Help understanding which power meter works with my bike

Ok y’all, I’ve been banging my head against the wall trying to understand the algebra of compatibility of power meters with my bike, aside from just going with pedals for power meters. Ideally I would go with a crank arm for price and so I can use the new shimano pedals I got last month. But I’m so friggin confused! And I suck at this kind of thing, begin honest. If any of you are whizzes at this, I’d appreciate any help :slight_smile: Here’s what I know:

-My bike: https://www.rei.com/product/164914/ghost-kato-59-29-bike-2020
-REI bike geek said I can’t use the 4iii crank from shimano, not compatible
-I saw SRAM has a crank power meter, but looking at specs, I don’t think it’s compatible with my bike
-I think this crank from Stages Cycling would work, but at the cost I’d just go with pedals Gen 3 Stages Power L | Stages Carbon For 30Mm - Sram, Race Face Next Sl, & Fsa 386Evo
-There’s the idea of swapping my crank set out for a shimano, but then there’s the issue if it’s compatible with the derailleur, etc.

So I don’t know, at this point I’m feeling like pedals would just be easier. I just sure do like my shimano pedals :stuck_out_tongue:

Ok, also to add here: Last month I got both new Shimano ME5 shoes (SPD cleats) and Shimano compatible pedals. Now I’m seeing that there’s a challenge in finding power meter pedals to match that. Obviously I’ve been doing things without know the full ecosystem of all the cycling pieces :stuck_out_tongue: Anyways, my goal still is to find the most affordable power meter option for my bike, however the hell it’s compatible :slight_smile:

Not cheap but likely the easiest option given what you’ve already purchased.

Unless I’m not looking in the right spot, the SRAM eagle crankset with the power meter isn’t a whole lot cheaper, maybe $80 before tax/shipping.

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Yeah I saw those which would be great, but think out of my budget :frowning: What I’m confused about on this SRAM option is if I would need everything vs. ‘already own’, because again am an idiot with this stuff.

If I need everything, then yeah also out of my price range. So frustrating that there are cheaper options but my whole setup can’t do it.

@ryanoelke Have you considered just riding without a power meter? Depending on the MTB riding you do you may not find the data as useful versus if you were riding on the road. I ride MTB and just go with RPE and wear a HR strap for measuring overall effort. It isn’t perfect but I am not convinced that I would be that much better of with PM data.

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While I think about it, favero assimos have a conversion for spd to but it’s not supported officially. The assimos are relatively inexpensive and have proven to be quite a good meter. You can save some more and go with the uno if you really wanted to go on the cheap.

Pedals

Conversion video

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@JSampson Yeah, I’ve been doing my trail rides without a power meter and to be honest there’s some benefit to it in just learning to subjectively feel out my pacing. I would honestly do road riding instead but I really don’t trust the roads and the drivers around my city and county, so I choose to go with MTB, but I’m more or less doing trail riding, but we have nice elevations (Blue Ridge Mountains). No plans for single track stuff, etc. I’ve been thinking about a gravel bike as something in between. Anyways, I don’t NEED a power meter lol, but I would really like one just to get a sense of the connection to what I’m doing/seeing on my trainer vs. outside.

@Sir_Alan cool! I’m going to check out the hack to see if I feel confident to do it. If it’s reliable, Uno would be just fine for me.

From the specs in the link you posted, your bike has a DUB bottom bracket. This means the crank spindle will be 29.0 mm diameter. Shimano crank spindles are either 24.0 mm or 30.0 mm diameter, so won’t work in your existing bottom bracket. You would need to change out the BB to use Shimano cranks - this is doable, either by your local bike shop, or yourself if you’ve got the right tools.

There is some information on bottom bracket standards here: Crankset standards chart

Regarding the SRAM XX1 Eagle Power Meter you linked to, there is no option for the 135 mm rear hub that the specs for your bike list. My guess (and it’s only a guess) is that the power meter calibration is different in some way for the different rear hub widths. I think the boost/non-boost options are to set the chainline for the chainring. If you do decide to get this power meter, you’d want to choose the 142 mm option, but only after confirming that it will fit your bike. You should be able to leave off the bottom bracket in the configurator, and maybe the chain ring if the hole pattern on the XX1 crank is the same as yours. Crank arms - that would all depend on how the power meter attaches to the cranks. I’ve never had my hands on one of these power meters, so I don’t know how they all go together. Update: I think these attach in place of the spider, so you may be able to just buy the power meter.

Your best bet might be to go and talk to your local bike shop. They’ll be able to advise you on the compatibility of all the different parts. Or go with the pedal option - then it’s just a question of having the right cleats for your shoes!

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Thanks a bunch, @way9e0 ! I was at REI last night and they were helpful to get me in the right direction, but I might swing back now with the info you’ve provided. I think my shimano me5’s are only compatible with the 2-bolt cleat, but if I’m misunderstanding that, let me know!

Thanks for your help!
-Ryan

You’re correct, Shimano ME5 shoes are only compatible with 2-bolt cleats. So your pedal options are the Garmin Rally, or the hacked Xpedo/Favero Assioma, or the SRM pedals (https://www.ridesrm.com/x-power). There may be other pedal options too.

Looking more at the SRAM power meter option, it looks like it would replace the spider on your crankset, which means that you might be able to get away with just getting the power meter, and put it on your cranks in place of the existing spider. However, you would need to check all the compatibilities first - spider attachment to cranks, chainring bolt pattern, spacings etc.

