Just acquired a giant tcr that comes with its own 'giant power pro' power meter. The power reading is well down on my 2 stages cranks, which are both reasonably in line with my tacx flux.
Now whilst the stages are both left sided only, the fact they are reasonably consistent with the flux suggests my left/right leg balance is reasonably even. But the new giant power pro shows up to a whopping 70/30 split in favour of the left leg. Is that remotely feasible?
If so then obviously my real power output is far lower than the stages led me to believe, however my outside times up hills and in tts leads me to believe the stages is reasonably accurate.
Surely a 70/30 split would have me walking around in circles?
Would seem very extreme. Which foot would you naturally kick a football with? And which leg do you think about when you ride? One tip I got as a young rider by an old pro was to 'think' about my non dominant leg when I ride. I am left dominant so I focus on my right leg when I'm thinking about my riding style. My dominant leg then mirrors the one I'm thinking about without issue.
Could you have subconsciously tweaked the way you ride to give you big numbers on your stages?
Just to keep you cheery, when I was competitive an increased power imbalance was the first sign of a fairly terminal hip issue that finished me off.
I'm right footed, both legs look the same size, and I don't think about individual legs when pedalling.
The thing that makes me think its wrong (and obviously I want it to be wrong as other wise I'm far weaker than I thought I was) is:
1 - it's far lower than my turbo trainer power, which doesn't take in to account left right balance
2- when I climb a hill next to my mate,if our times are the same our power to weight ratios are almost identical. Which makes sense.
3 - it's a new power meter..and I'm assuming the paying customer is being used as a beta tester. If it hadn't come as part of the bike there is no way I'd be buying one!
Could you have subconsciously tweaked the way you ride to give you big numbers on your stages?
This rings true for me. Before I fitted a PM (left crank) my legs were the same size. However, after 2 years of riding and training with the left side PM, my left leg is noticeably bigger and stronger then the right. Probably not a 70/30 split though!
Can you get on a Wattbike or other bike with a left & right PM and check?
No access to either I'm afraid.
I might ask a mate to sit on it and see what readings they get however
I might ask a mate to sit on it and see what readings they get however
Not a bad shout. One thing I remember reading about imbalance was well trained riders often have a noticeable imbalance when jra. But when close to the limit and pushing harder it goes away. Would be interesting to try again and do a ftp test and see what it looks like then.
Just sat on the turbo for 20 min and when input the power down the difference does come down drastically.
Bimbling along it's on average 60/40 split, but when I move up to around ftp it's closer to 56/44, which I assume isn't massively off.
The issue I have is I have absolutely no requirement for a power meter that gives me readings that are different than other my meters, even if they are more accurate. I spend quite alot of time lokming at the numbers when im training and on the climbs, so having to use 2 sets into really an option. It's bad enough with having an indoor and outdoor number without the faff of having a different ftp per bike.
Reckon ill sell it and get another stages for consistency.
Probably a stupid question, but even though it's new have you a) done whatever zeroing required, and b) changed the battery? My Garmin Vectors are notorious for giving random readings when I haven't zero'd them or changed the battery in awhile.
#EDIT - OK I see they are rechargeable. Still - recalibrate, and maybe check firmware is up to date?
What bike goes on the turbo? My summer bike lives on the turbo (neo) which has a power meter on it. Zwift etc are clever enough now that it uses the power and smart aspects of the turbo to vary the virtual terrain and the meter on the bike to measure my effort. Therefore my efforts indoors and out are being recorded through the same tool.
But you are right, consistency is more important than accuracy. Apart from zwift racing which is a bunch of arse.
The power meters on the Tacx Flux turbos can easily inflate your real power output by ~20%, they have awful accuracy.
The stages is on the turbo, it's just that my numbers indoor are about 5-10% lower than outdoors, which appears to be a common occurance on the turbo.
Giant Meter has been zerod and firmware updated. I'm going to pop round to my local gym and sit on one of their watt bikes in a bit to check if the inbalance is correct. If it is then I'll replace, as has been pointed out, consistency is pretty important when it comes to power meters.
The usual reason for indoor power numbers being lower than with the same power meter outdoors is because many riders don't ride their turbos frequently enough at a high enough intensity to let their body adopt fully to the heat and humidity of turbo sessions compared to lots moving air passing over you outdoors.
Consequently, for the same sub threshold power ballpark, many riders have a noticeably higher heartrate indoors.
If you train approx three or four times a week indoors for at least 30mins (of which a lot of session is at least high zone 3 power), within ~3 weeks you will get very comparable power thresholds indoor and outdoor.
Can you apply an offset to the new PM? On Golden Cheetah you can to that.
Listening to the TrainerRoad podcasts, they do say different PMs will always read differently.
56/44 seems quite common, again from listening to the TR podcasts.
This is quite interesting: https://gplama.com/2019/06/29/shimano-crankset-power-meters/
It suggests that the current crop of Shimano cranks are not well suited to power meters fitted to the drive side.
Well I just popped across the road to the local gym and sat on a couple of their watt bikes. They showed my power to be pretty much bang on 50/50 balance, maybe with it fluctuating a couple of percent either side. Assuming I can trust 2 watt bikes over my meter, the good news is my power is kinda where I thought it was.
Bad news is my new power meter is useless.
Can you apply an offset to the new PM? On Golden Cheetah you can to that.
Pretty sure you can't do that. I am running it with a garmin 810.
As an aside, how good are watt bikes. They actually feel like a proper bike, unlike my mid range turbo trainer.
Do a Google. Others seem to have been posting similar stories.
Update! Turns out giant don't seem to confident in their power meter as they agreed it was faulty and rather than swap it for a new one they replaced it with a dual sided stages. A quick spin on it yesterday and my power split was 51/49, so much more in line with what was expected.
Apparently a mark 2 giant power meter is coming out in October. It does make me frustrated that companies are putting out tech that clearly has issues, and expecting the buyer to be the beta tester. I'd expect more from a company like giant. Then again, credit to them for replacing straight away, didn't even want to see the old one back to test themselves.
Also, big shout out to Edinburgh bikes who sorted the warranty despite me not buying from them. I've used then extensively in past and will do so again based on helping me out.
Anyhow, good result all in all. Bought the giant tcr advanced pro 0 at a fairly hefty discount, so have ended up with a di2 equipped bike with carbon wheels and a stages power meter for 3.5k, which is a bit of a bargain.