Using Newton on a Touring Bike

KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Zoltan wrote:where cell B4 is (average) altitude in meters, B21 is temperature in Celsius, B24 is barometric pressure in hPa and B25 is relative humidity in %. As I remember I could find many formulae, but all of them used not more than three of these four variables. I am not good at physics, so did not understand why none of the formulae used all the four variables, so I tried to incorporate all the four and I succeeded. But even I was shocked that finally this long formula gave me plausible values.
You don't need both altitude and barometric pressure since they are related. The iBike uses a barometric altimeter to determine altitude from the barometric pressure. I back calculated the barometric pressure from the rho value in the iBike file using relative humidity (RH) of 50% then recalculate rho using the correct RH. This gives you the correct pressure at all points during the ride.
-- Ken
Zoltan
Posts: 213
Joined: Mon Jan 23, 2012 9:47 am
Location: HUNGARY

Re: Using Newton on a Touring Bike

Post by Zoltan »

Sorry but I disagree. You may need barometric pressure, because in my case it is the air pressure at sea level, which is corrected by your altitude to get the air pressure at that altitude.
At least in my country the air pressure published by all the national weather data station are adjusted to sea level. Unless you have a mobile pressure gauge device like ibike, you do need both data. And my Excel sheet is from that time when I had no gadget with me when cycling , just a Garmin 60csx and when I returned home I checked the weather data on the web.
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Fair enough. When you included barometric pressure I didn't realise you meant a reference pressure at sea level.
If you are using altitude from your Garmin there's a couple of tricks when calculating power etc...
- Use the uncorrected altitude to get an accurate barometric pressure
- Correct the altitude for pressure drift to get an accurate elevation gain
-- Ken
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

So I did a couple of quick tests recently but I hasten to add the conditions were not great with strong gusty winds.
First test was a calride, coast downs, 6.4km out and back then two downhill rolls with my touring bike and the second the same with my new road bike. I had to calibrate both anyway. The tourer because I previously had the wrong wheel circumference and the road bike because its new.

Conditions were worst with the tourer so I'll have to redo them next chance I get. I did a tilt cal and wind cal in the garage at home before heading over to my cal ride/coast down site. The wind was changing during the cal ride so chances are the WSF is out. Plus by the time I finished and was about to start the coast downs 20 minutes had passed and Newton made me redo the tilt cal and wind cal out in the open so they are a bit suspect also.

With the tourer if I let Isaac determine the Crr from the coast downs it came out with Crr of .0096 and CdA .535
Plugging in the downhill roll into my spreadsheet gave a Crr of .018 and CdA .301
However, one mistake I made was to start pedalling down the hill first rather than a standing start. A standing start is important so that speed is low and rolling resistance dominates over aero.

For the road bike with better conditions and a standing start for the downhill rolls I got:
From the coast downs Isaac gives Crr .0026 and CdA .386
The downhill roll gave Crr .0024 and CdA .375
So a confidence boosting correspondence there. But I am intrigued that I always seem to get better Crr values than expected
-- Ken
Zoltan
Posts: 213
Joined: Mon Jan 23, 2012 9:47 am
Location: HUNGARY

Re: Using Newton on a Touring Bike

Post by Zoltan »

"So a confidence boosting correspondence there. But I am intrigued that I always seem to get better Crr values than expected"

Yep, these numbers are very low, I mean in casoe of road bike. Do you have a clincher or tubular? For a clincher
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

