and I took my lock off too just in case that was it. :p

I did however lower my seat like 2 cm and that seemed to help a lot: the placebo effect rules. I wish people would just tell me everything I buy is carbon kevlar adamantium so I'd be uber-fast

jeff

It looks like OneTinSloth and Billig are flying solo (or tandem) on this one.


Dude. I was trying to tell you that the gearing was exactly the same. Wasn't that clear?

crap you're right. my bad.

is a 52/13 good?

If you enjoy visits to the Orthopedist...

Maybe try a 53/11... Your knees will hate you ! :-)

jeff

when did i say the gearing wasn't exactly the same? it FEELS different...but it's the same.

whoa, you guys shouldn't let me post anymore. I keep misreading everything everyone writes. I'm on sabbatical as of now...go!