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Racer Tech Thread

Old 07-07-15, 08:58 AM
  #2001  
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My SRMs read lower than my PT and Quarq did.

My two SRMs seem to match each other.

Average power is fine for gauging how hard a ride was overall, but I'm more concerned about power during intervals, which can be a short as 10 or 15s. Not having precision or accuracy at that level would make my PM worthless.
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Old 07-07-15, 10:52 AM
  #2002  
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Originally Posted by caloso View Post
Yeah, I had a monster ride the day after the daylight savings time change, and the Garmin ate the file. At least I was able guess at my 20' power, but I sure would have liked to have the whole data.
That's what I (in consultation with The Coach) ended up doing. I had looked at the NP for the test on the Garmin after finishing, so there's some determination of a result there.
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Old 07-07-15, 11:04 AM
  #2003  
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Originally Posted by topflightpro View Post
My SRMs read lower than my PT and Quarq did.

My two SRMs seem to match each other.

Average power is fine for gauging how hard a ride was overall, but I'm more concerned about power during intervals, which can be a short as 10 or 15s. Not having precision or accuracy at that level would make my PM worthless.
Whereas I'm not super concerned about pacing intervals really tightly by power. I prefer to pace by RPE, though power can be a rough guide. It's all about being aware of how the power meter works for your methods and what its limitations are. I have a Stages and what I've seen seems to pass the basic sniff test in consultation with other people, but I try to remain aware that below 5 minutes or so it can read very differently from other PMs. In general, I think it's probably smart to regard what you're calculating for W/kg at any given duration with a grain of salt.

I think the point about historical utility of data is an interesting one to consider, but I also think that it's probably worth getting one of the less expensive power meters vs not having one at all. But you have to be aware that it might read high (or low, I suppose), or otherwise is probably giving a less than 100% accurate picture of your output.
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Old 07-07-15, 11:40 AM
  #2004  
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It's only a matter of time before I take the leap and order an SRM, and every time I read threads like this that time grows sooner. I remain certain, however, that the market is going to continue to force price adjustments, and that SRM will jump on the wagon the day *after* I do.
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Old 07-07-15, 12:34 PM
  #2005  
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A used SRM is money well spent.

I also have a Stages on another bike. If I had a second head unit I could compare them side by side as they are both BB30. However by RPE they appear to be pretty close. A lot closer than 20%. 250w feels significantly different to me than 225w. If the Stages was that far off I'd know it. For the few times I rely on it for accuracy versus my SRM standard, it's fine. Even if I undershot or overshot my interval by 10% that day because I was using the Stages, what's the net effect? Not much. What had a profound effect on me was when my last Quarq was drifting low over time. Workouts at the same level kept getting harder and harder so I kept adding rest, which helped for the first day back but the next day was hell. It was demoralizing and counterproductive. This is why I say that accuracy is important but stability is more important.

Last edited by shovelhd; 07-07-15 at 12:38 PM.
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Old 07-07-15, 12:46 PM
  #2006  
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Just sent some questions to a seller on eBay about a used one. Nearly half price would be great, assuming I can still get it serviced by SRM USA.
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Old 07-07-15, 01:05 PM
  #2007  
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SRM Colorado will service any modern SRM no matter where you bought it.
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Old 07-07-15, 05:28 PM
  #2008  
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Okay, so last Friday I had a flat on a tubular Gatorskin. The inflator can of Effeto Mariposa Espresso pretty much refused to go in, so I ended up riding gingerly about two miles on the mostly-flat tire to my truck. I put part of a bottle of Stan's in the tire at the shop - used the whole bottle, but much of it ended up on the floor - and at first it seemed to not have helped, but now the tire is holding air.

Is this tire okay to ride, or did I kill it by riding it mostly flat? Externally it looks okay, no lumps or bumps.
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Old 07-07-15, 07:00 PM
  #2009  
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It's a Gatorskin. Garden hose. If it holds air, ride it.
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Old 07-07-15, 07:04 PM
  #2010  
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Originally Posted by revchuck View Post
Okay, so last Friday I had a flat on a tubular Gatorskin. The inflator can of Effeto Mariposa Espresso pretty much refused to go in, so I ended up riding gingerly about two miles on the mostly-flat tire to my truck. I put part of a bottle of Stan's in the tire at the shop - used the whole bottle, but much of it ended up on the floor - and at first it seemed to not have helped, but now the tire is holding air.

Is this tire okay to ride, or did I kill it by riding it mostly flat? Externally it looks okay, no lumps or bumps.
The Stan's plug may blow out at some time. Carry more Stan's. That stuff does get the wheel off balance. Common to race, get a flat, use Stan's then use for training.
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Old 07-07-15, 07:07 PM
  #2011  
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When the tire went flat and slid out from under me on a corner, I wasn't sure if it was because it was a flat, or...well...because it was a Gatorskin. The 303s came with these things glued on and almost no miles on them. I keep talking myself out of replacing them because they're so unworn. Don't know how much longer I can keep that up.
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Old 07-08-15, 12:47 AM
  #2012  
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Originally Posted by grolby View Post
Did an FTP test. Went to upload file to Cycling Analytics. "Could not parse file." ARGH. Is there any hope of rescuing this file?

