cobra_kai

I find riding with power very useful on the road and want to have it on my soon to be built gravel bike if it doesn't compromise things too much.

Some additional requirements: I'm only interested in 2 sided power and I'm planning to use spd pedals. The bike will have disc brakes.

The only options I see are a powertap disc hub or a Quarq/power2max spider with a 1x crankset. I'm not enamored with either because I want multiple wheelsets which would be a large investment in hubs and a 1x crank sacrifices either range or spacing.

Are others using anything that avoids these concerns? Or am I stuck trying to have my cake and eat it too?

DrIsotope

There's nothing that says you can only run 1X on a power2max. I have mid-compact 52/36 on one, and my other came with a set of Praxis 50/34 compact rings (which I took off for my narrow-wide 1X ring.) If you're not super concerned about weight, right now power2max will sell you a Type S meter for about $540, and throw in FSA Gossamer arms and Praxis rings (including 46/36) for free. Lighter arms will run you about $150 more, if memory serves. Would have liked a second set of Rotor arms, but I cheaped out.

cobra_kai

You are definitely correct about that, on my road bike I have a power2max with 52/36 rings. However running a double on a 110 BCD spider your smallest chain ring is going to be 34, which I'm not sure would get me low enough gearing for light touring/bikepacking as it only gets down to about 25 gear inches. I don't have a lot of experience but most things I've read recommend trying to get near 20 gear inches.

motorthings

curious why the 2 sided power requirement.

cobra_kai

Because doubling left only is a waste of money IMO, especially since I have a 2 sided meter and know I don't have perfect 50/50 balance.

motorthings

so how do you use the 2 sided power differently than you would use 1 sided (knowing you are not 50/50)?
not being argumentative, just curious.

i used to have a power meter, assumed i was not even, but never felt like i needed an additional depth of data to track my fitness/FTP/CTL/ATL. perhaps your goals are more lofty.

Seattle Forrest

Say you have a 45/55 L/R imbalance. A left-only power meter will only show 90 % of your power. A 40/60 split would show you 80 %, a 55/45 split would report 110 % of your power. Over the course of your ride, your kJ and TSS will be off by however much it works out to.

Most people don’t actually have a constant split, though. Your L/R balance can be all over the place from one second to the next.

A lot of people feel it isn’t worth paying many hundreds of dollars to still not know your power output. A power meter that captures the output from both legs (could be a dual-sided meter, or it could be measuring a place that inherently captures both sides, like at the hub or crank) typically has a maximum error of 1.5 %, but if you’re only capturing one leg, you don’t really know.

motorthings

makes sense...i guess i was just never enough of a data junkie.
as long as I was seeing improvements in my FTP, and was able to track ATL/CTL, that was enough for me.
and now i require none of it, as old knees made much more progress unlikely, and then we had a little human, and on and on.

thanks for the enlightenment!

cobra_kai

Seattle Forest covered one big reason for me, the other is Chung aero testing. While admittedly this isn't much of a concern for an adventure bike, when trying to tease out small differences in equipment a several percent error as balance varies would dwarf any differences in the equipment itself.

IronM

Honestly, I put a single-sided PM on my gravel bike My gavel buddies frown on a PM on gravel, but so be it. I know my left leg is a bit stronger than my right, but feel that variance in that is offset by the non-absolute nature of FTP, which is the reference basis for TSS. With all the averaging and smoothing going on anyway, I don't think I'm looking at real numbers to begin with, be it L or L,R. I'm fairly OK with thinking of PM numbers as ballpark estimations, so spent my $ instead on upgraded wheels.
Also.. I'll be swapping wheel's for grave & road; and there is always the possibility of changing up the crankset too - i might even go 1x at some point. So a Stages was a logical choice for me.

Seattle Forrest

It's a shame nobody makes an SPD power meter.

I'm using Vectors. They work pretty well, but road shoes aren't great for walking, and the cleats jam with mud.

My bike uses BBRight so that limits my crank options. You might want to go 1x, that limits your options there. Swapping wheels for rough gravel is fairly common. Power meter options are more limited on gravel.

I don't know why you wouldn't want to measure your power output just because you're riding on unpaved surfaces though. You can ignore the number if you're having too much fun. You can still look at the data later.

Sullalto

Yeah most of the time I'm just riding, not training. I always ride with a trunk bag, so most of the time I just chuck the computer or phone in the bag. Every once in a while I look at the data, just to compare fitness.

I also live in the middle of nowhere these days and don't do any group riding or races.

cobra_kai

Even if there were spd power meters I'm not sure they would be the best choice considering the much greater risk of pedal strikes compared to road. They would have to be pretty robust.


I think I'm leaning towards a 1x setup with two wheelsets, a 700c and a 650b and a different cassette on each wheel. Probably the sram 10-42 cassette on the 650b wheels for offroad use and maybe the new 3T overdrive cassette on the 700c for more road oriented gearing, paired with a 40 or 42 tooth chainring. That would cover me for most situations and I could get a smaller 36 or 38 chainring for more uncommon loaded bikepacking type situations.


