gsteinb

troll post?

globecanvas

My question was sincere, but I did some searching and apparently this is not an unusual SRM setup. I'd never heard of it before (not that I have a lot of experience with SRMs).

shovelhd

I've never seen it. SRM power meters should be calibrated after chainring changes to different rings, but if you have the proper equipment that does not require a trip to Colorado.

Alaska Mike

I don't have any experience with SRMs, which is why I originally posted.
To be honest, I'm glad he brought up the part about possibly having to re-calibrate for different size chainrings. My Quarq S975 requires the same thing, but not the Riken. It completely slipped my mind. I'll have to see when it was last calibrated/serviced when I get it and make a decision from there.

Racer Ex 

All you need is a known weight, though I've rarely seen much movement if any swapping rings as long as they are torqued evenly. I would regularly change rings on my TT set up, anywhere from 53-56 both Q rings and round and I never saw the slope move.

Hang the weight on each pedal, take readings loaded and unloaded. There's a spreadsheet out there for the last decade that you enter the numbers into and it gives you the slope. If you need it PM me. G has it as well. When new you may see a little movement as things bed in, or if it comes out of service. Otherwise most are pretty rock solid, my old DA model didn't move for 5 years.

The crank in the pictures was the older SRM solution to allowing a 110 BCD small ring. Did the same thing on a couple of other makes. They eventually went to a 110 spider.

As far as a manual you don't really need much of one. Set up a magnet to turn it on and off and produce a cadence number. Pair with whatever head unit. Ride for a buncha years and eventually send it in and have them replace the battery. I am probably due, it's been 3-4 years since I had my current unit replaced.

Alaska Mike

Thanks. I was hoping it was about that easy. From the looks of it, this one hasn't been used excessively, so I'd imagine the calibration and battery life are still pretty solid.
I'm hoping that SRM keeps records by serial number about service, so I can check to be sure.

tetonrider

actually, they really don't require it. IMO with many SRM setups, slope does not change when moving from one pair of rings to another of the same size (e.g. different brands of rings). i'm obsessive so i always check calibration, but even going from 53/39 to 56/44 (about as big a change as you can have) only changed the slope by 0.4%.

quarqs, especially older generations, are VERY sensitive to ring changes -- not only size but also brand of rings. they claim the riken/newer versions don't require recalibration, but in my experience that is not true. the newer ones DEFINITELY needed it.

IMO with SRM it's not a big worry if you are moving to a new set of the same size rings and you are confident in the unit's existing slope.

yes, they do keep those records.

tetonrider

SRM actually created a solution for a 34T inner before shimano did. that said.....you need to be very careful with FD setup. you still might find that shifting is not as amazing as it is with a setup properly designed for compact or mid-compact use.

now that 52/36 setups are more common, you may find rings that are designed to be used together; used to be that your setup was used with a 53T outer and a 34T inner, and those rings were not designed to be paired together (i.e. not perfectly-matched shifting ramps).

post up when you have it running.

no, that's not the case. and, yes to your 2nd question, as above.

Alaska Mike

I was going to run a 52/36 setup, and with the TT bike's friction front shifter I am hoping to avoid any shifting issues that crop up as the result of the interesting 130/110 configuration. We'll see.

cmh

Cycling Analytics users, is there any way to add a ride without uploading data? I just want to enter a fixed gear ride and estimate TSS. It seems like a lot of work to upload dummy data or something. What am I missing? Thx

furiousferret

Click on date; add manual.

Jubail

Stages powermeter useres, I have a question for you!

I have been looking at the stage powermeter. However, I am a bit hesitant to buy one.
mainly because my right leg is shorter than the left and I use a shim under the right cleat for balance. But, even with the shim I feel like I always push a bit harder on the right leg. Also, when I do intervals, the unbalance becomes more apparent to me. I am not sure if that's just me imagining things because of the suffering or the unbalance is real.
Because of this, I'm afraid that getting a Stage will be a waste of money, so does anyone of you has a similar problem and got a stage? Please let me know your experience.

furiousferret

LR Balance is always a hot topic here. My opinion, get a pm that does both first and ideally tracks both. Most people do not have much LR variance, maybe within 5% but some do. I have an issue with the right leg that causes the balance to go from 52-48 to 60-40.

