Calculating Cadence

[justinb]

Hi All,

I am looking at a new bike, but before I jump into it there is one question I cannot find the answer to, or work out.

If the bike that I am looking at buying has:
26" wheels;
Crankset has 44 teeth
Cassette has 9 teeth

If I am travelling at 50km/h what will my cadence be?

There must be some mathamaticians out there.. :)

[dunk]

http://www.analyticcycling.com/

[I-AM-TEH-FASTEST-11]

what gear are you in? What's the opposing wind restiance? Are you on flat ground?
Are your brakes rubbing?
Are your tires flat?

Cadence is based off revolutions of the cranks, Flight Deck bases it off a gear/speed ratio, but it's not very accurate.

Most of the time you want to be around about 100 cadence, no matter what speed. Higher is better with cadence, if you can push +120 then you're doing well

[justinb]

what gear are you in? What's the opposing wind restiance? Are you on flat ground?
Are your brakes rubbing?
Are your tires flat?

Cadence is based off revolutions of the cranks, Flight Deck bases it off a gear/speed ratio, but it's not very accurate.

Most of the time you want to be around about 100 cadence, no matter what speed. Higher is better with cadence, if you can push +120 then you're doing well

I should of elaborated.

I am just about to buy a hard tail with these statistics. I'd like a road bike, but cannot afford 2 bikes.

I just wanted to make sure that while cycling to and from work on the road, I wasn't about to commit to a bike that required a cadence of over 150 to maintain 40 km/h on the road... :)

Generally I try and average around 80rpm :)

Cheers

[thecat]

Generally I try and average around 80rpm :)

Cheers

80rpm is a pretty low cadence and you wouldn't be getting much efficiency from it.

As IATF said 100rpm is generally good so you may want to up it anyway.

Never seen a 9t sprocket on a MTB maybe 9 speed? In which case you'll be looking at either 11T or 12T high gear. The page Dunc linked to gives me a cadence of 98 on a 44-11.

You'll also need to take into account that the smaller diameter wheels and wider tyres of a MTB aren't going to roll as quick as a road wheel set. Maintaining 40 on the flat is going reasonably hard, I struggle to keep it over 30km/h around town

[DaGonz]

If the bike that I am looking at buying has:
26" wheels;
Crankset has 44 teeth
Cassette has 9 teeth

If I am travelling at 50km/h what will my cadence be?

There must be some mathamaticians out there.. :)


Cadence = ( Desired_speed_in_m/sec * small_gear tooth ) / ( 3.14 * Wheel_OD_in_m * Chain_ring_teeth ) * 60

so roughly 85 rpm going on your numbers or 105 using a more probable 11tooth casette

of course I've never seen a 9 toothed cassette and if simply having a one bike does all thing is your concern then I'd be surprised if you regularily get up to 40 or 50km/hr unless you have a lot of down hill stuff or a constant strong tail wind. In which case the upright position, tyres and other factors of the mountain bike are going to be more of an issue for you.

Even the road bunches around homebush (relatively flat) don't seem to avg much more than the high 30's...

*shrug*

Cheers
Gonz

[justinb]

Sorry... you are right, it is a 11 tooth rear cog.

My current (soon to be replaced) bike I would be up around the 130rpm for 50 km/h. THis was downhill, I'll give you that.

I was planing to roll on/off road tyres for when communting to work etc... this would reduce RR? not a good idea?

Cheers

[GrubNut]

Sorry... you are right, it is a 11 tooth rear cog.

My current (soon to be replaced) bike I would be up around the 130rpm for 50 km/h. THis was downhill, I'll give you that.

I was planing to roll on/off road tyres for when communting to work etc... this would reduce RR? not a good idea?

Cheers

Slick tyres will make a very big and noticable difference to rolling resistance, compared to knobbies, also off road tyres wear quite quickly on the road. However most people find that changing tyres all the time gets to be such a PITA that they don't bother.

You might be better off getting two wheelsets, but this can cause other problems such as disc rotor not aligning with calipers.

Really the only solution is to get a cheap`n'cheerful bike set up just for commuting. I find an old steel singlespeed road bike to be perfect for this. If you scrounge well it's possible to set up a decent singlespeed for not a whole heap more than the price of a couple of good slick tyres.