Help me understand smart trainer "% grade" ratings
03-06-20, 07:55 AM
#1
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Help me understand smart trainer "% grade" ratings
Alright. The deal is at the end of the day it's how much torque the assembly can apply to oppose your force at a given RPM and gear ratio. The "% grade" rating to me should be directly correlative to the max power rating. It's just math of some kind to give people a warm fuzzy about how big a virtual hill they can climb.
To me, the figures missing in the math when they provide this "% grade" rating are the rider/bike weight combination and the gear inches or ratio the rider is using.
It's a big difference to say a trainer can simulate 20% grade for a 70kg rider/bike combination (pure climber) versus someone more like Joe Public who'll be about 90kg rider/bike combinaiton. Also, what if Joe Public has a 34/32 combo at disposal but other dude has a 39/28? I'd assume the 39/28 would 'lower' or stress the % grade rating more since your theoretical RPM 'might' be lower and you'd be trying to grind out something to get up the hill.
I'm 70kg rider and I tend to spin. So, if a trainer is rated lower slope I'd assume that I wouldn't notice the de-rating of the hill as soon as a masher that requires more torque from the unit.
I'm just trying to justify down to a little more affordable smart trainer. I don't need 2000w. Can't do that, never will. But.........800w is kind of junk. Probably enough to never "race" on Zwift and train but not enough.
Any help appreciated. Some stellar deals on some older units going on right now too. Seeing stupid low prices on Tacx 2 Neo's and the 2018 Hammers. Those have plenty of "oomph" but the Neo on stupid low price still grabs the wife's attention a bit much.
Any opinions on that original Hammer? Saris' website claims it's honoring the warranty if purchased new with receipt to show original owner.
I'd like to do some shorter races on Zwift like crits to fill in some HIIT workout space, so do need something that can register over 800w. But, no need to go up to 2000w necessarily. I don't care about weight or looks. It just has to work without fuss for about 2000mi a year for several years without destroying itself.
I tried a used Wahoo Snap and returned it to the guy. It was a refurb from Wahoo and I smoked the bearings 2nd ride. So, anything in the pre-2019 Wahoo range is for sure out.
To me, the figures missing in the math when they provide this "% grade" rating are the rider/bike weight combination and the gear inches or ratio the rider is using.
It's a big difference to say a trainer can simulate 20% grade for a 70kg rider/bike combination (pure climber) versus someone more like Joe Public who'll be about 90kg rider/bike combinaiton. Also, what if Joe Public has a 34/32 combo at disposal but other dude has a 39/28? I'd assume the 39/28 would 'lower' or stress the % grade rating more since your theoretical RPM 'might' be lower and you'd be trying to grind out something to get up the hill.
I'm 70kg rider and I tend to spin. So, if a trainer is rated lower slope I'd assume that I wouldn't notice the de-rating of the hill as soon as a masher that requires more torque from the unit.
I'm just trying to justify down to a little more affordable smart trainer. I don't need 2000w. Can't do that, never will. But.........800w is kind of junk. Probably enough to never "race" on Zwift and train but not enough.
Any help appreciated. Some stellar deals on some older units going on right now too. Seeing stupid low prices on Tacx 2 Neo's and the 2018 Hammers. Those have plenty of "oomph" but the Neo on stupid low price still grabs the wife's attention a bit much.
Any opinions on that original Hammer? Saris' website claims it's honoring the warranty if purchased new with receipt to show original owner.
I'd like to do some shorter races on Zwift like crits to fill in some HIIT workout space, so do need something that can register over 800w. But, no need to go up to 2000w necessarily. I don't care about weight or looks. It just has to work without fuss for about 2000mi a year for several years without destroying itself.
I tried a used Wahoo Snap and returned it to the guy. It was a refurb from Wahoo and I smoked the bearings 2nd ride. So, anything in the pre-2019 Wahoo range is for sure out.
03-11-20, 06:34 AM
#2
Senior Member
I think you've pretty much answered your own question, but I found Shane Miller's
a few years ago to be a good explanation
Personally, I went with a Wahoo Kicker SNAP wheel on trainer 3 years ago, mainly because the old bike I could dedicate to the trainer downstairs had a 7 speed rear that none of the wheel off trainers supported. But, I also decided I didn't need the high ends. I wasn't trying to make the indoor ride seem identical to my outdoor riding feel - it never will be - and at my FTP, even doing Tabata type intervals I could live within the 1500w rating
That has proven pretty much true for 3 years now - I put the Time Crunched Cyclist workouts on Zwift as custom workouts and haven't had a problem with over 5,000 miles on the trainer now.
Personally, I went with a Wahoo Kicker SNAP wheel on trainer 3 years ago, mainly because the old bike I could dedicate to the trainer downstairs had a 7 speed rear that none of the wheel off trainers supported. But, I also decided I didn't need the high ends. I wasn't trying to make the indoor ride seem identical to my outdoor riding feel - it never will be - and at my FTP, even doing Tabata type intervals I could live within the 1500w rating
That has proven pretty much true for 3 years now - I put the Time Crunched Cyclist workouts on Zwift as custom workouts and haven't had a problem with over 5,000 miles on the trainer now.
