Powermeter choices

Alex_Simmons/RST

twotyred wrote:

Riding on a trainer in a room with a reasonably constant temperature will not affect the unit

But that's not what many users are reporting. Some units seem stable under such conditions, while others are not. Why?

amaferanga

rozzer32 wrote:

The data would drop so some rides you'd have no data, some rides it would work fine. Then the reading would be way off, like read 80 watts when you're sprinting ( I know I'm bad but I'm not that bad). Then the problem sorted itself, then re-appeared and then sorted itself again. I think the torque tube was going and I have read a lot of threads about people having to have torque tubes replaced and it's about £300 to do so. But I don't know if these issues have been solved with the G3.

However I would prefer a crank based system. I'm leaning towards the Power2max now but like I've said I will see what these new models are like first.

£425 to replace a torque tube on a Pro+ hub. Not far off what you can buy a new hub for which begs the question - just how much money are Saris/Paligap making from repairing their hubs that fail after a couple of years?

Just had an email from P2max confirming that I will be receiving one of the updated power meters

amaferanga

Alex_Simmons/RST wrote:

twotyred wrote:

Riding on a trainer in a room with a reasonably constant temperature will not affect the unit

But that's not what many users are reporting. Some units seem stable under such conditions, while others are not. Why?

I'm only aware of a few people grumbling, on the Wattage forum. Unfortunately they make a lot of noise. Are you aware of many, many people that have issues with their P2M?

rozzer32

Alex_Simmons/RST wrote:

rozzer32 wrote:

Bigpikle wrote:

2. P2M have never given any details on how the units auto zero, so people are wondering about what is happening to their numbers and what may, or may not, actually be changing in the recorded data. How they zero is a critical element in the reliability of the data, and many people place higher levels of importance on data reliability thatn others.

Why is this important?

There are several reasons, but here's a couple of questions for you to consider:

Would you trust a torque zero measurement made on any crank based power meter while still clipped into the pedals?

Let alone one that you don't know the circumstances of when it is applied?

Can the auto torque zero be disabled, so the user can check and control how and when this occurs?

But doesn't the Quarq auto zero while you're clipped in. I know you pedal backwards but you're still clipped in.

danowat

amaferanga wrote:

danowat wrote:

I know someone who uses P2Max, and they say it's very repeatable, however, the figures don't bear much relation to "real world" figures.

Not heard that one before. What's he comparing the figures with to come to that conclusion? The only issue I've heard with the P2max is the drift problem, but this is (was?) only an issue until the unit warms up and if there are big temperature changes during which you don't stop pedalling at all.

To say the numbers are offset from reality (again, what does that mean though?) suggests that that particular unit may be faulty and should be returned to P2max for repair or replacement.

Only going on what someone who has the unit, and has tested it against a couple of calibrated powertaps, has said.......

paul2718

Does anyone know if the Rotor 3D+ would fit BB86 BB that I run on my Scott Addict?

I think you need the Rotor 3D rather than the '+' which is for BB30.

FWIW I have an Addict/P2Max 130mm/Rotor 3D combination which are all compatible.

The potential wrinkle with a P2Max on the Addict (and I guess many other carbon frames) is if you want the 110BCD compact version which may intefere with the frame. P2Max may now have specific compatibility information.

Paul

rozzer32

paul2718 wrote:

Does anyone know if the Rotor 3D+ would fit BB86 BB that I run on my Scott Addict?

I think you need the Rotor 3D rather than the '+' which is for BB30.

FWIW I have an Addict/P2Max 130mm/Rotor 3D combination which are all compatible.

The potential wrinkle with a P2Max on the Addict (and I guess many other carbon frames) is if you want the 110BCD compact version which may intefere with the frame. P2Max may now have specific compatibility information.

Paul

I'm not so sure. From reading here http://www.rotoruk.co.uk/PressFit.html I could use the BB86 converter bearings which allow use of the 3D+.

I run standard 53/39 so I'd get the 130 BCD anyway.

Alex_Simmons/RST

amaferanga wrote:

Alex_Simmons/RST wrote:

twotyred wrote:

Riding on a trainer in a room with a reasonably constant temperature will not affect the unit

But that's not what many users are reporting. Some units seem stable under such conditions, while others are not. Why?

