what actually is FRIC, help with profile please

[geoffsuperturbo]

the FRIC number seems to vary an awful lot when i am looking at calibration rides and coast downs trying to find my best fitting profile. if i use ibike settings or crr fixed, then the FRIC changes but is constant through all coast downs, but if i use Crr adjusted, then the FRIC numbers are all over the place, and that is just making a small adjustment.

I have just moved my Ibike onto my TT bike. this morning i did a fast start and cal ride (4miles) and 1 CD in the wind, then it rained before i could do more. i downloaded the ride and thought i might have a reasonable profile from it but wanted to be sure with more coast downs.
later in the day i decided to try another cal ride on a different road to compare, again 4 miles with more coast downs as i want to fine tune my CdA for accurate power, or more accurate than estimated. i didnt do another fast start before this cal ride

i performed 7 coastdowns, same piece of road, same direction. i noticed riding back to my start point after the first CD that the power in the coast window seemed high, anyway i completed the coastdowns, then decided to do another Cal ride 2.8 miles, same road but shorter. after all were done, i rode home and noticed the power reading was huge, i knew something had gone wrong.

i downloaded all coastdowns and cal rides but didnt see much in the way of consistency for the 3 cal rides. i also noticed that my wheel circ has changed from the morning ride, no idea how, it was fine after i sent the profile to the Ibike. i checked the EST aero in the Ibike , somehow it said .639 no wonder the power was so high on the ride home. it was .248 when i left home.

Anyway i set about trying to fine tune, 1 or all 3 cal rides, using the CD's so i could get to a number for Aero and Cda that looked right.. the thing is i ended up with different numbers for all 3 Cal rides. i used 3 to 5 of the best consistent CD's but ended up with different numbers so now i am confused which to use. I realise i may be trying to be too fussy about .01 here and .02 there but i would like to get it near right.
Best looking seems to be Aero of .257 and CdA of .244,this is using fixed Crr of .0030. i have fast rolling tyres. veloflex and conti supersonic. i think Crr on smooth chip and seal should be closer to .3 than .55. although these numbers look like they may be ok, the FRIC is 12.068, i'm wondering if that is at all relevant, is there a limit to what the FRIC should be, does it matter, it just seems high , but if i try to lower it the Aero and CdA will rise and the power will be unrealistic.

Any expert able to look over these if they have time? i wasn't able to add CD's too. but i could email them if needed. thanks

[racerfern]

A couple of things to note:
The moment you complete a calride, the results of that calride become the current profile.
The moment you finish a coastdown, the results of that coastdown become part of the current profile. If you do another coastdown then THOSE results become part of the current profile. IOW, don't pay attention to data shown on the iBike immediately after doing coastdowns.

You really need to look at the coastdown data after downloading and come up with an average of them. So take what shows after a calride and/or coastdown with a grain of salt until you actually get home and download all the data.

That said, you provided the rides, as opposed to the calibration file so I can't see what the coastdowns looks like. However, from the data supplied I used the earliest of the three since that has good wind data.

Try using the attached profile and you should be really close to a good profile.

Sorry, I'm not sure why the FRIC number is skewed on a couple of the calrides, again it's tough without the actual calibration ride.

[geoffsuperturbo]

ok thanks a lot, i guessed the coastdown had had some effect on the aero numbers or something, in fact the first one or two coast downs looked awful when i compared them to the rest, they must have thrown out all following calculations. i don't know why, as i was constant in my position and i began to coast in a very similar spot on the road and finished the coast in a similar place, so i don't know why there is a difference in data, i expected a very close set of numbers in the results as coastdowns seemed to go great. i did get 3 or 4 which had very similar results so used them only along with the cal ride i did immediately before them to get a profile, which as i said has very high FRIC.

sorry i am new at using the software. i dont seem able to view the file/profile that you have sent me, when i click on the file, windows tells me it cannot open it, i tried to view it and i tried to save it, neither appears to work. windows just tells me the file does not have an Ibike header so it wont open. i saved the file in the ibike rides folder but it doesnt appear in the .ibd or .csv rides list.
could you just tell me the numbers for aero and CdA you came up with for the profile and i can compare them to the ones i have. thanks for the advice. i will double check the coastdowns against the cal ride to make sure i am on the right lines

[geoffsuperturbo]

so is it ok to use CD's with a cal ride that was performed in the morning if i performed the Cd's in the afternoon after cal ride #2?
i presumed i may have to use CD's performed immediately after a cal ride to get accurate results. but strangely when i am doing that, i appear to be getting a bad profile from it with low aero and CdA numbers.
but by using the first cal ride 4.4 miles( which i think you suggested too) and adding to it the consistent CD's performed later in the day after cal ride 2, i get good looking numbers which i would expect from a racing TT bike.