Edit: nevermind. Obviously it's gone - file size is 4 KB for some reason (!?), normally they're at least 10 times bigger. WHY TODAY OF ALL DAYS.
Damn. That sucks.

We had a whole thread a while back where I got bashed for citing data integrity as one reason I liked the pc7 (many felt it was overpriced and could not get over lack of GPS). A few chimed in that the garmin corruption thing is a non-issue (same with the press-start-to-record and God forbid you don't hit stop and hold reset before you power off). Always seems to happen on the important files and never the recovery rides.

Once is too much.
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Old 07-08-15, 12:49 AM
  #2013  
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Originally Posted by Hls2k6 View Post
Just sent some questions to a seller on eBay about a used one. Nearly half price would be great, assuming I can still get it serviced by SRM USA.
Talk to me before you go used. Used meters can be amazing deals, and I steer many people that way vs some other devices. 2015 prices dropped a bit. May be able to help you out depending on model.
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Old 07-08-15, 12:52 AM
  #2014  
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Originally Posted by grolby View Post
Whereas I'm not super concerned about pacing intervals really tightly by power. I prefer to pace by RPE, though power can be a rough guide. It's all about being aware of how the power meter works for your methods and what its limitations are. I have a Stages and what I've seen seems to pass the basic sniff test in consultation with other people, but I try to remain aware that below 5 minutes or so it can read very differently from other PMs. In general, I think it's probably smart to regard what you're calculating for W/kg at any given duration with a grain of salt.

I think the point about historical utility of data is an interesting one to consider, but I also think that it's probably worth getting one of the less expensive power meters vs not having one at all. But you have to be aware that it might read high (or low, I suppose), or otherwise is probably giving a less than 100% accurate picture of your output.
its not so much about pacing by power as it is data analysis after the fact and historical trends.

You can't really pace a 10" effort by power.

His stuff can matter a bunch or not at all, depending on who you ask. When I coach people, data integrity and the type of meter they use is very important. I am not riding with them and have to read quite a bit into the ride based on small things in their files. If their data is bad, then those small differences can get lost, and much of the valuable stuff (subtle nuances that tell me things about how a rider is riding) are lost.

Of of course some folks just need AP and TSS and call it good.
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Old 07-08-15, 04:01 AM
  #2015  
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Originally Posted by tetonrider View Post
Talk to me before you go used. Used meters can be amazing deals, and I steer many people that way vs some other devices. 2015 prices dropped a bit. May be able to help you out depending on model.
Thanks very much. Apparently, I don't post here enough to send a PM, but I tried. If you PM me an email, I'll write there. In the meantime, I ride Dura Ace 9000, so I doubt new pricing would be very favorable, but I'd be happy to be proven wrong. Anywhere between 175 & 180 (with longer best) in traditional gearing.
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Old 07-08-15, 05:05 AM
  #2016  
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Originally Posted by Hls2k6 View Post
Thanks very much. Apparently, I don't post here enough to send a PM, but I tried. If you PM me an email, I'll write there. In the meantime, I ride Dura Ace 9000, so I doubt new pricing would be very favorable, but I'd be happy to be proven wrong. Anywhere between 175 & 180 (with longer best) in traditional gearing.
You can PM after 50 posts. You're nearly there.
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Old 07-08-15, 05:08 AM
  #2017  
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I ride 9070 and use a Sram SRM with Red 22 rings. Works fine. I'd love a 9000 SRM but even with a killer discount I don't have that kind of coin.
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Old 07-08-15, 05:10 AM
  #2018  
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Originally Posted by tetonrider View Post
We had a whole thread a while back where I got bashed for citing data integrity as one reason I liked the pc7 (many felt it was overpriced and could not get over lack of GPS).
We just like to bash you.
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Old 07-08-15, 11:27 AM
  #2019  
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Originally Posted by tetonrider View Post
its not so much about pacing by power as it is data analysis after the fact and historical trends.

You can't really pace a 10" effort by power.

His stuff can matter a bunch or not at all, depending on who you ask. When I coach people, data integrity and the type of meter they use is very important. I am not riding with them and have to read quite a bit into the ride based on small things in their files. If their data is bad, then those small differences can get lost, and much of the valuable stuff (subtle nuances that tell me things about how a rider is riding) are lost.