I've got clinchers. GP4000S 700x23 @ 100psi on Campag Zonda wheels

Maybe a result of the wind conditions. If the wind ever eases up here I'll try again but that may be a while off yet.
-- Ken
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Today I got out on the tourer to do some more testing. I found a good spot with a dished road so I can roll down then roll up the other side then repeat from the other direction without having to brake. I did 4 repeats (4 times each way) which came to a distance of over 3.2km so enough to also do a Check Calibration in Isaac afterwards. By turning around in the same spot at each end I could also make sure the elevations and slopes are accurate. There are three spots to check -one at each end and a third at the bottom of the dip.
Procedure was to pedal one turn at most to get started then accelerate down the slope and coast down to 8km/h on the uphill side. Then pedal to the turnaround point, do a U turn and repeat - no braking.
There was a moderate wind and a bit gusty but not as bad as when I did the last calride
From the previous calride and coastdowns I had WSF 1.096, Crr .0096 and CdA .535
Check Calibration on this ride said the WSF needed tweaking (not surprising)
Tilt was also way out (=-0.6 versus -0.1) but maybe due to the low speed coasting. I think I read that when doing coast downs you put more weight on the handlebars and this affects the tilt cal.
I applied the corrections to the file and exported to CSV.
Plugged the elevation profile from iBike and Garmin into a spreadsheet and also calculated a profile from the iBike slope values. I made various adjustments to line these up using the three checkpoints then took an average for the "true" profile and gradient.
The spreadsheet also graphs P/v against va squared where:
P is the difference between power as measured by Newton/Isaac and the theoretical power
v is road speed
va is air speed
This basically gives a linear relationship where the y-intercept is related to Crr and the slope is related to CdA
A linear regression indicated that Crr should be .0072 and CdA .566
Note: The difference in power is also related to a calculated elevation difference which came out with values generally less than 0.2 metres so possibly/probably noise due to the precision of the elevation measurements.
Nevertheless I plugged those numbers into the Newton along with the tweaked WSF
I then decided t repeat the exercise but also add in a 10km out and back ride to double check the WSF and also threw in some high speed downhill coasts to check CdA. Also did a tilt cal prior to heading out By now the wind had picked up quite a bit from earlier
The procedure for the high speed roll was to start at the top of a 7% grade from a slow rolling start, coast down to the bottom, brake (hard) then return to the top, repeat , being sure to turn at the same spot at the bottom then return to the top to get multiple elevation calibration points.
Results of those were:
Check cal for the 4x roll downs said WSF should be .904 and from the out and back .918 so no need to change
Tilt cal for the roll downs was still -0.6 (and presumably the result of my tilt cal) but the out and back said tilt should be -0.2. Something to keep an eye on
Plugging the numbers into the spreadsheet indicated Crr of .0058 and CdA .617
The high speed coast analysed in Isaac suggested CdA of .581 for one run and .566 for the second
My spreadsheet indicated Crr of .0056 and CdA .581
As before the elevation difference could be just noise so I'll stick with Crr .0072
CdA of .566 seem pretty well dialled in but could need to be a tad higher. But ok for now.
What have I learnt from this?
Measuring Crr is problematic. It needs to be done at low speed but then other issues come in like imprecise elevation measures, bike wobbling, bumps in the road... I suspect I'll need to find a perfectly flat track to get this one right
The CdA measurement in Isaac is the easiest way to do it but works best with a long downhill. Ideally with an uphill afterwards so you can avoid braking

Next step now is to fit the panniers and see how the calculations go
-- Ken
Zoltan
Posts: 213
Joined: Mon Jan 23, 2012 9:47 am
Location: HUNGARY

Re: Using Newton on a Touring Bike

Post by Zoltan »

I am not an expert in ibike calibration, but my finding was that best method for estimating Crr is making out and back cal rides at a speed being close to the average riding speed of everyday use.

Maybe, I am wrong, but that what I experienced with gen3.
Last edited by Zoltan on Sat Jan 05, 2013 2:24 pm, edited 1 time in total.
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Wow you guys are rocking along! This is a great thread, for obsessive tweekers and perfectionists :-)
Of course it is also a practical thread for those with bike parameters outside the norm, it seems.

Anyway Ken, your work sound both productive and quite impressive!
Only additional idea I have is, from a paper I read though they used other equipment, to walk the bike down and up the hill to measure slope. If a dead on tilt is done first, this should eliminate the weight shift on tires due to slope, for the most part, haven't tried that yet.

I am also puzzling through Zoldan's beautiful spread sheet. I mean it is a work of art and science but more variables than I yet understand the nomenclature for and a very complex spreadsheet for this novice :-) Thanks Zoldan!

I am also beginning to get into the simplified derived power formulas enough to begin calculating my own except (besides eventually decoding - or bugging the author) for Zoldan's method, I have yet to find one that includes wind, rho and slope. I am not advanced enough to derive my own from the basic equations of motion. I have started playing with a backdoor tweek for iBike wind data to use with cyclinganalytics Terminal Velocity tool, not sure of my method yet but looks promising, but not ideal.

Ken, I am collecting everything I can find, in that regard, would you care to share your spreadsheet?
It sounds a bit more directly suited for what we are trying to do.

