[Closed] Power Meter - worthwhile investment?

Yes if you know what to do with the data.

My brothers got one. I like the idea of one but in reality I'd just use it as a passing interest to know what I'm doing at any given time, so too expensive for such a frivolity. But my brother is properly geeking out on it as he's competing in Triathlon and he gets a crap load of useful information from it to gauge the progress of his fitness and hone it and direct his training. It is also his key tool for pacing. So if you use it properly then it's the number 1 most useful thing you can invest in. forget wheels, electronic gears and fancy carbon frames, none of that lot made my brother faster - just poorer, but the powermeter has lifted his performance and fitness into another league.

If you're mainly just riding with a group of mates then it's not worth it.
If you're doing a load of training on your own, it's definitely worth it.

Why Quarq? Because that's what he's got?

4iiii in a 5800 arm is only £379, less common than ubiquitous Stages but also appears to be more reliable.

If you're serious about racing and training then it'll probably be the best ~400 quid you can spend - deep section wheels (for example) essentially buy you a one-off speed improvement whereas you'll keep making gains with structured power based training.

If you're just riding with mates then it's a very expensive cadence sensor that adds a bit of interest to your strava uploads.

they are good and I have used single arm and BePro pedals...

The pedals are best IMHO, you get a good quality road pedal included in the price and its super easy to swap between bikes.

Really good for pacing out an effort in training rather than going off too hard and blowing up.

The "what power meter" may be best left for [url= http://singletrackworld.com/forum/topic/which-power-meter-stages-or-power2max ]another thread[/url] 😉 Though I would recommend getting one that measures total power like the Quarq, or if cash is an issue, one that can be upgraded to dual sided later (e.g. Vectors.)

If you're doing a load of training on your own, it's definitely worth it.

I'd agree with this. A power meter is a harsh mistress when out training on your own, there's no slacking off!

Yes if you know what to do with the data.

+1

I wouldn't say you need to be a massive geek or a whizz with "numbers" but I guess you need to be prepared to put a bit of thought and reading in (or get a coach to do it for you)

If you want to get fitter and faster then it is a great tool to help with being more efficient in doing so and takes a lot of the guess work out of things.

As someone else said, if you are riding with a group of friends then it likely won't change anything for you.

There are plenty nowadays which won't break the bank and they seem to have good second hand value so why not give it a crack if you think it might suit

As above, you have to understand the figures, but its not rocket science, and once you do, then yes they are great. I used to find i would just crucify myself every ride and conversely found i was getting slower, probably overtraining. I now understand the concept of recovery rides and sticking to certain zones. It also means i can take stock of where i am when i use the Wattbike we have at the rig i work on. Whether its coincidence or not i dont know, but my FTP has gone from around 260W to over 300W in this time. Its also nice to be able to see exact figures in front of you - you can see what you're putting on flat sections, or hills, and it means you can gauge how hard you're pushing, and if in danger of blowing up. I use Stages, and find them to be absolutely fine.

Yes if you're serious about training/wanting to have a measurable performance increase. If just for group rides then no.

I've only slowly started to use mine properly, mainly polarisation rides (sticking to the allocated zones). It's too early to tell if it's made a difference or not yet though.

Highly recommend a 4iiii, the app is very easy to use and gives battery % unlike the stages one. They start from £349: http://www.hinderacingltd.com/4iiii-precision-power-meter---various-cranks-29780-p.asp

I've only slowly started to use mine properly, mainly polarisation rides (sticking to the allocated zones). It's too early to tell if it's made a difference or not yet though.

Zones and power targets for intervals is one aspect. Post ride/race analysis too.

Other aspect is planning and managing load and recovery. Use something like Training Peaks to give you data like NP and TSS for rides (basically quantifying the loading.) That then feeds into a Performance Management Chart with parameters for CTL, ATL and TSB (copied by Strava for their Fitness and Freshness.) Things like the ramp rates for those parameters are important (at least for me) to make sure I'm progressing with load but also not over-training. E.g. a typical winter looks like...

[img] [/img]

With a steady ramp up of CTL (fitness) while the TSB bounces up and down with load/recovery cycles.

By contrast, the traditional method of balancing volume and intensity will also get you a long way. PM's provide data that can be useful, but I ride volume on my own at a target speed (100 km circular look so average speed = average power), and get intensity from racing, where a PM will be only useful to show how hard you went (unless you TT).

