Struggling with ibike for TTing

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gerrard
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Struggling with ibike for TTing

Post by gerrard »

Have been using the ibike for several months now and it's give me a lot of insights into my riding and training. However I'm still struggling with getting the best out of it in TT position.

I custom mounted very similar to this http://www.ibikeforum.com/viewtopic.php?f=27&t=1350, did a new cal ride, and made a manual adjustment to my profile for the rough roads I ride on. I tend ride outside once a week for up to 4h, with 2-3 trainer (Kenitic road machine) sessions in between.

The things that are currently bugging me are:

1) Indoors I have an FTP around 302 watts but on the road can only get it to 269 watts (have retested before and after changing to TT position and got very similar results). I recognise there will always be difference indoors vs outdoors but what could I do to get them closer (and which is more accurate - indoor I assume given the trainer has a known resistance curve?)

2) I can't ride areo position 100% so when I sit up on the hoods (traffic, intersections, tight roads, got swallowed by a large bunch for a while the other day, etc) power readings drop dramatically. Fernando explained why and I understand this is just the way the ibike works, but if I have to much riding out of position then it's much less useful

3) The majority of our roads are rough, but there are some smooth patches too. Some of the routes I take end up with long stretches (5km - 25km) on a smooth road. When I'm on smooth roads the power reading goes up (estimate 25% or more from where it was on the rough road). I assume this is just because I'm going faster because of less road resistance therefore ibike calculates I must be putting out more watts.

Points 2 and 3 above mean that the numbers I'm seeing on screen during a ride (power, kJ, IF, etc) are not accurate, and this carries though to the data I'm analysing afterwards. This makes it very difficult to ride to power during a session, or properly analyse afterwards. Lately I've found myself riding to HR a lot more simply because it is a more consistent measure across all these variables.

Can I do anything to make it more accurate across these issues, or have I hit the limitations of ibike?

Thanks
Gerrard
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Morocco Mole
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Re: Struggling with ibike for TTing

Post by Morocco Mole »

Hi Gerrard

Don't assume the indoor trainer mode is correct, I used some of the included power curves for my Kurt Kinetic but couldn't really get accurate enough without using a powertap to generate my own Trainer Profile. Even then it seems to vary, possibly due to tire pressure, resistance on the roller etc. Regarding the issues of not riding in the aero position (traffic, intersections, tight roads, got swallowed by a large bunch for a while the other day, etc) I would argue that in these situations it's not that important as you are probably not smashing along at threshold power, it's too dangerous anyway and really requires a quiet section or loop without interuptions.

So yes, you have found the limitations of the ibike, so it's a matter of using it as a tool where it is effective. For TT training, which should be all about increasing your Power at Threshold or FTP, I have found a loop where I can do anything from 5 mins to 1 Hour in a safe situation, without stops. My ibike TT profile is tuned for this loop in the aero position and I use the USER Interval Mode to record my efforts. In this way the ibike enables me to compare my performance and progress within the Training zones that matter for this event, I don't worry too much about the variablility or inaccuracy while riding to or from the circuit, which is really just the warmup, recovery, cool down portion of the ride. You won't be able to view IF, TSS, NP on the iBike while you are doing these efforts, but the ibike software (or WKO+, GC etc) will allow you see that when you have downloaded the file.

If your ride does have a couple of distinct sections you could always do a TRIP RESET at each leg, eg Ride with Group, 2 x 20 FTP, Ride Home cool down. This would give you 3 seperate files where you could apply a different profile to each when you got home. I would still ensure the active Profile is the one that matches the important part of the ride eg 2 x 20, so that way you get accurate live data during that part of the ride. The benefit of splitting the ride up would be that you would get a more accurate total IF, TSS etc which may be important if you are tracking TSB\CTL\ATL .

One last thing, I tried a bunch of mounting options on the TT bike, everything became much more accurate in all positions when I installed the RWS, definately a worthwhile upgrade IMO

Hope this helps

Regards
Jim
gerrard
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Re: Struggling with ibike for TTing

Post by gerrard »

Hi Jim - thanks for the quick reply.

Yep I've got a RWS. Good point about not assuming the training is totally accurate too.

The ibike's given me a great start but I guess my decision now is whether to spend the bigger $$ for a different one (hmmm, new bike or power meter...). In the mean time I'll definitely keep using it on the trainer since I spend a reasonable amount of time there, and I like your idea of tuning / calibrating it for a common route too.