Regards,
Russ
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Guys,
I guess Kens inspired me and I did another calride today, wind was not too bad so gave it a crack!

I found that the windscaling was a teeny bit higher than I have been using but the more worrysome thing about that was a three lap around a large industrial size block for an out and back would have dropped the wind scaling just enough to think it would impact the coast down data some amount.

After the initial out and back calride, I did 3 CD's in my usual place but realized there was a slight tailwind. So next I did four in the opposite direction further up the out and back road with a bit less slope. Then I did the three around the block wind check O & B. Finally I traveled back to my neighborhood and did four CD's on a road just a bit less smooth and last 4 CD's on quite rough pave.

In the calibration function of Isaac, I selected the five middle of the pack CD's not including the rough pave ones. This gave me a reasonable Cda and Crr pair. I was using my high speed coastdown data to guide me towards the Cda. Finally I selected only the last four rough pave CD's and used fixed and uped the Crr until the Cda matched the first. See pix below!

Russ
Attachments
130105_cal_data_Ti_AP_Hoods.ibcd4m
The actual cal ride file
(389.92 KiB) Downloaded 352 times
Cal ride with four rough pave CD's selected
Cal ride with four rough pave CD's selected
130105_Tibik_AP_hoods_calride-rough.jpg (150.44 KiB) Viewed 25843 times
Cal ride with five optimum smooth pave CD's selected.
Cal ride with five optimum smooth pave CD's selected.
130105_Tibik_AP_hoods_calride.jpg (149.56 KiB) Viewed 25845 times
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Just thought I would add a few qualifying comments about the above post.

1. My Cda is higher than in my earlier measurements of .407 or so to .414-.421 depending on my measurement runs. This is due to heavier, looser jersey and insulated legs and new disk brakes on the bike.

2. So I selected a 'target' Cda to intelligently 'guide', or sanity check may be a better saying, the subset of 'best' CD's to not remove for analysis. It also turns out that they are in fact the middle of the pack when not using the first three due to the tailwind case and not using the last four except for the separate 'rough pave' analysis.

3. My concern about the wind scaling possibly needing to be lower, if my thinking is not backwards, would suggest tempering the Cda and or Crr values a tad higher since the actual wind would have been a bit lower and thus falsely raise the measured values. I also think a 'feature request' to be able to edit the wind scaling in the cal ride analysis window would allow improved post processing as better wind scaling emerges from later ride analysis. I am not sure if it would be possible or necessary, with this edit, to scale the aero values from the individual CD's accordingly.

Regards,
Russ
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Well I finally got a day with moderate winds (not as light as I would like and a bit gusty but beggars can't be choosers) and did a cal ride which I think has improved my WSF.
Before getting too obsessed with Crr and CdA I thought it would be a good idea to see how sensitive the power readings are to variations in these and other things.
For my purposes I was interested to see what changes would result in about 4W difference at 30km/h for my unloaded touring bike setup
My current Crr is 0.0096 and CdA 0.530.
A Crr of 0.0091 gives about 4W less at 30 km/h and Crr 0.0101 about 4W more.
A CdA of 0.519 also gives about 4W less at 30 km/h and CdA 0.541 about 4W more
I also had a look at how much error in slope or wind would have the same effect and it came out as about 0.05% for slope and 0.22 km/h wind.
So as we know, a good cal ride is important.
But also, it would seem to me that I'm already seeing pretty stable Crr numbers coming from the coast downs so I need to make an offering to the God of Wind for a calm day sometime soon to get a good cal ride and coast downs
-- Ken
Zoltan
Posts: 213
Joined: Mon Jan 23, 2012 9:47 am
Location: HUNGARY

Re: Using Newton on a Touring Bike

Post by Zoltan »

" but beggars can't be choosers)"

Except on beggars' banquet. ;-)
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Yesterday was a better than usual day for wind (I thought, or maybe it was) So off I went for a full set of iBike cal and CD's plus attempts at terminal velocity of two different grades.