That said, I pace my TTs using a powerpod and will move to a force meter for CdA measurement.

I won't post my increase in fitness this year, but it's dramatic.

I won't post my increase in fitness this year, but it's dramatic.

Powerpod calibration issues 😉

Yeah I forgot the post analysis stuff, it's very useful in monitoring how you're reacting to training.

Example, I'm 12 days into my plan and haven't done today's workout yet:
[img] [/img]

Powerpod calibration issues

Bwahahah - actually I only use the HR only one! Too many bikes you see 😉 The original Bannister model used HR and was applicable to all endurance sports. It's nice to see the effects of periodisation.

Highly recommend a 4iiii, the app is very easy to use and gives battery % unlike the stages one. They start from £349: http://www.hinderacingltd.com/4iiii-precision-power-meter---various-cranks-29780-p.asp

Dave Hinde????

I got my 4iii from Evans also for about £350.

Can you use the 4iii ones with a Garmin 810? I've been looking at these and just realised I've got £80 worth of Evans vouchers in my drawer.. will make it £300 for a power meter 🙂

I use my 4iii with a Garmin 810.

I just got one this season and I'm a big fan. The biggest advantage for me is that all my rides have a purpose, and my available time to train is as effective as it can be. Went for power tap pedals so I can swap between bikes easily.

Any deals about for Stages or 4iiii? Can't find any myself and am seriously tempted to buy a unit.

Is anyone doing an mtb spd pedal system yet, or are they still all road based?

That's the one thing that's putting me off at the moment - I need to be able to swap between bikes but off-road.

I have the ultegra 4iiii unit - use it with my garmin 820. Had it about a month, seems to be faultless so far and the values on it compare well to my mates bike when we ride side by side (we weigh almost exactly the same).

Haven't seen an MTB pedal system yet, but Stages do some MTB crank arm versions.

I got ProBikeKit to price match http://www.hinderacingltd.com/4iiii-precision-power-meter---various-cranks-29780-p.asp
/p>

Then used cash back and one of their discount codes to bring it down either further, think it was £395 all in for an Ultegra version.

Evans have the 105 for £379 (that's what I have) or the Ultegra for £469 if you want to pay more for a tiny amount less weight.

Cheapist 4iiii 105 5800 units I can find is at Hinde for £349.

PBK nor Evans have no stock of 175mm black 105 😐

The reasons I was looking at Quarq were:

1. that I use SRAM force kit, and the Quarqs are compatible with the BB's
2. they measure "both sides"
3. they're on offer at PBK, although I'd also need a head unit so was looking at around £250 for a Garmin 520 inc heart rate kit, which might also be useful (?)

All up that's an investment of around a grand, which is a lot I know……

I only have a Garmin 200 currently so whatever I do, I'll need the investment in a new head unit anyway….so minimum of around £750 inc a 105 4iiii plus 105 chainset, BB, head….

Mmmmmm….

Has anyone had a decent amount of time on a 4iii one? I'd be really interested to know your thoughts on it.

That's why I think the [url= https://www.dcrainmaker.com/2016/09/power-meters-buyers-guide2016-edition.html ]DC Rainmaker's[/url] review is great, doesn't force a recommendation but explains the facts to allow you to chose the best one for you 8)

For me it's Stages or 4iiii as I have Shimano cranks and both my best road bike and Croix de Fer, so I can swap arms as required, and I want to keep cost low.

Luckily I upgraded to a 520 last year so no additional cost there. That said I can recommend the 520, great head unit.

Have you done a structured training programme with a heart rate monitor yet?

That would be a cheap(er) way of seeing whether you can stick to a training programme and, if you do, see some improvements.

Do that for a year then reward yourself with a power meter.

I've had 2 sets of first gen Vectors, first was warrantied 2nd has been upgraded to a 2nd gen via warranty too.

I've a Powertap G3 on my commuter as it can be locked to something.

If I was going to start spending money on power meters again I'd get as many G3's built into wheels as my budget allowed.

Been using structured power meter training ever since I bought a Taxc Fortius 8 years ago. So always power indoors and heart outdoor. Seems like there's enough experience now with power meters and the price has come down enough that I'd like to invest so I can train outside with power as well.

I've just bought a Quarq DZero BB30 from powermeter24.com for £549 delivered as they had a 10% extra discount a couple of weeks ago. PBK have some really good prices on GXP version.

