POWER METERS: Crank, Hub or Pedal-based?

[Niner]

Can anyone tell me how the PT range works? I see Elite, SL, SL + etc what is what.

Interested in a hub based system but not sure what is what.

 

Why is it that the local surpliers are R2600 more than international like CRC?

[Minion]

Can anyone tell me how the PT range works? I see Elite, SL, SL + etc what is what.

All PTs use a torque tube with strain gauges in the hub to measure pedalling torque. This is combined with rotation speed to give power.

 

All of the Powertap models that end in a "+" are wireless and work with ANT+ head units that support power (Edge 500 etc.). The Elite+ has a steel axle and an all metal shell and weighs more than 600g. As you go up in the range, they get lighter, going to aluminium axles, then to carbon windows in the hub shell and I think the very top-end SLC+ has ceramic bearings. Functionally, they are identical.

 

The 2012 models are the G3 and the Pro. The G3 is significantly lighter (and more expensive) than previous models and is all black. The 2012 Pro looks like it has the same specs as the Pro+ model, but it's black, rather than silver.

 

Finally, Powertaps come as a hub only or as a complete system (includes HR strap and CycleOps Little Yellow Computer). Most people who already have an ANT+ computer will go for the hub only.

 

In the past I've found that prices for new models from Bicycle Power Trading and CRC are within 10% once VAT etc. is added. This still seems to be the case for the G3 and the 2012 Pro. CRC is now offering 25% discounts on the 2011 models which probably explains the difference. Also make sure you're comparing the prices for hubs only vs. complete systems.

Edited February 27, 2012 by Edman

['Dale]

From cyclingnews.com, a nice example of the use of PM data:

 

 

 

Losing power over the course of a ride

 

Hi

I have a question about training and losing power during a longer ride:

I am encountering what seems to be a persistent problem with my power output on longer rides. Today i did a 5h ride, and toward the end I couldnt increase my power output and HR. I just couldnt get anymore power out due to my legs feeling dead.

Mt LT threshold is 244w, but the normalized power for the ride was only 156w.

Other stats for the ride

Peak 5m power 228w

Peak 10m 209w

Peak 20m 197w

Peak 30m 194w

Peak 60m 182w

Ryan

Scott Saifer says:

Hi Ryan,

We call that getting tired on a long ride. It's possible that 5 hours is simply beyond your endurance ability but it's also possible that you are making poor gear choices, riding too hard for the distance, not drinking enough or not eating enough to keep youself strong. What is your typical cadence, how do you pace yourself, how much do you drink and eat on a ride, and what?

Edited February 29, 2012 by ' Dale

['Dale]

@ edman and spinnekop,

 

How is one lactate threshold determined, at what wattage?

 

*looking at the post above, the writer's LT threshold is at ......watts.*

Edited February 29, 2012 by ' Dale

[Spinnekop]

@ edman and spinnekop,

 

How is one lactate threshold determined, at what wattage?

 

*looking at the post above, the writer's LT threshold is at ......watts.*

 

Unfortunately you have to do the test where they prick your finger and determined through blood.

[Minion]

@ edman and spinnekop,

 

How is one lactate threshold determined, at what wattage?

 

*looking at the post above, the writer's LT threshold is at ......watts.*

Spinnekop got it right: LT is done with a blood test while you're riding (usually IDT).

 

Most power training is done based on Functional Threshold Power (FTP). This is defined as the maximum power that you can sustain over an hour time trial. There're a couple of ways to estimate this that don't involve hurting yourself for 60min. One of the most popular is to do a 20min trial and use 95% of that power as your FTP. All of it is covered in detail in Coggan's book.

 

There is some correlation between FTP and power at LT.

[Spinnekop]

Spinnekop got it right: LT is done with a blood test while you're riding (usually IDT).

 

Most power training is done based on Functional Threshold Power (FTP). This is defined as the maximum power that you can sustain over an hour time trial. There're a couple of ways to estimate this that don't involve hurting yourself for 60min. One of the most popular is to do a 20min trial and use 95% of that power as your FTP. All of it is covered in detail in Coggan's book.

 

There is some correlation between FTP and power at LT.

 

Spot on.

 

To confirm.....my measured LT is at 168. My FTP is sitting at 164 HR....so very close.

 

As Edman correctly stated, you don't really need your LT tested if you are going to base your training on Power.

['Dale]

Uh okay -

 

Just saw in the correspondence that his LT is at x watts..

So, lactate threshold is only in use with HR.

 

Hmmm... Thanx!

[Minion]

Just saw in the correspondence that his LT is at x watts..

So, lactate threshold is only in use with HR.

Sort of. Lactate threshold is the point when the lactic acid in your blood exceeds a certain concentration. They record your power and your heart rate while taking periodic blood samples. This gives you a power at lactate threshold (LTP) and a heart rate at lactate threshold (LTHR).

 

You could also base your power zones on LTP. Aside from the practicality of testing, there was another, more technical reason given for why they prefer to use FTP, though.

['Dale]

Sort of. Lactate threshold is the point when the lactic acid in your blood exceeds a certain concentration. They record your power and your heart rate while taking periodic blood samples. This gives you a power at lactate threshold (LTP) and a heart rate at lactate threshold (LTHR).

 

You could also base your power zones on LTP. Aside from the practicality of testing, there was another, more technical reason given for why they prefer to use FTP, though.

['Dale]

Got an opinion today from a major bike shop that there's no after sales support for Quarg.

They therefore do not stock it (yet).

[Minion]

Got an opinion today from a major bike shop that there's no after sales support for Quarg.

They therefore do not stock it (yet).

Do they realise that Quarq is a SRAM product and comes in through, and is supported by, the SRAM supply chain?

 

Edit: The support I've received to my queries both directly from Quarq in the US and from CCS locally has been good. If something goes wrong with the electronics, it would probably have to be sent overseas for repair. Likewise for SRM, P2M and possibly Powertap (I know they can service the hub mechanicals, but I'm not sure how much electronic repair they can do).

Edited March 4, 2012 by Edman

['Dale]

 

Do they realise that Quarq is a SRAM product and comes in through, and is supported by, the SRAM supply chain?

 

Edit: The support I've received to my queries both directly from Quarq in the US and from CCS locally has been good. If something goes wrong with the electronics, it would probably have to be sent overseas for repair. Likewise for SRM, P2M and possibly Powertap (I know they can service the hub mechanicals, but I'm not sure how much electronic repair they can do).

 

Er, I meant there's no local support...

Okay. I wonder what the turnaround time is on a repair.

 

And, battery replacement. Easy to do by oneself?

[Minion]

And, battery replacement. Easy to do by oneself?

Very easy. You just open the cap and swap the battery. It uses an easy to find CR2032 battery too.

 

If you've got an iPod Touch, iPad or iPhone and an ANT+ dongle or bike case you can use the Qalvin app to completely calibrate the Quarq yourself (i.e. check the slope and change if necessary).

http://www.quarq.com/qalvin

http://youtu.be/4IZL3QXtYv0

Edited March 4, 2012 by Edman

['Dale]

Edman,

 

Your input.

So valuable.

['Dale]

Getting me a Garmin in the meantime...

Have some time to decide on the PM.