Gear ratios, are these normal, and is there a formula to use

daniel_b
daniel_b Posts: 11,580
edited September 2007 in Road beginners
Hi guys,

just checked the gearing on my Felt and on my gf's Trek.

Trek: 52/38 and at the rear 26/12
Felt: 53/42 and at the rear 24/12

I'm assuming that gives me a marginally higher top gear, but can't tell how a 42/24 compares to a 38/26

Is there some formula I can pump into excel to give me all the ratio's in figures that I can then compare??

Also, are both sets what you would expect, or is either bike missing out on high or low end.

Cheers

Dan
Felt F70 05 (Turbo)
Marin Palisades Trail 91 and 06
Scott CR1 SL 12
Cannondale Synapse Adventure 15 & 16 Di2
Scott Foil 18

Comments

  • daniel_b
    daniel_b Posts: 11,580
    Thanks George, have worked them all out now.

    What's a good combination for a fast downhill run on a roadbike, would it be best to up the size of the large front cog, and or fit an eleven to the rear?

    Dan
    Felt F70 05 (Turbo)
    Marin Palisades Trail 91 and 06
    Scott CR1 SL 12
    Cannondale Synapse Adventure 15 & 16 Di2
    Scott Foil 18
  • nolf
    nolf Posts: 1,287
    If you up the size of a the front chainring, you'll find you rarely use it on the flat or ever except downhill.

    You're better off just tucking in as I find even on my 50-12 I've got up to 50mph- I spun out at 35mph, but past that I just pulled in my knees, rested my hands on the top of the handlebars and pushed my chin down on top of my hands.

    This will get you a lot faster than a bigger chainring.

    If you really want to though, I would have thought you would be better off changing the rear casette as they cost less (I think) and you always have a spare with smaller gears for winter or if you wear new ones out.
    "I hold it true, what'er befall;
    I feel it, when I sorrow most;
    'Tis better to have loved and lost;
    Than never to have loved at all."

    Alfred Tennyson
  • Daniel B wrote:
    Thanks George, have worked them all out now.

    What's a good combination for a fast downhill run on a roadbike, would it be best to up the size of the large front cog, and or fit an eleven to the rear?

    Dan

    You do not need more than a 53/12.
    If your going down such a steep hill your spinning out then you should just adopt an aero position and you will go faster than you would with a 56/11.

    See what max speed you can hit pedalling the gear you have :D You can get over 40mph pedalling such a gear if you can sprint down an incline before you spin out :D