[geoffsuperturbo]

finally, out of interest, what would be considered "too low" for CdA and aero numbers for a TT bike with good rolling resistance? do you have a record of what that bike and 161lb riders profile should be like? i ask because when i am tweaking the calibration rides and the CD's i did i come up with aero of .226 and CdA of .209 with fixed Crr of .0032. i'm no expert but they seem quite low, that also gives me FRIC of 12.9. on my road bike with tri bars fitted i was somewhere close to .296 aero and .288 CdA so i would expect lower on my aero frame and wheels and a lower position, but how low is too low for aero numbers?

[geoffsuperturbo]

have enclosed 2 pictures of the cal ride and coast down info using 2 different cal rides and most consistant CD's, which looks best for my set up? thanks

[racerfern]

OK, a couple of things. I didn't realize this was a TT bike. So... a reasonable CdA would be about .259 depending on your individual setup. I didn't realize this was a TT setup so take the file I sent you previously and discard it, sorry.

BTW, the file I sent you is a profile. So you save it on your computer then go into the iBike software, go to Profiles > Edit Profiles and click on Import. That will add the profile to your list of profiles. From there you can edit it if you want and of course accept any changes. Then you can send it to your iBike.

AERO and FRIC numbers are just that, numbers. They are the math result when taking into account all the variables affecting you and your bike such as weight, wind, tilt correction, Crr, CdA etc. That said, they're just numbers and can vary greatly. The key to a good profile is good Crr and good CdA. So a TT bike on tubulars would have Crr in the .003x range and CdA in the .259 range based on "typical" riders at your weight.

Next thing: When you are in the cal ride/coastdown screen or which you just posted screenshots, there are save and open buttons at the bottom. These save and open special files that contain ALL your cal ride and coastdown data. They have an extension of "ibcd4m". You can save this file then upload it to the forum so someone else can view it. This is also how you save previous calride/coastdowns and can erase them from the iBike.

It seems like you've got your head wrapped around it pretty well and the top picture looks like a winner with a CdA of .244. You can always edit the profile and push the CdA up slightly by clicking the radio button next to WIND so the wind doesn't change, then kick the CdA up a notch. The AERO number will automatically adjust itself. You should do things like this on a copy of your profile so you can always revert.

I hope this clears things up a bit. Speak up if you're stuck.

[geoffsuperturbo]

thats great advice and clears up a lot of doubts i had, will post again if i can't get it figured out

[travispape]

Fernando, Great stuff. Thanks for jumping in.

Geoff, it would really help if you can post that *.ibcd4m file that Fernando described. If you already deleted the data from the iBike, you can still find the file in a folder called "calibration rides" in your ride files folder. (It automatically gets saved when you send the new profile to your unit. If you cancel, it does not get saved.)

Here's general tips about the value of FRIC and doing coast-downs. If you can generate a set of coast-downs with a fairly well-clustered set of values of FRIC, you have done the difficult thing of prying apart the contribution of aero drag (CdA) and rolling resistance (Crr). Congratulations! Use the Crr adjusted value to measure both CdA and Crr independently.

If your FRIC results are scattered, don't worry about it. It is hard to isolate rolling resistance. The good news is that the AERO and FRIC pair of results taken together still give a good measurement of your drag, it just not partitioned between the aero and rolling components as accurately. Use the "Crr Fixed" setting and enter a reasonable value for Crr (0.0055 for typical road tires) and save your profile and you will still get excellent power measurements.

When your FRIC results are scattered, it is usually due to the wind conditions. Coast-downs are sensitive to any little wind gusts and especially tail wind. Also, be sure you did a good wind cal with the unit temperature thoroughly soaked at your riding temperature. (If you do another wind cal, start over with your set of coast-downs and cal ride.) Also, make sure your coast downs don't last too long--don't go downhill. Use a flat, or ideally a very gentle uphill.

Travis

[geoffsuperturbo]

ok, i managed to find 4 ibcd4m files saved from the date in question. i have included 3 of them, i presume each is a different cal ride which i have played around with in an attempt to get a good profile. any advice welcome.