I dont think Stages is a bad product, I have one and its better than having no power. Its mainly used for my Commuter / TT bikes, and my main bike has Vectors, so I typically know what % I'm running. If my leg is off my avg could be off by 30 watts. That being said, with a perceived exertion of a LR imbalance I'd go with something else. Maybe Power2Max if money is an issue.

spdntrxi

I blew my left knee all to hell a few years ago and got the vectors for L/R power. Turns out my left leg is pretty consistently putting out more power.. 52/48 is the norm. Mt TT bike has the stages and it works well too.

Alaska Mike

If you only have one power meter and it puts out consistent power readings (repeatable), what does it matter?

You're looking for a standard to measure progress against. That standard could be number of duck farts a minute, and it wouldn't matter.

If you have another power meter, the difference can be noted and accounted for.

Quarq has aluminum arm GXP or BB30 model without chainrings for $799 now (Riken AL), so if it matters to you that much you could spend a couple extra dollars.

I have 2 Quarqs, a Stages, and an SRM in the mail. That may sound excessive, but I have a few bikes and don't like swapping out power meters constantly between bottom bracket standards. GXP to BB90 to BB86 with all of the different washers just gets annoying (especially during stage races), so I just have power meters on each bike. The Quarqs have tracked consistently with each other, and the Stages tracks with them over longer efforts (shorter intervals show some variance). I'm hoping the SRM will be close to the Quarqs.

Stages has made great strides in their product since I bought mine, and firmware upgrades and other refinements have brought it closer to the Quarqs. I still don't trust mine 100% after it failed on a rainy ride and didn't recover for a week, but I have the new battery covers now that are supposed to fix that issue. I will say their customer service was excellent, and they really do care about refining their product. The market is packed with all sorts of power meters right now, but this is a company I can see lasting for a while.

Given the various options, I still prefer the spider-based power meters. YMMV.

Blackdays

Slightly off topic - I'm using the external BB ring magnet on my Quarq right now, but am switching frames to a pressfit this weekend. Any suggestions on how to mount the magnet? I've heard the putty solution isn't great.

shovelhd

I use Amazing Goop. Works great. Stack the magnets until you get a consistent reading.

Alaska Mike

I've used the Quarq putty and JB Weld in impressive "magnet volcanoes" with much success. Ugly as hell, but I haven't knocked one off and they're hidden by the crankset anyway. I got a roll of magnets off of eBay a couple years ago for cheap, and haven't begun to use them all.

Grumpy McTrumpy

Clear two part epoxy, fast set. If you need to remove it use a sharp chisel

Wylde06

If you have one of the newer generation of Quarqs, no magnet needed with one of the last firmware updates. Mine fell off and I didn't realize it for a week

Blackdays

Great, thanks for the suggestion guys.

Looks like epoxy+magnet stack is the answer.

@Wylde - I'm still on the Cinqo.

cmh

Thanks ferret.

Jubail

I have some questions about Avg power vs normalized power in shorter intervals.
A friend gave me his powertap wheel and I have been playing around with it this week. First, I did the 20min FTP test and ended up with 279W Avg Power and 280W NP.

Today, I did 4x5min intervals to see how they feel at FTP and here is the result:

1. 290 AP, 285 NP
2. 280 AP, 275 NP
3. 275 AP, 271 NP
4. 271 AP, 265 NP

First, is it normal to see a drop in power between intervals? Second, is the difference between Avg and normalized power normal or should I try to be more steady/consistent with my efforts?

https://connect.garmin.com/modern/activity/940598195

Thank you!

Ygduf

if you pace your intervals perfectly they are all the same power. but people get tired so a drop is not unusual.

normalized power for 5 minutes is meaningless. it's really only pertinent over 20+ minute timespans and then has mixed value other than to look at and say "oh that race was hard"

globecanvas

Agree.




NP is the basis for calculating TSS, because in theory NP reflects the actual physiological cost of all of the efforts, unlike AP. So it's pretty useful. I never look at AP, personally.