hac4 or powertap?
- Thread starter Penzoil
- Start date
I have both.Penzoil said:
Pt is the real deal. I consider the HAC4 mostly for entertainment. I have yet to put them side-by-side to see how far off the HAC4 really is. One thing's sure -- it reacts slowly and measures in 20w chunks.
I would never consider buying the HAC4 for power measuring/training.
HAC4 is no good for power based training, go for the powertap.....check out this threadPenzoil said:
http://www.cyclingforums.com/t155509.html
gooders said:
Hac4 Plus for me has been excellent for power training. My readings have come out almost identical to all my lab test readings for peak power. Obviously, the monitor can't track an 'explosive' effort, say 30 second sprints/accelerations, but over longer hill efforts/intervals/races, the hac is fabulous. I also use it in combination with the cadence metre, which has made me learn hugely about my own performances. The Hac is less accurate on the flat, but you dont need to use it on the flat, if you can train with it on a hill and get pretty accurate power readings - you can see where you are fitness wise.
Consistency is what you are actually looking for in power training recording accuracy - so that you can compare your rides and see your improvements - Hac is tops for this! Batteries last ages and the monitor is really durable to all weather conditions - certainly by far the best 'all in one' quality 'computer' I've used in years.
It DOES require you to sit down and learn how to properly set up the thing. Afterall the Hac IS a computer, and in my opinion, an excellent one at that.
Biking-bec
The hac4 is not a "real" power meter - it just estimates the power output based on the inputs of 1.) your weight, 2.) your speed 3.) your elevation gain, and 4.) a fixed factor that estimates air/rolling resistance. For this reason, it will not be very accurate as a power meter, especially on flats or downhills, and will not compensate for wind, etc. It does, however, give you a rough idea as to where your output is.Penzoil said:
The power meter is only once of numerous other VERY valuable features of the Hac4. Although its power meter may not be the best, the other features make it by far the best cyclocomputer available. I can't imagine riding without a Hac4 anymore - I DEFINITELY recommend getting a Hac 4, and then getting a real power meter later if you find that you need a truly accurate power meter - the 50 Hac4 features are more important than just having an accurate power meter.
WINGNUTT said:
Training by power is the single most beneficial training aid available today other than a good coach. If you don't have a real power meter, any old cycling computer will do just fine for a fraction of the dough*.
*This is assuming your goal is to get faster, not to have the coolest gizmo on your bike.
I guess you don't consider it important to know your cadence and have the ability to record and download your speed / HR / elevation gain / cadence / etc. etc. etc. Personally I'd take the 50+ features of the Hac 4 before I invested in a really good power meter... the additional accuracy of a good power meter does not outweigh these features. Being able to download to the computer and review and compare your performance over time and various conditions is in itself a more valuable tool than additional accuracy in the power meter. Plus the good power meter is 3x as expensive. If you don't have a good cyclocomputer, then you aren't ready for a good power meter IMO.beerco said:
WINGNUTT said:
The problem with your logic is that power is the only true way to compare performance over time and various conditions. Speed, cadence etc. etc. are all severely influenced by external forces (i.e. "various conditions") which are not recorded thus making an apples to apples comparison impossible. e.g. 25mph is no big deal with a 50mph tailwind where it's a very big deal with a 50mph headwind. Power does not have this same problem 250w is 250w irrespective of wind, grade, etc. (altitude is the one thing that is missing although below about 4000' it's not really an issue at all).
HAC 4 - neat, yes. Better for training than a $15 astral - not really.
WINGNUTT said:
Hi Wingnutt, I agree
Well no computer is going to make you go faster on the road. It is how you interpret the data from the computer, then apply specific training to improve overall performance. So whatever the system used, it then depends on the interpreter!
The Hac certainly gives a pretty good all round 'picture' of my efforts, and for me, is all that is necessary to help me work on my development. I don't think SRM or PTap would make me cycle any faster, or interpret any more about myself than I already do at present...Be careful of paying way over the odds when not ready, as Wingnutt above mentions. I'd only ever use the SRM cranks if I was in the running for Olympic selections, where every split second could count!
Yes the combination of understanding/interpretting power output and cadence to TT (Time Trial)performance is critical to TT success in my opinion. If you use 'a device' that can give you this as a clear download, AND you know how to train AND you know not to take all readings too seriously, then yeh, the Hac is great.
