the uncalibrated default setting is 2.00 (page 14).

Did you change press-on force?

yes I did... when I first tested it, it was at 1.05 so i added force up to 1.87.. but I thinkI forgot to press F3 to save... would more press on force decrease my power?

would more press on force decrease my power

it may, if nothing else it may give you a bad power reading, as the tire drag is starting to add to the resistance.

if your tire wasn't slipping at 1.05 then you already have enough press-on force, too much will just increase tire drag. decreasing press-on force, without causing the tire to slip, ensures the load generator is controlling the resistance and not tire drag.

there is at least one or two notes in the manual that says there is nothing optimal about a 2.00 calibration number. It's just the default.

1.87 versus 2.00 (assuming that's what the calibration was registered at) is about 5-6W higher power than actual. Less differential if you're riding slowly ....

rmur

Sorry to butt in on this thread but your response is interesting. I used to ride with just over 1lb of press-on (which did not cause any tire slip) but I increased it to around 2lbs because I thought that was "better".

If I interpret your comments correctly, you are saying it does not matter if you ride with a lower press-on as long as you calibrate for this lower force and the tire does not slip. Further (and I guess this is the important bit) if you overdo the press-on then the power calibration will be wrong because it won't be factoring tire drag on the unit and will in essence be under recording your power. Do I have it right? If so I might wind my machine back a bit.

Thanks

you overdo the press-on then the power calibration will be wrong because it won't be factoring tire drag on the unit and will in essence be under recording your power.

Yup that's what the book says

"You should always set the press-on

force appropriate to the workload to be encountered. If a flat course, then less press-on force. Hill climbs will

require more. Again, if it doesn’t slip with less press-on force -- this is always better because the Load Generator

will be then controlling the resistance and not tire drag." (note at bottom of page 15, Pro Basic stand-alone guide)

I increased it to around 2lbs because I thought that was "better".

One major misconception is that the "optimum" rolling calibration number is 2.00,

which is our default. This is not true. 2.00 was the average value of many tires tested.

Depending upon tire composition and a tire width, and all the above mentioned items that

affect rolling drag, you may find 2.00 pounds to be too much -- or not enough. Simply

put -- if the tire slips, increase Press-On. If it doesn’t, you may get away with much less. (page 14 of same guide)

Jim

Great. Thanks very much for your help.

yeah I am confused too.. I want to know if it drastically changes my performance the number it's calibrated at.. I warmed up today and i guess it was 1.05.. that feels a heck of a whole lot easier at 150 watts then when I am at 2.00.. know what I mean? then when i do these courses, my av wattage may suffer.. coach tells us to keep it around 2...

I have been confused ever since I got it - August 2001. Had a coach that wanted 2.5lbs but at that amount it was really hard work. Now I just use default and not bother with calibration, as long as there is no tire slip. I either use the ergo mode or the computer and increase or decrese worklad by manipulating watts, the course, and/or gears. Most of the time dont pay any attention to watts/spinscan/speed etc. Also the spinscan confuses me as well!

As the saying goes - you get there when you get there! LOL

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Simple Simon
Where's the Fried Chicken??

coach tells us to keep it around 2

Tell him to read the friggin' book!!! There is NOTHING special/optimal about 2.00. Telling everybody to keep it around 2 is like telling a whole group to all keep their heart rate at 170...

I quoted the manual a couple times, so it's not like I'm pulling this out of thin air.

BOTTOMLINE: LESS PRESS-ON FORCE = MORE ACCURATE LOAD-GENERATOR-PRODUCED READINGS and RESISTANCE. THE ONLY REASON TO INCREASE PRESS-ON IS If your tire slips.

Of course 2.00 will feel harder than 1.05 because you are probably introducting a WHOLE bunch of tire drag. What's harder, riding with a flat tire or one at 120psi????

Had a coach that wanted 2.5lbs

Somebody else pulling numbers out of his ass.

"today we are going to ride up MT Washington and we are also all going to wear flack jackets with SAPI plates...."

I agree with you, tire sliggage is the key. I always calibrate, if for no other reason to eliminate variables and ensure acurate numbers during testing.