Chasing good data
Posted: Sun Jan 11, 2009 10:26 am
I've been riding with iAero GIII for the last month. Pretty satisfied so far albeit with some reservations about the devices quirks which I am learning about. I'm in a bit of a learning curve now and could use any assistance anyone can offer here.
I find myself "chasing" good real time data while riding. Before I continue, although no expert, I have assiduously read what you smart folks have put here on the forums, not to mention the owners manual. I have delved into the IB3 software and am learning how to use it. I'm a careful user of my device and pretty well think I know how to set it up and use it daily. So there is that. Not saying I'm an expert of course, but maybe better than a novice!
Anyway, I just recently received a DFPM (PT to be exact) and have been wanting to incorporate it into my rides particularly for cDA info. Well the PT is not (yet) ANT+ sport so that's out for now. What I have been trying to do is to dial in the two PMs so that OUT THE DOOR they both read pretty consistently and pretty closely. This will give me confidence in any cDA #s I come up with later on and allow me to make changes to my setup. Primarily I ride triathlons but am using my road bike at the moment for most of my training.
So Thursday I had a not so good ride in comparing the two PMs. PT was reading significantly different than the iAero for the whole ride. Frustrating. After making a post, I looked at my wind scaling factor as the ambient wind was not reading "0". So did the calculation provided to me and changed the wind scaling # in the iBike profile. So on my ride yesterday, the ambient wind was in fact 0. Hooray! Yet the two PMs still differed significantly! I made a tweak to the cRR and that made the two graphs align well and also caused the Pavg to be within about 6w of each other...totally acceptable in my mind. Yet I didn't like that I had to do all that tweaking POST RIDE...I am looking for good data while riding. I do a lot of interval riding and it does me no good to have the iAero either over or under report my wattage while riding intervals...I need to be within a fairly narrow range on the watts and I need to see that while I'm riding.
So after making a tweak to the cRR I decided to add that updated number to my iBike profile for today's ride. Today's ride was the EXACT SAME course as yesterday's, in nearly identical weather. The only difference was that I did a different set of intervals. Yesterday was 1x12 and 2x15, today was 2x15.
So for the entire ride today, I could easily tell the iAero was WAY under reporting wattage (so I used the PT CPU on my ride to ride my intervals). Came back an downloaded both files. Lo and behold, the ambient wind was -1.3 for today's ride! And the average wattage was wayyy lower then the PT file indicated, not to mention my intervals were way lower than what the PT file indicates. According to the PT file, my first int was ~237w and my second was ~225w (goal was 225-237w). According to IB, first int was 195w and second int was 190w...a major major difference.
Before you give advice, here are some backgrounds to eliminate easy stuff:
1. 7 coastdowns and a flat 4 mile cal ride. Original cRR was computed as .062 which seems a bit high. Orig wind scaling factor was something like 2.85 I think. I changed it to the current value of 2.565 after reviewing a few ride files where the ambient wind was not 0.
2. A wind offset is performed prior to every ride.
3. I do NOT do a tilt cal prior to every ride.
4. Indoor temp was within 7 deg of outdoor temp prior to riding. In any case, I am happy to ignore first 10 mins worth of data as it is my warmup.
So here is the crux: I really think that the IB is a pretty cool device and has a lot going for it. Not being a GI or GII user, I can't comment on the upgrade to GIII but the tilt functions and the stability of the mount and the device in general seem pretty good to me. My major complaint at this point is REPEATABILITY. I guess in the end it does not really matter if the iAero mirrors the PT because if all I ever had was the iAero it would be all I know. However, I am seeing in comparison to the PT that it is not putting out the same data day to day...and that is not good. If my ambient wind was 0 yesterday, for today's ride on the same course it should also be zero! So somewhere along the line something isn't quite "right".
I'm hoping that some smart folks can give me some ideas so I can stop chasing good data, or using the IB software to obtain good data...I need to be certain that the IB is reliable enough to give me solid data in real time and that the data I'm seeing day to day is accurate enough for me to use in the training environment I ride in.
I am attaching the Powertap CSV file and today's ride file if anyone wants to monkey around with them. Again, I can go into IB and get the two ride files to marry up; what I'm looking for is a solution that will allow me to do this OUT THE DOOR each and every day and not have to rely on the IB software to do it post ride.