[racerfern]

I looked at the calride/CD files and still come up with the same numbers. .259 for CdA and for Crr I need some more info. Are you on tubulars or clinchers? Also, can you upload a picture of you, in your typical TT riding position?

FWIW, your coastdowns tend to have a nice grouping then all of a sudden there are a couple of outliers. As Travis said, the purpose of coastdowns is to separate CdA from Crr. It's relatively easy to determine total drag, but how much belongs to Crr and how much to CdA is tougher to determine. The "perfect" set of coastdowns would have little or no wind (always try into a headwind), a slight uphill of about +1% and road surface similar to what you typically ride on. You would like to have your coastdown drop from 20mph to 8mph within 15-30 seconds. If you're coasting for a minute, you're just allowing more time to introduce error. In addition you would not have any car traffic and certainly no other cyclists. How's that for tough requirements?!? Let's face it, LIFE isn't friendly for coastdowns.

This is one of the reasons the fast setup and/or the setup wizard work so well, as they eliminate the variables that inevitably crop up. BTW, when doing coastdowns, it's important that you hold your riding position without shifting around on the bike, taking a drink, etc.

[geoffsuperturbo]

yes i always keep the same position on the bike for coast downs and do not move at all, i even try to begin coasting at around the same part of road.
on the 6 or 7 CD's i did last, the last 2 i tried a different hand position to see if it affected results, the last was also in a different direction into different wind, so you can ignore the last 2 that i did.
i found a nice quiet road slightly uphill, but expecting a still day just isn't going to happen, i think still days are a thing of the past.
i ride high pressure clinchers, a veloflex record and a conti supersonic, both supposed to have crr around .00250 i think, so on the roads i ride i think ..30 to 32 is going to be close so i like to fix that value in calculations.
will try to take a picture of myself tomorrow.
i have a 2up tt tomorrow(if it isn't raining, which might also be too much to hope for) it will be interesting to see the results of that and see how the effects of drafting show up on the power graph, and to see how close i am to the power i would expect when i am on the front.
my current profile has Aero .265 cdA .251 and a Crr of .0030 which is a user edited profile(due to the Crr adjustment i think). if my power seems high using this profile then i intended to change to aero.257 and .244 Cda with crr of .0032 which i got from the same cal ride and coast downs, unless you can come up with better suggestions in the meantime.
pictures to follow, thanks

[geoffsuperturbo]

here are 3 pics of my ibike set up on the bar end, best place i can find for clear view of the wind, and i think clear of turbulents from my hands.
todays TT was a disaster, the profile is hopelessly wrong. firstly for some reason pulse failed and i had to ride on feel alone, so have no pulse data, secondly the Ibike was showing very high watts for my effort on warm up and in the race. my aero and CdA numbers are quiet low but need to be lower or the FRIC number is throwing things out. looks like i need to go back to the drawing board on this and do another cal ride and try to get better coasts. the power i was getting during the event was useless. i don't know if it can be tweaked in the analyser. i did a tilt and wind before the event when the unit had cooled down, but it didnt help, the profile is off, way off.

[racerfern]

I'll review the info I have on you. That's a pretty unique setup. Stand by.

[geoffsuperturbo]

ride file of the 2 up, conditions very windy, headwind/side wind out. i dont know if any useful info can be gotten from this file, hopefully an expert can tweak something. analyze wind doesnt look right so it may be something to do with that which is throwing the numbers out. i did a calc wind before the event, maybe it was too soon before?

[geoffsuperturbo]

I'll review the info I have on you. That's a pretty unique setup. Stand by.

lol, im well known for my uniqueness

[racerfern]

Right off the bat as I sit here at work, I see a potential problem as your arms are completely blocking any wind coming from your left side. Whether a cross wind or even a 45 degree headwind, your forearms and hands will probably have a significant effect.

That said, with the iBike out in the wind flow, having a wind scaling of 1.x makes sense though the crosswind issues are a concern.

[geoffsuperturbo]

ye i can see how wind from the left will be affected, but for the time being there is no other place i can set up. i was considering fitting an extra tri bar extension which drops down at 45 degrees so the uniot would be between the top of the wheel and the bottom of my arms but i couldnt get the unit level and it looked kind of cumbersome too. plus i'd be adding drag and weight to the bike. i will have another look at positioning before i ride again or do cal ride, but the problem is in the profile rather than position of th unit i feel.

