Power2max vs Quarq - cheap crank powermeter questions...

timothyw

So i'm looking at treating myself to a new powermeter, I've almost managed to narrow it down but I've still got a few questions that could do with answers, ideally from people with direct experience!

All my bikes at the moment run Shimano cranks and bottom brackets, with 5 bolt, mostly 110bcd chainrings. I'd like to be able to use the powermeter with all of them, but don't envisage swapping more than every few weeks.

Is anyone using the FSA Gossamer Megaexo Power2Max with shimano bottom brackets out there? Any particular gotchas or things worth knowing? I understand fit might be a bit snug.....

I know the rotor 3d24 is the officially sanctioned option for Shimano but I'm loath to spend another 150 euros for 100g of weight saving when the likelihood is that the Gossamer will also work.

Onto the Quarq options, does anyone know how much of an issue or otherwise the Hidden Bolt thing is? I'm looking at the base Dzero GXP option (yes, I know I will need to change bottom brackets...)

So far as I can tell you can just unscrew the spider and fit the chainrings with the arm out of the way (and maintain shift quality by rotating chainrings 180 degrees from usual) so it doesn't seem like much of an issue if I want to use my existing chainrings?

The other idea that occured, was given the spider to axle interface doesn't appear to be keyed, can you just mount the spider at 180 degrees from intended, so converting the hidden bolt into a non hidden bolt? I imagine this would have the effect that L/R balance results would be backwards but otherwise shouldn't have any effect?

StillGoing

The Quarq has the benefit of easy access to change the battery, but it isn't such a hassle to remove the cranks to change the battery with a P2M, particularly if like me, you do switch between bikes. That said, the battery life is bloody long. I changed the battery in my Type S earlier this year having bought it in 2014.

The FSA Gossamer will work with threaded and PF BBs having fitted one for a friend on his Noah Ridley last year replacing his Shimano cranks. I do recommend the 3D24 version though if you can convince yourself to spend the extra. If you contact the gurus at P2M with any questions, they're usually pretty quick to respond.

philbar72

rotor for the win. its a better crank.

timothyw

Hmm. Another problem with the Rotor option is the annoying 30 Euro tool which you can use for literally nothing else:
https://www.power2max.com/en/product/sp ... otor-3d24/

Unless I spend the 680 for the older type S it isn't included...

I've been offered one of the new Dura Ace powermeters at trade and once I start looking at the price of the rotor unit the Dura ace actually starts to look worth considering.

In short, down that road lies bankruptcy and insanity.

wongataa

I have a Power2Max FSA MegaEXO Gossamer power meter and a Shimano Hollowtech II bottom bracket in my bike.

The FSA axle that goes through the bottom bracket was a tighter fit in the bearings than the Shimano crankset it replaced. Light tapping with a rubber mallet was required to get it through. The wavy washer it came with is not required. If you put it on and torque up the nut holding the LH crank on then the crankset was too tight to rotate freely. Leaving it out solved that problem.

Put some threadlock on the nut holding the LH crank on. It can unscrew itself (this happened to me - mid ride I suddenly had my left foot attached to a pedal and crank that wasn't attached to the bike!) This may have been down to the fact that I had the wavy washer installed and a lower torque used to keep things from binding.

Other than that I have had no issues.

MisterMuncher

That's an issue with the FSA self-extracting bolt, has been for years, tight up and down the range. Keep an eye on the bolt, tighten it every once in a while.

timothyw

Alright, well that's good enough for me, I've ordered the NG Eco in FSA Gossamer flavour and some loctite 243 ;-)

naavt

TimothyW wrote:

Alright, well that's good enough for me, I've ordered the NG Eco in FSA Gossamer flavour and some loctite 243 ;-)

I'm a bit late since you already made your choice, but I'm VERY happy with my Velocomp PowerPod, and since you mention that you have several bikes, it would have been a very good choice IMHO.

timothyw

naavt wrote:

TimothyW wrote:

Alright, well that's good enough for me, I've ordered the NG Eco in FSA Gossamer flavour and some loctite 243 ;-)

I'm a bit late since you already made your choice, but I'm VERY happy with my Velocomp PowerPod, and since you mention that you have several bikes, it would have been a very good choice IMHO.

Funnily enough I already have one of those!

I fell out of the habit of using it somewhat, I found it a bit of a faff taking it off and on the bike each time - I always found the data looked better if I transferred the ride data from the powerpod directly, which then became a bit of a faff, merging in the garmin file.

I could never quite convince myself to trust the data, and doing most of my training on the turbo at the time it didn't really work so well on that anyway.

Anyhow, now getting a proper 'DFPM' I'll be able to confirm the trustworthiness of the data, and the new toy factor will hopefully drive me actually using the thing....

naavt

TimothyW wrote:

Funnily enough I already have one of those!

I fell out of the habit of using it somewhat, I found it a bit of a faff taking it off and on the bike each time - I always found the data looked better if I transferred the ride data from the powerpod directly, which then became a bit of a faff, merging in the garmin file.

I could never quite convince myself to trust the data, and doing most of my training on the turbo at the time it didn't really work so well on that anyway.

