hac4 or powertap?

Penzoil

Which one would be the best buy. Keeping in mind that the powertap is about 3 tiems more expensive. Or is there somethin else that is better?

Aztec

I have both.

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.

claytid

That's because it's a real pm...the hac is not. And it's pretty hard to go wrong w/ the PT.

velomanct

the hac4 is nearly a complete waste of money.

get the PT

gooders

HAC4 is no good for power based training, go for the powertap.....check out this thread

http://www.cyclingforums.com/t155509.html

biking-bec

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

WINGNUTT

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.

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.

beerco

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.

WINGNUTT

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

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.

biking-bec

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.

biking-bec

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??

beerco

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.

beerco

Hmm. funny. I use a powertap for the exact opposite reason: I have a day job which limits my time to train. To make the limited training time I have more effective than the rest of guys I race against, I use a powermeter.