[KenS]

Or get the Remote Wind Sensor (RWS)?
http://www.ibikesports.com/detail.aspx?ID=72

[racerfern]

OK, you've got to get to a more conventional setup. Because of the location you've got vibration issues which can be seen by clicking Analyze Route then clicking Show Tilt Plot. The light grey band that should be virtually nonexistent on G3 units extends for a very long time. This is unacceptable.

You NEED to get the unit close to center and use the RWS. Note that you can put the end of the RWS out where the iBike is now, that will work but still with the limitations of crosswinds as previously mentioned. Perhaps you can set the RWS to be below the arms.

Also for these test times can you please switch to one second recording?

If you were to increase the wind scaling by .1 more then it seems better for wind however, that raises your wattage even higher. What are you expecting to see for watts based on your experience because your profile can't be off by very much.

[geoffsuperturbo]

ok thats interesting to know about the vibration, i presumed the bar would be quite solid in that respect, obviously not. i'm not really sure i have room on the stem to mount the unit as my arm pads are close, i will look into it again, i'm currently trying to set up the ibike on an aerobar extension which slopes down to between the top of the tyre and my arms, similar to the Topeak extension method, but being out on an extension i'd expect even more vibration than on current bar position so maybe i'm wasting my time trying that. obviously the unit needs to be somewhere i can see the output so it is tricky with my bar set up the way it is. i have an important race next weekend and i think i'll struggle to get a set up and profile before then.
i went out today on my training bike for a longer ride and the GEN1 behaved itelf and i was happy with the power numbers it was showing, they seemed realistic against my percieved effort, while the TT bike was nowhere near. i was an average today of around 320 watts on the climbs at around race effort or trying very hard i could hold 420 for a minute or so. On the flat i may struggle to average so much as 320, maybe i could average 280 to 290 for an hour, which would be around 4watts p/kg. it is hard to judge as the power jumps around a lot during a ride. i was seeing over 400 too often on the TT bike and with less effort, even over 500 at times, clearly something very wrong. even riding to the event the numbers were way too high for such a low effort.
well at least i seem to have a good profile for the training bike. thanks for the input

[geoffsuperturbo]

Fernando, i have looked at mounting the Ibike on the stem, it is not possible, firstly the stem is oversized and the mount will not fit, secondly there are cables running over the stem that are in the way, 3rdly the stem angles upwards and the unit would not be close to level. in other words, forget stem mounting.
therefore i am working on a set up similar to the topeak extender, it is not going to be pretty but i will be able to set the unit below and between my arms and central, for full view of wind from all sides. if i can find a way to bend some piping i can do a neater job later. will post a photo in a day or two.
then i think i need to get out for a new cal ride and coast downs as the data i collected so far is not usable for whatever reason.
thanks
geoff

[racerfern]

I can see the stem in the picture. IIWY I would still try to come up with some kind of modified bracket for it. All that you really need is that the screws pass on either side. You can buy longer screws at a hardware store. They are american thread 4-40.

Search the forums here for ways to make a mount out of epoxy that sits on top of the stem and makes the wireless mount level. I put a layer of electrical tape on my stem and then built my epoxy base onto that. It's easily removable if necessary. Someone else used some special material to epoxy directly to the stem. Another user has made a bracket that attaches to the holes that hold the stem cap onto the stem. I'm using it on a bike and it works very well.

There are solutions, there always are.

[racerfern]

Here are two shots of my friend's custom mount. Can you make something along these lines work?

Also a picture of my homemade stem mount for a high angle stem. This, with some 1.5 inch long 4/40 screws and you're home free, I used a rubbery filler piece from a light that is supposed to go around a seat post. I shaped it to my needs then filled it with two part epoxy. It's ugly as sin but under the mount you don't even notice it.

