Why can't I get a good wind offset easily?

[JR_70]

Hey there...this is my only frustration so far with this wicked little unit.

I have set up my profile and the data all looks good. However, whenever I try to do my wind offset prior to riding - it is taking me like 20-40 mins to get the numbers down to anything close to 0.0.

A couple of things - 1 - does it have to 0.0 - or is 0.3 good enough?
2 - any tips to get a good reading? I don't have a garage or anything like that - and today I even tried to bring the bike inside - however, it was still taking a long time to get down to 0.4 - and then it jump back up to 1.1 or somewhere in that range.

Just curious about what I can do to get a quick and easy reading.

Cheers!

JR

[Morocco Mole]

JR

I notice the same thing so try this. When you press the button and offset drifts towards zero, you may find it stopping higher\lower than zero. Press the button again and you should find it gets down to zero. You may need to do it 2 - 3 times, don't ask me why but multiple presses bring it down to zero quicker. Once you get to zero you are good to go, don't worry if it's starts drifting around as this is normal as the unit is very sensitve and will pick up any wind\pressure movement, especially outdoor. If you can't do the calibration indoors at least try and find a sheltered spot and use your hand to shield the front air port, don't block it, just cup your hand around it. Hope this helps

M. Mole

[JR_70]

Hey MM....

Thanks so much for the tip - I'll give it a go tomorrow and see - I think you may be on to something though - as I have found that in the past as well - or else if I have been riding for about 10 minutes - it seems to drift to "0" much faster as well? But I like your suggestion.

Cheers!

JR

[MultiRider]

Someone suggested putting a plastic baggie around the unit and pressing the button through the baggie. This seems to work well for me. It doesn't block the port which would impact the pressure readings, but it does stop the wind and the variation. I use a very thin baggie and hit the button twice. I haven't seen an official Velocomp approval of this method, but it makes sense and seems to work.

[mds]

There is no reason to spend a long time trying to get a small wind offset value. Anything around 0.5 or smaller is fine. The reading displays dynamic pressure in units of pascals. To estimate the effect of a nonzero wind offset on power, use the forumla Dp*CdA*Vb where Dp is the offset and Vb is bike velocity in meters per second. Example 0.5 offset, 0.35 CdA, Vb 22mph or 10 m/s. Error in power = 0.5*0.35*10 = 2 watts. Bottom line: reasonably small wind offset errors produce a very small effect on power.

[cure]

hi, a little off topic but when i was looking at my ipro i notice a the hole for wind/pressure? and started wondering if bugs would get stuck inside and throw off information? has that ever happened, if it does, how do you clean that?

[lorduintah]

Shake first - the least invasive -

Tweezers - if it does. It is not a very large opening, but I have gone through swarms of gnats during my rides. Or you could put the port in the hose of a vacuum cleaner...

A can of dust-off might work - but don't let the liquid spray inside and don't use full force from the can. The sensor might not like the effects of either of these.

Tom

[cure]

Thanks Tom again!

I see your from Dallas...I'm from Austin. but currently working in NYC.