cyclisteaux

OK, on my S3, I got a Di2 53/39 172 crank and on my P4 I got a Zipp Vumachronos 170 53/39. WTF do these numbers mean? I have no idea....Just took the advice of some bike pro.

I got 7 Dura Ace 7900 cassettes: 11-21, 11-23, 11-25. A buddy told me I need a 28 for a hilly road race so I'm gonna get one of those. Why? No idea.

I see that there are also available cassettes numbered 12-21, 12-23, etc.....

What's the diff between the "11s" and the "12s??"

How's an average shmoe like me supposed to decifer all these numbers???

(scratches head with total befuddlement)

Thanks again for your patience and input.

ericm979

A 28 will turn you into a girl. Use the 11-21.

rruff

Hire me as your consultant. For a mere $100/hr ($200 minimum) I will explain it all to you... and more. We can even get into what tires and tubes to use.

rbart4506

You have an S3 and a P4 and have no clue....Wow...

It's early and I need a few secs to blow so here goes...

172, 170 are the crank length...Thingy that your pedal screws in that you turn to make your bike go...

11s, 12s....Number of teeth on the rear cassette...28 gives you a higher gear that makes it easier to spin going up hill...11 will allow you to go faster on the flats, assuming you can push the gear...

Ride, train and read...

hammy56

41

KD5NRH

For $150/hr ($600 minimum) I will tell you to pedal the damn thing and figure it out that way.

gsteinb

+ everything and the house

chasm54

I'm finding the OP rather hard to believe. Those bikes, SEVEN dura-ace cassettes, and he doesn't know what gears are? Nah.

gsteinb

NJ is filled with dentists who buy bikes in July.

Hocam

kevrider

so you just do what he tells you to do, no questions. shouldn't you ask these things *before* you buy something? you can go to mfg websites (or pricepoint) and read up on your parts. or, perhaps, look closely at the parts.

cyclisteaux

Sorry, not a troll or DDS. I'm just not a technical guy and a little intimidated with anything mechanical so I pay a professional to work on my bike. Slowly trying to do things myself but unfortunately this sometimes backfires on me. For instance, I travelled with my bike and had to reassemble it. Tried making experimental adjustments to the rear derailleur (Those tiny screws). Day before a race, in a test run, the chain derails behind the cassette and gets jammed!

Had to hitch-hike to a bikeshop and pay a mechanic to fix it.

Makes sense to learn about all this stuff, hence, my stupid questions. Too embarrassed to ask my cycling buddies. ;-)

How does a 12-23 compare with an 11-23? What does the 11/12 refer too?

chasm54

See rbart4506 post above.

cyclisteaux

Thx. I saw that, but when would one use a "12?"

ericm979

That's a lower gear, not higher. 39x25 is a 1.56:1 gear ratio (rear wheel turns 1.56 times for every crank revolution). 39x28 is 1.39:1. 1.39 is lower than 1.56, hence it is a lower gear ratio.

ericm979

when you don't need an 11.
a 11-25 has 11,12,13,14,15,17,19,21,23,25
a 12-25 has 12,13,14,15,16,17,19,21,23,25

That 16t cog that's on the 12-25 is awfully handy. The 11-25 has a large gap from the 15 to the 17. So if you're riding at a speed where the 16t cog would be ideal, you have to either turn the pedals faster on the 17t, or slower on the 15t. If you don't use the 11t then using a 12-xx cassette would avoid this problem.

chasm54

The more teeth on the rear sprocket the lower the gear, therefore the easier to push. So a 12 sprocket is almost 10% lower/easier than an 11, and so on. People use a cassette with a 12 as its lowest gear if they find they rarely go fast enough to need the 11, or want a bigger sprocket at the top end for climbing, without sacrificing the close ratios implied by moving up in small steps. Personally I can't be bothered swapping cassettes/ wheels all the time, and there's a lot of severe climbs round here, so I usually run a 12-27. I don't race, so don't really need the 11 for sprinting (I can barely sprint out of sight on a dark night anyway LOL) and having the 27 means I can climb virtually anything. The price I pay is a more substantial step up between gears - the cassette goes 12, 13, 14, 15, 17, 19, 21, 23, 25, 27.

I'm giving you the benefit of the doubt here, but I still can't really believe that anyone who claims to race bikes doesn't know this stuff.

cyclisteaux

OK, thx for the info, guys.

And yes, I'm a troll that has nothing better to do than to make believe I'm a new bike racer asking detailed questions on gearing.

ericm979

Highest.

KD5NRH

But what if i'm riding at a speed where 18 would be ideal? Can't they wedge four more cogs in there so I never have to face that problem?

echappist

+1

too many POS threads here

withsriracha

I just can't get past the SEVEN cassettes....

wanders

Jens Voigt's cassette goes 11-11-11-11-11-11-11-11-11-12 (for the hills).

Jens Voigt's cranks have 2 chainrings, a 56 and a 56.

Homebrew01

Wouldn't be the first time.

https://coachlevi.com/cycling/complet...ears-shifting/

Creakyknees

Allow me to introduce you to the late, great Sheldon Brown. Read and learn.

https://www.sheldonbrown.com/gearing/index.html