Power meter weight penalties

Discuss light weight issues concerning road bikes & parts.
n808
Posts: 103
Joined: Sun Mar 16, 2014 3:09 pm
Location: Seattle, WA | Gjøvik, Norway

by n808

I rode a quick test ride with my new Stages PM and it works... That's all I can say for now about the functionality before I start learning how to use it and analyze the data better. The biggest drawback from a ww perspective is that the SRAM Rival crank arm is a beast at 210g + 20g for the Stages PM ( = 230g total). The SRAM Red arm that it had to replace is 135g. So for SRAM Red owners, the Stages weight penalty is 95g and not 20g.
(2012/2014) Scott Addict R1, SRAM Red 6.6kg | 2012 Scott Scale Pro, SRAM X0, 9.4kg

by Weenie


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theremery
Posts: 2673
Joined: Sun Jun 12, 2005 10:56 am
Location: New Zealand

by theremery

My quarq has crapped out twice in 8 months....both times on wet rides (though the local distributor said it wasn't water ingress).
Good things:
-it's easy to replace a battery.
-Pretty light.
-Looks good (my opinion)
-good replacement (second time was over the weekend)
-data is consistent and decent once you use a qualvin app and a known mass.

Bad things:
-2 breakdowns.
-each time it's been sent back, it's been miles out from accurate and needed re-calibrating using Qualvin to get it sorted (which would be a pain if my coach didn't have that stuff and an obsessive hatred of inaccurate data, so I CAN get it fixed promptly).

I may just be the least lucky person in NZ with Quarqs but it has severely tried my patience as each breakdown has coincided with a holiday period starting (i.e. when I'm likely to do some serious K's!!)....second one was recent and really caused a temper tantrum.
Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!
Edit: 2015: darn near won the best South Island series (got second in age
-group)..woo hoo Racy Theremery is back!!

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itsacarr
Posts: 729
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by itsacarr

Another specialized SRM user here in standard BCD - lightest SRM I have used. Not a whole lot of weight penalty for the reliability and getting to use cranks I wanted.

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
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by eric

I think the Quarq numbers are questionable at best. They're no longer available on FSA cranks, so I suspect that weight was the previous generation unit.

The standard Quarq Riken these days is Sram crank based and weighs 739 for GXP and 733 for BB30g. The comparable Sram Red crank is 609 in GXP and 557 in BB30.
The difference is 130g GXP, 176g for BB30.

Neither of my Quarks have broken or lost accuracy yet. But it's only been four years for the older one.

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djconnel
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Location: San Francisco, CA
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by djconnel

On the subject of Stages, or the new left-only Rotor... I get L-R balances like the following very reliably with Vector:

Image

Measuring just the left side would thus result in a significant power error in the low-power range.

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HammerTime2
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Joined: Thu May 04, 2006 4:43 pm
Location: Wherever there's a mountain beckoning to be climbed

by HammerTime2

Then go with Stages or the left-only Rotor. Your all-important high-end power* will increase. :beerchug:

* as indicated by the multiply left-side power by 2 algorithm, ha ha

Edit: For NiFTY's benefit, at the very highest power shown on the graph, djconnel's right leg percentage tends to be below 50, therefore, his left leg percentage tends to be above 50, so doubling left leg percentage will overstate power, hence his <indicated> power will increase by use of a left-leg only power meter. QED.
Last edited by HammerTime2 on Fri Jul 18, 2014 7:20 pm, edited 1 time in total.

NiFTY
Posts: 1061
Joined: Sat May 26, 2012 11:26 pm

by NiFTY

Actually Hammertime calculated power will decrease for djconnel. I have a Quarq which estimates balance and mine is normally 48-49% L and 51-52% R. I know that my FTP set on my quarq is going to be slightly higher than that on my stages. Does 1-2% really matter, not really. Power fluctuates a fair bit on any real road surface so trying to hold a wattage to a single watt is almost impossible. I also don't stare at my stem with the intensity of Froome so a general band of band of watts +/- 10/15 of target is my goal. Now I am waiting so someone to say that on their SRM they sit on exactly their target wattage within 0.5W and notice no fluctuations over a regular road as they have their legs so well tuned to road irregularities. Activate powermeter trolls now.
Evo 5.02kg SL3 6.77 Slice RS 8.89 viewtopic.php?f=10&t=110579" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

RyanH
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by RyanH

Here's another way to look at it: as a complete drivetrain:

SRAM Red 2013 Quarq - 793g
HSC BB w/o Sleeve - 81g
Speedplay Ti Zeros - 164g

Total = 1,038g
Price = $2,000 + $110 + $335 = $2,445

THM M3 SRM w/ FSA Compact Rings - 698g (cyclingtechblog)
THM English BB - 72g (according to Fairwheel)
Speedplay Ti Zeros - 164g