Also, it seems that the SRAM power meter rear hub selection is to allow for different chainlines, with the boost option placing the chainring slightly further out from the centerline of the bike. Nothing to do with calibration. I’ll edit my previous post.

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@way9e0 you rock! This is so dang helpful. I’m now understanding a bit better all the parts involved and how to talk about it with the shop. If I can get away with just the spider, I might do that, or the hacking the cleats option, and if not, I guess I’ll wait until I can dump more money into things :stuck_out_tongue: Thanks so much!

Good luck!

Just to be clear, the Xpedo/Favero option looks like attaching a set of Xpedo pedals to the power meter part of the Favero pedals. If you do that, you’ll need a set of Xpedo cleats for your shoes. All the hacking is on the pedal side - the cleats (XPTs by the look of them) will fit your shoes without any modification.

I guess I just want to caution you to make sure you confident with what you’re doing before proceeding - get proper advice from a local shop, don’t just use the info you’re getting from me.

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@way9e0 totally hear you! I’m definitely going to go in and talk to the local shop, but I definitely feel more confident on what to ask them now :slight_smile: Thanks for all the help!

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Happy to help. Let me know if you have any other questions. Hope it all works out well!

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There is also the velocomp powerpod. I don’t own one myself, or know anyone who does. But dcrainmaker did a more or less positive review on the first version, so by now it might be even better. Might be a good option to start with.

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@ryanoelke, the conversion is super simple, the only thing you’ll want is a torque wrench (and they’re worth having if you’re going to do any work at all on your bike anyway). It’s basically a case of removing the end cap, one nut, then the pedal body slides off, put the new body on, do up the nut, do up the cover.
I’ve got modded duos and they are brilliant.

That said, I’d also echo what @JSampson said. If you mostly ride off-road then the data is far more “noise” than road data and tells you far less.
My primary bike is a gravel bike that gets used for everything from fast road rides, through gravel and trails to true MTB tracks and downhill.
The power meters are useful on the road…
That’s basically it, I don’t look at power at all off-road unless it’s relatively smooth gravel/trails that I’m trying to race down, but anything where you’re bouncing about and stop-start pedalling just becomes power-data nonsense. I’ll still look at my power at the end of the ride as a good guide to how much work I’ve done, but that’s just because I already have the data, I certainly wouldn’t pay for it if that was my primary use.

Here’s some comparative data from the same ride and the off-road data here is a lot cleaner than a lot of my other rides.
The on road data is the top section, a 2 mile stretch where you can see my cadence and speed barely move at all, the off-road data is the bottom section and it’s all over the place, completely useless for making any decisions while you’re actually riding. As mentioned, it’s still useful if you have it to give an impression of how much work you’ve actually done, but you absolutely can’t use it while riding to make decisions on your riding effort and while I love my power meters for road riding I also wouldn’t buy them for an off-road focused bike.

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… and I come to realise I’ve not answered the actual original question.

I would strongly recommend a pedal based solution for multiple reasons

  • They’re the most direct record of your power output. Any other point of recording has at least one point of contact between it and you so you’re getting consistent data, but not your data. Pedals are the closest to an accurate representation of what you are actually doing even if the variance is only a percent or two.
  • They are compatible with pretty much any bike. Own multiple bikes? You can use your PMs on all of them. Go on holiday where you’re planning to rent a bike? Take your PMs with you. Borrowing a friend’s bike/Yours in for service and using a loaner? Still got your PMs.
  • An extension of the above. You decide to change your bike somewhere down the line or expand your stable? Move your pedals across. They might have been more expensive to buy in the first place, but in this instance you could suddenly find they are cheaper than having to sell your old one and buy new for the new bike, or have one bike with and one without. Or you get a bike fit and the fitter recommends a different length crank? No problem.
  • Single-sided is sufficient for pretty much any casual rider and keeps the price down, however if you choose to go from Uno to Duo (in the case of the Assioma) then it’s a simple process of buying the right-sided pedal and you’re done.

As per my above post, whether or not a power meter is actually worthwhile if you’re going to ride mostly off-road is a decision you’ll need to think about. For me I don’t think they’re worthwhile off-road.
If you do decide to go the route of power meters though, I can’t sing the praises of converted Assiomas enough.

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If you decide to go for a crank based meter, it would be a good opportunity to dump the SRAM DUB bottom bracket, which are notoriously short lived, and switch to a Shimano one. Compared to the cost of a $$$ power meter, a new bottom bracket is just a few $.

I’d agree with others recommendation for a pedal based power meter, based on my own experience of my non-power meter pedals outlasting multiple bottom brackets and cranksets.

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Thanks @Jon and @JGreengrass! Helpful to hear about the difference between road and off-road. Honestly so far, what I’ve been doing is much more gravel riding. It’s in the mountains with a few good climbs, but wide, pretty smooth gravel for the most part. However, I might in fact just wait until I get a gravel bike and start doing more of that. I’m definitely curious to see the info after the ride just have a sense, but might not be worth it for moment. I did figure out costs a bit more and it seems like switching out the bottom bracket and getting a single pedal would be the most affordable option, and I agree, would be way better to switch between bikes. REI had a pair of used Garmin power meter pedals, good price, but really not sure about them being used, and sold as-is, so passed on them.

Going to contemplate this more but you all have been incredibly helpful! This has been such a tricky thing to make sense out of, but I feel much clearer when I’m ready to go for it :slight_smile: Thanks!

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