Training with Power

MDL said:

Anyone have any experience using the "Tacx Grand Excel"? I'm looking to buy a trainer that will
measure power to use over the winter. Any feedback aprpeciated.

I don't have any experience with the Grand Excel but since you say that any feedback is appreciated
I'll mention that the cost of a built-up Power Tap wheel plus a regular trainer is in the same
ballpark. Each approach has advantages and disadvantages. The main advantage of the PT/trainer
approach is that you can take it on the road when the weather turns nicer.

"MDL" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Hi, Anyone have any experience using the "Tacx Grand Excel"?

I used one all last winter and it provides more variety than a simple turbo, Good for ramp tests
etc. But still a very uninspiring way to ride my bike. All the best Dan Gregory

"MDL" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Hi, Anyone have any experience using the "Tacx Grand Excel"? I'm looking

to buy

Quoted message said:

a trainer that will measure power to use over the winter. Any

feedback

Quoted message said:

aprpeciated. Thanks.

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at level 3
with a Power Tap, I recorded the following (in watts):

Quoted message said:

PT Level 3 Tacx 150 150 175 170 200 190 225 210 250 230 275 250 300 270 325 290 350 310 375
330 400 350

The tacx correlated differently at different level settings which tended to indicate that it was the
source of the error. I always found that comparative estimating was just as useful (or useless) as
absolute power values. In my opinion the tacx will still be a useful training tool.

Phil Holman

Phil Holman said:

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at level 3
with a Power Tap, I recorded the following (in watts):

Quoted message said:

PT Level 3 Tacx 150 150 175 170 200 190 225 210 250 230 275 250 300 270 325 290 350 310 375 330
400 350

The tacx correlated differently at different level settings which tended to indicate that it was
the source of the error. I always found that comparative estimating was just as useful (or
useless) as absolute power values. In my opinion the tacx will still be a useful training tool.

Phil, I remember when you posted these data:

google.comgroupsOpen ↗

I went back through that thread, but I didn't see whether you guys had done a rolldown calibration
for the Tacx before this. Had you?

Phil Holman said:

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at level 3
with a Power Tap, I recorded the following (in watts):

[snip]

Here's the top post in another thread, comparing the profile of a Tacx Grand Excel with the SRM:
groups.google.comgroupsOpen ↗

Thanks for all the great info!!!

"Robert Chung" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Phil Holman said:

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at level
3 with a Power Tap, I recorded the following (in watts):

[snip]

Here's the top post in another thread, comparing the profile of a Tacx Grand Excel with the SRM:

groups.google.comgroupsOpen ↗ .com

"Robert Chung" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Phil Holman said:

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at level
3 with a Power Tap, I recorded the

following

Quoted message said:

Quoted message said:

(in watts):

Quoted message said:

PT Level 3 Tacx 150 150 175 170 200 190 225 210 250 230 275 250 300 270 325 290 350 310 375 330
400 350

The tacx correlated differently at different level settings which

tended

Quoted message said:

Quoted message said:

to indicate that it was the source of the error. I always found that comparative estimating was
just as useful (or useless) as absolute power values. In my opinion the tacx will still

be

Quoted message said:

Quoted message said:

a useful training tool.

Phil, I remember when you posted these data:

google.comgroupsOpen ↗

Quoted message said:

I went back through that thread, but I didn't see whether you guys had done a rolldown calibration
for the Tacx before this. Had you?

I've only ever seen a calibration rolldown on a Velodyne. The Tacx unit belonged to someone I was
coaching and it had no calibration feature on it and no mention of it in the literature. Researching
the Grand Excel model, it is the same as the Excel plus a bunch of programming capability. What was
the reason for your question? Without taking into account tire rolling resistance, the difference
between a 25mm tire at 90psi and a 21mm at 130psi will result in a significant difference in actual
power generated with the Tacx unit.