Note that these 01/05 and 01/12 values are with 'adjusted' selected.
These, all three are with 700x32 Gatorskin Hardshell's both January cals are same kit, weight, etc.
Well first the iBike Cal and CD results tabulated with Jan 05 and Jan 12 results:
date desc bike CdA Crr WSF
01/05/12 Cal O&B, CDs cross .418 .0072 .743
01/05/12 3 laps check .693 corrected by Isaac
(I redid it with only the last 4 rough road CDs removed, so different from prior post on this cal ride)

01/12/13 Cal O&B, CDs cross .454 .0078 .658
01/12/13 O&Bx 1.5 check .681 corrected by Isaac

older (first) (slightly different kit, was using .407 CdA and .0075 Crr)
11/25/12 Cal O&B CDs cross .805
???? check .731 corrected by Isaac

I rode with the 11/25 corrected to .731 for awhile and most Isaac checks I did (but cancelled) fell
plus or minus .030 or so around this number. Now I have two newer cal rides that the corrected value falls a bit below that. However a quick check today put it back up to .761 but I think the wind may have changed on me.

The CdA measurements look like they are affected by the WSF being off. This is why I would like a post analysis ability to redo analysis with corrected WSF values, if possible to do. Heck a swag at it should still be an improvement :-)

When you do a CD with a slight HW off axis, I think this may drives up the CdA value.

And Yes, I am rarely motivated to get up early on a weekend and chase the still air but it may come to that yet :roll:
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Kens and Zoltan and all,

I am still tinkering along. I found, on the same day of my last cal ride and O&B check, another good check ride. I had gone back over the the 6% hill I have been using and did four high speed coastdowns. I also had walked it once to see if that gave any better hill data. Well, that is a vary straight road and the check feature landed WSF right in with the other in the .69 range so I am gaining confidence that it is actually the right value or very close. So I have learned that same day as cal ride O&B to check the calride and also short ones either around a not too large circuit or a true straight O&B are far better than using a longer ride as I had been doing.

The other possible gain was what appeared to be a very good CdA result if a tad low Crr from the Coastdown method and three downhill runs. I did have wind and the raw data did poorly so I thought about that and tried the cube root of the Vair, Vair, Vground speed product as a crude attempt to remove the 'error' or 'noise' from the wind. The CdA came in a .420 and the Crr and about .0056, by memory. Since I was trying to remove the tailwind, this reduced the speed in the CSV file fed to the web page. Remarkably the three lined up quite well, so I am interested in trying more of this and am scratching my head to figure if a more sophisticated correction would work better for both values. Probably a waste of time but a good learning exercise for me.

Finally special thanks to Zoltan for his spread sheet which, along with being another tool to use, provided me with a working example of the force equations which I had struggled with.

So Norbike and Tom in the Virtual Elevation Thread, I am not a racer and am probably have as much fun learning these things as achieving greater accuracy of all the setup values. Hope you enjoy my flailing away. Besides, with all the sprint training to get higher speeds for the downhill runs, I am getting stronger. My last set included one that broke 1KW, a first recorded on the road and it has been a long time since I did it on the trainer back when I first gave the Tabata sets a go several years back. :-)

Russ
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Just got back from a tour of Tasmania. I was hoping to get some good CdA numbers from some of the long descents but unfortunately heavy rain killed the Newton so its now in for repair.
What I did find however is that it seemed like the WSF was out as Newton was giving tail wind readings when I was definitely hitting headwinds.
I wonder if the front panniers change the airflow enough to affect the WSF. I use a RWS and it puts the wind port vertically above the panniers.
When I get Newton back I'll try to do a cal ride with front panniers fitted to see what happens.
-- Ken
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

So what did you figure out about the Panniers and wind scaling?
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

OK guys, so what can I take away from this as a solid method for setting up CX and touring bikes in the Newton?

Cal rides on the surfaces you ride on? Coast downs seem near impossible on anything other than smooth paved road. So maybe instead initial cal rides and coast downs on pavement to get the cda values, and then cal rides on the surfaces you are going to ride on?

Also, what can I apply to setting up my MTB? I have even greater challenges with that old beast as the carbon has gotten all flexy, and it is a full suspension. But I am looking for as accurate as possible with reasonable expectations, not perfect perfect. As I do ride to and from the trailhead from my house I have thought about making 2 profiles for my MTB. One for off road, one for on road, and just select between the two. Or maybe it's easier to change the profile for the ride in Isaac afterwards?