I did a lot of research and what swung it for me was native BB30 ( bikes a Super six evo), price, reviews and works with ANT+ and BLE. I've paired with an a ELEMNT and I've got to say it was simple to fit, looks great and just works. I'd heard a lot about reliability of stages with water ingress and Quarq being part of SRAM didn't hurt either.

I get the single crank option but I am coming back from injury so it is important to get an indication of L/R performance even if it's only based on crank position. Other options, P2M is similar cost to Quarq but would have had to also get a Praxis for BB30. FSA Powerbox is an interesting option but upgrade to BLE availability is a bit vague and the P2M platform it's based on isn't current generation.

Oh and to answer the question definitely worth the investment. Totally transforms approach to riding even for a casual rider like me and the cost keeps coming down as well.

Has anyone had a decent amount of time on a 4iii one? I'd be really interested to know your thoughts on it.

I've had mine for about 6 months and done 2000km+ with it. No issues with it at all and it's still on the original battery. I'm not really used it properly as a training tool yet however it has helped me understand my limits better and I find that very useful to pace myself properly.

My training objectives really revolve around just being fitter/healthier, probably more so than trying to aspire to 2nd cat or similar level…..

If this is the case then would working from HR (and maybe just using Strava's extrapolated Watts if you really want to see some sort of "Power" data) be [i]'enough'[/i] if you are simply looking to manage the general intensity/effort of your riding? rather than more focussed training for events/racing.

HR isn't a bad tool to use, it's pretty immediate and you can set targets/alarms on most devices now if you want to manage it that way...

A power meter just seems like quite a "Serious" racers tool, something to invest in if you're looking for quite specific training data...

I'd second what a couple of people have said about using a HRM first. In fact, understanding of how to build a structured training programme before that (or getting someone to do it for you)

IF you do get one, I recommend Joe Friel's Power Meter Handbook to help you make the most sense of the data you're getting. I use TrainingPeaks to analyse my data, but Strava Premium has some similar features as does Golden Cheetah.

I was able to get a stages 105 for £400, was looking at 4iiii first but they seem to have stock issues, glad I went with the stages because 6 months down the line the 4iiii is still not in stock in my length

I'm glad I got one anyway, it has told me things about the intensity which I ride at that I couldn't see (or feel) on my own

if you're into that geeky side of cycling and you can afford it then why not

I bought one as I was feeling flush one day.. Never trained with it properly ever..

The good.. It's really good at measuring effort.. Really saved myself blowing up on climbs..

The bad.. Tells me exactly how bad I am compared to anyone remotely good..

So, best new price I can find is for a 175mm silver 105 Stages G2 unit is from Powermetershop.de at £411. For the black 4iiii 105 unit its £349 from Hinde.

Is the Stages worth the extra £62?

Re Stages... worth having a read of the big power meter thread on here. You might get lucky and get a reliable one but I know a few people and have heard about many more who have had several warranty replacements and still have problems. Their warranty department is apparently very good, which is a good thing as you'll probably need to use it at some point.

Don't know many with a 4iiii. I'd do my research.

At that price, single sided, I'd likely split the difference and go bePro (if you're happy with Look pedals.)

Thanks for the reply, been researching for many months from reading the other thread, DC Rainmaker and other reviews decided to go Stages or 4iiii. I use Look for road but want to use this meter for CX also with SPDs.

Have read about the leaking Stages, but though generally this was all but fixed with the Gen2 units. Guess it's another reason to buy from a decent shop ref any warranty issues, and not from eBay from a cheap guy in Israel 😆

Is anybody using Watteam Power Beat power meter yet?

You can get dual sided for £436.50 at:
http://www.clevertraining.co.uk/watteam-powerbeat-the-world-s-first-add-on-pro-level-powermeter?acc=cfcd208495d565ef66e7dff9f98764da

Using DC rainmaker code DCR10BTF

Is the Stages worth the extra £62?

no. Stages has reliability issues, mitigated by good customer service. 4iii has a smaller pool of reviews but seems to have no issues. One blog review I remember was long-term and included a season of CX (mud, jet washes etc). When he returned his test loaner he went out and bought one. Got 2 in our household with no issues (other than my paltry FTP and still learning to make the most of it).

john_l - Member

Is anyone doing an mtb spd pedal system yet, or are they still all road based?

That's the one thing that's putting me off at the moment - I need to be able to swap between bikes but off-road.

but though generally this was all but fixed with the Gen2 units

I wonder if Haze from this forum would care to comment on that 😉

A lot of it depends on what you are looking to do with it. And some knowledge on how to use it.
Power is just a tool really, don't get hung up to much on the numbers.

