Cycling computers with Real Time Gradient feature

[sergen]

I know that the HAC4 has an accurate gradient feature that shows you what you're climbing in real time. This is why I am defintely being pushed towards this computer rather than a Polar 725 (which only lets you view gradient on the software).

Do any forum users use other computers that show you real time gradient?

[jmurray89]

I use the ciclosport CM-436M wireless
It's got alot of other features; altitude, gradient, temperature, and alot more.

http://www.bikesomewhere.com/bikesomewhere.cfm/product/56/297/652
check that one out.

There's also a model CM-434M that has gradient and is cheaper
http://www.bikesomewhere.com/bikesomewhere.cfm/product/56/297/651
theres the link to that one.

hope that helps.

[RapDaddyo]

I own two HAC4+ computers and I would not agree that they display real-time grade info. They derive grade from changes in barometric pressure, which has a built-in delay and assumes accuracy of the barometric pressure at your location (which changes continuously). There is a cycling computer that derives road grade info with different technology http://www.clino.it/ (after you go to the site, choose English). I don't own it, but the underlying technology is interesting (digital accelerometer, if I recall correctly). And, of course, the GPS units would have grade info together with a whole bunch of other data. The most interesting of these is the soon to be shipped (January was the latest predicted ship date) Garmin Edge 305 http://www.garmin.com/products/edge305/. What makes this unit appealing is the GPS receiver, said to be a quantum leap in signal quality (e.g., receives GPS signal virtually anywhere).

[sergen]

I own two HAC4+ computers and I would not agree that they display real-time grade info. They derive grade from changes in barometric pressure, which has a built-in delay and assumes accuracy of the barometric pressure at your location (which changes continuously). There is a cycling computer that derives road grade info with different technology http://www.clino.it/ (after you go to the site, choose English). I don't own it, but the underlying technology is interesting (digital accelerometer, if I recall correctly). And, of course, the GPS units would have grade info together with a whole bunch of other data. The most interesting of these is the soon to be shipped (January was the latest predicted ship date) Garmin Edge 305 http://www.garmin.com/products/edge305/. What makes this unit appealing is the GPS receiver, said to be a quantum leap in signal quality (e.g., receives GPS signal virtually anywhere).

The korotek certainly looks interesting - although it doesn't seem to have a HRM built in which would be a nice inclusion.

From your experience of the HAC4 gradient feature, do you at least get consistent readings even though those readings may not be 100%? For example, if you go up a short stretch of hill on each of your training rides, does the HAC4 always tell you the same gradient even though you may know that reading may be slightly out?

[RapDaddyo]

The korotek certainly looks interesting - although it doesn't seem to have a HRM built in which would be a nice inclusion.

From your experience of the HAC4 gradient feature, do you at least get consistent readings even though those readings may not be 100%? For example, if you go up a short stretch of hill on each of your training rides, does the HAC4 always tell you the same gradient even though you may know that reading may be slightly out?It's not bad if you set the actual starting altitude immediately before your ride and if the ride is not too long. I wouldn't trust it on a century, though, due to the possibility of significant pressure changes (other than from altitude changes) in the course of a ride. The problem is that the pressure change per 100' changes as a function of altitude. I can't remember the numbers offhand, but it's significant. Personally, I'd prefer a system such as GPS that was not dependent on changes in baro pressure. BTW, the watts feature of the HAC4+ is basically worthless.

[sergen]

BTW, the watts feature of the HAC4+ is basically worthless.

Oh don't worry, I'm well aware of that! But I don't have enough money for a Power Tap and given that there are also accuracy issues with the Polar 725's power feature (although I know these problems are not as bad as HAC4) I figure it's best not to worry about the power feature for the time being.

One of the real reasons I was drawn to the HAC4 was because the gradient feature could help you with gear selection over a long climb with a steady gradient. For example, if you had some 'objective' info telling you that you're climbing a 3.5% hill then depending upon your existing cycling abilities you might try to pace yourself in 39x21. Similarly, if you could see you were climbing a 5% hill you might drop into 39x25, or on an 8% hill use 30x23 (assuming you have a triple).

This is the main reason I'm drawn towards the gradient feature on the HAC4 - I believe it could help me with the correct gear selection on long climbs with a steady gradient.