Anyhow, now getting a proper 'DFPM' I'll be able to confirm the trustworthiness of the data, and the new toy factor will hopefully drive me actually using the thing....

Power meters will always have some discrepancies as you know, but I’m not seeing that when I ride the same route indoors with my Kickr.

Both PowerPod exteriors and Kickr indoors give about the same readings when doing the same route.

Remember that’s very important to do an extended calibration to make it more accurate.

As you’ve probably already noticed, I’m a Wahoo user and one thing that I became aware when swapped Garmin for Wahoo was the better and easier integration with all the other hardware and software, so no issues with Bolt/powerPod combo (I don’t know what type of PP you do have, but I’m running the newest BLE with Bluetooth).

N0bodyOfTheGoat

4iiiis are on offer at PBK when I checked earlier, ~£340 for 105 and ~£350 for Ultegra.

StillGoing

4iiii is nowhere near as accurate as a P2M or Quarq and is left side only unless you buy a dual set. As for the powerpod; I fail to see how a pod stuck on the front of the bike can have any accuracy that compares with strain gauges.

Re FSA; yes I remember riding with a buddy on a dangerous A road when his left crank came off of his Gossamer cranks. I'd sold it to him and felt awful thinking I hadn't fitted it correctly until I discovered its a common fault. Loctite FSA every time now.

naavt

philthy3 wrote:

(...) As for the powerpod; I fail to see how a pod stuck on the front of the bike can have any accuracy that compares with strain gauges.

Quoting Cyclist magazine:

“Since the advent of power meters at the crankset, we’ve interpreted power to be a measure of the force at the cranks using strain gauges.

But the deflection of the metal in one arms of a crankset, or from a single pedal, is an estimate of power too.

The PowerPod, in strict terms of mechanics and physics, makes perfect sense. It’s all too easy to forget that the reason we generate power is for one functional result – speed. More power results in more speed

Headwinds, climbs and cold weather mean that speed doesn't always accurately reflect the effort we put into the bike, hence why we want devices to measure power.

The PowerPod directly measures frontal wind force, along with elevation and atmospheric pressure. That leaves only rolling resistance and weight to be determined, and the latter can of course easily be measure by the user.

The PowerPod measures the intensity of the wind, and so can algebraically calculate the necessary power from the rider to achieve a given speed at a given elevation with that level of wind.”

If you are not convinced, head to YouTube and see DC Rainmaker test it against other 3 power meters (costing 3 times as much), at the same time and see how the results compare by yourself.

timothyw

I didn't/don't have any reason to doubt the accuracy of my powerpod, I just found it a bit more hassle to use on the commute than I had anticipated.

It's also fair to point out that mine was confused by blustery cross winds, and rain getting into the wind port - most of the time the numbers seemed reasonable enough, but it's a bit of a leap of faith if you've never used a more conventional power meter.

For the price I paid, which was about half what I've just paid for some pretty bottom of the line cranks, it's a decent option (and one of my riding buddies has already expressed an interest in taking it off my hands!)

I'm not interested in a left side only power meter, a crank based power meter can be had for not that much more and captures both legs, and I would expect if using one for training/intervals it would eventually lead to you favouring your left leg to hit the numbers, to the detriment of your overall power.

green_mark

TimothyW wrote:

The other idea that occured, was given the spider to axle interface doesn't appear to be keyed, can you just mount the spider at 180 degrees from intended, so converting the hidden bolt into a non hidden bolt? I imagine this would have the effect that L/R balance results would be backwards but otherwise shouldn't have any effect?

GXP spider to axle is indeed keyed, at least for Force22 and Rival22. I am not sure if it is keyed for Red, but in that case you no longer are looking at a cheap crank powermeter.

StillGoing

naavt wrote:

philthy3 wrote:

(...) As for the powerpod; I fail to see how a pod stuck on the front of the bike can have any accuracy that compares with strain gauges.

Quoting Cyclist magazine:

“Since the advent of power meters at the crankset, we’ve interpreted power to be a measure of the force at the cranks using strain gauges.

But the deflection of the metal in one arms of a crankset, or from a single pedal, is an estimate of power too.

The PowerPod, in strict terms of mechanics and physics, makes perfect sense. It’s all too easy to forget that the reason we generate power is for one functional result – speed. More power results in more speed

Headwinds, climbs and cold weather mean that speed doesn't always accurately reflect the effort we put into the bike, hence why we want devices to measure power.

The PowerPod directly measures frontal wind force, along with elevation and atmospheric pressure. That leaves only rolling resistance and weight to be determined, and the latter can of course easily be measure by the user.

The PowerPod measures the intensity of the wind, and so can algebraically calculate the necessary power from the rider to achieve a given speed at a given elevation with that level of wind.”

If you are not convinced, head to YouTube and see DC Rainmaker test it against other 3 power meters (costing 3 times as much), at the same time and see how the results compare by yourself.