Total = 934g
Total Cost = 2,745 (from SRM) + $160 (Praxis) + $335 = $3,240

THM M3 w/ Spider - 384g
Praxis Rings plus bolts - 130g
THM M3 English BB - 72g
Garmin Vectors - 350g

Total Weight = 936g
Total Cost = $996 + $160 + $1700 = $2,856 (THM from R2-Bike)

Rotor PowerMeter Compact w/ Praxis Rings - 761g
Rotor BSA 30 BB - 96g
Speedplay Ti Zeros - 164g

Total = 1,021g
Price = $90 + $2,400 + $160 + $335 = $2,985

No Powermeter
THM M3 w/ Spider - 384g
Praxis Rings plus bolts - 130g
THM M3 English BB - 72g
Speedplay Ti Zeros - 164g

Total Weight = 750g
Total = $996 + $160 + $335 = $1,491
Strava
Current Stable. The Snob Machine
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg | The Crumpton - 5.9kg

NiFTY
Posts: 1061
Joined: Sat May 26, 2012 11:26 pm

by NiFTY

Hollowgram stages

SISL2 compact 484g
+ stages arm (170 SI arm as SISL2 unavailable currently - 124g SISL2 arm weight) = +46g
+HSC BB w/o Sleeve - 81g
+Speedplay Ti Zeros - 164g
= 775g

$975 + $800 stages + $110 + $335 = 2220.
Evo 5.02kg SL3 6.77 Slice RS 8.89 viewtopic.php?f=10&t=110579" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

n808
Posts: 103
Joined: Sun Mar 16, 2014 3:09 pm
Location: Seattle, WA | Gjøvik, Norway

by n808

SRAM Red drive side + Rival w Stages left side (w eBay purchases)..

SRAM Red 53/39 GXP exogram rings drive side only: 474g
SRAM Rival left arm w Stages: 230g ( :( )
VCRC ceramic GXP BB: 93g
Speedplay CrMo w aftermarket Ti spindles: 160g
= 957g (182g heavier than Hollowgram combination posted above)

SRAM Red GXP $230 (new eBay) + Rival w Stages $500 (almost new eBay) + $89 VCRC (new eBay) + pedals $129 + $75: $1023

Note SRAM Red cranksets are around $290 now. And Rival arms are closer to retail $700. I was lucky.
(2012/2014) Scott Addict R1, SRAM Red 6.6kg | 2012 Scott Scale Pro, SRAM X0, 9.4kg

Tamu8104
Posts: 187
Joined: Sun Jan 16, 2011 2:45 am
Location: US
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by Tamu8104

I would echo what Showdown said. Started with a PT and it was a good introduction but limiting. Then went to wired SRMs. These were bulletproof, reliable, and consistent but eventually wanted to get away from wires. Had 3 Quarqs after that. Absolutely agree that they are very good products with exceptional customer service. I never had an issue with any of mine. Just recently moved to Stages as I like the flexibility of the new 9000 cranks and I like how inconspicuous it is. Also doesn't hurt that it's lighter.... I don't have a lot of experience on it yet but so far its been really good and the numbers aren't out of line with what I would expect.
Gaulzetti Cabron Disc = (weight unknown)
Rock Lobster Team Tig SL Disc = (pending)
Sold: Ridley X-Night Disc = 7.80 kg | Ridley Noah FAST = 6.86 | Ridley Fenix = 6.74 | Raleigh HiLife = 7.46 | Fuji SST = 7.34 | Van Dessel FTB = 7.58

earlfoss
Posts: 5
Joined: Sat Jul 26, 2014 5:27 am

by earlfoss

I took the weight penalty and went with the Power 2 Max based off of DC Rainmaker's review that "it just works."

It's performed flawlessly for the last 6 months in all kinds of conditions.




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overgeared
Posts: 27
Joined: Tue Mar 22, 2011 11:14 pm

by overgeared

As the author of the original content on CPL I wanted to chip in and say that, while it's one of a range of data people find interesting, I don't think weight should feature very highly on the list of priorities when choosing a power meter. It's a tool to help do the job of improving your watts/kilo way beyond any small weight penalty so the considerations should be more in terms of accuracy, reliability, usability, maintainability. I encourage people to think about total cost of ownership. At one end of the spectrum SRM's are for life, fault-free-availability will be close to 100% of days and resale values are good. At the other end some units have low upfront cost but are questionable on other criteria.

rijndael
Posts: 395
Joined: Tue Sep 20, 2011 12:54 pm
Location: Haines, AK - Temporarily

by rijndael

overgeared - well said, I fully agree.

by Weenie


broncr
Posts: 3
Joined: Sun Mar 13, 2016 3:33 pm

by broncr

has anyone tried the lightning road crank with the powertap chainrings?. if the lightning road crank is really 381g and the chainrings are really 120g, this seems like it might be the lightest option?

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