Currently I would avoid stages/4iii

Much better off with a power tap/quarq unit.

I'm on my 2nd Gen 2 Stages and am already having leaking issues after 6 months.

However, I wouldn't worry about where you buy it from - I've had mine sorted by going through Stages tech support even though I bought it from Germany. My replacements have been sent to me via Saddleback in the UK, but I didn't ever need to contact them myself - Stages did all of that for me.

I've used a 4iii for six months now. So far so good. Seems good on battery life

I had them for it to an xt crank which I swap between to mtbs. I had them fit it as I ride 165s, they turned it round quickly.

Great input, thanks.

Would you dare to buy a 2nd hand unit? If so how much cheaper would it need to be? And would it need sending back to the manufacturer for recalibration etc?

Currently I would avoid stages/4iii

Much better off with a power tap/quarq unit.

Would you dare to buy a 2nd hand unit? If so how much cheaper would it need to be? And would it need sending back to the manufacturer for recalibration etc?

Not if it was a Stages unless I was confident they'd honour the warranty (and is why I went for a new 4iiii from a proper retailer for peace of mind).

AFAIK most if not all PMs can be re-calibrated by the user - my Garmin prompts me as to whether I want to recalibrate mine every time it fires up.

sweamrs has a 4iii unit fitted to 105 cranks on her road bike for almost a year. Now admittedly it doesn't get the hardest life (trainer mostly with the odd road ride) but no problems yet.

Having taken up triathlon and training alone. I'm feeling it not having a power meter. I've got my first ironman on Sunday and my biggest worry is blowing it on the bike leg as it's an undusting course I've no idea how to pace the bike leg. Whereas I can pace a marathon down to 10 seconds per mile.

Currently I would avoid stages/4iii
Why?

I'd avoid Stages just because of all the moisture/battery issues they still seem to be having, even with G2.

Having said that, I did buy an XT Stages for the XC bike, it was very cheap in the sales and I rarely ride it so wouldn't be too bothered if I had to spend weeks on a warranty.

See no reason currently to avoid 4iiii. Could have been tainted in some minds with the cheap single sided crank arm Stages brush.

Much better off with a power tap/quarq unit.
Again, Why?

PowerTap is good but can be a pain in terms of servicing and bearing changes. I got years of use out of an old hub on the turbo but now need to send it off as the bearings are shot. And they often come back claiming the torque tube is no good and needs replacing too, which can be expensive. Tied to a wheel to so can be a bit limiting in terms of optimising wheels for the riding you're doing.

Quarq, only heard good things about them. No estimation going on as with single sided either. Out of the 4 mentioned I'd go for the Quarq if budget allowed.

Is going single-sided (either crank or pedal system) false economy - i.e. to people find themselves upgrading to a full system and if so, why?

John_l. Depends. If proper dual sided then it can give you a fair bit of extra info. E.g. what the balance is between left and right, and more importantly how that changes with effort and fatigue. For some people this might be big, others it might be small.

Not really a big issue if you aren't that serious about the data. It gets to be more of an issue the more performance analysis and modelling you do. And it's an issue if you have multiple PMs where some measure single sided and other total power, the data may not be directly comparable.

Thanks, that helps - I've got access to a Wattbike which gives me balance data. Seems the BePro S is discontinued, so I guess the Vector S2 is the only other pedal option?

Currently I would avoid stages/4iii

Why?
Much better off with a power tap/quarq unit.

Again, Why?
Would you dare to buy a 2nd hand unit? If so how much cheaper would it need to be? And would it need sending back to the manufacturer for recalibration etc?
Not if it was a Stages unless I was confident they'd honour the warranty (and is why I went for a new 4iiii from a proper retailer for peace of mind).

AFAIK most if not all PMs can be re-calibrated by the user - my Garmin prompts me as to whether I want to recalibrate mine every time it fires up.

There is currently a lot of literature with concerns about the stages, around validity, robustness, reliability etc.
there is a lot of deviation between stages themselves. Currently I would not be using a stage for any field based research. Only would I really be confident in SRM/Powertap.

Quarq and SRM allow you to calibrate on a first principle basis, which you can't really do with a powertap nor many others.