What about changes in gradient; how does it differentiate between up and downhill? How does it offer any input on L/R balance? I get that it is a cheap(ish) entry into power measurement, but I cannot see it as a substitute for the real thing.

naavt

philthy3 wrote:

What about changes in gradient; how does it differentiate between up and downhill?

Looking at the picture, notice the Point 2. (Up/down accelerometer)

philthy3 wrote:

How does it offer any input on L/R balance? I get that it is a cheap(ish) entry into power measurement, but I cannot see it as a substitute for the real thing.

From DC Rainmaker review:

"Lastly, there’s PowerStroke. This allows you to do analysis of your cycling stroke. Essentially, analyzing which areas of the stroke your power comes from. To enable this, you’ll need to buy their upgraded software package ($99, or was $49 for Kickstarter backers). It’s basically a software unlock option (just as it was on Newton). Note that you will need a cadence sensor with it."




I’ll reiterate my first DC R quote: “Since the advent of power meters at the crankset, we’ve interpreted power to be a measure of the force at the cranks using strain gauges.”

I think that’s why so many people are reluctant to admit that other stuff may work as well, or even better in some cases.

I’m reading Joe Friel’s Training Bible for the first time and laughed when he admitted that he was one of the majority that rant against clipping pedals when they came out for the first time.

I’m not immune to that. Even today, I’m all for rim brakes and don’t see myself buying a disc brake bike, even if the majority sees them as the near future.

For what matters, PowerPod even measures info that no other power meter, at any price, measures, like braking forces and drafting.

I’ve been learning a lot from my ride draft data, and it certainly is helping me to understand my position on the bike and how to improve it. There’s no other Power meter doing that on the market.

But of course, all it matters is accuracy, and about that, you can read the extensive DC R review where he sums up:

“All my bikes have at least 2, if not 3-4 power meters on them (direct force power meters), such as Quarq, PowerTap pedals, PowerTap hubs, and various other units. Using only a single additional power meter makes it difficult to know who is right, and who is wrong.

Yes, even the most expensive power meters out there can be wrong.

Figuring out which one and when they are wrong is the hard part.

I’d sum it up as: If you do a clean calibration ride – things are impressively accurate."

timothyw

philthy3 wrote:

What about changes in gradient; how does it differentiate between up and downhill? How does it offer any input on L/R balance? I get that it is a cheap(ish) entry into power measurement, but I cannot see it as a substitute for the real thing.

To answer in a more wordy way, it has an inclinometer - like a digital spirit level.

It spends the first five minutes of every ride working out if it has been moved and so calculates the new position which is 'level' using it's accelerometer.

It also confirms this against a barometer.

The easiest way to get bad results with the powerpod is to not properly fasten it to your bike (so that it can rock back and forth) - you'll get complete rubbish then.

Honestly, it is very good at this stuff, and it is a mature product - if it was bad at this, it'd be easy for DC Rainmaker or whoever to make the comparison and find the data was garbage, but it really ain't bad.

timothyw

green_mark wrote:

TimothyW wrote:

The other idea that occured, was given the spider to axle interface doesn't appear to be keyed, can you just mount the spider at 180 degrees from intended, so converting the hidden bolt into a non hidden bolt? I imagine this would have the effect that L/R balance results would be backwards but otherwise shouldn't have any effect?

GXP spider to axle is indeed keyed, at least for Force22 and Rival22. I am not sure if it is keyed for Red, but in that case you no longer are looking at a cheap crank powermeter.

I agree that is the case for normal SRAM spiders, but it looks like Quarq have switched to a different 8 bolt system which I couldn't see any keying on, it all looks symmetrical - there's some talk of them switching to this because it helps centre the unit.

Have a look at the picture here:
https://www.quarq.com/product/quarq-dze ... 1bexth88h8

mrsmith8

I have both an FSA Gossamer Classic P2M and Rotor 3D24 Type S P2M. The FSA crank does not play well with Shimano 24mm bearings. You can force it through with a rubber mallet but getting it off is a real challenge. When I removed the FSA from my BB90 Shimano bearings, he bearings came out of the shell. Bearing was stuck on the spindle and it took 3 mechanics to finally get it off. You’re best to use the FSA bearings in that case as the Shimano 24mm spindles work fine in those. Unfortunately the FSA bearing are known to be of lower quality. Besides that, I love the Rotor Crankset because its almost (not quite, close to) a full 1lb lighter than the Gossamer. The FSA Crankset is almost 1,000g with rings. I will say both P2M have been very durable rain, shine, cold, hot. Plan to buy another Rotor NG Eco at some point soon.

timothyw

I've been very happy with the FSA - takes a couple of whacks with the mallet to get it out but nothing I'm uncomfortable with. The rest of the process is by hand or with the Allen key.

I am using proper Shimano bottom brackets, not another Shimano compatible option (eg praxis conversion) which probably helps as they have the plastic inner surface that will compress a bit. If you do need to sand down the FSA cranks to get them to fit, you only need to sand the ends of the axle as the bit in-between is thinner (this also helps getting it in and out!)

I have had a couple of instances where the ngeco has stopped transmitting to my Garmin and I've had to pull the battery out to get it back - anyone got any ideas what might be happening there?