Summary: Junk. Junk. Junk. It's been warrantied twice. Here is the problem (s). The information transmission is ANALOGUE not Digital. Thus the heart rate function does not work under, or close, to power lines. Then other functions are not accurate because of the analogue transmitter. The only feature that works all the time is the altitude feature. That is very accurate - but who cares at $300 to get one feature! It's complicated to use. Do not be deceived like me because it's "German." Also it eats batteries like you wouldn't believe. Very expensive to keep at full strength. The Wheel sensor battery is a crazy sized 12volt that is very difficult to find and not cheap once found. I had a Polar for 10 years that I miss dearly and that's where I'm going. Moreover to the HAC4's problems, the heart rate feature is very inaccurate over 200bpm because of the analogue trans. You can only observe heart rate over 200 in the small display not the larger display, and what really makes me crazy and pissed, the HAC4 can't store max heart rate over 200bpm!!! It just gives you a "blank" in the saved ride feature when reviewing your tour (ride). That's how pathetic this device is. The most important feature - the heart rate at ultra high bpms - is the least reliable.
Summary: This is a very unreliable cycling computer. The only thing on this entire system that works well is the HR monitor strap! (It is compatible with all kinds of exercise equipment). The speedometer is rarely works, the cadence device failed, and there is NO...ZERO tech support. Sigma has awesome tech support!
It is complicated to use, the user's manual is a joke. Do not buy this product! Save your money.
Summary: I use the hac4 for power and heart rate. Mounted next to the hac4 I have a cateye for cadence and timer. The mount is weak in the respect that it indicates using the included rubber bands to secure. On my road bike I have it mounted on my stem. It is secured in place by two zip ties around the mounting harness. On my tribike I have one mounted on an aeropost but I replaced the mount with a cheap ring mount from an old computer (performance axiom). The power is usually 20 watts below normal. Power becomes more accurate during long climbs as does the %grade. The more consistent the power output through the pedal stroke, the more accurate the Hac4 is. Power is calculated using an algorithm factoring speed, cadence and altitude change. Hac4 will pick up the polars HR strap but not vice versa. The software provides good data but it isn't as user friendly as polars 4.0. The battery dies pretty quick compared to the polar models but it is a cr2032 so it's easy to find and easy to change out. When the battery gets weak there are more data errors. Only 2 lines of display. Someone needs to make a computer with cadence, HR, Power, and timer all on one display. I have a Hac4 titanium but I can't use the software that came with my other hac4 plus. Backlight takes to long to enact (4 sec). If you buy the hac4 titanium you will get raped on the cost of a new mount, cadence cable and download kit. Wait and see how the Hac5 performs. Get a used powertap on ebay for $500 and you will be happier, or a srm if you can afford it.
Strengths: Power, %grade, can use polar coded HR-strap, HR, Cadence, 2 HR zones, wireless speed
Weaknesses: Mount, only 2 lines of display, can't display power and cadence at the same time, slow download, short battery life, High mount, ski function??, wrist band, to bulky. Retail price is inflated. Hac4 titan doesn't include any of the ancillary material which makes the Hac4 an effective tool. Wired power and cadence.
Similar Products Used: cateye, performance, polar coach, s710, s510, s625x, s810, power tap, computrainer
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Bike Setup: Trek Madone 5.9 SL, Shimano Dura Ace, Time Pedals, Easton Ascent II Wheels.
Summary: There are many reasons for a cyclist to buy this product (it has everything you could want minus a power meter) and one important reason not to, its a piece of junk. I have owned this computer for 6 months now and it has maybe 1200 miles (hard to say since the odometer function stopped working) and maybe 30 rides on it. Already there are numerous functions that worked in the beginning but have stopped working, speed, cadence and odometer are thoe most notable and troubling. The average heart rate never did work even though the current heart rate function seems accurate and reliable.
The instruction manual is a joke with no real explanation of how anything really works. The manual will tell you to start and stop a function or save a measurement, but doesn't explain how to do this. Its either a really poor translation from German, or was just plain poorly written even in German.
I was really excited to be able to download all my ride info to my laptop, but have never been able to make this work.
I may not be the most technical person, but I have sold various software systems for the past 15 years and know my way around a computer. It just shouldn't be this difficult.
I'm switching to a Polar S725X with cadence.
Strengths: All the functions you could ever want
Weaknesses: Many functions have just plain stopped working. Horrible user manual.
Similar Products Used: Polar, Vetta, Cateye
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