Stage's are not sensitive, they are badly effected by vibrations; okay only proven at 48 Hz and 52 Hz.
across 13 units, it had a coefficient of variation 2.0% +/- 1.4 (statistically different from SRM and Power tap)
and a mean deviation of -2.9% +/-3.9. Which in the paper i'm quoting from was the highest reported. And stages assumes that there are no bilateral differences (debate for another time)

It would suggest that there is some form of gain error within stages, the bigger the W the bigger the error so you can't be sure if you have improved unless it is a big increase, in elite sport you need to be able to detect a change of 2%. You often get power spikes as well, hence why I said to avoid stages, plus numerous problems with them. Using similar designs and principles I can't see 4iii being any better. But I don't have much to substantiate 4iii either for or against, more just an educated guess on it.

For me personally, I would just never be 100% confident in what the screen is showing to be true! Hopefully over the next few years they will improve. For the money they seem like a good option.

Also calibrating on the Garmin headunit is not an actual 'calibration' it zero offset, only certain meters allow you to calibrate them so you can adjust the slope on them. typically done statically, with a known weight hanging off it in around 4 different position, in each ring and then you can adjust if needed.

There is already a what PM thread, but I wouldn't discount P2M or Rotor. Stages and similar are what they are... a gateway drug in to the world of PM's 🙂 Sure other options have advantages but you pay for it, depends what is important to you

a gateway drug in to the world of PM's

Is a bit like that. Started with a PowerTap hub, then a P2M, then a single sided Vector, a dual sided Vector upgrade, a PowerTap C1 for the turbo bike, and finally a Stages for the XC bike 😳

Is going single-sided (either crank or pedal system) false economy

Not claiming to be an expert but everything I've read and heard from those that are is that everyone has a left/right imbalance, and there is no value in trying to train against it, so what are you going to do with that information?

If you want to be swamped with and obsess over data then maybe go for it, but the only people I know of with double-sided are people with no budget constraints who always buy 'premium' rather than as a conscious training-related decision.

but though generally this was all but fixed with the Gen2 units

I wonder if Haze from this forum would care to comment on that

Bit late to this!

Well my 2nd gen was given an extended dry out on the radiator and clean with isopropyl as suggested by support, I followed it up with a quick spin in a light shower.

It was fine next morning but dead again within a few days, will try again with a fresh battery when I can be arsed to waste any more time on it.

I know others have had a bit more luck but personally I can't recommend.

Not claiming to be an expert but everything I've read and heard from those that are is that everyone has a left/right imbalance, and there is no value in trying to train against it, so what are you going to do with that information?

First PM was a PowerTap, rode that indoors and out. Then got a single sided Vector S. Saw a noticeable discrepancy in the power between both. So put the Vector pedal on the turbo bike and did some testing. Much discrepancy that varied quite a bit with fatigue and effort. I set the scaling factor on the Vector to an average of the discrepancy and that brought things more in line but it still wasn't tracking that well. Eventually got the second Vector pedal and that sorted the problem. Looking at the data it's obviously down to the left/right imbalance and, more significantly, the variable nature of that imbalance.

I don't do anything to work on the actual imbalance, I'm pretty sure that's a waste of time. You'd also need something like a Vector or PowerTap P1 to capture actual left and right, a Quarq for example is still estimating though from total power (my Vectors and P2M give different values for imbalance as they're based on different methods.) While the imbalance data is quite interesting, I don't think it's actually that useful. What is worth having is the measurement of total power.

It's a bit of a heresy, but if you want 30 second average power, or a more accurate summary than Strava, get a powercal HR monitor. Mine's been flawless, unlike the two stages I broke, and the powerpod that also had to be replaced.

The Powerpod is geeky smart, but needs careful setting up. Just done a 10 TT and paced to Powerpod power (310 Watts per lap average), and the results look very accurate indeed. Reproducibility is what matters, absolute numbers are less useful.

My next PM will be a Vector, but I probably should have paid the extra for a PM in the HED disc.

powercal HR monitor. Mine's been flawless,

Mine broke 🙁

Really? I have two. All I've ever done is change the batteries. I bought the first to replace a Garmin strap that died. The second I got free using incentives from work. I pass it around anyone that wants a go. I now use a wahoo tikr with the powercal as I though the powerpod might get get little upset trying to pair with something that's sending power Jim, but not as we know it!

The distribution of power is always too narrow but t mean is accurate.

Mine just seemed to stop transmitting.

Transmitting power and HR was occasionally a bit of a pain though as riding with it and a proper PM did occasionally frustrate when the Garmin would lose the proper PM signal momentarily and pair with the PowerCal instead.