[geoffsuperturbo]

i'm working on something at the moment which would set the ibike above my arms, i figured above or below makes no difference, it is going to be in the wind. the only problem i have now is that it is set too far back and i'm worried my breathing may actually affect wind reading, it would be just a few inches below my chin.
my new idea looks very extreme but is rock solid on a bar straight up from the stem. maybe i have it set a little high but im trying to avoid wind bouncing off my arms and into the ibike . it isnt pretty but i would think it will get a good view of wind if my breathing doesnt affect it. i may end up lowering it a touch so it doesnt look so wacky. i'd like to move it forward though if i can find a way to do it.
to me the ibike in your picture looks too high and close to the hands and bars and i would think there would be turbulents and blocking of the airflow to the ibike.
i was considering a set up like that but i thought if the ibike was on a long extension i may have vibration problems so i scarapped it.
i was working on having the ibike lower , well below hands and bars. just the vibration issue put me off doing it. but yes i can come up with something along those lines if you dont think my new idea is worth running with. i ll add a pic of my set up now, tell me how bizarre it looks and if i can lower it without getting my arms in the way of it.

[geoffsuperturbo]

actually it looks better on the pictures than from my view, just fits in that empty space nicely. still worried that breathing may mess up the wind though and lowering it may help, or moving it forward, i have some other ideas if this wont work

[geoffsuperturbo]

a piece of tubing clamped directly onto the stem,(which i have changed to a narrower one), this make a very solid base for the unit and i think less prone to vibration than having it on a horizontal arm. all connections very solid, should be no movement, and good view of the wind from all areas.

[racerfern]

I think you extended your leverage arm from a horizontal direction to a vertical one. Why don't you put it on the stem where it's solid and stable. Even my friend's small bracket initially had vibration issues until he made me a beefier one, and that was only two inches long.

Then you can run the remote wind sensor down and make a small bracket to have the end of the tube sit about the middle of the downtube. It doesn't have to stick way out in front and doesn't have to be way down. Maybe around the "mi" of Jamis. Think about running a thin piece of Al or other metal straight down from the junction of the stem and the bars with a hole or twist at the end so you can secure the remote wind sensor.

Good luck.

[geoffsuperturbo]

the tubing is cut short and clamped to the stem, not running from the bars, it is very solid . i may cut it a little shorter to lower it slightly.
To be honest i'm not too keen on the idea of importing a RWS as the price seems extortionate for what isn't much more than a piece of plastic tube. by the time i paid 60 dollars plus, and mail cost , and possibly import taxes, i'd be looking at a bill of 80 or 90 dollars, maybe more, for something which may look better but i dont see why it would work any better than a standard ibike unit, or surely they would be built into the ibike as standard for all bikes, not just TT set ups.

your advice has been great as always. i'm looking for a set up without an rWS . i'm not sure i could get a more solid set up than i have now but will look into ways to improve later. i only have 3 days to get this set up and a working profile in place before my event on sunday. the weather is terrible, the wind has been like a gale for days. i dont know how i am going to get a cal ride and useful coast downs done in time.
with your help i'm a bit more clued in as to what i should be looking for to make a profile, so hopefully i can manage it. if i do manage to get set up and calibrate, i'll post the results, and we'll see how far off i was with the last one, which obviously went wrong at some stage.
regards
geoff

[geoffsuperturbo]

i managed a ride today with the ibike set up as in the picture, just lowered slightly, at first sight it seems another hopeless attempt to get a good profile. the protocol of todays ride. i use the GEN1 as i want the GEN3 on my training bike to avail of the inbuilt training sessions.
i rode a couple of miles and then did 5 coast downs, then did another wind offset, then 3 more coast downs. all coast downs went well, though a car did go by on the last one i didnt feel much draft from it. the road was slight uphill and the wind was from the right, though not strong or gusting. a hedge also blocked most of it. i thought i would have very consistent results, but with Crr fixed i certainly dont, apart from 3 which are close.
Then as there is seemingly no cal ride in the GEN1 set up, i just did an out and back ride, around 7 miles. however, looking at the profile it doesnt look very out and back and i appear to be in a tailwind all the time when looking at the wind. i dont know what was going on and why the profile does not appear to mirror the first half in the 2nd half. the power on the first half was too high and after the turn it was rediculously high. wind scaling was also high. there were a few lorries on the road when i did the ride so got several gusts in the mid part of the ride on the main road.
i tried get a profile from the ride and coast downs but the CdA comes out very low and the aero a little higher than i would expect when using the Crr fixed, which i think i should as .0034 is a pretty accurate estimate of fast rolling tyres on reasonably smooth chip and seal road.
i'm getting very frustrated by the Ibike now. i will play around with the coast downs a bit longer and try to find some consistency in the results, but the wind scaling of 2 i presume is not a very good starting point for a profile. i thought the ibike had a good view of the wind and scaling would be better. i will post the first profile file that i made but i doubt it will be usable