Difference between aero and road helmet profiles

[thebilly_b]

So I recently recalibrated everything as I was worried my readings were a little low (on different days of different temperatures, which can't be helped, but did do a wind cal before both and it was on exactly the same course). My road bike helmet profile seems great now - I'm getting the readings I expect. My aero helmet profile I think is OK too but I won't get the chance to properly properly test it before my next race now. So the wind scaling on my road helmet profile is 1.685, and for my aero helmet profile is 1.450 - does this sound right to you, and do you think this will produce similar readings across the two profiles? I need to be sure of this so I can be certain of my pacing on race day.

[thebilly_b]

Also, when I download the cal ride, it comes up with 3 cal rides - one 2.6 mile (while I was riding to the course), one 4.0 mile (which is the actual cal ride that I started from the setup menu) and another, 2.8 mile ride where I took a slightly different route riding home again. After the 4.0 mile ride it did the usual "Cal Done" business, but can I be sure that is correctly using that 4.0 mile ride rather than the others?

[racerfern]

Rest assured, the profile after your 4 mie cal ride when you got CAL DONE is in effect.

[thebilly_b]

Thanks for this - any thoughts on the windscale numbers?

[racerfern]

Helmets have a huge effect on the aero and of course that will affect wind scaling though I don't know how much. That said, I do think your wind scaling difference is pretty significant so could you post your cal rides.

[thebilly_b]

I don't have my road bike cal ride anymore (at least it doesn't seem to download it) but here is the one from the aero helmet. Thanks for looking at this.

[thebilly_b]

Also I should mention this is using a TT set up, steerer tube and RWS, is this still the sort of number you'd expect to see?

[thebilly_b]

Sorry to add more to this but I just looked at a seperate ride I did yesterday with my road helmet profile and it's showing effort speed as pretty much always being higher than my actual speed i.e. headwind the whole way. I have the RWS on my left handlebar - right up by the brake - do you think this is right?

[racerfern]

Can you download this as just a regular ride rather than download it as a calibration ride with coastdowns please? It should end with .IBR extension.

[thebilly_b]

Sure, how is this?

[racerfern]

My issue with your profile is not the wind scaling, that looks pretty good. My issue is your tilt. At 3.2% it throws everything off. I suggest you redo your cal ride with the following considerations. Assuming this is a TT position your tilt should end up somewhere in the -.5 to +.5 range. It might go higher or lower but not by much.

1) Check your firmware and upgrade from 4.0 to 4.08. There are significant improvements to the cal ride process that will balance things out better.
2) Do a good wind offset prior to the cal ride.
3) Do a tilt offset prior to the cal ride. I realize the calride figures things out but you're starting so far off where you should be I'm not sure the calride is figuring things out correctly.
4) Ride to your calride spot as usual, do the calride, then turn around and immediately do another out/back ride on the same course as the cal ride. Don't do another calride, just a regular ride after the calride. Ride home.
5) Download and post.

[thebilly_b]

Thanks for this - I will try to do that some point this week. How do I do a tilt cal now that it's not in the setup menu anymore?

[thebilly_b]

Also, will this completely make my readings unreliable, or will they just be scaled slightly wrong - i.e. 210 watts on the Newton might actually be 230 in real life, but 220 on the Newton is 240 in real life, or is the relationship not linear? The reason I ask is that I did a FTP test yesterday just so that I had something to pace off for that profile for my race next weekend, even if it wasn't the correct scientific watts if that makes sense? Obviously if the relationship is gibberish I will have to redo it, but if not, could I just use that for the meantime? It might be hard to find the time to do another FTP this week in a taper.

[racerfern]

After upgrading to 4.08 you will find the tilt cal in the RACR menu.

Your readings may be off proportionately. So if you did a fitness test stick with that FTP result, train and race with those numbers. You're looking for IF numbers and AVG watts over the long haul and they will be in line.

When you have time and it fits into your schedule plan on doing the cal ride then out/back. Post those numbers and assuming it's all good you'll be able to plan a fitness test. But as you know, don't do this in the middle of your training for a race. As I said previously, stick with what you have for now.

[thebilly_b]

OK so I did as you said - I made a new profile so I could keep my old one just in case, I did a tilt cal first, rode to the site, did a wind cal, did the out and back cal ride, and then most of the out and back route again ( had to leave because of time but there is enough there). I have to say I'm still not convinced - I got home, put my bike in the tilt cal position, pressed the hill button and it said -0.7% This is on a completely flat automatically level concerete floor! Stuff like this is going to lead to 20-30 Watts difference. Other profiles have similar issues, my one I mentioned previously that I'm going to race with says 0.7% and my other one says 1%! This are obviously going to lead to insane differences, sort of negating the point of repeadabilty training with power and I'm getting quite frustrated now. Can I do a tilt cal again on all these profiles, WITHOUT losing my cal ride? And will this fix it? I've attached the files for you.

[racerfern]

There is no need to concern yourself with the tilt as the bike sits there. Once you've done the initial tilt cal, the rest is automatically set when you finish a ride and reset the ride data. Rest assured your tilt cal is not an issue. As far as the new data you attached I'll have a look later on and comment.

[thebilly_b]

Thanks for the info - but why does the unit not display 0.0% when it is on flat ground if this is the case?

[racerfern]

This has been discussed previously. The reason it doesn't show zero is because you're not on the bike and that's the tilt we're concerned about, not a bike just sitting there.

[racerfern]

You've got a good profile to use from here on. Unfortunately I can't absolutely confirm because you took a different course for the out/back but it does seem you've got a good profile. The wind scaling is in the range of the first one. I'm still surprised your tilt is as much as it is and have to ask:

Is this a TT bike? And of course I assume you are in the TT position if so. Without standing there watching you do a cal ride there is no way for someone on the other end of the internet to know the circumstances, hence the very specific questions.

IF you have issues with tilt then you need to look at a loose mount (at least not completely locked down) a loose head set, something out of the ordinary. You're quite light so I would not expect to see a huge difference from zero for tilt. The first time it was +3.2 and this time is it -1.6. Both those numbers are not something I usually see hence once again all the questions.

Lastly, these questions should not make you wonder if the Newton is working properly, it should make you wonder what in your setup could be askew. For now, ride with your original profile as you have an upcoming race and then later you can do a fitness test with this new profile.

If you can continue posting rides, I'll gladly look at them. Have fun!

[thebilly_b]

Thanks for all your help Fernando - you've put my mind at rest! I'm glad that's all working properly at that, as you said, my setup is dialed in now!

I am using a TT setup, with the steer tube mount - I'll post a picture soon and you can see what you make of it. It's all tightened down a lot so I don't think there's anything loose - there's quite a short stem on the bike (60mm) so I don't know if that's anything to do with it, affecting the accelerometer when I turn ect?

Thanks for looking at this, don't know if you are an iBike employee or not but it's been a great help - I'll post the ride file from my race and we can see what we make of it.