Fric numbers compared to CRR
Fric numbers compared to CRR
I recently moved my unit on my stem and removed a shim I had been using to level out the IBike. I then went out and did a cal ride to get the new tilt and wind scaling numbers so I could change them in my current profile I have been using. I actually went to a wireless mount which is why I changed the way I had it mounted. Anyways when I changed the tilt to the tilt I got on my cal ride (which I did two of them) it changed my fric numbers from 8.546 to .778. This was way lower than the previous fric numbers. I left my CRR the same. I also adjusted the wind scaling which did not change a whole lot. So my question is this...are the fric numbers important or is it the crr and tilt that are more crucial. The same goes for the Aero numbers or is it the cda and wind scaling numbers that are more important. Just thouhgt I would ask. I will get to try out the new profile numbers tomorrow, but like i said I am just curious.
Re: Fric numbers compared to CRR
Yes, the friction number is very important. What may have happened is that your riding tilt is off and this will effect the friction.
Your crr won't have changed by changing the mount, so keep the crr what is what before. Then check your riding tilt (I usually just put mine to -.3). This will change your friction number to the correct value.
As for your cda and wind scaling, these two value will create the cda number. The iBike will read aero and wind scaling, but the cda value is a good way to cross check those. Your cda value won't have changed with a new mount (well, maybe a very minuscule amount, let's not worry about it). But you wind scaling will have changed. To find out a new wind scaling factor you do the calibration ride. If you enter your new wind scaling number into your old profile and hold the cda value the same, you will now have a new aero value.
This may be the easiest way to create your new profile.
Your crr won't have changed by changing the mount, so keep the crr what is what before. Then check your riding tilt (I usually just put mine to -.3). This will change your friction number to the correct value.
As for your cda and wind scaling, these two value will create the cda number. The iBike will read aero and wind scaling, but the cda value is a good way to cross check those. Your cda value won't have changed with a new mount (well, maybe a very minuscule amount, let's not worry about it). But you wind scaling will have changed. To find out a new wind scaling factor you do the calibration ride. If you enter your new wind scaling number into your old profile and hold the cda value the same, you will now have a new aero value.
This may be the easiest way to create your new profile.
Boyd Johnson
http://www.boydcycling.com - high performance carbon wheels and accessories
http://www.boydcycling.com - high performance carbon wheels and accessories
Re: Fric numbers compared to CRR
Thanks coachboyd. What I did was another cal ride on my mountain bike after changing the way the IBike was mounted to my stem. Like I said I had a shim in the mount to level out the IBike which I now removed. I did the cal ride and got my new ride tilt and wind scaling numbers. I actually did this twice to make sure the numbers I got were pretty close to the same.
My old tilt was +0.4
fric=8.546
After changing my mount around
My new tilt +1.3
fric=.778
Now this is on my full suspension mountain bike so the tilt numbers are definately different. I did 2x20 min hill climbs up single track last night and all of the numbers seemed right on. My avg power was 263 and my NP was at 290watts. Considering my FTP is 275 I was happy with the numbers I got. On the flats it seemed pretty close to as far as RPE.
My old tilt was +0.4
fric=8.546
After changing my mount around
My new tilt +1.3
fric=.778
Now this is on my full suspension mountain bike so the tilt numbers are definately different. I did 2x20 min hill climbs up single track last night and all of the numbers seemed right on. My avg power was 263 and my NP was at 290watts. Considering my FTP is 275 I was happy with the numbers I got. On the flats it seemed pretty close to as far as RPE.