It seems I find I wish more and more I could lock in cda values and let the Newton calculate crr as the things I am interested in are related to rolling resistance. I don't want cda shots of if I'm aero, I want crr shots so I can see if those tubeless tires actually roll better, and if I am actually better off with 28c tires instead of 25cs where I'm so big, and what tire pressure has the least rolling resistance. Stuff like that. Also, with MTBing the terrain changes constantly.

My Newton should be here today, but it has been raining the last few hours and it looks like it will keep raining until I leave to go back to work on the ship on Monday, and won't be back home for 39 days. Oh cruel world. ;)

Thank you,
Rich
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

You should do the cal rides and coast downs on a good surface to get good baseline cdA and crr. That gave me cda of 4.5 and crr .0094 (Vittoria Randonneur Pro 26"x40)
To get cda with full touring kit I watched my dynamic cdA when coasting downhill on a good surface and found it was about 5.6 with panniers versus 4.5 without. Too hard to do coastdowns in full touring kit - it is hard enough to get up to 30km/h without the load :)

Adjusting crr for road surface needs to be done manually. I'm currently researching to find out how to make that adjustment. Most internet articles on crr are interested only in road tyres on sealed roads.

As a point for further investigation I found my cda on faster downhills was higher - around 6.0. This could be either from me sitting up more to rest and for aero braking OR maybe my crr was a bit high despite being measured by coastdown. Not a major concern at touring speeds.

On my last tour I set up a new profile for the touring setup to account for the extra weight but adjusted da and crr afterwards in Isaac. cda because I did not know what to use (but now I do) and crr because the road surface changed from day to day. With FW5 I'll now only load the touring profile from Isaac just before a tour so I can take advantage of APS.
-- Ken
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

Ken said:
" I found my cda on faster downhills was higher "

I have observed this in the past and now with the more recent firmware improvements (road bike and over sized cross bike used as a road bike) I am getting more stable cda displays....

I have now concluded there are two primary contributors to this, assuming wind sensor is properly zero'd. One is that the wind scaling is off slightly and the other, seen in my case, is that my most frequent downhill increases a little in roughness of the pave as my speed increases. Also consider similarly that at higher speed, the same non smooth roughness is increasing in frequency and probably amplitude of vibration. Vibration (from rough road) steels power and shows up as part of CRR.

So if the effective CRR is rising and the wind scale is perfect then the Cda displays a rising offset that actually comes from CRR!

I would also guess, depending on bike tires, pressure etc and on short hills, the early change in tilt from nose down more weight forward until the barometric correction is worked in, would contribute something too (haven't worked out in my head quite what at the moment).

Russ
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

Russ wrote:I would also guess, depending on bike tires, pressure etc and on short hills, the early change in tilt from nose down more weight forward until the barometric correction is worked in, would contribute something too (haven't worked out in my head quite what at the moment).
That makes sense Russ. If you have more weight forward Newton would see that as a steeper gradient and conclude that you should be going faster. But seeing as you are not it must be due to aero braking.
Another factor which I haven't included is the dynohub which at higher speeds would offer more resistance.
-- Ken
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

KenS wrote:Another factor which I haven't included is the dynohub which at higher speeds would offer more resistance.
Haha, yeah. was putting some of the parts that came in the mail today on my commuter build and realized that I built myself a dynamo hubed front wheel. Oh boy. ;)
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

So, what about doing a cal ride on the road, as well as coast downs under one profile (named ProFlex Road of course) to get an accurate Cda. Then doing another cal ride on a trail under "ProFlex Trail", and simply putting the Cda and wind scaling from "ProFlex Road" into "ProFlex Trail" and letting Isaac digest that? And the same for CX bikes, yes?

Thank you guys!
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
KenS
Posts: 141
Joined: Sun Feb 28, 2010 2:55 pm
Location: Melbourne, Australia

Re: Using Newton on a Touring Bike

Post by KenS »

You only need to do one cal ride per bike to get your wind scaling factor.
Then do a set of coast downs to get your CdA and Crr.
Cal rides don't determine Crr - they just work out your wind scaling factor and riding tilt. So no need to do one on a trail.
-- Ken
User avatar
Russ
Posts: 370
Joined: Sun Feb 10, 2008 4:08 pm

Re: Using Newton on a Touring Bike

Post by Russ »

I do not go off road much but here are my thoughts.
1. cal ride and CD's on smooth pave to establish the baseline Cda and Crr.
2. options:
A. CD's on chosen rough road, etc and force Cda back to above value. Actually I have only been able to 'try' various CRR's until the Cda comes to match baseline.
B. Use a 'recommended' offset CRR added to baseline.
C. Use dynamic Cda display starting with baseline values and raise CRR and redo until Cda comes back to match baseline.
Note that this method can be applied over long period of time on regular rides to establish the CRR for that target rough road/terrain. Either way the off road is going to be a SWAG to a large degree do to variability.

