ovoleg

I don't measure and look at the slope regularly, why? Because the data is consistent and the zero offset doesn't vary much. The weather conditions are good in SoCal and I don't see any reason to get all nervous about it.

I have a sense of RPE, it feels about right based on what the power meter is telling me.

himespau 

Interesting hypothesis that sort of makes sense.

shovelhd

Sigh. Another Cat4 that knows everything.

tetonrider

we've been through this before. yours may be good but to declare it so without verification may be a false sense of security.

readings can vary a slight bit centered around the actual value, but if the slope is off then the center point is consistently off. the only reason this is relevant is that many racers train all year to realize just a few % increase in some numbers, so when slope is off by a small bit it can lead to some frustrating things. a number of people on this forum can attest to the frustration that arises from having amassed bad data with units that were slowly going wrong.

you may be at a different end of the curve as far as gains go such that a few percent is noise relative to massive annual gains you are making (seriously, that is true for some), but many aren't or are no longer at that point.

RPE is great and most who train consistently with power have a good sense of their numbers, but it still is possible to have a bad unit.

in my experience, most people (not those on this forum) don't know what to look for and think that by having a power meter at all they can call it good. at one time i thought that way, too.

ovoleg

relax they didn't even have electric power when you were a cat 4

tetonrider

we don't really know what their broad practices are, but having lots of experience with them as they developed a new model i can tell you that i was getting new units after sending in old ones only to experience the same problem time and time again. there have been some design flaws in certain models that made them more prone to problems.

when the new models rolled out, some customers received them as replacements for older models; at that point in time there likely weren't enough refurb units of the newer kind, so they were more than likely getting new units.

i have had some returns (essentially refurbs, if your theory is true) that come back better than the original (new) version.

my real trouble with quarq has been the what is now long history of not really knowing what the issue is but sending out a new unit to see if that fixes the problem...or just keeps the customer quiet/happy. without going into all the details as we've covered much of them before, the "just try this one to see if it is better" approach gets old. every customer is essentially a beta tester, and sending in one's problem unit never results in "hey, we tested it and discovered a bad johnson switch, so we are replacing it with a new one where this is guaranteed not to happen again."

sure, they'll occasionally tell you the 'stuck reed switch' excuse, but that should be something incredibly rare and yet it happens with too much regularity. is it a product designed around an inferior small part? maybe.

globecanvas

This may be true, but the basic point is the same, which is that Quarq and Stages are spending a lot of company resources on support that I wish they would spend instead on developing a product that needs less support. Simplistically, it seems like there has to be some sweet spot on the (production cost) + (support cost) + (profit) = (retail cost) equation that results in a better product for the same price.

ovoleg

fair enough. Mine could be off but the tolerance is within a few % anyways so I rather not worry about it unless it's way off from RPE.

FTP = 300W, 2% of 300 = 6W. Sure it can be big but I'm usually targeting a range when I'm training. If I can't hit the numbers then I will have to do it at lower power, if I hit them too easily then I up the power. To me the raw number isn't such a big deal.

I checked the slope 2 months after I got it and then 6 months after that, it was practically the same number(within 0.1%). I stopped caring at that point. I might have to re-evaluate if my RPE is consistently all over the place relative to the PM.

tetonrider

depends on the model, but i've gotten refurb SRMs, with warranty for people (with pc7) for well below <$1700.

sort of depends on availability and exactly what one is looking for.

gsteinb

[PSA]
I have an SRM that went bad. I don't know when it went bad. I didn't know it went bad until I started training consistently on another bike. Suddenly the same workout on one bike was a lot harder than on the other bike. Any of it the end of the world? No, but…I have a heap of failed FTP tests over a long period of time because I was aiming for numbers I thought I should hit, but since I was reading low I was cracking. Can't say for certain, but I imagine it didn't help anything on the racing front. It's definitely worth checking things with regularity.
[/PSA]

tetonrider

ah, ok. new info that you have checked the slope. in my experience, the slope measured 1-2 months after receiving a unit can vary from the factory setting, but it often settles down. sometimes they are wrong direct from the factory (regardless of brand).

if yours tested good twice AND the RPE & ZO are checking out, then that is a very good sign.

many users out there never check ZO before & after rides (and some don't check it at all), and almost none check the slope.

i still check mine periodically (every 6 months or so) because it takes no time and i just like to confirm things at the start/end of the season.

i agree that at 300w 2% = 6W, but if one's meter is consistently reading 2% low, it can REALLY frustrate a rider who works all year to get to peak form, only to see numbers that are a few % low. all this stuff is ranges, i agree. however, people get attached to a number and after months of training if they hit 294 vs 300w on their 20' test, some get discouraged. (the meter that is low could read ~288-300 for that same effort, while one with the correct slope would read 294-306.)

sweating over 6w is silly, and yet we have people who obsess over 15 grams, eating an extra cookie, working so hard they get overuse injuries, etc.

garbage in, garbage out is perhaps too strong a phrase, but at some point an error in the measuring device introduces garbage. maybe it is not at 1/2%, or 1% or even 2%...but it occurs at some value.

tetonrider

exactly. and i know we all dismiss things like checking slope, it is one more thing we can do to avoid this scenario. it might not have worked in your case, but it doesn't hurt.