Phil Holman

"Phil Holman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Robert Chung" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Phil Holman said:

Accuracy was a concern and has been discussed here before. In a test comparing the Tacx at
level 3 with a Power Tap, I recorded the

following

Quoted message said:

Quoted message said:

(in watts):

> PT Level 3 Tacx 150 150 175 170 200 190 225 210 250 230 275 250 300 270 325 290 350 310 375
> 330 400 350

The tacx correlated differently at different level settings which

tended

Quoted message said:

Quoted message said:

to indicate that it was the source of the error. I always found that comparative estimating
was just as useful (or useless) as absolute power values. In my opinion the tacx will still

be

Quoted message said:

Quoted message said:

a useful training tool.

Phil, I remember when you posted these data:

google.comgroupsOpen ↗

Quoted message said:

Quoted message said:

I went back through that thread, but I didn't see whether you guys had done a rolldown
calibration for the Tacx before this. Had you?

I've only ever seen a calibration rolldown on a Velodyne. The Tacx unit belonged to someone I was
coaching and it had no calibration feature on it and no mention of it in the literature.
Researching the Grand Excel model, it is the same as the Excel plus a bunch of programming
capability. What was the reason for your question? Without taking into account tire rolling
resistance, the difference between a 25mm tire at 90psi and a 21mm at 130psi will result in a
significant difference in actual power generated with the Tacx unit.

Robert asked because a standard procedure for coast-down calibration of the Tacx has been proposed
and adopted by at least some. If followed, the Tacx tends to give more accurate power data than what
you're reporting.

Andy Coggan

If you get the tacx you could program in some hills & use a video like mine here as a way of helping
to relieve any boredom turbovids.netDVDTempoHills.htmOpen ↗

Phil

"Andy Coggan" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Phil Holman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Robert Chung" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Phil Holman wrote:

> Accuracy was a concern and has been discussed here before. In a

test

Quoted message said:

Quoted message said:

Quoted message said:

> comparing the Tacx at level 3 with a Power Tap, I recorded the

following

Quoted message said:

> (in watts):
>
>> PT Level 3 Tacx 150 150 175 170 200 190 225 210 250 230 275 250 300 270 325 290 350 310 375
>> 330 400 350
>
> The tacx correlated differently at different level settings

which

Quoted message said:

Quoted message said:

tended

Quoted message said:

> to indicate that it was the source of the error. I always found that comparative estimating
> was just as useful

(or

Quoted message said:

Quoted message said:

Quoted message said:

> useless) as absolute power values. In my opinion the tacx will

still

Quoted message said:

Quoted message said:

be

Quoted message said:

> a useful training tool.

Phil, I remember when you posted these data:

google.comgroupsOpen ↗

Quoted message said:

Quoted message said:

Quoted message said:

I went back through that thread, but I didn't see whether you guys

had

Quoted message said:

Quoted message said:

Quoted message said:

done a rolldown calibration for the Tacx before this. Had you?

I've only ever seen a calibration rolldown on a Velodyne. The Tacx unit belonged to someone I
was coaching and it had no calibration feature on it and no mention of it in the literature.
Researching the Grand Excel model, it is the same as the Excel plus

a

Quoted message said:

Quoted message said:

bunch of programming capability. What was the reason for your

question?

Quoted message said:

Quoted message said:

Without taking into account tire rolling resistance, the difference between a 25mm tire at 90psi
and a 21mm at 130psi will result in a significant difference in actual power generated with the
Tacx unit.

Robert asked because a standard procedure for coast-down calibration

of the

Quoted message said:

Tacx has been proposed and adopted by at least some. If followed, the

Tacx

Quoted message said:

tends to give more accurate power data than what you're reporting.

Andy Coggan

Sounds reasonable. Calibration would therefore be via adjustment of tire inflation/roller pressure?
Based on my data, I could see that a higher pressure and narrower tire would tend to make the unit
read more accurately. Someone must have been busy with a calculator.

Phil Holman