Changing weight post-ride?

[sl@enposte.net]

I had a great day to do some aero testing yesterday. Only problem was the scale I took didn't work. So I had to guestimate weight and ended up under by a little over a two kg (about 3lbs, 183 used, should have been 188lbs.)

I did two sets of coast downs and 4 mile rides for two different wheelsets. The numbers look reasonable. But presumably are off slightly due to weight being under by about 2-3%.

Is it possible to fix in ibike2 application?

For the record:

P2C - Aeolus 6.5 - Veloflex Record - 120PSI Cda 0.200 Crr 0.004
P2C - Aeolus 5.0 - Bontrager XXX LIte - 120PSI Cda 0.195 Crr 0.006

The Cda numbers look a little iffy. The 6.5's are a deeper (65mm) profile than the 5.0s(50mm). The Crr numbers look a bit better. The Veloflex Record Tubular is supposed to be very good for Crr.


Thanks.

[Hyde]

I don't know if it's good to do your coast downs with an inaccurate weight but I change my weight daily on my main bike depending on what I'm carrying in my pack. My assumption, & I could be wrong, is that you would want to do your coast downs with everything correct.

Sounds like you have a nice ride, BTW.

[travispape]

I had a great day to do some aero testing yesterday. Only problem was the scale I took didn't work. So I had to guestimate weight and ended up under by a little over a two kg (about 3lbs, 183 used, should have been 188lbs.)

I did two sets of coast downs and 4 mile rides for two different wheelsets. The numbers look reasonable. But presumably are off slightly due to weight being under by about 2-3%.

Is it possible to fix in ibike2 application?

For the record:

P2C - Aeolus 6.5 - Veloflex Record - 120PSI Cda 0.200 Crr 0.004
P2C - Aeolus 5.0 - Bontrager XXX LIte - 120PSI Cda 0.195 Crr 0.006

The Cda numbers look a little iffy. The 6.5's are a deeper (65mm) profile than the 5.0s(50mm). The Crr numbers look a bit better. The Veloflex Record Tubular is supposed to be very good for Crr.


Thanks.

You can change your coast-down weight after-the-fact. Go to "profiles->edit profiles...->advanced profiles settings..."

[sl@enposte.net]

Yes, but that doesn't redo the calculations for the coast-down etc...

Is there anyway to fix that? Or does it matter all that much?

[travispape]

Yes, but that doesn't redo the calculations for the coast-down etc...

Is there anyway to fix that? Or does it matter all that much?

The error in the weight setting in the iBike did not invalidate your coastdown results--the fric and aero numbers would have been the same if you had the correct weight setting in the iBike's setup page at the time. However, the weight does make a difference in the reported Crr that is calculated from the coastdown results. Yes, for the small weight error you are talking about, it is only a small change in the Crr that you will get. Also, you do not have to worry about the weight error for the 4 mile ride.

Note, however, that the weight setting in the iBike does make a difference for the power measurements during a normal ride. Again, for the small 3 lb error it is only a small difference, but you can correct it using the "iBike Settings..." button in the "Detailed" tab.

Travis