I’m all set up and ready take my initial “virtual power” FTP test, and I was curious how to set my trainer up for maximum accuracy. I understand that consistency from one training session to the next is the most important, but I’d still like to have as close to an accurate measurement of my actual FTP as possible.
So what is the recommendation for tire pressure, and trainer pressure against the tire and all that?? I have a Cycleops Mag trainer and a regular bike tire if that helps.
Also, any tips for the actual test? I hear it’s pretty tough…
I don’t think there’s anything you can do for accuracy. Your goal will be a repeatable setup.
As for the test itself… It’s a learned thing. Don’t go out too hard. If you aren’t quivering and barely able to function at the end you didn’t go hard enough
Use a consistent tire preasure (e.g., 110 psi) and use a fixed number of turns on the friction wheel wheel from the point of contact between the tire and the friction wheel. The diameter of the tire will change a bit as it wears, but that probably isn’t a big deal.
Start at a pace a bit lower than you think you can hold and increase your output bit by bit if you aren’t on the verge of hurling.
Set small goals if you are doing the 20 minute test, especially towards the end, as your body screams for you to stop, disengage your legs from your brain and just force them to spin. Think, I can do this for another 30 seconds or a minute.
Try to spin a faster gear as opposed to a harder gear, your legs will give out much faster than your cardio.
Be careful with the 5 minute hard section before the 20 minutes. Your legs are fresh and you try to be a hero and pay for it in the 20 minute section.
Almost everyone on the first couple tests they do, starts out too hard and dies like a dog. Not only does that lead to inaccurate results (e.g. a lower number than you could get with good pacing) it hurts like hell and totally sucks. So don’t do that.
There is nothing more painful physically or more demoralizing mentally than suffering through the last couple minutes of the test at a power number 25 watts below your previous FTP
Like others suggest make the setup repeatable. The aspects you want to consider are:
Tire Pressure
Tire Type (Indoor Trainer vs Old Outdoor)
Cleanliness of System
Correct Power Curve for your trainer
Tire Pressure - Pick a pressure you can easily fill to with each session. I recommend inflating to 5-10 PSI lower than your top end (presumably 120) and spin for 10-15 minute warm up which may lead to air pressure increasing. I’ve gotten more trainer flats inflating a “Cold system” to 120 PSI than I care to mention before figuring this one out
Tire Type - The different tire materials can lead to different rolling resistance and what not. Always use the same type of tire to ensure this is not a factor
Cleanliness of System - It’s a good idea to wipe down both the tire and roller with some Isopropyl alcohol and a cloth to remove any and all oil. This will reduce the slipping that may occur on the indoor trainer. Do it again after the check for the tire pressure as the warmth brings some more to the surface believe it or not.
Correct Power Curve - When using the VP feature make sure you’ve selected the closest or exact model of trainer you’re using. This will set you up to have consistent results.
I know this sounds like a lot but it typically takes you no more than 5 minutes depending on your setup to complete. I’d also get a bucket you can hurl in when you’ve completed the test. If you’re doing it correctly you’ll need that 50% of the time. Good luck and enjoy the suffering!!
Everyone else has posted great information but I didn’t see this. Make sure you have a couple of fans pointed on you for air flow. I overheated during my first TrainerRoad FTP test because of this.
You forgot clamping force of the trainer.
Which is very hard to control.
Like others suggest make the setup repeatable. The aspects you want to consider are:
Tire Pressure
Tire Type (Indoor Trainer vs Old Outdoor)
Cleanliness of System
Correct Power Curve for your trainer
Tire Pressure - Pick a pressure you can easily fill to with each session. I recommend inflating to 5-10 PSI lower than your top end (presumably 120) and spin for 10-15 minute warm up which may lead to air pressure increasing. I’ve gotten more trainer flats inflating a “Cold system” to 120 PSI than I care to mention before figuring this one out
Tire Type - The different tire materials can lead to different rolling resistance and what not. Always use the same type of tire to ensure this is not a factor
Cleanliness of System - It’s a good idea to wipe down both the tire and roller with some Isopropyl alcohol and a cloth to remove any and all oil. This will reduce the slipping that may occur on the indoor trainer. Do it again after the check for the tire pressure as the warmth brings some more to the surface believe it or not.
Correct Power Curve - When using the VP feature make sure you’ve selected the closest or exact model of trainer you’re using. This will set you up to have consistent results.
I know this sounds like a lot but it typically takes you no more than 5 minutes depending on your setup to complete. I’d also get a bucket you can hurl in when you’ve completed the test. If you’re doing it correctly you’ll need that 50% of the time. Good luck and enjoy the suffering!!
And as we have seen with multiple threads on the topic, that indoor power number will likely be lower than your outdoor power number (mine is ~15% off) so while the 20 minute test may be a great baseline for riding indoors, you will likely have to test again if you want to use power outside.
A lot of people say cooling. The other potential reasons are visual stimulus and ability to change positions.
I also stand a good deal while climbing outside and seem to be able to put out more power out of the saddle. May be a fit issue or a strength issue (which will be immediately shot down by ST Pundits).
And as we have seen with multiple threads on the topic, that indoor power number will likely be lower than your outdoor power number (mine is ~15% off) so while the 20 minute test may be a great baseline for riding indoors, you will likely have to test again if you want to use power outside.
This is essential…indoor FTP is meant for indoor workouts…if you have power outside you absolutely must retest your FTP outside. It is foolish to try and use the same FTP indoor and outdoor. Man/Woman up and do the test in both environments if you’re serious about training/racing with power indoor and out.
Any explanation available as to why outdoor power is greater than indoor?
cooling and/or different inertia (pedal force velocity patterns are different) and/or motivation
the cooling issue will get astronomically more complex the taller or more talented you are, as the amount of extra heat a body produces grows very fast as watts go up.
This is essential…indoor FTP is meant for indoor workouts…if you have power outside you absolutely must retest your FTP outside. It is foolish to try and use the same FTP indoor and outdoor. Man/Woman up and do the test in both environments if you’re serious about training/racing with power indoor and out.
I use my outdoor FTP for all my workouts and I mainly ride on my trainer (ride outside only once a week on the weekends). Never once had any issues hitting my power numbers during intervals on my trainer. I’m fairly confident I could hit the same FTP indoors on my trainer. To anyone that says I didn’t try enough on my test… Trust me, I got every watt out of that test I possibly could.
For the people that have a big gap between indoors/outdoor FTP, I firmly believe it mainly has to deal with cooling (not enough fans).
Be careful with the 5 minute hard section before the 20 minutes. Your legs are fresh and you try to be a hero and pay for it in the 20 minute section.
that’s kind of the point. you need to go all-out otherwise 95% of the 20’ test will tend to overestimate peoples’ threshold. it’s tempting to do this to get a bigger number, but it’s not accurate.
(and, yes, then 95% of 20’ is just an average. even with a proper test, some people cannot hold 95% of their 20’ power for an hour and others can hold a bit more. best way to figure out where one stands is to eventually do an all-out hour – but if the 5’/20’ test is done wrong …)