I'm only aware of a few people grumbling, on the Wattage forum. Unfortunately they make a lot of noise. Are you aware of many, many people that have issues with their P2M?

I'm aware of others not on wattage forum. Contrary to popular belief, I don't spend my life on forums

Doobz

Alex_Simmons/RST wrote:

I'm aware of others not on wattage forum. Contrary to popular belief, I don't spend my life on forums

Crikey.. You sure? When googling "power2max review" your name appeared in pretty much every forum offering your thoughts.. Cool huh?

Anyway.. If anyone is interested in some real world data from the P2M compared to a PowerTap check the link below. You will need to translate..

http://nyx.at/bikeboard/Board/showthrea ... test-fotos

paul2718

I'm not so sure. From reading here http://www.rotoruk.co.uk/PressFit.html I could use the BB86 converter bearings which allow use of the 3D+.

I believe you're right.

Paul

Alex_Simmons/RST

Doobz wrote:

http://nyx.at/bikeboard/Board/showthread.php?140445-power2max-leistungsmesser-im-test-fotos

Data from that link on P2M's website comparing P2M and Powertap:

3h Power2max
152 Watt Schnitt
185 Watt NP
79 RPM Schnitt

3h Powertap
156 Watt Schnitt
189 Watt NP
89 RPM Schnitt

6h Power2Max
152 Watt Schnitt
200 Watt NP
71 RPM Schnitt

6h Powertap
155 Watt Schnitt
202 Watt NP
76 RPM Schnitt

8h Power2max
156 Watt Schnitt
200 Watt NP
74 RPM Schnitt

8h Powertap
159 Watt Schnitt
201 Watt NP
79 RPM Schnitt

That tells me straight away that one and/or both of those units are out of spec.

rozzer32

Sorry Alex am I missing something? Sorry if it's obvious but you're naturally much more experienced when it come to power than I am.

Alex_Simmons/RST

rozzer32 wrote:

Sorry Alex am I missing something? Sorry if it's obvious but you're naturally much more experienced when it come to power than I am.

Well for a start, having power at the hub reporting higher than at the crank suggests something's not right.

But really, an inspection of overall average data is a crude way to assess a power meter's performance.

Google up Robert Chung's rosetta stone comparison for some thoughts.

rozzer32

Alex_Simmons/RST wrote:

rozzer32 wrote:

Sorry Alex am I missing something? Sorry if it's obvious but you're naturally much more experienced when it come to power than I am.

Well for a start, having power at the hub reporting higher than at the crank suggests something's not right.

But really, an inspection of overall average data is a crude way to assess a power meter's performance.

Google up Robert Chung's rosetta stone comparison for some thoughts.

That makes sense. But say the Power2max is 20 watts off "real values" does that really matter? As it will always be 20 watts off? So is it consistency that matters or absolute values? As I can see the other side of the coin that says if you're power is reading 20 watts out then you could think you're training is say zone 5 but in reality it's zone 4.

disgruntledgoat

Perhaps I'm being thick here... But power is something I'm just stating to flirt with in my mind. Which of the P2 models would work on a standard Campag Ultratorque (Italian BB) set up, do they come with both cranks and what is the difference between the non-rotor models.

Doobz

rozzer32 wrote:

Alex_Simmons/RST wrote:

rozzer32 wrote:

Sorry Alex am I missing something? Sorry if it's obvious but you're naturally much more experienced when it come to power than I am.

Well for a start, having power at the hub reporting higher than at the crank suggests something's not right.

But really, an inspection of overall average data is a crude way to assess a power meter's performance.

Google up Robert Chung's rosetta stone comparison for some thoughts.

That makes sense. But say the Power2max is 20 watts off "real values" does that really matter? As it will always be 20 watts off? So is it consistency that matters or absolute values? As I can see the other side of the coin that says if you're power is reading 20 watts out then you could think you're training is say zone 5 but in reality it's zone 4.

I look at it the same way as you do.

Do a threshold test with the P2M and adjust zones based on the values acquired. Go out and train on those Values..

Doobz

disgruntledgoat wrote:

Perhaps I'm being thick here... But power is something I'm just stating to flirt with in my mind. Which of the P2 models would work on a standard Campag Ultratorque (Italian BB) set up, do they come with both cranks and what is the difference between the non-rotor models.

if you have a look here it will hopefully answer your question. Email em and ask is probably your best bet..

http://www.power2max.com/techdetails_ko ... litaet.php

disgruntledgoat

So those are Bottom Brackets on the list there. I thought I was missing something!

