POWER METERS: Crank, Hub or Pedal-based?

['Dale]

Which do you recommend and why??

 

Money is but one consideration.

Overall value and accuracy is very important.

 

Thanx for the feedback, in anticipation, Fellow Riders!

 

B)

Edited February 5, 2012 by ' Dale

[kent77]

Crank obviously! So you can change wheelsets for training and racing and then still use your power meter. It's good to view your numbers post race in comparison to just training with it. The only concern for some people is the financial aspect. Hub is a cheaper option. It you can afford it go with a crank option.

[Tiny K]

Crank - more accurate measurement.

 

It's like when you do torque measurements on a motorcycle - you will get a higher reading at the drive shaft that what you would get on the wheel.

 

Edit: typo

Edited February 5, 2012 by Tiny K

[kent77]

Crank - more accurate measurement.

 

It's like when you do torque measurements on a motorcycle - you will get a higher reading at the drive shaft that what you would get on the wheel.

 

Edit: typo

 

The differences are minuscule. You just need something that is constant. Hub technology is very accurate. Powertap being the best.

[Zac.A]

Crank, in the process of an upgrade, my new crank PM should arrive sometime this month after a small delay.

 

Hub pm's are good, but there will always be the aspect of the worn chain.

Go for the crank one, Then you can use your cosmic carbones for racing.

 

Those are some of the reasons.

Edited February 26, 2012 by Zac.A

[Minion]

The differences are minuscule. You just need something that is constant. Hub technology is very accurate. Powertap being the best.

I recorded differences of around 3-5% between a Quarq and a Powertap. Not insignificant, but both are highly consistent, so it's only really a problem if you're comparing rides done with a crank-based meter to ones done with a hub-based one.

 

Stated accuracy for the PT is +-1.5%, the normal SRM and Quarq are +-2% and the new Red Quarq is +-1.5%.

 

Some of my most valuable power data comes from post-race analysis, so I think it's important to have a PM for both racing and training. Which PM you then choose depends a lot on how many wheelsets you'll use and how important weight is to you.

 

If you're only using one wheelset and you don't mind weight, the base-level PT is about 40% of the price of a Quarq, provided you don't need to buy a new rim to go with it. The lighter PT hubs are about 2/3rds to 90% of the price of a Quarq (more, once you've accounted for new spokes and wheelbuilding). You're limited in your choice of wheelsets to those with normal spoke patterns (no Campag Shamals etc.)

 

If you're using two wheelsets, the PT may still be cheaper, but only if you stick to the base model.

 

If you're using multiple bikes, a hub-based PM may be more convenient, but only if you regularly swap between bikes. If you're only swapping every two weeks or so, if may be more convenient just to swap the crank (a 5min job). There are some reports that regular swapping can strip the crank bolt, in which case it would cost around R2000 to replace the crank arms.

 

If you use the IDT a lot with a hub-based PM, bear in mind that you may have to swap the tyre every time you use it. If you use a Lemond Revolution and want power readings, you'd have to spend R4000 for a Power Pilot or buy an ANT+ USB stick and software so you can get power readings on your PC.

 

Weight-wise, my experience has been:

Zipp 404 vanilla vs. 404 with PT 2.4+ - PT adds 250g (Elite+ PT would add 400g).

SRAM S900 crank vs. SRAM S975 Quarq - Quarq adds about 113g.

Campag Record 180mm 53/39 cranks w. BB vs. SRAM S975 Quarq 175mm 50/34 w. BB - Quarq adds 206g.

 

Finally, if you're thinking of buying only in the next 2-3 months, you might consider waiting until the Garmin pedal-based PM is released in March.

Edited February 5, 2012 by Edman

[milky4130]

Crank obviously! So you can change wheelsets for training and racing and then still use your power meter. It's good to view your numbers post race in comparison to just training with it. The only concern for some people is the financial aspect. Hub is a cheaper option. It you can afford it go with a crank option.

and weight difference vs lets say a powertap hub?

[milky4130]

Oops only just saw the weight post now, apologies.

[kosmonooit]

What about the (new) 3rd option - Pedals? Garmin have a system now, also gives individual readings for each side.

[bontie]

So does Look and Polar. Mr Look shoudl be able to give details.

 

The cost is the barrier though - I think the system is about R20k...

['Dale]

What about the (new) 3rd option - Pedals? Garmin have a system now, also gives individual readings for each side.

 

Cool - let me tweak the title of this thread.

['Dale]

Very interesting input thus far, Fellow Riders.

 

@ Edman, thanx for that detailed input!

 

['Dale]

I'm definitely less likely to go the hub-based route.

Have 3 sets of hoops and will not invest more in that area.

 

Pedal or crank far more likely.

[Christie]

I've ridden powertaps on my race bike for about 4 seasons - had a set of Campy Neutrons with a PT and a set of Reynolds tubbies with a PT. With a box rim, the PT was structurally happy, but it had some electronic failure (replaced under warranty.) I also had to have the shaft and bearings repaced after 4 years (for my account.)

 

The PT in the Reynolds wheels was a disaster - hub lasted well, but the expensive Sapim CX-ray spokes kept breaking. Was built 2x by 2 different very good wheel builders, with special low stress nipple seats etc. Problem is that the big diameter hub and deep section rim cause the spokes to bent through a bigger angle at the nipple, meaning higher bending stress, meaning much shorter spoke life. I would say stay away from a PT in a deep section rim, unless it is a rim with spoke holes drilled at an angle for PT.

 

I rode 2 seasons with an SRM on my TT bike, it was ultra reliable and I was very happy with it. Only disadvantage imo. is having to send it out of country to replace the battery. If you buy a unit out of warranty, though, you can do it at home with a soldering iron.

 

Quark looks nice, too. Early models had problems with their plastic battery caps breaking, but they have sorted that out now.

[Man with no name]

I have two Quarqs and very happy with both - as Christie mentioned, the plastic caps are not that great, but to replace the batteries cost R 7.50 and last about 3 months. The oldest one is now 3 years old and not a days problems. The cost of the two units together is still cheaper than an SRM. I had an SRM and the battery replacement is a HUGE issue, other than that it also never had any problems.

[Mr LOOK]

Watch this space.

 

http://roadcyclinguk.com/news/look-keo-power-pedals-first-look.html

 

http://lookcycle.com/en/int/route/pedales/keo-power.html