Well I've committed now and bought a 4iiii unit that I can share between road & trainer bikes. Now considering a Powercal unit as my heart band is playing up, then I can use this for XC. Plus is I run both on my Taxc I can see how the result compare etc.

Will try this for the rest of the year and see how it goes, can always change later if not happy or new tech comes out.

Staineypants, surely if you've been training without a power meter you can do it on average speed (taking into consideration weather, wind etc) feel and heart rate? I've done 2 Ironmans without a power meter and planned my bike leg on that one, first one was perfect, second one less so but I knew the issue and decided to ignore it. Yes a power meter is a better gauge but remember you can sometimes get hung up on numbers.

I now have a power meter and I'm slowly learning how to use it! Just seems to blow my mind with complexity at the moment!

Power Meter - worthwhile investment?

Depends are you superfit already and just trying to find those little extras?

If not then getting fit first would be the way to go, you dont need a power meter to tell you that you need to get out for a training session.

I've gone from using HR monitors etc to just going out and riding/running and Im much fitter now. IMO using tech can be just an excuse when what is actually needed is graft.

Transmitting power and HR was occasionally a bit of a pain though as riding with it and a proper PM did occasionally frustrate when the Garmin would lose the proper PM signal

Indeed. My powerpod was flat at my [url= https://www.strava.com/activities/1008089942 ]last road race[/url], so I quickly swapped HR monitor from Wahoo to Powercal. Then had to pair both HR and power to the garmin, whilst truing to get it to ignore the other 60 riders! Results looked fine though. It was a pretty easy race after the attack had gone.

I still like it though.

IMO using tech can be just an excuse when what is actually needed is graft.

Well I never, I dug the PowerCal out from the bottom of a box, shoved a new battery in and it's come back to life! At least as far as Zwift goes. Maybe it was a Garmin problem and not the PowerCal?

IMO using tech can be just an excuse when what is actually needed is graft.

What's really needed is a plan that you stick to.

Good thing about PM's IMO is that you can start putting a lot more numbers into the plan. Be more specific about load and recovery. And have specific targets for rides (interval power, overall TSS, etc.) A plan with targets and a PM to tell me I'm not going hard enough made me graft like I never have before!

Btw, I ran for years without a HR. Then got one of the early Polar HR which was great. Then one of the early Garmin GPS watches to add things like pace targets. Even used a little beeping metronome to work on run cadence. Bits of technology can definitely enhance your training and improve the effectiveness of your graft.

I've just started using a smart turbo with power and have to say the info is invaluable.

You've got an exact reference point to how hard you are working compared to previous sessions, great for telling yourself if you are slacking and also if feeling fresh a real boost when you can produce numbers that you couldn't the week before.

Having the same info on the fly when outdoors is a great thing, half way up a climb you can see if you are going to blow up or also you can have a word with yourself if you aren't putting enough effort in.

Yes you can do this by feel... but not to the same precision points

I've got a Quarg - it seems bombproof. Ridden it all winter & it's never missed a beat.

I previously had some PowerTap chainrjngs - good for about 3 months & then they gave up. I think water ingress was the issue.

Power is great if you know what you're doing with it - but I wouldn't buy a power meter just for kicks.

IMO using tech can be just an excuse when what is actually needed is graft.

Definitely some truth in that - however blasting yourself all the time can lead to overuse/over training. A little bit of tech & knowledge goes a long way to preventing this from happening.

I've got a Quarg - it seems bombproof. Ridden it all winter & it's never missed a beat.

I'm surprised that's improved your power, if I'm honest.

[img] [/img]

Lol at Quarg 😆

Those with PowerCal; if I already have a Garmin cadence and speed sensor can these be used by the PowerCal or must I have the PowerCal sensors anyway?

Ah what you haven't realised about Quarg is:

A. It's an excellent power meter.
B. You never go hungry on a ride.
C. It's better than Stans for sealant.
D. Can be used as chain lube in an emergency.
E. A tasty sunscreen.

The list goes on!

Those with PowerCal; if I already have a Garmin cadence and speed sensor can these be used by the PowerCal or must I have the PowerCal sensors anyway?

Do you mean PowerPod? PowerCal is just a chest strap that doesn't need anything else.

Powertap Powercal can be bought with speed and candence sensor, just wasn't sure if they were needed if I have the Garmin sensors?