This is the consequence of not buying a BB since Ultratorque wqas launched!

Doobz

On the left you have the crank options.. on the right you have the BB that the cranks will fit into..

disgruntledgoat

Doobz wrote:

On the left you have the crank options.. on the right you have the BB that the cranks will fit into..

None of them are to fit the Campag 135mm diameter! Ho hum, back to dreaming about being able to afford power!

rozzer32

Well for me the Power2max Rotor 3D+ crank, rotor chainrings and chainring bolts comes in at just over £1000. With the 2 year warranty as well that seems pretty decent. It's cheaper than the powertap.

danowat

rozzer32 wrote:

Well for me the Power2max Rotor 3D+ crank, rotor chainrings and chainring bolts comes in at just over £1000. With the 2 year warranty as well that seems pretty decent. It's cheaper than the powertap.

Which powertap?, my SL+ was less than £500, and my Quarq was £1100, at those prices, I'd pick either over a P2Max

rozzer32

danowat wrote:

rozzer32 wrote:

Well for me the Power2max Rotor 3D+ crank, rotor chainrings and chainring bolts comes in at just over £1000. With the 2 year warranty as well that seems pretty decent. It's cheaper than the powertap.

Which powertap?, my SL+ was less than £500, and my Quarq was £1100, at those prices, I'd pick either over a P2Max

G3 hub on IRD Aero rims http://www.wheelsmith.co.uk/powertap-0

Where did you get a Quarq for £1100??

danowat

It was probably closer to £1200 with the BB..... I got a good deal on it.

ric/rstsport

Doobz wrote:

rozzer32 wrote:

Alex_Simmons/RST wrote:

rozzer32 wrote:

Sorry Alex am I missing something? Sorry if it's obvious but you're naturally much more experienced when it come to power than I am.

Well for a start, having power at the hub reporting higher than at the crank suggests something's not right.

But really, an inspection of overall average data is a crude way to assess a power meter's performance.

Google up Robert Chung's rosetta stone comparison for some thoughts.

That makes sense. But say the Power2max is 20 watts off "real values" does that really matter? As it will always be 20 watts off? So is it consistency that matters or absolute values? As I can see the other side of the coin that says if you're power is reading 20 watts out then you could think you're training is say zone 5 but in reality it's zone 4.

I look at it the same way as you do.

Do a threshold test with the P2M and adjust zones based on the values acquired. Go out and train on those Values..

Except, what will you do when your power meter breaks or needs repairing or re calibrating and all your previous data is junk? or you decide to change it to a different unit in the future? etc etc.

Doobz

Perform another threshold test with the new unit?

rozzer32

I can see where Ric is coming from.

Say you start the year at 300 watts. Then in May your FTP is 350 watts. Then you get a new pm etc in July and your FTP is now 450 watts. Is that extra 100 watts geuine or some of it due to the power meter. Although you'd hope any difference would be minimal between units

Doobz

I can see as well. Hopefully from a coaches POV you will have improved your threshold a little but not 100w 8)

If the new power meter is out by even 50w then I would be worried.

Accuracy has never been the issue with the P2M units. Its always been about the data drift due to temp issues which they have now sorted.

I have a pretty good idea that something is wrong / out of calibration if the perceived HR effort does not correlate to Power Effort.

To be fair though. I am probably more laid back then most. I used to train with the PowerTap and I think in the 12 months I used it, I only "calibrated" it like 5 times.

ric/rstsport

If you only zeroed the torque 5 times in 12 months on your power tap, then almost certainly the data isn't data. it's junk.

if you start at say 300 W, and increase to 350 W, and then change your power meter (when your previous one wasn't correct) then your new one could say 320 or 380 or whatever. I can't stress enough how important it is to have consistent, accurate, data.

I've seen incorrect data - some power meters have been way out. but even when the error is small it makes a huge difference.

if you're not interested in accurate, calibrated data, then i'd suggest not getting a power meter. having a power meter is a bit like having a pet. you have to look after it.

rozzer32

But is there any evidence to say the Power2max are inaccurate? I thought it was the drift that was the issue.