Cheers
Gerrard
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Morocco Mole
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Re: Struggling with ibike for TTing

Post by Morocco Mole »

Another point regarding the calibration for a known route or circuit, my profile even considers that I am doing 40kph - 45kph+ during my work intervals. For the life of me I cannot get a profile that is accurate at normal riding speeds eg 30kph , and still accurate at higher speeds. I often ride with a powertap so I'm using that as a baseline for testing and tweaking of the profiles, I also note this behaviour on my road bike as well as the TT bike as I use both for threshold training. At high speed I need to drop the CDA a little (from 3.5 to 3.3), not sure if I subconciously get more aero when going faster, although I'm in the same position (on hoods on roadbike, aerobars on TT Bike) I might get a bit more compact, your heads tucks in, elbows in etc ?

Not sure how this can be incorporated into the coast down process which is used for determination of your CDA. Velocomp, what is the affect of starting the coastdowns at say 45kph (28mph) instead of the current recommendation? Would this produce a more accurate high speed profile?

If I recall, there used to be a setting somewhere in the iBike software\profile where you could define a cutover point where it would switch profiles depending on speed, although I can't find it anymore. Was I dreaming?
Last edited by Morocco Mole on Mon Sep 19, 2011 12:53 am, edited 1 time in total.
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Morocco Mole
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Re: Struggling with ibike for TTing

Post by Morocco Mole »

Morocco Mole wrote:Another point regarding the calibration for a known route or circuit, my profile even considers that I am doing 40kph - 45kph+ during my work intervals. For the life of me I cannot get a profile that is accurate at normal riding speeds eg 30kph , and still accurate at higher speeds. I often ride with a powertap so I'm using that as a baseline for testing and tweaking of the profiles, I also note this behaviour on my road bike as well as the TT bike as I use both for threshold training. At high speed I need to drop the CDA a little (from 3.5 to 3.3), not sure if I subconciously get more aero when going faster, although I'm in the same position (on hoods on roadbike, aerobars on TT Bike) I might get a bit more compact, your heads tucks in, elbows in etc ?

Not sure how this can be incorporated into the coast down process which is used for determination of your CDA. Velocomp, what is the affect of starting the coastdowns at say 45kph (28mph) instead of the current recommendation? Would this produce a more accurate hight speed profile?

If I recall, there used to be a setting somewhere in the iBike software\profile where you could define a cutover point where it would switch profiles depending on speed, although I can't find it anymore. Was I dreaming?
Ha,Ha, found it "Add 2nd CDA"
2nd_CDA.jpg
2nd_CDA.jpg (40.1 KiB) Viewed 21362 times
See comment from Travis at the end of this thread

http://www.ibikeforum.com/viewtopic.php ... +cda#p2136

another good reference on 2nd CDA http://www.ibikeforum.com/viewtopic.php ... d+cda#p968
gerrard
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Re: Struggling with ibike for TTing

Post by gerrard »

I've got to say I am constantly amazed at all these small cleaver things you can do with the ibike. If you're prepared to spend the time and understand all the ins and outs of it then you can get a lot out of it that's for sure.
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Morocco Mole
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Re: Struggling with ibike for TTing

Post by Morocco Mole »

Well I went looking for the "Second CDA" function in the ibike software last night, couldn't find it. Does anyone know if it was dropped in one of the updates. I have a GEN III iAero reference manual from 2009 where it is mentioned but the screens don't seem to match the current software.
TriBike
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Re: Struggling with ibike for TTing

Post by TriBike »

I must say I agree that there can be some variances using the iBike on a trainer, I tend to see bigger numbers when I use it on a trainer too. I use a CycleOps Fluid 2. We are also creating a software that will be available shortly to help "tweak" your profile. The program will recognize mis-calibrations, and help you to dial in your profile numbers. I have used the preliminary trials of the software here at the factory, and I think it is absolutely amazing. I think you all will be impressed when it is released.
Todj
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Re: Struggling with ibike for TTing

Post by Todj »

TriBike wrote:I must say I agree that there can be some variances using the iBike on a trainer, I tend to see bigger numbers when I use it on a trainer too. I use a CycleOps Fluid 2. We are also creating a software that will be available shortly to help "tweak" your profile. The program will recognize mis-calibrations, and help you to dial in your profile numbers. I have used the preliminary trials of the software here at the factory, and I think it is absolutely amazing. I think you all will be impressed when it is released.
Any idea (roughly) when this is likely to be? :)
Regards,
Richard
gerrard
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Re: Struggling with ibike for TTing

Post by gerrard »

I'd be happy to idiot test it if you need someone in the field ;)

Interestingly I went and did a VO2max test yesterday which pegged my FTP at 306watts. My testing on the trainer comes out at 302, and on the road 269. That suggests the trainer is reasonably accurate so I'm now wondering how I go about changing my profile to better reflect reality when on the road.