[dhk]

It's not bad if you set the actual starting altitude immediately before your ride and if the ride is not too long. I wouldn't trust it on a century, though, due to the possibility of significant pressure changes (other than from altitude changes) in the course of a ride. The problem is that the pressure change per 100' changes as a function of altitude. I can't remember the numbers offhand, but it's significant. Personally, I'd prefer a system such as GPS that was not dependent on changes in baro pressure. BTW, the watts feature of the HAC4+ is basically worthless.
Believe the pressure change is about 0.1 inches per 100 feet; that's how the baro altimeters work. I've got a watch with a baro altimeter, and it's also fairly useless for rate of climb info. It can be fairly accurate when in the mountains, usually within +/- 30 feet, but have to calibrate first to a known elevation (eg, summit sign). Also takes time to read since it has a 15 second sampling interval. Doesn't do well on small elevation changes overall.

Believe the best device for reading instant gradients might be the calibrated bubble-level that mounts to handlebars. I've seen them in ads for $25, but haven't bought one yet. Would like to hear experiences with those if anyone has one.

[RapDaddyo]

Believe the pressure change is about 0.1 inches per 100 feetBut, isn't the pressure change per 100' a function of altitude? IOW, isn't the pressure change per 100' significantly different at, say, 3000' versus sea level? I've got some notes on that somewhere (I'm a pilot). I'll look for it.

[RapDaddyo]

Oh don't worry, I'm well aware of that! But I don't have enough money for a Power Tap and given that there are also accuracy issues with the Polar 725's power feature (although I know these problems are not as bad as HAC4) I figure it's best not to worry about the power feature for the time being.

One of the real reasons I was drawn to the HAC4 was because the gradient feature could help you with gear selection over a long climb with a steady gradient. For example, if you had some 'objective' info telling you that you're climbing a 3.5% hill then depending upon your existing cycling abilities you might try to pace yourself in 39x21. Similarly, if you could see you were climbing a 5% hill you might drop into 39x25, or on an 8% hill use 30x23 (assuming you have a triple).

This is the main reason I'm drawn towards the gradient feature on the HAC4 - I believe it could help me with the correct gear selection on long climbs with a steady gradient.I understand why you want the info. I am suggesting that the lag and accuracy may defeat your purpose. I actually don't think many climbs are of constant grade. Most climbs are of varying grade and the variations are sufficient to result in pretty large power variations if you stay in the same gear and maintain the same speed. The price might be prohibitive, but if I were looking for a bike computer today without power I would look carefully at the Garmin Edge 305. Not only would you have real-time data including grade but you could do post-ride analysis with the tracking file. I don't have any vested interest in Garmin. I am just passing along the bike computers I would be considering if I didn't have a PM.

[alienator]

Oh don't worry, I'm well aware of that! But I don't have enough money for a Power Tap and given that there are also accuracy issues with the Polar 725's power feature (although I know these problems are not as bad as HAC4) I figure it's best not to worry about the power feature for the time being.

One of the real reasons I was drawn to the HAC4 was because the gradient feature could help you with gear selection over a long climb with a steady gradient. For example, if you had some 'objective' info telling you that you're climbing a 3.5% hill then depending upon your existing cycling abilities you might try to pace yourself in 39x21. Similarly, if you could see you were climbing a 5% hill you might drop into 39x25, or on an 8% hill use 30x23 (assuming you have a triple).

This is the main reason I'm drawn towards the gradient feature on the HAC4 - I believe it could help me with the correct gear selection on long climbs with a steady gradient.

Why don't you select a gear according to a comfortable cadence if you're looking to pace yourself? That would be better. An 8% grade early in a ride will prolly be managed a lot easier than an 8% grade at the end of a ride.

[dhk]

Agree with alienator. I like to have grade info too, but don't need it to determine the right gear to use. Shifting by cadence and feel is a much better way, IMO. Besides, I often climb at different speeds, depending on the training goal, or who I'm chasing.

You should be able to tell when your legs are "loading up" with high-force effort (gear too big) or when you're spinning too fast. For me, it's better to start the climb in a smaller gear, then shift up if it gets easy. Can't tell you how many times I've gotten dropped at the bottom of a long climb by going onto the granny ring, then passed the same riders struggling with a big gear (or walking) halfway up the climb.