Powertap vs SRM

I'm not sure that the advantage of being able to use a PT on multiple bikes is really such an advantage. You certainly couldn't use it on the MTB or track bike, both because of different spacing (track bike's probably 120mm, MTB 135mm and road bikes 130mm), and different requirements (track needs to be fixed, disc on the MTB?)
That leaves switching it between the road and TT bikes. Assuming you use a different cassette for each, it's probably just as quick to change a chainset as to change a rear wheel, and you'll have to swap the computer over no matter which you choose.

I've been using a PT for a while now, first a wired one, then a wireless model. Getting a little tired of putting on a wheelcover ever time I went to a TT, so I've just bought a Quarq for using with a disc on the TT frame.
Changing cassettes is no issue on PT's and Quarqs can be changed form one bike to another fairly quickly, too (You need SRAM BB's though).
IMHO, to run a power device on all your bikes, you'd need three devices!

I use my powertap wheel across 3 bikes regularly. It was an important consideration when choosing a powertap. However changing the Quarq between bikes is just about as fast as changing the wheels (probably faster for me but wouldn't be if I had somewhere to hang the bikes without wheels)

The moving between bikes is not an advantage of the PT - cost is, it's still a fair bit cheaper than a Quarq. SRM has no real advantages over Quarq for most people and the being sent to germany to change a battery means losing it for at least a week.

SteveR_100Milers wrote:

Quarq looks interesting, but its a crankset device not chainring? Its not clear from their website - I read from @whyamihere's post that its the chainring assembly.

It's in the spider the same as with SRM essentially. There's also the Power2Max similarly in the spider but I don't know if anyone has yet seen one.

SteveR_100Milers wrote:

The problem with PT is fitting it into a decent rim - I guess you cant (easily) stick it into a proprietary wheel such as a cosmic carbone.

You can buy rims of most wheels with PT spacing. My wife has a 650c Jet 60 PowerTap wheel, just call HED to get a powertap spaced rim.

The Carbone is available ready built wheel with a powertap in (even wiggle has them) I'm not sure about retro fit.

Steve, wrong question. Should be.

SRM or TWO powertaps.

Multiple bikes then buy two of them and it's still cheaper than the SRM. (I think)

You can buy powertap track hubs but then the expense starts going up. You can definitely get powertap mtb hubs.

I use one for a training wheel then the other one sits on the turbo in winter and then becomes covered up and nice tired up to become the race wheel in the season. Absolutely ideal for me.

I don't know what I'd do if I road raced tbh I can see the advantage of a lighter wheel but I can also see the advantage of having power measurement. If that was a priority then perhaps Quarq.

Pokerface wrote:

hopper1 wrote:

IMHO, to run a power device on all your bikes, you'd need three devices!

If they ever get those power-measuring pedals working, then we'll all have a portable solution for all our bikes!

Well Look/Polar do theirs, but it's more expensive than a SRM! I've been holding out for the MetriGear system, but I'm not sure when it's going to arrive. Once I've payed back some credit cards and payed back my parents :oops: I can start saving for a SRM/Quarq, if the Garmin/MetriGear system comes out in the mean time, bingo, if not, when I have the cash I'll be posting "SRM vs Quarq"

Something Important to think about here is....

The SRM & QUARQ are "Water Proof"

The Powertap is "Water Resistant"

Personaly id be more confident of the SRM & Quarq holding up to wet conditions, where as if i was doing a race and it started raining id be concerned that my Powertap might die.

As it happens ive just ordered a Powertap but i wont be taking it out in the rain, if i get caught in the rain so be it.

SteveR_100Milers wrote:

Of the two PT users I know, this have never been an issue in 12-18 months of regular (daily) riding

we ride our PT's in all weathers, I have killed the bearings in one of them but they were replaced under warranty. And it was after a lot of miles anyway.

jibberjim wrote:

Quarq.

SRM has the ludicrous requirement to be sent back to have a battery changed.

SRM batteries are rated to 1400 hours of use.

Quarq is not suitable for the track and has the ludicrous requirement to be sent back to the factory if you need it calibrated (which is required e.g. if you change chain rings).

For example, a simple change of rings of the same type has been reported as changing Quarq slope calibration by more than 5%.

SteveR_100Milers wrote:

Which one?

Race track, TT and road maybe. Train on 4 different bikes (inlc MTB)

I can see initially that powertap can be used on more that one bike, but there has to be some compromise on the rest of the wheel. SRM appears to be limited to one bike only.....

SRM for the track, Powertap for the road, forget the MTB, unless that's the majority of your riding.

Alex_Simmons/RST wrote:

I'm not sure if Paligap services Powertaps in the UK, I think so.

Correct

jibberjim wrote:

Alex_Simmons/RST wrote:

Quarq is not suitable for the track and has the ludicrous requirement to be sent back to the factory if you need it calibrated (which is required e.g. if you change chain rings).

No it doesn't. You just send it an ANT command with the new slope - a Garmin ANT stick and a computer can do it.

Alex_Simmons/RST wrote:

For example, a simple change of rings of the same type has been reported as changing Quarq slope calibration by more than 5%.

Sure, if you change the rings you check and change the calibration if necessary - same needs doing on an SRM and it's no more complicated with a Quarq than an SRM - the difference is in the device you use to send the command.

I get more than 1400 hours out of my chain rings so even if it did have to be sent away it would be sent away less than the SRM.

Also Quarq are close to releasing the Qalvin Iphone App which is a means of doing calibration yourself.

So instead of a couple of presses of the buttons on the SRM Powercontrol which takes a few seconds and is simple, you need either a special stick and programming skills, or an iphone for an ap that isn't out yet.

So you buy a power meter, and now you need an iphone as well?

Sounds like an SRM isn't quite as expensive when you factor in this stuff, although I don't know the relative pricing in the UK. Certainly I sell SRMs here for less than price of Quarqs anyway.

Why not just make it so the Quarq slope can be reset in the head unit? Why make it so complicated? I mean the Garmin can reset the SRM's slope, why not the Quarq's?

Not many Quarqs have passed the 1400 hour use mark, so we'll wait and see on that.

As for the chainrings, the reality is, for someone looking at swapping power meter over bikes, they are quite possibly going to consider different chainrings suitable for the different jobs.

On the track, the SRM doesn't suffer slope changes with chainring changes because of the design of the SRM track spider. it is specifically built for that purpose.

Don't get me wrong, I think Quarqs are great, and recommend them. But the battery change needing to go back to SRM comment is a bit rich, especially when one of the failures of the Quarq has been broken battery case caps taking unit out of action for over a month.