Current profile attached if anyone cares to offer suggestions.

Thanks
Gerrard
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Todj
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Re: Struggling with ibike for TTing

Post by Todj »

@gerrard

I'm certainly no expert on profiles and I'm trying learn as much as I can from the gurus.

No doubt the experts will be along shortly, but my observations would be:-

1) Wind scaling looks high. You and I look to be about the same size, and on my TT bike I was advised to go to circa 0.700.
2) Riding tilt for a TT machine looks low at -0.1%. On my road bike I'm on -0.5% and on the TT bike with more weight on the front it's nearer -1.0%.
3) Cda looks about right (mine is 0.270 in skinsuit and pointy hat, rather than your winter clothing, but I have a physical spinal problem that stops me getting very low)

Hope that helps. ;)
Regards,
Richard
gerrard
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Re: Struggling with ibike for TTing

Post by gerrard »

Todj wrote:@gerrard

I'm certainly no expert on profiles and I'm trying learn as much as I can from the gurus.

No doubt the experts will be along shortly, but my observations would be:-

1) Wind scaling looks high. You and I look to be about the same size, and on my TT bike I was advised to go to circa 0.700.
2) Riding tilt for a TT machine looks low at -0.1%. On my road bike I'm on -0.5% and on the TT bike with more weight on the front it's nearer -1.0%.
3) Cda looks about right (mine is 0.270 in skinsuit and pointy hat, rather than your winter clothing, but I have a physical spinal problem that stops me getting very low)

Hope that helps. ;)
Ah, and thus the secret to ibike - knowing what all the numbers mean and do!

Crr is the only thing I have manually adjusted before, on advice from another NZer to account for our fabulously bumpy chip seal roads. Although it was after I made this adjustment I started to notice bigger variations in the reported power between smooth and rough road surfaces.

Wind scaling comes directly from my calibration ride (I believe). My cal ride was not on a perfectly calm day as that's almost impossible to achieve round here. There was a tail wind of 5 - 10kph on the way out, and headwind returning. Should I just change the wind scaling manually and see what that does to the numbers, or is it all related to how the ibike is mounted etc?

What does the tilt do / mean? Again, related to the mounting, or something else?

Cheers
Gerrard
gerrard
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Re: Struggling with ibike for TTing

Post by gerrard »

Bump. Can anyone help to tweak my profile / advise what to do to get better power readings?
gerrard wrote:
Todj wrote:@gerrard

I'm certainly no expert on profiles and I'm trying learn as much as I can from the gurus.

No doubt the experts will be along shortly, but my observations would be:-

1) Wind scaling looks high. You and I look to be about the same size, and on my TT bike I was advised to go to circa 0.700.
2) Riding tilt for a TT machine looks low at -0.1%. On my road bike I'm on -0.5% and on the TT bike with more weight on the front it's nearer -1.0%.
3) Cda looks about right (mine is 0.270 in skinsuit and pointy hat, rather than your winter clothing, but I have a physical spinal problem that stops me getting very low)

Hope that helps. ;)
Ah, and thus the secret to ibike - knowing what all the numbers mean and do!

Crr is the only thing I have manually adjusted before, on advice from another NZer to account for our fabulously bumpy chip seal roads. Although it was after I made this adjustment I started to notice bigger variations in the reported power between smooth and rough road surfaces.

Wind scaling comes directly from my calibration ride (I believe). My cal ride was not on a perfectly calm day as that's almost impossible to achieve round here. There was a tail wind of 5 - 10kph on the way out, and headwind returning. Should I just change the wind scaling manually and see what that does to the numbers, or is it all related to how the ibike is mounted etc?

What does the tilt do / mean? Again, related to the mounting, or something else?

Cheers
Gerrard
TriBike
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Re: Struggling with ibike for TTing

Post by TriBike »

The best way I can explain the tilt to you all is basically, the calibration teaches the unit what "level" is on the bike, as often the unit will appear to be at an angle when mounted, it will know that the bike is level. Hope that this helps.
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lorduintah
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Re: Struggling with ibike for TTing

Post by lorduintah »

Tilt - I think you could easily add to not just knowing what level is - since rocking back and forth while riding, how the iBike was mounted and so on - tilt allows estimating the effects of gravity while you and the bike are in motion. Ultimately if you start riding in a circle - regardless of how many hills you climb and descend in between, you have a net zero tilt, if you go back to the point of origin on a ride. In between you fought gravity and gravity made part of your ride a little easier.

Tom
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