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Bike questions - gears to be exact
CREATED: 05/29/09 by HillOE REPLIES: 4
HillOE's ravatar HillOE    JOINED: 3/2/09    POSTS: 78
Bike questions - gears to be exact
POSTED: 5/29/09 8:10 AM

I bought a bike, and I love LOVE it ....I'll plug Conte's here - they were/are fantastic! However, I have a concern about the crank. I hear repeatedly that “gnashing” of the pedals is bad…you know using the bigger crank. So the bike I have is a 50/34 crank/bottom bracket configuration. I’m 5-10 and am very comfortable using the larger ring….not big into fast revolutions of the legs. My previous/commuter bike is a hybrid and I think it’s high 40s chainring plus 2 additional gears in the front. I’m mostly on the higher ring.

So off on the maiden voyage of the bike and I tried the smaller ring….I couldn’t gain speed or maintain the revolutions for long on the smaller ring. What am I looking to maintain with regards to revolutions so as not to have my legs give out for the run or be gnashing my gears?

I was thinking of switching out the smaller ring for something in the low 40s, maybe high 30s…but maybe I’m thinking this completely wrong…don’t want too much overlap….want to have versatility in the gears for that day when I try a hill. I do have a happy gear on the larger ring and mid to smaller ring-area in the back.

Any help? Figured I'd ask before I head back to Conte's just so I have some thoughts other then "this is not the chain ring I'm looking for"

Cheers - OE

matr's ravatar matr    JOINED: 2/28/09    POSTS: 44
RE: Bike questions - gears to be exact
POSTED: 5/29/09 8:44 AM

What you have is a compact crank, and they are inteded for climbing. In recent years these pretty much replaced road tripples. I'm not sure that you can find a bigger inner chainring for that bolt pattern, maybe you can, but that kind of defeats the purpose of a compact.

By "gnashing gears" you may mean cross chaining, which is riding in big ring/big cog or little ring/little cog. This is a bad idea as it decreases the lifespan of your drive train, increases friction, and could break the chain.

If you want to stomp a bigger gear, which taxes your big muscle groups as opposed to making you go into oxygen debt, go ahead and ride in your big ring most of the time, if your knees are up to it that is. Other options you may look at that are cheaper than a whole new crank are replacing the cassette with one with a 11 cog if you are not there already, or go with a bigger big ring like a 52 or a 53. Switching to a larger big ring may cause a few dropped chains on the down-shifts however.

Anyway, with something like a 50/34x11/23 you should have a really nice gear selection.

karlaj's ravatar karlaj    JOINED: 2/28/09    POSTS: 201
RE: Bike questions - gears to be exact
POSTED: 5/29/09 8:50 AM

OE,
Most folks will say 90 rpm for your cadence. That's a good number, +/- 5.

You have what's called a compact crank, and I think you'll be happy with it when you understand it a little better. 53/39 used to be a standard double chainring setup, but 50/34 became the new black when cycling folks figured out that the 50/34 double setup works almost as well as a triple chainring, w/o sacrificing too much speed on the top end.

As such, it's not surprising your small ring is mostly useful towards the small end of the cassette (11-15 range) on flats. Or, just use the big ring. However, when you do climb a real hill for the first time, it'll be abundantly clear what that small ring is for. Below are the approximate speeds (mph) you could expect for the gear combos spinning at 90 rpm:

34 50
11 20.2 29.7
12 18.5 27.2
13 17.1 25.1
14 15.9 23.3
15 14.8 21.8
16 13.9 20.4
18 12.3 18.1
21 10.6 15.5
23 9.7 14.2
25 8.9 13.1
27 8.2 12.1

Again - approximate b/c I don't know your cassette.

Happy riding!
-Jason

HillOE's ravatar HillOE    JOINED: 3/2/09    POSTS: 78
RE: Bike questions - gears to be exact
POSTED: 5/29/09 8:55 AM

Thanks!

OK I think I used wrong terms here - not bike lingo savvy yet. Jason hit the nail on the head with what I was looking for and matr - yes I think when I practice a hill or two I will appreciate the smaller crank.

Off to find hills this weekend!

OE

vatriathlete    JOINED: 2/28/09    POSTS: 682
RE: Bike questions - gears to be exact
POSTED: 5/29/09 10:07 AM

depending on your abilities, the compact cranks may or may not be the best for you.

granted they are the new "in thing" for people to have and if you need the lower gears for climbing hills or alpine passes they are great, however, generally around the dc/nova area compact cranks may not be the best thing.

but remember everyone is different i may not like compact cranks and they may work perfectly for someone else, its up to you to decide.

also just so you know yes you can get larger chainrings for your compact cranks, i believe fsa makes chainrings so that you can put on a 52/39 or such so that you can convert a compact crankset to almost a standard crankset with the 110mm bolt pattern. so even if you dont' like the compact chainrings you can replace one or both of the rings to your liking.

the catch= if you don't replace the chainrings in "matched" sets the shifting may not be perfect but it will work fine.

also if you are using shimano products, general rule of thumb is that their "matched" chainring combinations are just about the best there is out there for shifting performance, basically all the aftermarket stuff will work fine but its not going to be "as perfect" as the oem stuff.

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