AeroPod, PowerPod and Newton

I just did 2 cal rides, 1 for each bike(mtn bikes). After doing each cal ride and coast down saved it to the appropriate profile in IB3. Was wandering if someone might take a look and give me there opinion on them. One bike I train on the road and the other is my xc race bike so for that one I did coast downs on dirt road. I am also concerned about the wind scaling numbers. Both are mounted on the stem of the bikes.

Both of your wind scaling numbers are fairly similar (.643 vs. .594) so that's definitely not a problem. Plus it's on two different bikes so I would expect the wind scaling numbers to be different.
The riding tilt numbers are pretty different between the two units and on the one off road you had a positive .4 (which I could see happening with a squishy back wheel and a center of gravity a lot further back then on a road bike. By any chance do you have slick tires on the bike you ride on the road?

Using the estimated cda feature will NOT be accurate on a MTB, the formulas were developed with road bikes in mind. Keep in mind that when you switch between dirt roads to grass to road to mud, your crr will be drastically changing (much more so than changing between different asphalt conditions)

The one I ride on the road uses bald tires I wore out racing and training. Kenda small block 8's to be exact with around 35 pounds of air in front and back wheel. My xc race bike uses another type of Kenda tire running 22.5 lbs in front and 24lbs in rear.

I know that changing around the type of ground will drastically change numbers. Just as a note I will only use my road version on the road and my xc on dirt as far as my training is concerned. Here in SOCal almost every single fire road or trail I raced on had about the same kind of surface as each other, but that being said I understand that if I ride on a different type of dirt terrain I will not have accurate numbers at all.

Like I said all I am looking for is some kind of consistency between the 2 bikes so I can do my intervals and workouts with a little confidence that they are pretty close(power zones) in numbers. So if using an estimated cda is not a good idea how should I go about accomplishing this task? I sure hope it does not require more cal rides and or coast downs, I have done so many that I know where every little stone is laying on the road where I do them at.

So is there anything you can do to help me out? Maybe after the first of the year I can get a road bike to train on, but until then I have to use what I have. Thanks again for your time.

Maybe I need to set my road bike to .0070 and the xc bike to .0130 instead of using the est feature??

How similar is the position between the two bikes.

If you are in about the same position, I would recommend having the same cda for both bikes. It looks like about .46 will be a good estimation. You will want to change the aero numbers in each profile and keep the wind scaling where it is to match the cdas.

Now, for the bike you are going to use on the road I would estimate about .007 for rolling resistance. You will want to adjust the friction numbers and keep the riding tilt the same until you hit .007.

For the bike you are going to use on the dirt (with knobby tires), I am going to estimate .010, you can use the same procedure as above.

A little hint to make this go faster. If you put your cursor next to a number and use the up and down arrow keys, the number to the left of the cursor will increment by one. . .so it's easier to get to a specific number in another field.

This should help me to get a better understanding of things, although not near enough to know what values to put where. Thank you for pointing me in the right direction.

Now of course I have one more question, would it be beneficial for me to do another cal ride using est aero set to hoods yes but then not use est fric=no or even set it to .0070? And then if so would I still do 5 or so coast downs??


Thanks coachboyd again.

Nope, using the estimated aero on a MTB has no benefit whatsoever.
When you enter your height and weight and then position, it's meant for a road bike riders position. Because yours is going to be so different your numbers will always be off if you use the estimated aero.

Thank you coachboyd!!!

I changed the profile on my road mtb (the way you told me) and from what I can tell all looks good. I had consistant power readings while climbing, on the flats, and even on downhills. A little higher than when I originally did my FTP test though, but very consistent and RPE seemed to be equal all around compared to what the power meter was reading. I feel the numbers are a little high(20watts or so) but I am not sure, maybe and most likely my FTP was wrong to begin with(262) I guess I can not picture it being even higher than that right now but maybe it is. I could do a new FTP test and find out after my next 2 big races are done with in the next week- 2 weeks. I don't suppose there is a way to tell is there, or just do the new FTP test and be done with it?? Thank you again and hope to be done bothering you. Next will be my XC race bike, I hope it comes out just as good as the first bike.

Now if wattage is higher/lower compared to my first bike(road), which numbers on the xc race bike would I tweak to get it closer to my other bike,CRR,CDA,FRIC??