the pain of collecting bad data can be pretty awful relative to the few minutes every 6 mo or year to remove one more potential source of error.

sorry for your (data) loss. ;-)

Ygduf

That's why god gave us Strava. My Mt. Diablo time lives on, despite the bad power data attached to it!










now before anyone responds, realize I am just ****ing with you to get a rise.

rkwaki

seeing your picture on strava gives me a 'rise'....
oh
And and training with power is a fad...

ovoleg

I check ZO every ride and if I started weee early in the morning in the cold, I'll recalibrate(ZO) later on the ride. But that's very easy with the headunit, I don't have to get an iTouch out with an ANT+ receiver etc

Ygduf

wat?

tetonrider

i agree. the promise of a better way is out there and still has yet to be proven.

quarq's whole M.O. was to deliver a power meter that was sub-$1k...years before they came out with a product. they wanted to make it more affordable than SRM (and it was the whole reason i followed their project). after much development, they came out with a product (first version) that cost around $1800. along the way they found that it just costs a bunch of money to do a decent job at these devices.

metrigear came along with the goal to deliver a meter around $800. years and years pass and we have the garmin vector at $1700-1800 or so.....and not yet shown to be durable.

brim brothers promised a cheaper cleat-based solution but has yet to deliver.

stages hit a good price-point but has not yet shown longevity...or reliability in all scenarios. time will tell on that one and i hope they'll improve.

for whatever reason, making these devices in a way that is accurate and reliable turns out to be hard -- and if you add in cheap that is nearly impossible (so far). i say nearly as many consider quarqs more "attainable", and yet SRMs can be had for the same ballpark pricing if you know where to look/who to talk with.

(on a funny note, i have a friend who bought the vectors partly because he didn't want to deal with crank swaps. that is a common point of intrigue for metrigear/vector customers. we recently flew to a bike race and as we were packing up our bikes i removed my pedals and....he removed his crankset! getting the vector pedals set up properly turns out to be more difficult than most of us assumed (i've installed them for people), that some people consider it easier just to remove the crankset! funny.)

i do think every meter has pros and cons, and there are target markets. in fact, i know a few people that NEEDED the pedal-based solution regardless of accuracy due to having no other options they were willing to take for their situation, e.g., someone unwilling to sell an indoor spin bike who is therefore unable to use a crank-based solution.

topflightpro

How do I check the slope on my Quarq?

tetonrider

which is actually a cool thing. all that matters is time in that scenario...or results in a race. i know people who have won TTs and fretted about low power. who cares? it's about going fast.

for your diablo effort, it was obviously something that was quite important to you (i have my own personal hill climb demon). have you gone back and done any calculations to figure out what your true power might have been? i don't know enough about that climb to know how much wind/ambient conditions might matter or might differ from prior efforts, or if you can exclude the effect of equipment and weight changes.

i know if i trained for a long time then cranked out a best-ever effort on my local 30' climb i'd be a bit bummed if the data was borked.

ovoleg

use their Qalvin app with an iOS device that can take a ANT+ Receiver.

Ygduf

get their ap. get a reference weight, the mass of which, you reliably know to within .02%. Hang known weight off pedal at 90*. let app do the torque math and set the slope.

Or I imagine aaronmcd had an excel spreadsheet for this.

rkwaki

This sounds like dirty foreplay...

Ygduf

I was a bit bummed that the data was borked, and it was the longer effort at a known grade against previous results that made me confident the meter was off.

Power that day was likely around 385. Data showed 365. Impossible to know for certain, wind matters over 11 miles, but otherwise my weight was about the same when I did my other solo run of 51:30. Power that day was 380, iirc. I believe most of my time improvement came not from higher power (subsequent climbs back this up) but from stripping about 1kg off my bike (tubulars), and better application of power through the climb.

Anyway, my training plan of non-interval riding means that if my power is a bit off it's annoying, but I'm not doing workouts in the wrong zones or something. So far the meter I received back after this round of warranty is holding pretty steady and data is true to known w/kg times from historical data.

tetonrider

you need a calibrated weight. super important. there are a few ways to do it, but essentially you measure the zero offset with no weight then with the known weight. you can do this with a simple spreadsheet or you can get the quarq app. with a quarq you need the wahoo ant+ dongle. with an SRM you don't need anything special.

here are some instrux quarq posted a while back:
Calibrate Slope Help

it's the type of thing that seems complex until you do it once. then it takes just a few minutes. hardest part is getting a weight that is both accurate and of appropriate mass. >=10kg is ideal. get a certified weight if you can. others can tell you how accurate you want that weight to be. (solid engineering principles dictate that the accuracy should be a certain %age of the thing being measured, and in this case if the weight is off even by a small amount it can mess up the calculation--moreso with smaller weights than large ones.)

tetonrider

if someone is bothering to do it, check the ZO without a weight with both left and right pedals forward (not at the same time! ;-)) with the chain on the big and little rings. repeat with the known mass. 8 measurements.

some meters actually report different readings with the chain on the little ring. i've seen some where you can produce consistently "better" efforts depending on what gear you're in. now *that* is not something people assume would happen when they shell out for their quarq!

doing tests in a consistent manner (e.g., the same 20' hill such that one uses similar gearing or on a trainer/rollers in the same gear) turns out to be important for many subtle reasons.