brett jerk

hey, I used bikely to track my route today and i did 22.3 miles and had an elevation gain/loss of 1125 feet. I'm trying to play around with these numbers so that I can compare energy expenditure on different routes and try to get a baseline now that I'm back in a more "training" mindset (aka its warm out and I'll be taking real rides all the time). I used bikely.com to get my distance/elevation, short of buying a cycling computer and/or counting my cadence, is there any way I can calculate this (with my times at various checkpoints) to figure out what my speed would be on flat ground? I'm looking either for the shell of a formula (I can do the math myself) or a web page that'll do it for me.

google wasnt much help, and I don't know how to even begin to search that on here and get any valid results

thanks in advance!

barba

An HRM or power meter would give you a better sense of your effort. There are a lot of variables to control for when you measure speeds.

brett jerk

I'm "college broke" and have no money for anything like that. I'm looking for some rough math, I don't need anything super complicated or precise, I'm just looking to get a ballpark figure for my speed

genericbikedude

meh, just ride your bike a lot. 22 miles aint ***** for training.

barba

To my knowledge there is no such math. I would find a standard training loop and begin keeping records of your times. Also note the conditions that day (wind, etc.). Cadence is easy to work out if you know your gearing and average speed.

dirtyphotons

short answer: not really.

you're not going to find a formula that accounts for wind and mechanical resistance, there are too many variables. in the absence of those two factors (and assuming you don't brake), your speed on flat ground would just increase and increase, nothing would ever slow you down.

your speed on flat ground per calorie of energy is still dependent on a lot of things, many of which are out of your control (wind, most notably). so it's really not a good measuring stick.

the way you tell how much energy you're putting into your bike is by measuring power and that is why road weenies shell out so much money for power meters.

the "college broke" method of gauging your effort at different points throughout the ride is to do the same ride many times and get average split times, then try to beat them.

bike computers and heart rate monitors are the next step, and they're not that expensive. but they're also not necessary. if you ride hard you'll get faster.

ianjk

my jackarse answer:

Instead of trying to figure all that out, take the time and ride a little more

I do like gmap pedometer for occasionally figuring out how far I went and the elevation changes.

example: https://www.gmap-pedometer.com/?r=1756113

If you really want to know, take distance/gear inches and get pedal revs

roadgator

theres no way to get good correlation between power and speed on flats (without knowing your CdA, which is about impossible to estimate accurately enough), but if you have a proper hill you can get a rough estimate of average power.

First, you need a big hill. One that you never get going more than 15Mph on (so wind and rolling drag is negligible) and takes at least a few minutes to get up is ideal. You can only correlate your power for the time you are on the hill. So if it takes you 10 minutes, all you will know is your average power for 10min. Very short hills aren't good because you can roll into them with momentum and then sprint out.

You need to measure:
(h) The elevation of the hill, preferably with GPS.
(t) Time to ride the hill, in seconds.
(m) MASS of you AND the bike, hold the thing with bottles and everything while you stand on a bathroom scale

Plug it into this to get your MINIMUM (because drag is not accounted for) average power output (P):

P= Work/time = mgh/t.

If you are using kilos and meters, g=9.8, and P will be in watts. 745 watts =1hp

Have fun!

roadgator

you can also do a time trial.

find a nice loop to ride, preferably one that wont have traffic signals to interfere with the pace. ride it every few weeks, keep track of the times. There are lots of variables, but if you are getting stronger you will see a steady trend of decreasing times.

Going in a loop tends to cancel out the effect of wind, so as long as the weather isnt doing something completely ********, it will be a pretty good apples to apples comparison.

dobber

Distance ridden (feet) /12 * Change in elevation (Inches)

sivat

You might be able to do something with energy. Your total energy at the top of the hill with be 1/2mV^2+mgh. Thats the kinetic plus potential energy, where m is your mass in kg, V is you speed in m/s, g is 9.8m/s^2 and h is the change in altitude in meters. To find the speed on flat ground, take the total energy at the top of the hill (E) and plug it into sqrt(2E/m) to get your speed. The problem with this is it makes a lot of assumptions that are not particularly accurate. It assumes your speed is constant going up the hill, and it neglects wind resistance, which increases with the square of velocity.

sivat

In retrospect, you would probably want to use your average energy climbing the hill, so h should be the elevation/2.

Yoshi

I think this is what you want: https://www.kreuzotter.de/english/espeed.htm

Highly inaccurate, of course, but it should give you a ballpark figure.