Of of course some folks just need AP and TSS and call it good.
Yeah, I see where you are coming from. For me, for the time being - my coach knows me, which helps, and I'm not super concerned with the specific details of my power at durations below 5'. Not that it isn't nice to know, to get an idea of where I stand, or what happened in a given race (e.g. looking at 2-3 minute intervals in a road race where I got dropped the third time up a really steep climb). Shockingly, different people have different needs! So I can see why the problems with something like a Stages would be more concerning to someone else. It does ease my mind that the numbers I've seen with it even at short durations are consistent with previous measurements I've made, but the thing is that could still be off by 20 watts one way or another and I wouldn't be able to tell. Still, I'd rather my 3' power be off by 20 watts than my 20' power!
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Old 07-08-15, 08:17 PM
  #2020  
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Originally Posted by grolby View Post
Shockingly, different people have different needs! So I can see why the problems with something like a Stages would be more concerning to someone else.
oh, no, it is absolutely not shocking at all. the thing is sometimes someone new to power (or anything) doesn't realize what will be important down the road. and i get it -- it is hard to know what we don't know.

it's why the precise-but-not-accurate-is-ok argument works; that user has not been through the cycle of a warranty repair, a 2nd unit, an upgrade, etc.

Originally Posted by grolby View Post
It does ease my mind that the numbers I've seen with it even at short durations are consistent with previous measurements I've made,
what measurements?

Originally Posted by grolby View Post
but the thing is that could still be off by 20 watts one way or another and I wouldn't be able to tell.
you can tell if you spend 5' calibrating your meter. (if stages allowed it, that is.)

Originally Posted by grolby View Post
Still, I'd rather my 3' power be off by 20 watts than my 20' power!
why? if one is off, how can you have any confidence in the other?

these are earnest questions. not picking on you. i've made many mistakes with power early on and it cost me time, data and money. one reason i help many people (mostly offline) is that i enjoy seeing them get right to what is important without stumbling, wasting time, losing data and/or $$$.
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Old 07-08-15, 08:25 PM
  #2021  
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Originally Posted by shovelhd View Post
We just like to bash you.
makes me feel comfortable, kind of like hanging with my family.
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Old 07-08-15, 08:50 PM
  #2022  
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Originally Posted by tetonrider View Post
i would NOT adjust the slope of one meter to match the other, particularly when you do not know which one is correct. that is throwing good money after bad, IMO. the PT cannot be adjusted by the end user (which is one reason why i, personally, don't use them; this is important to me), but you can check it and if it is wrong you CAN send it back to them.

hope this helps. feel free to ask any other questions. i'm really sorry this happened. i lost a few years of data.
Great info, thanks!

Let me rephrase the question:

You have two bikes, A and B. A is your nice race bike, with an SRM. B is your retired race bike, turned commuter, with PT. The SRM reads significantly lower than the PT. However, you spend most of your time on bike B training/commuting (75% of hours).

So the data gathered from the SRM at races is massively lower than your training, making it less than useful.

Ideally, I'd like the two to read as closely as possible in order to have seamless data gathering.

Phrased in this situation, would you still not recommend tweaking the slope of the SRM until the data gathered is roughly the same?
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Old 07-08-15, 08:54 PM
  #2023  
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Originally Posted by echappist View Post
static calibration test to see if the slope is indeed correct. anything else that anyone else says is just a guess.
Proof of the pudding is in the _________.

Rather than spending a bunch of money on a known weight... maybe it's just easier to measure a known quantity of water as the test mass.
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Old 07-08-15, 08:57 PM
  #2024  
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Originally Posted by Hls2k6 View Post
Thanks very much. Apparently, I don't post here enough to send a PM, but I tried. If you PM me an email, I'll write there. In the meantime, I ride Dura Ace 9000, so I doubt new pricing would be very favorable, but I'd be happy to be proven wrong. Anywhere between 175 & 180 (with longer best) in traditional gearing.
i just got home. will send you a note. basically it is up to you to say what you need. a nice thing about SRM 9070s is that one can choose the rings they want off the bat (50/34, 52/36, 53/39, 54/42, 55/42)--especially so for people who want, say, a TT setup; they don't have to buy 53/39 rings they won't use.

as shovel says, below, other than "matching" there is no reason you can't use another crankset, like sram, FSA, etc. there are cheaper models.

DA rings are amazing, though.
Originally Posted by shovelhd View Post
I ride 9070 and use a Sram SRM with Red 22 rings. Works fine. I'd love a 9000 SRM but even with a killer discount I don't have that kind of coin.
hard sayin', not knowin', as they used to say up in alaska.
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Old 07-08-15, 09:00 PM
  #2025  
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Originally Posted by Matt2.8NJ View Post
Great info, thanks!

Let me rephrase the question:

You have two bikes, A and B. A is your nice race bike, with an SRM. B is your retired race bike, turned commuter, with PT. The SRM reads significantly lower than the PT. However, you spend most of your time on bike B training/commuting (75% of hours).

So the data gathered from the SRM at races is massively lower than your training, making it less than useful.

Ideally, I'd like the two to read as closely as possible in order to have seamless data gathering.

Phrased in this situation, would you still not recommend tweaking the slope of the SRM until the data gathered is roughly the same?
under no circumstance do i recommend adjusting a device -- particularly one that has been calibrated in the last year (and calibrated SRMs tend to hold it) to match a non-tested meter, no matter the brand.

either test your slope (PT) and then send to saris, or just send it to saris for testing....but don't tweak a known-good meter.

accept the data corruption and start collecting good data going forward.
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