Power Meter options for MTB

[kophinos]

I am looking at getting a PM for my Santa Cruz Tallboy before Leadville this summer. To me, it appears the best option for the cost would be a P2M unit with a Rotor crankset. The Tallboy is BSA, but I am debating getting the 3D+ and using Rotor's BSA30 BB to run it on the Tallboy, but this will allow me to future proof my purchase since *most* MTBs are BB30 or similar and who knows what my next bike will be. Does anyone see any problems with this? Should I just save ~$130 and stick with the 24mm 3D model?

Another option would be to get one of those DA arms that Stages is blowing out and mate it to an XT or XTR crankset. Its a frankenstein solution, but might actually be the least expensive option.

Any input is appreciated.

[DanW]

I went for Stages SRAM X9 for the low cost here in the UK. XT is also pretty cheap so no need for anything Frankenstein-esque. People are quite passionate about whatever it is they end up buying so I'd either go cheap (Stages X9 or XT) or go the full whack with something top end. The middle ground doesn't offer enough over a cheap Stages unit IMO. Rotor InPower is another nice looking, cheap PM to consider too perhaps?

[ryan_sherlock]

I have been running a Rotor P2M with Q-Rings for a few months now (about 250hrs on it at this point) - flawless so far. You can see the data from my training/races (most of the last few months is MTB) on my strava page: https://app.strava.com/athletes/8492

[devinci]

I'd go 24mm spindle with an adapter.

I am a former MTB quarq and SRM user, I am now on P2M and love it, it just works, everytime.

[jooo]

Unless the price makes a huge difference to you, I'm not sure why you'd pick the 24mm over the 30mm?

Rotor's 30mm aluminum spindle is compatible with every BB standard apart from Trek. The cranks are both lighter and stiffer than the 24mm steel spindle version.

[LeDuke]

Not sure if they still have any, but Stages was blowing out their remaining Dura Ace 7900 models for like $450 last week.

Compatible with any other (modern) Shimano MTB crank. Sure, not an "MTB" crank, but it's a power meter for $450.

[kophinos]

I found out that the DA arms will not work on a MTB crankset due to Q factor issues. For instance, the XTR M985 (the race version) measures to 160mm and the DA7900 measures at 147.5mm.  If you did mount a DA arm on the XTR crankset you are looking at around 6.25mm of narrower offset on your NDS crankarm.  Mounting to the M980 crankset with its 167mm q-factor leads to a 9.75mm offset.  Additionally, there is a good chance you will encounter some chainstay clearance issues with the narrower road arm as well.

Those of you that are using power on your MTBs, how are you using it? Do you find it is worth it dude to the changing nature of MTB terrain? Given that climbs are usually shorter and more explosive, it would be difficult to use it for pacing. I've talked with many people in the past few days who nearly have me convinced that it is not really worth it unless you're a pro, doing tons of interval work on your MTB, or doing sub-6000ft races with long non technical sections. Given that I largely wanted to use it for pacing in Leadville this might be an unnecessary expense.

Of course I have PMs on my road bikes and find them extremely useful.

[devinci]

I love my PM on my mtb. For races analysis it is great. But I ride 100% on the MTB, even when on the roads, so the PM is a must for me

[jooo]

@kophinos - Are you sure about the Q/offsets? I'm happy to be proven wrong if it's something you've measured yourself but the numbers don't quite add up to me.

I'd guess a 7900 arm on a M985 crankset could work. Remember the MTB crankset is wider not just because of the arms but also because of the spindle. If I use your numbers, I'd guess the 7900 arm would only be 3.75mm narrower than the M985. That could almost be cancelled out by playing around with the BB spacing. Instead of using a single 2.5mm spacer on the drive side, you could use a 0.7mm on the DS and then put a 1.8mm on the NDS.

edit: Actually, it might be a good idea to ignore me on this
Maybe that setup could work for someone but I think I've read that depending on the model, the Tallboy won't fit SRAM Q156 or M985 cranks.

[albertop07]

I use Stages on my road bike, but they don't like wet conditions...

[LeDuke]

I use Stages on my road bike, but they don't like wet conditions...

I've used my Stages in rainy conditions for more than a year now. The wettest winter and spring here in the last 50 years, actually. No problems.

Is yours from 2013 or so?

[JensW]

maby http://www.velotechservices.co.uk/shop/ ... 188&cat=83 ?

[choiboi]

My stages (mid 2014) is also allergic to water.

[Jepas]

I use a XTR 980 Stages on my MTB since December 2014. I would like to tell that I experienced no issues with water, but that is not true. A month ago I opened the battery cover to find water inside the unit. I contacted Stages USA and sent some photos and they noticed a hairline crack on the powermeter shell responsible for that. The powermeter was swaped within one week.

I really like the concept of it: is small, stealth and simple. It should be cheaper, but it is the price to pay for a new gadget at this point of time.

As long as Stages keeps the good costumer service I will be a costumer for their products, but I have to admit that the desing has some flaws regarding water entering issues.

[schmiken]

I use an XT Stages on my MTB. I don't use it so much in racing (apart from tracking data for post-race), but find it very helpful for training purposes.