Thanks!
I find myself "chasing" good real time data while riding. Before I continue, although no expert, I have assiduously read what you smart folks have put here on the forums, not to mention the owners manual. I have delved into the IB3 software and am learning how to use it. I'm a careful user of my device and pretty well think I know how to set it up and use it daily. So there is that. Not saying I'm an expert of course, but maybe better than a novice!
Anyway, I just recently received a DFPM (PT to be exact) and have been wanting to incorporate it into my rides particularly for cDA info. Well the PT is not (yet) ANT+ sport so that's out for now. What I have been trying to do is to dial in the two PMs so that OUT THE DOOR they both read pretty consistently and pretty closely. This will give me confidence in any cDA #s I come up with later on and allow me to make changes to my setup. Primarily I ride triathlons but am using my road bike at the moment for most of my training.
So Thursday I had a not so good ride in comparing the two PMs. PT was reading significantly different than the iAero for the whole ride. Frustrating. After making a post, I looked at my wind scaling factor as the ambient wind was not reading "0". So did the calculation provided to me and changed the wind scaling # in the iBike profile. So on my ride yesterday, the ambient wind was in fact 0. Hooray! Yet the two PMs still differed significantly! I made a tweak to the cRR and that made the two graphs align well and also caused the Pavg to be within about 6w of each other...totally acceptable in my mind. Yet I didn't like that I had to do all that tweaking POST RIDE...I am looking for good data while riding. I do a lot of interval riding and it does me no good to have the iAero either over or under report my wattage while riding intervals...I need to be within a fairly narrow range on the watts and I need to see that while I'm riding.
So after making a tweak to the cRR I decided to add that updated number to my iBike profile for today's ride. Today's ride was the EXACT SAME course as yesterday's, in nearly identical weather. The only difference was that I did a different set of intervals. Yesterday was 1x12 and 2x15, today was 2x15.
So for the entire ride today, I could easily tell the iAero was WAY under reporting wattage (so I used the PT CPU on my ride to ride my intervals). Came back an downloaded both files. Lo and behold, the ambient wind was -1.3 for today's ride! And the average wattage was wayyy lower then the PT file indicated, not to mention my intervals were way lower than what the PT file indicates. According to the PT file, my first int was ~237w and my second was ~225w (goal was 225-237w). According to IB, first int was 195w and second int was 190w...a major major difference.
Before you give advice, here are some backgrounds to eliminate easy stuff:
1. 7 coastdowns and a flat 4 mile cal ride. Original cRR was computed as .062 which seems a bit high. Orig wind scaling factor was something like 2.85 I think. I changed it to the current value of 2.565 after reviewing a few ride files where the ambient wind was not 0.
2. A wind offset is performed prior to every ride.
3. I do NOT do a tilt cal prior to every ride.
4. Indoor temp was within 7 deg of outdoor temp prior to riding. In any case, I am happy to ignore first 10 mins worth of data as it is my warmup.
So here is the crux: I really think that the IB is a pretty cool device and has a lot going for it. Not being a GI or GII user, I can't comment on the upgrade to GIII but the tilt functions and the stability of the mount and the device in general seem pretty good to me. My major complaint at this point is REPEATABILITY. I guess in the end it does not really matter if the iAero mirrors the PT because if all I ever had was the iAero it would be all I know. However, I am seeing in comparison to the PT that it is not putting out the same data day to day...and that is not good. If my ambient wind was 0 yesterday, for today's ride on the same course it should also be zero! So somewhere along the line something isn't quite "right".
I'm hoping that some smart folks can give me some ideas so I can stop chasing good data, or using the IB software to obtain good data...I need to be certain that the IB is reliable enough to give me solid data in real time and that the data I'm seeing day to day is accurate enough for me to use in the training environment I ride in.
I am attaching the Powertap CSV file and today's ride file if anyone wants to monkey around with them. Again, I can go into IB and get the two ride files to marry up; what I'm looking for is a solution that will allow me to do this OUT THE DOOR each and every day and not have to rely on the IB software to do it post ride.
Thanks!