WINGNUTT said:
Just one challenge point to Wingnutt - err how do you define power output in a mathematical formulae? You say that, "The hac4 is not a "real" power meter - it just estimates the power output based on the inputs of 1.) your weight, 2.) your speed 3.) your elevation gain, and 4.) a fixed factor that estimates air/rolling resistance"
This IS how power output if calculated! So what is the magic ingredient in the PTap that qualifies it as 'a power meter' any more than the Hac??
biking-bec said:This IS how power output if calculated! So what is the magic ingredient in the PTap that qualifies it as 'a power meter' any more than the Hac??
That is how power is calculated, but now how it is measured. The powertap makes direct force (torque) measurements using strain gauges on the hub. This in conjunction with an accurate angular velocity (hub rpm) sensor allows a direct calculation of power without having to worry about all of those other factors (power/1rev = (ave torque x angular velocity for that rev)).
The Hac's power estimate isn't even in the same ballpark in terms of accuracy or precision.
I think beerco's reply is accurate - "real" power meters will actually measure the power that is created at the hub, whereas the Hac just estimates based on known inputs.biking-bec said:Just one challenge point to Wingnutt - err how do you define power output in a mathematical formulae? You say that, "The hac4 is not a "real" power meter - it just estimates the power output based on the inputs of 1.) your weight, 2.) your speed 3.) your elevation gain, and 4.) a fixed factor that estimates air/rolling resistance"
This IS how power output if calculated! So what is the magic ingredient in the PTap that qualifies it as 'a power meter' any more than the Hac??
I will concede to beerco that the PT is much more accurate than the HAC4 with respect to this feature. I disagree with him that this additional accuracy is as important as he says it is relative to the other benefits the HAC4 has over a $15 cyclocomputer. I guess everyone has their own way of training, but I fail to see how the accuracy of the PT makes it even close to as valuable of a training tool as the Hac4.
WINGNUTT said:
Why not ask Ric Stern, or Hunter Allen, or Chris Carmichael or any other coach who's "seen the light" wrt power which training tool they prefer?
Instead of re-inventing the wheel, I'll steer you to this link: http://www.midweekclub.com/powerFAQ.htm also check out: http://www.cyclingpeakssoftware.com/power411.html
If you still don't see it*, only time and further reading on your part can help.
(again, this is only if your goal is to get the most bang from your training buck.)
Beerco... those articles were pretty much irrelevant to this discussion- all they talk about is how good of a training tool a power meter is. I didn't say that power meters weren't good training tools. I just disagree that it is more important than a Hac4. I have not used a power meter, so I am kind of talking out of my ass, but I do know that the cadence and computer analysis features of the Hac4 have made a huge difference in helping me improve. Without the foundation that I have built using the HAC4, I don't think the PT would be of tremendous use to me.beerco said:
WINGNUTT said:
Once you have an accurate and reliable power meter on board, pretty much all other variables become meaningless. measures such as cadence don't really tell us much, and i find that it only becomes vaguely useful when working with track riders, and even then if yoiu know the time taken to do a lap and the gear they're in, cadence is irrelevant or can be calculated.
Heart rate is more useful and i do use it as an approximate guide if no power meter is available. if one is available it can't tell you anything you don't already know.
speed is completely meaningless, because it's so dependent on the topographical conditions involved in your ride. on the other hand, if you know the velocity at which you're travelling and the altitude you're gaining then you can work out by hand your power output.
altitude is a neat little function, which i sometimes find fun and use my S720 for.
given a choice, power is way more important than the sum of all the other metrics by a long way, as it tells you exactly what you need to know. obviously, you need to be able to interpret the data and that may be a different issue. i find the other functions are just there as a fun value.
ric (been collecting and analysing power data since 1993)
ric_stern/RST said:
I concur. In my short experience with power training (about a month), I have found power to be so much more revealing than any other measure. I've learned a lot from it -- for example, during intervals my HR slowly creeeeeeeeeeeeps up, as much as 10bpm over a 20 min interval. Were I training by HR only, I would be slacking off as the interval progressed (note: I could be overtraining by NOT slacking off!... we'll see).
I have a HAC4 on another bike, which I train on about half the time. WOW, do I miss the power reading when I ride it!
I think the bottom line is that power is everything. It's the root of all training. HR is just an indicator of what your body perceives as effort. HR in itself pretty meaningless.
Back to the HAC4 v. Powertap... Sometime within a month or so, I'll have a chance to have both on the same bike (swapping wheels around). I'll report on how similar the power readings are.
Aztec said:
Here's something you should do as a good test. Do two 2x20 efforts on different days (hopefully with climatic or terrain differences) with the same power target and check the ave power between the two units for the intervals. If there is a constant error between the two days (e.g. HAC always reads 10% high) it might be useful. If the error varies with terrain or wind, the HAC power calculation is worthless.
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