Calories burned - Is this right ???

cntl

Hi

Recently I installed a Cateye computer on my MTB. All is fine, the right wheel size is set (and the distance shown is almost identical to the one shown by the odometre when driving, so it must be right!). However, with average speed 14-15 MPH, the calories burned per 7.5 mile trip--according to the computer--are between 170-180! This can not be right? This is quite an intensive ride for me that includes a few slopes. Internet based calorie-calculators indicate that is should be something more of a 400-450 calories per trip. None of these websites showed a value THAT low. Am I missing something here?

Ale

Does the computer have a power meter (or HRM), or is it simply estimating power from your speed?

If the latter, it's not going to be accurate at all.

cntl

>>Does the computer have a power meter (or HRM), or is it simply estimating power from
>>your speed? If the latter, it's not going to be accurate at all.

Yes, it estimates power from the speed. Still, I would not think it to be that inaccurate. Well, never mind, I use it primarily for MPH, distance and timer.

MentalRaver

Obviously it will be inaccurate if using speed.

There's a BIG differance between 10mph up hill and 10 mph on the flat, let alone down hill.

I'd totally ignore it!

Ale

Other big factors would include headwind/tailwind, or whether you have a MTB with half flat knobbly tires or a carbon roadie with 23mm tyres at 150psi, how much you weigh, how fit you are....

farrell

Sorry, I'm being pedantic, but

150psi on a 23mm tyre will actually slow you down. Best use 113-120psi for optimal rolling resistance.


Btw, I do 7 miles to my studio and it takes me 20 - 25 mins (depending on traffic lights / amount of traffic / blasted road works / .etc ) and my HRM tells me that I use 210 (give or take 20) calories with an average HR of 130 - 145bpm.

Ale

Why do you think 150psi in a 23mm tyre will slow you down?

I assume it also depends on rider weight and bike stiffness

janm399

My HRM tells me my 10mile commute at about 40 km/h at HR averaging around 150, with maximums around 185 - 190 costs me around 550 calories. It's on a road bike and it is fairly flat. .
I wonder what would a real power meter say.

farrell

Ale, just copied this from the Zipp website:-

Volumes of data have been produced showing decreased tire performance at high
tire pressures, and our studies have been no different. We recommend 100–110
psi for all nylon-cased tires (such as Michelin, Continental, and Vittoria Ultra Speed),
and 110–125 psi for cotton and softer material-cased tires (such as Vittoria CX,
Vredestein, and Veloflex). Pressures above these will decrease tire grip and actually
increase rolling resistance on most road surfaces, as the tire generates more heat
conforming to the uneven road surface...............Remember, increased tire pressure will cause the rider to experience more high frequency
road vibration, possibly giving the feeling of going faster, but actually
sapping energy as the tire bounces over road imperfections instead of absorbing
them. Higher tire pressure significantly reduces grip and increases tire wear as well,
so if you are wearing through tires quickly or feeling skittish on less than perfect
roads, you might be running too much tire pressure. Therefore we rate our clincher
rims at 12 psi MAX.

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dodgy formatting, sorry

I'm no expert in these matters btw.........riders weight would be a factor too, I guess.

Ale

Thanks for the quote farrell,

I'd assumed the lower grip thing, but didn't know about the increased rolling resaistance.
I'll have to do more research!