I've also been curious about a 1x setup and this is probably a better application for it than my road bike, although the one size fits all situations of a sub compact crank with a wide cassette is still appealing to me.

cobra_kai

Just a quick update to this thread. I've discovered that the Rotor 46/30 spider-ring is compatible with the Rotor 2inpower meter. Unfortunately, the 2inpower is $1500 msrp, which is way more than I am willing to spend and also seems ridiculously overpriced. In a world where power2max will be offering the NG eco spider for $490 and cranksets are available from Quarq and power2max for as little as $600 it's hard to believe anyone would fork over $1500 for the rotor.

cobra_kai

Continuing to post my musings here in case anyone else is exploring similar options.


Another possibility is to run a standard compact crankset with a shimano setup which would allow pretty much any crank based power meter to be compatible. Using a wolftooth tanpan, the shimano STI shifters can be mated to a XT or XTR SGS rear derailleur enabling the use of an 11-40 or 11-42 cassette. Even with the slightly narrower 11-40 cassette this gives a massive 535% gear range and when used with a 650b 45mm tire a gear inch range of about 22.5 to 120. The 11-42 can get you a little lower to 21.5 gear inches. This setup would also be much easier to convert between 1x and 2x simply by adding/removing the front derailleur and swapping the double chain rings for a narrow wide single ring.


With the 11-40 cassette gaps are also slightly improved over the Sram 10-42 cassette while adding one higher gear and one lower gear when the 10-42 is paired with a 40 tooth chain ring. Comparison: Bicycle Gear Calculator


Of course the gaps are still pretty bad compared to what I'm used to on the road bike using a 11-28. According to Wolftooth's site the tanpan with a SGS derailleur does allow the use of an 11-32 cassette which would have much more manageable gaps for road riding but Shimano's site for the derailleurs says a minimum large ring of 40 teeth. Anyone have experience using a XT or XTR derailleur with an 11-32 cassette?

blazin

You could consider the new Watteam Powerbeat offering double sided power on any aluminum crank for $399.

https://www.dcrainmaker.com/2017/09/...s-pricing.html

It seems like an attractive option, but for gravel riding I’d want to wait to get some real world reviews on both a) durability of these units in wet/muddy conditions; and b) accuracy over rough terrain.

cobra_kai

Yep if they have accuracy and durability nailed it's a pretty compelling price. I definitely have concerns about durability for off road usage.

blazin

Actually, on further reflection, I would actually be willing to take a gamble on the Watteam system, if I didn’t already have carbon cranks.

In fact, that is my biggest obstacle to getting a power meter at this point—all the components that I have invested in for my gravel rig are largely incompatible with any of the existing systems: I bought nice wheels and hubs, I don’t want to pay to either rebuild them with a powertab or buy a new wheel. My crank/chainring (Easton EC90 SL) is incompatible with current chainring- and crankarm-based units. Pedal-based units are out for gravel. The only option available to me is the Easton Cinch, a left only system and, like you, if I’m going to invest in power, I want it to be double sided. But if Watteam can get an offering that works with carbon crankarms or one of the other systems like 4iiii or Stages make an Easton-compatible product, I’d probably be all over it.

I guess there’s only one other option I haven’t seen mentioned in this thread. Have you taken a look at Infocrank, OP?

cobra_kai

I'm aware of infocrank but hadn't really considered them because if I remember correctly it's on the high end of the price range of crank based systems, and yeah just checked their site and it's $1400. Since it's also only available in 130 or 110 BCD it wouldn't gain you anything on the chain ring size front.

I think the problem is rooted in that almost all of the meters were developed for road or time trial applications, so that's why there are only 3 bolt pedals and cranks with 110 or 130 BCD.

At this point I think I'm pretty set on a crank spider system from power2max or quarq but I need to decide whether I want to go with a 1x system or the compact road double with mountain derailleur bastard system.

trainsktg

I use a Stages left side PM that I swap between the cranks of three different bikes (endurance, road, gravel). Left side only power seems accurate to the results I get with my two side Wahoo Kickr. Seemed to be the least hassle option to have power on all of the bikes I wanted to have power on.

Edit - One of these bikes is a bastard setup, running 105 11sp 50/34 in front with 11-40 XT 11sp cassette, 105 long derailleur and Wolftooth Roadlink in the rear.

Keith

cobra_kai

How do you like the bastard setup? Any lessons learned or recommendations?

chas58

as I have multiple bikes, it would be nice to be able to have a shared system.

I am so curious as to how well this works (for $249 and easily movable from bike to bike???)

Arofly, the worlds's smallest power meter? | VeloNews.com

redlude97

it doesn't.

Seattle Forrest

Long thread in the road forum about Aerofly, it's like Strava power but more expensive.

trainsktg

The mountain cassette is actually on my TCR. I like it very much because at my relatiively low power/weight, it allows me to keep spinning in 34-40 at 250-300w on long 10%+ climbs (in excess of 1 mile) instead of grinding in 34-28 or 34-32 at 250-300w and blowing up. According to the Roadlink folks, 11-40 should only work on a 1x system, but I'm running it on 50/34 and the RD is far from maxed out...I'm guessing that might be due to the relatively short chainstays on the TCR. I've got at least a 1000 miles into the mod so far with no issues, so it definitely worked for me.

I forgot to include my TT bike in my previous list of bikes that I swap one Stages power meter between, so it does quadruple duty on four different bikes...two 11sp, two 10sp...all from Tiagra to Dura-Ace. That's pretty darn good versatility for one purchase.

Keith