D. Convince John to automate some of the ideas here in firmware/Isaac. Oh, maybe some of this is in his future surprises???

I have tinkered with some of these methods over time. I claim success as my main 'test' hill lately has only had the Cda value rise by about .02 typically of late. This hill usually is where my highest speed on the ride is recorded, most rides. Also it has a smoother section at the top and get a bit rougher along the way. That said, on some days - cross winds and gusty winds and maybe a temperature variation from baseline I get as much as .06 variation all but very worst case. Off road your mileage may vary a bit more, so to speak :-) Now my typical hill to a very smooth place I get a swing downward in Cda displayed.

It could be useful if someone would work up a function or graph to use Cda offset detected to output a CRR offset.

Russ
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

KenS wrote:You only need to do one cal ride per bike to get your wind scaling factor.
Then do a set of coast downs to get your CdA and Crr.
Cal rides don't determine Crr - they just work out your wind scaling factor and riding tilt. So no need to do one on a trail.
Ahhh. That is really helpful actually.

Also had a thought about them adding a feature. IF the rider sets his sag perfectly before the cal ride, the tilt could be used to pop up a "check sag" message after say a mile and it notices the tilt is off. If you air pressures are good then you have a tilt issues.
Last edited by jazclrint on Sat Oct 11, 2014 11:55 pm, edited 1 time in total.
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

Russ wrote:I do not go off road much but here are my thoughts.
1. cal ride and CD's on smooth pave to establish the baseline Cda and Crr.
2. options:
A. CD's on chosen rough road, etc and force Cda back to above value. Actually I have only been able to 'try' various CRR's until the Cda comes to match baseline.
B. Use a 'recommended' offset CRR added to baseline.
C. Use dynamic Cda display starting with baseline values and raise CRR and redo until Cda comes back to match baseline.
Note that this method can be applied over long period of time on regular rides to establish the CRR for that target rough road/terrain. Either way the off road is going to be a SWAG to a large degree do to variability.

D. Convince John to automate some of the ideas here in firmware/Isaac. Oh, maybe some of this is in his future surprises???

I have tinkered with some of these methods over time. I claim success as my main 'test' hill lately has only had the Cda value rise by about .02 typically of late. This hill usually is where my highest speed on the ride is recorded, most rides. Also it has a smoother section at the top and get a bit rougher along the way. That said, on some days - cross winds and gusty winds and maybe a temperature variation from baseline I get as much as .06 variation all but very worst case. Off road your mileage may vary a bit more, so to speak :-) Now my typical hill to a very smooth place I get a swing downward in Cda displayed.

It could be useful if someone would work up a function or graph to use Cda offset detected to output a CRR offset.

Russ
OK, very helpful as well, but questions:

For "a", I read costdowns on a rough surface are a no-no. Is that a debunked myth?

For "b", yah, those are a bit all over the place. Check out my MTB thread I started to try to consolidate MTB information.

For "c", how do you do that?

For "d", oh I hope so. He has hinted at it. First though I would like to see them ditch the 26"X2.125 tire size in the menu selection, and add 2.25. And then add 27.5" tire sizes. The shop I work at has been selling them like hot cakes since last year when they came out big, as we are a Giant and GT dealer. It's clearly not necessary but I feel it would communicate that they want MTB customers enough to keep up with things. Some trail love, if you will.

Yeah, I'm not expecting perfection, but it seems the Newton has a lot to offer in the way of accuracy if I just give it the tools it needs.
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Using Newton on a Touring Bike

Post by jazclrint »

Either way I won't be able to play with things for a while. I am leaving for my main job (5 weeks out to sea) Monday morning and left my unused Newton with my bike shop boss today, and a message to the local road club's president that they can try my Newton out while I am gone. But please don't let that stop the conversation.
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
Post Reply